Co-reporter:Katelyn P. Reighard, Camille Ehre, Zachary L. Rushton, Mona Jasmine R. Ahonen, David B. Hill, and Mark H. Schoenfisch
ACS Biomaterials Science & Engineering June 12, 2017 Volume 3(Issue 6) pp:1017-1017
Publication Date(Web):May 15, 2017
DOI:10.1021/acsbiomaterials.7b00039
Nitric oxide (NO)-releasing chitosan oligosaccharides were modified with ester functional groups to examine how the mucoadhesive nature of the scaffold impacts the ability of NO to degrade mucins from human bronchial epithelial cell cultures and clinical sputum samples collected from patients with cystic fibrosis (CF). Agarose gel electrophoresis experiments indicated that the mucoadhesive NO-releasing chitosan oligosaccharides degraded both the purified mucins and sputum, while control scaffolds (without NO release or mucoadhesive ligands) had no effect on mucin structure. Microscopic observations of sputum treated with the mucoadhesive NO-releasing chitosan oligosaccharide confirmed degradation of the mucin and DNA networks. Similarly, the viscosity and elasticity of sputum were reduced upon treatment with the mucoadhesive NO-releasing chitosan, demonstrating the potential utility of these NO-releasing scaffolds as mucolytic agents.Keywords: cystic fibrosis; mucins; mucolytic; nitric oxide;
Co-reporter:Micah D. Brown
ACS Sensors - New in 2016 December 23, 2016 Volume 1(Issue 12) pp:1453-1461
Publication Date(Web):November 16, 2016
DOI:10.1021/acssensors.6b00596
The presence of biological interferents in physiological media necessitates chemical modification of the working electrode to facilitate accurate electrochemical measurement of nitric oxide (NO). In this study, we evaluated a series of self-terminating electropolymerized films prepared from one of three isomers of phenylenediamine (PD), phenol, eugenol, or 5-amino-1-naphthol (5A1N) to improve the NO selectivity of a platinum working electrode. The electrodeposition procedure for each monomer was individually optimized using cyclic voltammetry (CV) or constant potential amperometry (CPA). Cyclic voltammetry deposition parameters favoring slower film formation generally yielded films with improved selectivity for NO over nitrite and l-ascorbate. Nitric oxide sensors were fabricated and compared using the optimized deposition procedure for each monomer. Sensors prepared using polyphenol and poly-5A1N film-modified platinum working electrodes demonstrated the most ideal analytical performance, with the former demonstrating the best selectivity versus nitrite. In simulated wound fluid, platinum electrodes modified with poly-5A1N films proved superior with respect to NO sensitivity retention and detection limit.Keywords: 5-amino-1-naphthol; electropolymerization; eugenol; nitric oxide; permselectivity; phenol; phenylenediamine; polymer-modified electrode;
Co-reporter:Robert J. Soto, Jonathon B. Schofield, Shaylyn E. Walter, Maggie J. Malone-Povolny, and Mark H. Schoenfisch
ACS Sensors - New in 2016 2017 Volume 2(Issue 1) pp:
Publication Date(Web):November 28, 2016
DOI:10.1021/acssensors.6b00623
Nitric oxide (NO)-releasing polymers have proven useful for improving the biocompatibility of in vivo glucose biosensors. Unfortunately, leaching of the NO donor from the polymer matrix remains a critical design flaw of NO-releasing membranes. Herein, a toolbox of NO-releasing silica nanoparticles (SNPs) was utilized to systematically evaluate SNP leaching from a diverse selection of biomedical-grade polyurethane sensor membranes. Glucose sensor analytical performance and NO-release kinetics from the sensor membranes were also evaluated as a function of particle and polyurethane (PU) chemistries. Particles modified with N-diazeniumdiolate NO donors were prone to leaching from PU membranes due to the zwitterionic nature of the NO donor modification. Leaching was minimized (<5% of the entrapped silica over 1 month) in low water uptake PUs. However, SNP modification with neutral S-nitrosothiol (RSNO) NO donors lead to biphasic leaching behavior. Particles with low alkanethiol content (<3.0 wt % sulfur) leached excessively from a hydrogel PU formulation (HP-93A-100 PU), while particles with greater degrees of thiol modification did not leach from any of the PUs tested. A functional glucose sensor was developed using an optimized HP-93A-100 PU membrane doped with RSNO-modified SNPs as the outer, glucose diffusion-limiting layer. The realized sensor design responded linearly to physiological concentrations of glucose (minimum 1–21 mM) over 2 weeks incubation in PBS and released NO at >0.8 pmol cm–2 s–1 for up to 6 days with no detectable (<0.6%) particle leaching.Keywords: biocompatibility; continuous glucose monitor; foreign body response; glucose biosensor; in vivo sensor; nitric oxide; silica nanoparticle;
Co-reporter:Dakota J. Suchyta
RSC Advances (2011-Present) 2017 vol. 7(Issue 84) pp:53236-53246
Publication Date(Web):2017/11/16
DOI:10.1039/C7RA09899E
In this study, fast and slow nitric oxide (NO)-releasing liposomes (half-lives of 2.5 and >72 h, respectively) were prepared by encapsulation of N-propyl-1,3-propanediamine/NO (PAPA/NO) and diethylenetriamine/NO (DETA/NO), respectively, via reverse phase evaporation. The anticancer activity of the otherwise equivalent fast and slow NO-releasing systems was evaluated against several distinct pancreatic, colorectal, and breast cancer cell lines. The anticancer assays (via cytotoxicity) over 72 h revealed that the slower NO-releasing liposomes consistently required lower NO payloads (LD50 < 3 μg mL−1) relative to the fast NO-release system (LD50 > 6 μg mL−1) to elicit cytotoxicity. The mechanism of intracellular NO build-up in cancer cells was studied using confocal fluorescence microscopy and flow cytometry, the results of which indicated that a more gradual NO accumulation was characteristic of the slow NO-release system. Protein expression via western blot analysis revealed that slower NO release resulted in more necrotic/apoptotic cells, while faster release reduced the number of mitotic cells to a greater extent. Overall, these studies demonstrate the potential of NO-releasing liposomes for anticancer therapy and highlight the significance of release kinetics (and NO payloads) required to induce cell death.
Co-reporter:Robert J. Soto, Jackson R. Hall, Micah D. Brown, James B. Taylor, and Mark H. Schoenfisch
Analytical Chemistry 2017 Volume 89(Issue 1) pp:
Publication Date(Web):November 6, 2016
DOI:10.1021/acs.analchem.6b04251
Co-reporter:Dakota J. Suchyta;Robert J. Soto
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 16) pp:2552-2558
Publication Date(Web):2017/04/18
DOI:10.1039/C7PY00123A
Chitosan was selectively monophosphorylated via reaction with phosphorus oxychloride (POCl3) to enhance water solubility while avoiding polyphosphate formation. The use of POCl3 resulted in negligible product degradation (i.e., breakdown of O-glycosidic bonds) even after a 3 d reaction period (<5% weight loss). X-ray photoelectron spectroscopy (XPS) characterization of the POCl3-phosphorylated chitosan (P-chitosan) revealed a phosphorus to nitrogen (P/N) atomic ratio of 0.30. Phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy verified the monophosphorylation of chitosan's primary and secondary alcohols, and primary amines. The calcium chelation efficiency for the phosphorylated product approached 0.05 mg Ca2+ per mg of P-chitosan as measured by inductively coupled plasma-optical emission spectrometry (ICP-OES), indicating improved chelation over native chitosan. This selective monophosphorylation approach proved useful for modifying other biopolymers, including cellulose and alginate.
Co-reporter:Robert J. Soto, Lei Yang, and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 3) pp:2220
Publication Date(Web):December 30, 2015
DOI:10.1021/acsami.5b10942
Nitric oxide-releasing mesoporous silica nanoparticles (MSNs) were prepared using an aminosilane-template surfactant ion exchange reaction. Initially, bare silica particles were synthesized under basic conditions in the presence of cetyltrimethylammonium bromide (CTAB). These particles were functionalized with nitric oxide (NO) donor precursors (i.e., secondary amines) via the addition of aminosilane directly to the particle sol and a commensurate ion exchange reaction between the cationic aminosilanes and CTAB. N-Diazeniumdiolate NO donors were formed at the secondary amines to yield NO-releasing MSNs. Tuning of the ion exchange-based MSN modification approach allowed for the preparation of monodisperse particles ranging from 30 to 1100 nm. Regardless of size, the MSNs stored appreciable levels of NO (0.4–1.5 μmol mg–1) with tunable NO release durations (1–33 h) dependent on the aminosilane modification. Independent control of NO release properties and particle size was achieved, demonstrating the flexibility of this novel MSN synthesis over conventional co-condensation and surface grafting strategies.Keywords: drug release; macromolecular nitric oxide donor; mesoporous silica; N-diazeniumdiolate; nitric oxide; silica nanoparticle
Co-reporter:Christopher J. Backlund, Brittany V. Worley, Mark H. Schoenfisch
Acta Biomaterialia 2016 Volume 29() pp:198-205
Publication Date(Web):1 January 2016
DOI:10.1016/j.actbio.2015.10.021
Abstract
The effect of nitric oxide (NO)-releasing dendrimer hydrophobicity on Streptococcus mutans killing and biofilm disruption was examined at pH 7.4 and 6.4, the latter relevant to dental caries. Generation 1 (G1) poly(amidoamine) (PAMAM) dendrimers were modified with alkyl epoxides to generate propyl-, butyl-, hexyl-, octyl-, and dodecyl-functionalized dendrimers. The resulting secondary amines were reacted with NO to form N-diazeniumdiolate NO donor-modified dendrimer scaffolds (total NO ∼1 μmol/mg). The bactericidal action of the NO-releasing dendrimers against both planktonic and biofilm-based S. mutans proved greatest with increasing alkyl chain length and at lower pH. Improved bactericidal efficacy at pH 6.4 was attributed to increased scaffold surface charge that enhanced dendrimer–bacteria association and ensuing membrane damage. For shorter alkyl chain (i.e., propyl and butyl) dendrimer modifications, increased antibacterial action at pH 6.4 was due to faster NO-release kinetics from proton-labile N-diazeniumdiolate NO donors. Octyl- and dodecyl-modified PAMAM dendrimers proved most effective for eradicating S. mutans biofilms with NO release mitigating dendrimer scaffold cytotoxicity.
Statement of significance
We report the antibacterial and anti-biofilm efficacy of dual-action nitric oxide (NO)-releasing dendrimers against S. mutans, an etiological agent in dental caries. This work was undertaken to enhance the anti-biofilm action of these scaffolds by employing various alkyl chain modifications. Furthermore, we evaluated the ability of NO to eradicate cariogenic biofilms. We found that at the lower pH associated with dental caries (pH ∼6.4), NO has a more pronounced antibacterial effect for alkyl modifications less capable of biofilm penetration and membrane disruption. Of greatest significance, we introduce dendrimers as a new macromolecular antibacterial agent against the cariogenic bacteria S. mutans.
Co-reporter:Brittany V. Worley, Robert J. Soto, Paige C. Kinsley, and Mark H. Schoenfisch
ACS Biomaterials Science & Engineering 2016 Volume 2(Issue 3) pp:426
Publication Date(Web):February 29, 2016
DOI:10.1021/acsbiomaterials.6b00032
The fabrication of electrospun composite polyurethane fibers capable of dual-action antibacterial dendrimer release is reported. Generation 4 (G4) poly(amidoamine) dendrimers were functionalized with octyl alkyl chain or quaternary ammonium (QA) moieties followed by modification of the resulting secondary amines with N-diazeniumdiolate nitric oxide (NO) donors to produce dual-action antibacterial dendrimers. Control and NO-releasing dendrimers were doped into polyurethane solutions prior to electrospinning of the polymer to yield well-defined dendrimer-doped composite polyurethane fibers. The fiber mats were semiporous (≥30% porosity) and exhibited high water uptake (>100% relative to fiber mass). Dendrimer- and NO-release characteristics (rates and totals) were dependent on the dendrimer modification and polyurethane composition, with total dendrimer- and NO-release amounts ranging from 10–80 μg/mg and 0.027–0.072 μmol NO/mg, respectively. The antibacterial action of the fibers was evaluated against Gram-negative and Gram-positive bacterial strains. Nitric oxide-releasing fibers demonstrated broad-spectrum bactericidal action at short (2 h) and long (24 h) time scales.Keywords: antibacterial; electrospinning; N-diazeniumdiolate; nitric oxide; poly(amidoamine) dendrimer; wound dressing
Co-reporter:Yuan Lu, Anand Shah, Rebecca A. Hunter, Robert J. Soto, Mark H. Schoenfisch
Acta Biomaterialia 2015 Volume 12() pp:62-69
Publication Date(Web):15 January 2015
DOI:10.1016/j.actbio.2014.10.028
Abstract
S-Nitrosothiol-modified chitosan oligosaccharides were synthesized by reaction with 2-iminothiolane hydrochloride and 3-acetamido-4,4-dimethylthietan-2-one, followed by thiol nitrosation. The resulting nitric oxide (NO)-releasing chitosan oligosaccharides stored ∼0.3 μmol NO mg−1 chitosan. Both the chemical structure of the nitrosothiol (i.e. primary and tertiary) and the use of ascorbic acid as a trigger for NO donor decomposition were used to control the NO-release kinetics. With ascorbic acid, the S-nitrosothiol-modified chitosan oligosaccharides elicited a 4-log reduction in Pseudomonas aeruginosa viability. Confocal microscopy indicated that the primary S-nitrosothiol-modified chitosan oligosaccharides associated more with the bacteria relative to the tertiary S-nitrosothiol system. The primary S-nitrosothiol-modified chitosan oligosaccharides elicited minimal toxicity towards L929 mouse fibroblast cells at the concentration necessary for a 4-log reduction in bacterial viability, further demonstrating the potential of S-nitrosothiol-modified chitosan oligosaccharides as NO-release therapeutics.
Co-reporter:Rebecca A. Hunter and Mark H. Schoenfisch
Analytical Chemistry 2015 Volume 87(Issue 6) pp:3171
Publication Date(Web):February 25, 2015
DOI:10.1021/ac503220z
A 530 nm light emitting diode was coupled to a microfluidic sensor to facilitate photolysis of nitrosothiols (i.e., S-nitrosoglutathione, S-nitrosocysteine, and S-nitrosoalbumin) and amperometric detection of the resulting nitric oxide (NO). This configuration allowed for maximum sensitivity and versatility, while limiting potential interference from nitrate decomposition caused by ultraviolet light. Compared to similar measurements of total S-nitrosothiol content in bulk solution, use of the microfluidic platform permitted significantly enhanced analytical performance in both phosphate-buffered saline and plasma (6–20× improvement in sensitivity depending on nitrosothiol type). Additionally, the ability to reduce sample volumes from milliliters to microliters provides increased clinical utility. To demonstrate its potential for biological analysis, this device was used to measure basal nitrosothiol levels from the vasculature of a healthy porcine model.
Co-reporter:Dakota J. Suchyta
Molecular Pharmaceutics 2015 Volume 12(Issue 10) pp:3569-3574
Publication Date(Web):August 19, 2015
DOI:10.1021/acs.molpharmaceut.5b00248
The rapid decomposition of nitric oxide (NO) donors in aqueous environments remains a limitation for applications requiring extended NO release. Herein, we report the synthesis of dipalmitoylphosphatidylcholine-based liposomes capable of extended NO release using low molecular weight NO donors and a reverse-phase evaporation technique. The encapsulation of the NO donors within the liposomes enabled both prolonged NO release and enhanced storage compared to free NO donors alone. The NO-releasing liposomes also demonstrated enhanced efficacy against human pancreatic cancer cells. These NO-release vehicles represent attractive anticancer therapeutics due to their potential to store the majority of their NO payload until reaching cancerous tissue at which time the lower pH inherent to such environments will trigger an avalanche of NO.
Co-reporter:Brittany V. Worley; Kelci M. Schilly
Molecular Pharmaceutics 2015 Volume 12(Issue 5) pp:1573-1583
Publication Date(Web):April 15, 2015
DOI:10.1021/acs.molpharmaceut.5b00006
Herein, we describe the synthesis of nitric oxide (NO)-releasing alkyl chain modified poly(amidoamine) (PAMAM) dendrimers of various sizes (i.e., generations). Generation 1 (G1) through generation 4 (G4) dendrimers were modified with either short (i.e., butyl) or medium (i.e., hexyl) alkyl chains via a ring-opening reaction. The resulting secondary amines were subsequently modified with N-diazeniumdiolate NO donors to establish NO payloads of ∼1.0 μmol/mg. The bactericidal efficacy of these dendrimers was evaluated against Gram-negative and Gram-positive biofilms, including antibiotic-resistant strains. The anti-biofilm action of the dendrimer biocides was found to be dependent on dendrimer generation, bacterial Gram class, and alkyl chain length, with the most effective biofilm eradication occurring when antibacterial agents were capable of efficient biofilm infiltration. The addition of NO release markedly enhanced anti-biofilm activity of dendrimers incapable of effective biofilm penetration.
Co-reporter:Wesley L. Storm;Justin A. Johnson;Brittany V. Worley;Danielle L. Slomberg
Journal of Biomedical Materials Research Part A 2015 Volume 103( Issue 6) pp:1974-1984
Publication Date(Web):
DOI:10.1002/jbm.a.35331
Abstract
Recent research has demonstrated that silver sulfadiazine and small molecule nitric oxide (NO) donors kill a number of bacterial species synergistically in solution-based assays. Herein, we report on multilayered silica-based xerogels that release both NO and silver. Release of each agent was achieved by exposing amine-modified xerogels to high pressures of NO, and doping silver nitrate (AgNO3) into an alkyl-silane xerogel. Total achievable releases were 3.5 μmol cm−2 and 1.7 ppm for NO and Ag+, respectively, with release of each agent controlled independent of the other. The NO/Ag+-releasing coating reduced bacterial adhesion and exhibited greater-than-additive killing against both Pseudomonas aeruginosa and Staphylococcus aureus. In contrast, cytotoxicity assays against L929 fibroblasts suggest that the combination does not cause greater-than-additive killing to mammalian cells. Such materials may prove useful in the design of biomedical devices prone to infection such as bone and surgical screws. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 1974–1984, 2015.
Co-reporter:Wesley L. Storm, Jonghae Youn, Katelyn P. Reighard, Brittany V. Worley, Hetali M. Lodaya, Jae Ho Shin, Mark H. Schoenfisch
Acta Biomaterialia 2014 Volume 10(Issue 8) pp:3442-3448
Publication Date(Web):August 2014
DOI:10.1016/j.actbio.2014.04.029
Abstract
Superhydrophobic nitric oxide (NO)-releasing xerogels were prepared by spray-coating a fluorinated silane/silica composite onto N-diazeniumdiolate NO donor-modified xerogels. The thickness of the superhydrophobic layer was used to extend NO release durations from 59 to 105 h. The resulting xerogels were stable, maintaining superhydrophobicity for up to 1 month (the longest duration tested) when immersed in solution, with no leaching of silica or undesirable fragmentation detected. The combination of superhydrophobicity and NO release reduced viable Pseudomonas aeruginosa adhesion by >2-logs. The killing effect of NO was demonstrated at longer bacterial contact times, with superhydrophobic NO-releasing xerogels resulting in 3.8-log reductions in adhered viable bacteria vs. controls. With no observed toxicity to L929 murine fibroblasts, NO-releasing superhydrophobic membranes may be valuable antibacterial coatings for implants as they both reduce adhesion and kill bacteria that do adhere.
Co-reporter:Robert J. Soto, Benjamin J. Privett, and Mark H. Schoenfisch
Analytical Chemistry 2014 Volume 86(Issue 14) pp:7141
Publication Date(Web):July 1, 2014
DOI:10.1021/ac5017425
The in vivo analytical performance of percutaneously implanted nitric oxide (NO)-releasing amperometric glucose biosensors was evaluated in swine for 10 d. Needle-type glucose biosensors were functionalized with NO-releasing polyurethane coatings designed to release similar total amounts of NO (3.1 μmol cm–2) for rapid (16.0 ± 4.4 h) or slower (>74.6 ± 16.6 h) durations and remain functional as outer glucose sensor membranes. Relative to controls, NO-releasing sensors were characterized with improved numerical accuracy on days 1 and 3. Furthermore, the clinical accuracy and sensitivity of rapid NO-releasing sensors were superior to control and slower NO-releasing sensors at both 1 and 3 d implantation. In contrast, the slower, extended, NO-releasing sensors were characterized by shorter sensor lag times (<4.2 min) in response to intravenous glucose tolerance tests versus burst NO-releasing and control sensors (>5.8 min) at 3, 7, and 10 d. Collectively, these results highlight the potential for NO release to enhance the analytical utility of in vivo glucose biosensors. Initial results also suggest that this analytical performance benefit is dependent on the NO-release duration.
Co-reporter:Brittany V. Worley, Danielle L. Slomberg, and Mark H. Schoenfisch
Bioconjugate Chemistry 2014 Volume 25(Issue 5) pp:918
Publication Date(Web):May 5, 2014
DOI:10.1021/bc5000719
Herein we describe the synthesis of nitric oxide (NO)-releasing quaternary ammonium (QA)-functionalized generation 1 (G1) and generation 4 (G4) poly(amidoamine) (PAMAM) dendrimers. Dendrimers were modified with QA moieties of different alkyl chain lengths (i.e., methyl, butyl, octyl, dodecyl) via a ring-opening reaction. The resultant secondary amines were then modified with N-diazeniumdiolate NO donors to yield NO-releasing QA-modified PAMAM dendrimers capable of spontaneous NO release (payloads of ∼0.75 μmol/mg over 4 h). The bactericidal efficacy of individual (i.e., non-NO-releasing) and dual action (i.e., NO-releasing) QA-modified PAMAM dendrimers was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria. Bactericidal activity was found to be dependent on dendrimer generation, QA alkyl chain length, and bacterial Gram class for both systems. Shorter alkyl chains (i.e., methylQA, butylQA) demonstrated increased bactericidal activity against P. aeruginosa versus S. aureus for both generations, with NO release markedly enhancing overall killing.
Co-reporter:Yuan Lu, Danielle L. Slomberg, Mark H. Schoenfisch
Biomaterials 2014 35(5) pp: 1716-1724
Publication Date(Web):
DOI:10.1016/j.biomaterials.2013.11.015
Co-reporter:Alexis W. Carpenter, Justin A. Johnson, Mark H. Schoenfisch
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014 Volume 454() pp:144-151
Publication Date(Web):20 July 2014
DOI:10.1016/j.colsurfa.2014.03.094
•Surface modification of silica nanoparticles to tune nitric oxide-release kinetics.•Hydrophobic modifications result in extended nitric oxide-release duration.•Method allows for reduced particle leaching from polymers.Hydrocarbon- and fluorocarbon-based silanes were grafted onto the surface of amine-containing silica nanoparticles to achieve materials of varied surface hydrophobicity. X-ray photoelectron spectroscopy and direct polarization solid-state nuclear magnetic resonance spectroscopy were used to confirm the presence of surface-grafted functionalities. Changes in hydrophobicity were illustrated by assessing the stability of aqueous particle suspensions using dynamic light scattering. Following surface modification, the amines were converted to N-diazeniumdiolate nitric oxide (NO) donors to yield nanoparticles with tunable nitric oxide (NO) release kinetics dependent on the rate of water uptake into the silica structures. Moreover, modification of the particle surface hydrophobicity allowed for the preparation of NO-releasing electrospun polymer fibers with improved particle incorporation and decreased particle leaching compared to fibers doped with unmodified particles. Methods for tuning particle surface chemistry (e.g., hydrophobicity) while maintaining control over size and structure will enable the optimization of such NO-release vehicles for specific therapeutic applications.
Co-reporter:Scott P. Nichols, Ahyeon Koh, Wesley L. Storm, Jae Ho Shin, and Mark H. Schoenfisch
Chemical Reviews 2013 Volume 113(Issue 4) pp:2528
Publication Date(Web):February 7, 2013
DOI:10.1021/cr300387j
Co-reporter:Danielle L. Slomberg, Yuan Lu, Angela D. Broadnax, Rebecca A. Hunter, Alexis W. Carpenter, and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 19) pp:9322
Publication Date(Web):September 5, 2013
DOI:10.1021/am402618w
Nitric oxide (NO), a reactive free radical, has proven effective in eradicating bacterial biofilms with reduced risk of fostering antibacterial resistance. Herein, we evaluated the efficacy of NO-releasing silica nanoparticles against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus biofilms as a function of particle size and shape. Three sizes of NO-releasing silica nanoparticles (i.e., 14, 50, and 150 nm) with identical total NO release (∼0.3 μmol/mg) were utilized to study antibiofilm eradication as a function of size. To observe the role of particle shape on biofilm killing, we varied the aspect ratio of the NO-releasing silica particles from 1 to 8 while maintaining constant particle volume (∼0.02 μm3) and NO-release totals (∼0.7 μmol/mg). Nitric oxide-releasing particles with decreased size and increased aspect ratio were more effective against both P. aeruginosa and S. aureus biofilms, with the Gram-negative species exhibiting the greatest susceptibility to NO. To further understand the influence of these nanoparticle properties on NO-mediated antibacterial activity, we visualized intracellular NO concentrations and cell death with confocal microscopy. Smaller NO-releasing particles (14 nm) exhibited better NO delivery and enhanced bacteria killing compared to the larger (50 and 150 nm) particles. Likewise, the rod-like NO-releasing particles proved more effective than spherical particles in delivering NO and inducing greater antibacterial action throughout the biofilm.Keywords: antibacterial; antibiofilm; nitric oxide; particle shape; particle size; silica nanoparticles;
Co-reporter:Wesley L. Storm and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 11) pp:4904
Publication Date(Web):May 7, 2013
DOI:10.1021/am4006397
Nitric oxide (NO)-releasing xerogel materials were synthesized using N-diazeniumdiolate-modified silane monomers that were subsequently co-condensed with an alkoxysilane. The NO-release characteristics were tuned by varying the aminosilane structure and concentration. The resulting materials exhibited maximum NO release totals and durations ranging from 0.45–3.2 μmol cm–2 and 20–90 h, respectively. The stability of the xerogel networks was optimized by varying the alkoxysilane backbone identity, water to silane ratio, base catalyst concentration, reaction time, and drying conditions. The response of glucose biosensors prepared using the NO-releasing xerogel (15 mol % N-diazeniumdiolate-modified N-2-(aminoethyl)-aminopropyltrimethoxysilane) as an outer sensor membrane was linear (R2 = 0.979) up to 24 mM glucose. The sensitivity (3.4 nA mM–1) of the device to glucose was maintained for 7 days in phosphate buffered saline. The facile sol–gel synthetic route, along with the NO release and glucose biosensor characteristics, demonstrates the versatility of this method for biosensor membrane applications.Keywords: enzymatic glucose sensor; N-diazeniumdiolate; nitric oxide; sol−gel;
Co-reporter:Ahyeon Koh, Alexis W. Carpenter, Danielle L. Slomberg, and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 16) pp:7956
Publication Date(Web):August 5, 2013
DOI:10.1021/am402044s
Electrospun polyurethane fibers doped with nitric oxide (NO)-releasing silica particles are presented as novel macromolecular scaffolds with prolonged NO-release and high porosity. Fiber diameter (119–614 nm) and mechanical strength (1.7–34.5 MPa of modulus) were varied by altering polyurethane type and concentration, as well as the NO-releasing particle composition, size, and concentration. The resulting NO-releasing electrospun nanofibers exhibited ∼83% porosity with flexible plastic or elastomeric behavior. The use of N-diazeniumdiolate- or S-nitrosothiol-modified particles yielded scaffolds exhibiting a wide range of NO release totals and durations (7.5 nmol mg–1–0.12 μmol mg–1 and 7 h to 2 weeks, respectively). The application of NO-releasing porous materials as coatings for subcutaneous implants may improve tissue biocompatibility by mitigating the foreign body response and promoting cell integration.Keywords: controlled release; electrospun fiber; nitric oxide; polyurethane; porous biomaterial;
Co-reporter:Rebecca A. Hunter, Wesley L. Storm, Peter N. Coneski, and Mark H. Schoenfisch
Analytical Chemistry 2013 Volume 85(Issue 3) pp:1957
Publication Date(Web):January 3, 2013
DOI:10.1021/ac303787p
Despite growing reports on the biological action of nitric oxide (NO) as a function of NO payload, the validity of such work is often questionable due to the manner in which NO is measured and/or the solution composition in which NO is quantified. To highlight the importance of measurement technique for a given sample type, NO produced from a small-molecule NO donor (N-diazeniumdiolated l-proline, PROLI/NO) and a NO-releasing xerogel film were quantified in a number of physiological buffers and fluids, cell culture media, and bacterial broth by the Griess assay, a chemiluminescence analyzer, and an amperometric NO sensor. Despite widespread use, the Griess assay proved to be inaccurate for measuring NO in many of the media tested. In contrast, the chemiluminescence analyzer provided superb kinetic information in most buffers but was impractical for NO analysis in proteinaceous media. The electrochemical NO sensor enabled greater flexibility across the various media with potential for spatial resolution, albeit at lower than expected NO totals versus either the Griess assay or chemiluminescence. The results of this study highlight the importance of measurement strategy for accurate NO analysis and reporting NO-based biological activity.
Co-reporter:Rebecca A. Hunter, Benjamin J. Privett, W. Hampton Henley, Elise R. Breed, Zhe Liang, Rohit Mittal, Benyam P. Yoseph, Jonathan E. McDunn, Eileen M. Burd, Craig M. Coopersmith, J. Michael Ramsey, and Mark H. Schoenfisch
Analytical Chemistry 2013 Volume 85(Issue 12) pp:6066
Publication Date(Web):May 21, 2013
DOI:10.1021/ac400932s
Standard photolithographic techniques and a nitric oxide (NO) selective xerogel polymer were utilized to fabricate an amperometric NO microfluidic sensor with low background noise and the ability to analyze NO levels in small sample volumes (∼250 μL). The sensor exhibited excellent analytical performance in phosphate buffered saline, including a NO sensitivity of 1.4 pA nM–1, a limit of detection (LOD) of 840 pM, and selectivity over nitrite, ascorbic acid, acetaminophen, uric acid, hydrogen sulfide, ammonium, ammonia, and both protonated and deprotonated peroxynitrite (selectivity coefficients of −5.3, −4.2, −4.0, −5.0, −6.0, −5.8, −3.8, −1.5, and −4.0, respectively). To demonstrate the utility of the microfluidic NO sensor for biomedical analysis, the device was used to monitor changes in blood NO levels during the onset of sepsis in a murine pneumonia model.
Co-reporter:Ahyeon Koh, Yuan Lu, and Mark H. Schoenfisch
Analytical Chemistry 2013 Volume 85(Issue 21) pp:10488
Publication Date(Web):September 18, 2013
DOI:10.1021/ac402312b
The active release of pharmaceutical agents and the use of porous sensor membranes represent the two most promising strategies for addressing the poor tissue biocompatibility of implantable glucose biosensors. Herein, we describe the combination of these approaches to create nitric oxide (NO)-releasing porous fiber mat-modified sensor membranes. An electrospinning method was used to directly modify needle-type glucose biosensors with the NO donor-loaded fibers. The resulting NO-releasing fiber mat (540 ± 139 nm fiber diameter, 94.1 ± 3.7% porosity) released ∼100 nmol of NO per mg of polyurethane over 6 h while maintaining a porous structure without leaching of the NO donor, even in serum. The porous fiber membrane did not influence the analytical performance of the biosensor when ≤50 μm thick.
Co-reporter:Scott P. Nichols and Mark H. Schoenfisch
Biomaterials Science 2013 vol. 1(Issue 11) pp:1151-1159
Publication Date(Web):17 Jul 2013
DOI:10.1039/C3BM60130G
Nitric oxide (NO) is an endogenous antibacterial agent produced by immune cells in response to pathogens. Herein, the NO fluxes necessary to reduce bacterial adhesion of different bacteria (S. aureus, methicillin-resistant S. aureus, S. epidermidis, E. faecalis, E. coli, and P. aeruginosa) were investigated to ascertain the sensitivity of these bacteria to NO. S-Nitrosothiol NO donor-modified xerogels were selected as a model NO-release surface due to their extended NO-release kinetics relative to other NO donor systems. The xerogels were coated with poly(vinyl chloride) (PVC) to achieve consistent surface energy between NO-releasing and control substrates. Fibrinogen was pre-adsorbed to these materials to more accurately mimic conditions encountered in blood and promote bacteria adhesion. Nitric oxide fluxes ranging from 20–50 pmol cm−2 s−1 universally inhibited the bacterial adhesion by >80% for each strain studied. Maximum bacteria killing activity (reduced viability by 85–98%) was observed at the greatest NO payload (1700 nmol cm−2).
Co-reporter:Alexis W. Carpenter, Katelyn P. Reighard, Joseph E. Saavedra and Mark H. Schoenfisch
Biomaterials Science 2013 vol. 1(Issue 5) pp:456-459
Publication Date(Web):24 Jan 2013
DOI:10.1039/C3BM00153A
O
2
-Protected N-diazeniumdiolate-based silanes were grafted onto mesoporous silica nanoparticles to yield a scaffold with an NO payload of 2.4 μmol NO per mg and NO release half-life of 23 d. Adhesion of Streptococcus mutans to dental restorative materials doped with these NO-releasing particles was reduced by 3-log compared to controls.
Co-reporter:Yuan Lu, Danielle L. Slomberg, Anand Shah, and Mark H. Schoenfisch
Biomacromolecules 2013 Volume 14(Issue 10) pp:
Publication Date(Web):August 20, 2013
DOI:10.1021/bm400961r
A series of amphiphilic nitric oxide (NO)-releasing poly(amidoamine) (PAMAM) dendrimers with different exterior functionalities were synthesized by a ring-opening reaction between primary amines on the dendrimer and propylene oxide (PO), 1,2-epoxy-9-decene (ED), or a ratio of the two, followed by reaction with NO at 10 atm to produce N-diazeniumdiolate-modified scaffolds with a total storage of ∼1 μmol/mg. The hydrophobicity of the exterior functionality was tuned by varying the ratio of PO and ED grafted onto the dendrimers. The bactericidal efficacy of these NO-releasing vehicles against established Gram-negative Pseudomonas aeruginosa biofilms was then evaluated as a function of dendrimer exterior hydrophobicity (i.e., ratio of PO/ED), size (i.e., generation), and NO release. Both the size and exterior functionalization of dendrimer proved important to a number of parameters including dendrimer−bacteria association, NO delivery efficiency, bacteria membrane disruption, migration within the biofilm, and toxicity to mammalian cells. Although enhanced bactericidal efficacy was observed for the hydrophobic chains (e.g., ED), toxicity to L929 mouse fibroblast cells was also noted at concentrations necessary to reduce bacterial viability by 5-logs (99.999% killing). The optimal PO to ED ratios for biofilm eradication with minimal toxicity against L929 mouse fibroblast cells were 7:3 and 5:5. The study presented herein demonstrated the importance of both dendrimer size and exterior properties in determining efficacy against established biofilms without compromising biocompatibility to mammalian cells.
Co-reporter:Peter N. Coneski and Mark H. Schoenfisch
Chemical Society Reviews 2012 vol. 41(Issue 10) pp:3753-3758
Publication Date(Web):24 Feb 2012
DOI:10.1039/C2CS15271A
Nitric oxide's expansive physiological and regulatory roles have driven the development of therapies for human disease that would benefit from exogenous NO administration. Already a number of therapies utilizing gaseous NO or NO donors capable of storing and delivering NO have been proposed and designed to exploit NO's influence on the cardiovascular system, cancer biology, the immune response, and wound healing. As described in Nitric oxide release: Part I. Macromolecular scaffolds and Part II. Therapeutic applications, the preparation of new NO-release strategies/formulations and the study of their therapeutic utility are increasing rapidly. However, comparison of such studies remains difficult due to the diversity of scaffolds, NO measurement strategies, and reporting methods employed across disciplines. This tutorial review highlights useful analytical techniques for the detection and measurement of NO. We also stress the importance of reporting NO delivery characteristics to allow appropriate comparison of NO between studies as a function of material and intended application.
Co-reporter:Alexis W. Carpenter and Mark H. Schoenfisch
Chemical Society Reviews 2012 vol. 41(Issue 10) pp:3742-3752
Publication Date(Web):24 Feb 2012
DOI:10.1039/C2CS15273H
A wide range of nitric oxide (NO)-releasing materials has emerged as potential therapeutics that exploit NO's vast biological roles. Macromolecular NO-releasing scaffolds are particularly promising due to their ability to store and deliver larger NO payloads in a more controlled and effective manner compared to low molecular weight NO donors. While a variety of scaffolds (e.g., particles, dendrimers, and polymers/films) have been cleverly designed, the ultimate clinical utility of most NO-releasing macromolecules remains unrealized. Although not wholly predictive of clinical success, in vitro and in vivo investigations have enabled a preliminary evaluation of the therapeutic potential of such materials. In this tutorial review, we review the application of macromolecular NO therapies for cardiovascular disease, cancer, bacterial infections, and wound healing.
Co-reporter:Daniel A. Riccio and Mark H. Schoenfisch
Chemical Society Reviews 2012 vol. 41(Issue 10) pp:3731-3741
Publication Date(Web):24 Feb 2012
DOI:10.1039/C2CS15272J
The roles of nitric oxide (NO) in physiology and pathophysiology merit the use of NO as a therapeutic for certain biomedical applications. Unfortunately, limited NO payloads, too rapid NO release, and the lack of targeted NO delivery have hindered the clinical utility of NO gas and low molecular weight NO donor compounds. A wide-variety of NO-releasing macromolecular scaffolds has thus been developed to improve NO's pharmacological potential. In this tutorial review, we provide an overview of the most promising NO release scaffolds including protein, organic, inorganic, and hybrid organic-inorganic systems. The NO release vehicles selected for discussion were chosen based on their enhanced NO storage, tunable NO release characteristics, and potential as therapeutics.
Co-reporter:Daniel A. Riccio, Peter N. Coneski, Scott P. Nichols, Angela D. Broadnax, and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 2) pp:796
Publication Date(Web):January 18, 2012
DOI:10.1021/am201443r
The synthesis of a tertiary thiol-bearing silane precursor (i.e., N-acetyl penicillamine propyltrimethoxysilane or NAPTMS) to enable enhanced NO storage stability at physiological temperature is described. The novel silane was co-condensed with alkoxy- or alkylalkoxysilanes under varied synthetic parameters (e.g., water to silane ratio, catalyst and solvent concentrations, and reaction time) to evaluate systematically the formation of stable xerogel films. The resulting xerogels were subsequently nitrosated to yield tertiary RSNO-modified coatings. Total NO storage ranged from 0.87 to 1.78 μmol cm–2 depending on the NAPTMS concentration and xerogel coating thickness. Steric hindrance near the nitroso functionality necessitated the use of photolysis to liberate NO. The average NO flux for irradiated xerogels (20% NAPTMS balance TEOS xerogel film cast using 30 μL) in physiological buffer at 37 °C was ∼23 pmol cm–2 s–1. The biomedical utility of the photoinitiated NO-releasing films was illustrated by their ability to both reduce Pseudomonas aeruginosa adhesion by ∼90% relative to control interfaces and eradicate the adhered bacteria.Keywords: antimicrobial; nitric oxide; photolysis; S-nitrosothiol; sol−gel;
Co-reporter:Daniel A. Riccio, Steven T. Nutz, and Mark H. Schoenfisch
Analytical Chemistry 2012 Volume 84(Issue 2) pp:851
Publication Date(Web):December 14, 2011
DOI:10.1021/ac2031805
The concentration of S-nitrosothiols (RSNOs), endogenous transporters of the signaling molecule nitric oxide (NO), fluctuate greatly in physiology often as a function of disease state. RSNOs may be measured indirectly by cleaving the S–N bond and monitoring the liberated NO. While ultraviolet photolysis and reductive-based cleavage both decompose RSNOs to NO, poor selectivity and the need for additional reagents preclude their utility clinically. Herein, we report the coupling of visible photolysis (i.e., 500–550 nm) and amperometric NO detection to quantify RSNOs with greater selectivity and sensitivity. Enhanced sensitivity (up to 1.56 nA μM–1) and lowered theoretical detection limits (down to 30 nM) were achieved for low molecular weight RSNOs (i.e., S-nitrosoglutathione, S-nitrosocysteine) by tuning the irradiation exposure. Detection of nitrosated proteins (i.e., S-nitrosoalbumin) was also possible, albeit at a decreased sensitivity (0.11 nA μM–1). This detection scheme was used to measure RSNOs in plasma and illustrate the potential of this method for future physiological studies.
Co-reporter:Danielle L. Slomberg and Mark H. Schoenfisch
Environmental Science & Technology 2012 Volume 46(Issue 18) pp:10247-10254
Publication Date(Web):August 13, 2012
DOI:10.1021/es300949f
The phytotoxicity of silica nanoparticles (SiNPs) was evaluated as a function of particle size (14, 50, and 200 nm), concentration (250 and 1000 mg L–1), and surface composition toward Arabidopsis thaliana plants grown hydroponically for 3 and 6 weeks. Reduced development and chlorosis were observed for plants exposed to highly negative SiNPs (−20.3 and −31.9 mV for the 50 and 200 nm SiNPs, respectively) regardless of particle concentration when not controlling pH of the hydroponic medium, which resulted in increased alkalinity (∼pH 8). Particles were no longer toxic to the plants at either concentration upon calcination or removal of surface silanols from the SiNP surface, or adjusting the pH of the growth medium to pH 5.8. The phytotoxic effects observed for the negatively charged 50 and 200 nm SiNPs were attributed to pH effects and the adsorption of macro- and micro-nutrients to the silica surface. Size-dependent uptake of the nanoparticles by the plants was confirmed using transmission electron microscopy (TEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) with plant roots containing 32.0, 1.85, and 7.00 × 10–3 mg Si·kg tissue–1/nm3 (normalized for SiNP volume) for the 14, 50, and 200 nm SiNPs respectively, after 6 weeks exposure at 1000 ppm (pH 5.8). This study demonstrates that the silica scaffolds are not phytotoxic up to 1000 ppm despite significant uptake of the SiNPs (14, 50, and 200 nm) into the root system of A. thaliana.
Co-reporter:Scott P. Nichols, Ahyeon Koh, Nga L. Brown, Michael B. Rose, Bin Sun, Danielle L. Slomberg, Daniel A. Riccio, Bruce Klitzman, Mark H. Schoenfisch
Biomaterials 2012 33(27) pp: 6305-6312
Publication Date(Web):
DOI:10.1016/j.biomaterials.2012.05.053
Co-reporter:Bin Sun, Danielle L. Slomberg, Shalini L. Chudasama, Yuan Lu, and Mark H. Schoenfisch
Biomacromolecules 2012 Volume 13(Issue 10) pp:
Publication Date(Web):September 26, 2012
DOI:10.1021/bm301109c
The antibacterial activity of a series of nitric oxide (NO)-releasing poly(propylene imine) (PPI) dendrimers was evaluated against both Gram-positive and Gram-negative pathogenic bacteria, including methicillin-resistant Staphylococcus aureus. A direct comparison of the bactericidal efficacy between NO-releasing and control PPI dendrimers (i.e., non-NO-releasing) revealed both enhanced biocidal action of NO-releasing dendrimers and reduced toxicity against mammalian fibroblast cells. Antibacterial activity for the NO donor-functionalized PPI dendrimers was shown to be a function of both dendrimer size (molecular weight) and exterior functionality. In addition to minimal toxicity against fibroblasts, NO-releasing PPI dendrimers modified with styrene oxide exhibited the greatest biocidal activity (≥99.999% killing) against all bacterial strains tested. The N-diazeniumdiolate NO donor-functionalized PPI dendrimers presented in this study hold promise as effective NO-based therapeutics for combating bacterial infections.
Co-reporter:Alexis W. Carpenter, Brittany V. Worley, Danielle L. Slomberg, and Mark H. Schoenfisch
Biomacromolecules 2012 Volume 13(Issue 10) pp:
Publication Date(Web):September 21, 2012
DOI:10.1021/bm301108x
The synthesis of quaternary ammonium (QA)-functionalized silica nanoparticles with and without nitric oxide (NO) release capabilities is described. Glycidyltrialkylammonium chlorides of varied alkyl chain lengths (i.e., methyl, butyl, octyl, and dodecyl) were tethered to the surface of amine-containing silica nanoparticles via a ring-opening reaction. Secondary amines throughout the particle were then functionalized with N-diazeniumdiolate NO donors to yield dual functional nanomaterials with surface QAs and total NO payloads of 0.3 μmol/mg. The bactericidal activities of singly (i.e., only NO-releasing or only QA-functionalized) and dual (i.e., NO-releasing and QA-functionalized) functional nanoparticles were tested against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa. Particles with only NO release capabilities alone were found to be more effective against P. aeruginosa, while particles with only QA-functionalities exhibited greater toxicity toward S. aureus. The minimum bactericidal concentrations (MBC) of QA-functionalized particles decreased with increasing alkyl chain length against both microbes tested. Combining NO release and QA-functionalities on the same particle resulted in an increase in bactericidal efficacy against S. aureus; however, no change in activity against P. aeruginosa was observed compared to NO-releasing particles alone.
Co-reporter:Daniel A. Riccio, Julia L. Nugent, and Mark H. Schoenfisch
Chemistry of Materials 2011 Volume 23(Issue 7) pp:1727
Publication Date(Web):March 7, 2011
DOI:10.1021/cm102510q
We report the synthesis of S-nitrosothiol-modified silica particles capable of nitric oxide (NO) release. The thiol precursor modification to form S-nitrosothiol NO donors was introduced into the silica network via co-condensation of mercaptosilane and alkoxysilane precursors. Both the concentration of reactants (i.e., water, ammonia, and silane) and the silane feed rate into the reaction proved important in the yield of monodisperse, spherical particles with tunable diameters ranging from 241−718 nm. Subsequent nitrosation resulted in NO storage approaching ∼4.40 μmol NO mg−1, as determined by total NO release. Behaving similar to low molecular weight S-nitrosothiol NO donors, the NO release from the macromolecular silica vehicles was influenced by light, temperature, and metal ions.Keywords: nitric oxide release; silica particles; Stöber synthesis; therapeutic; tunable size;
Co-reporter:Yuan Lu, Bin Sun, Chenghong Li, and Mark H. Schoenfisch
Chemistry of Materials 2011 Volume 23(Issue 18) pp:4227
Publication Date(Web):August 29, 2011
DOI:10.1021/cm201628z
Structurally diverse secondary amine-functionalized poly(propylene imine) (PPI) dendrimers capable of tunable nitric oxide (NO) release were synthesized in a straightforward, one-step manner using ring-opening or conjugate-addition reactions with propylene oxide (PO), styrene oxide (SO), acrylonitrile (ACN), poly(ethylene glycol) methyl ether acrylate (average Mn = 480) (PEG) or 1,2-epoxy-9-decene (ED). N-Diazeniumdiolate nitric oxide donors were formed on the resulting secondary amine-functionalized G2-G5 PPI dendrimers by reaction with NO gas in basic solution. The NO storage and release kinetics for the resulting dendritic scaffolds were diverse (0.9–3.8 μmol NO/mg totals and 0.3 to 4.9 h half-lives), illustrating the importance of the exterior chemical modification (e.g., steric environments, hydrophobicity, etc.) on diazeniumdiolate stability/decomposition. Tunable NO release was demonstrated by combining two donor systems on the exterior of one macromolecular scaffold. Additionally, a mathematical model was developed that allows for the simulation of dual NO release kinetics using the NO release data from the two single NO donor systems. The approaches described herein extend the range and scope of NO-releasing macromolecular scaffolds by unlocking a series of materials for use as dopants in biomedical polymers or stand-alone therapeutics depending on the exterior modification.Keywords: dendrimers; diazeniumdiolate; nitric oxide; tunable release;
Co-reporter:Peter N. Coneski, Jessica A. Nash, and Mark H. Schoenfisch
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 2) pp:426
Publication Date(Web):January 20, 2011
DOI:10.1021/am101010e
The preparation of electrospun polymer microfibers with nitric oxide (NO)-release capabilities is described. Polymer solutions containing disodium 1-[2-(carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate (PROLI/NO), a low-molecular-weight NO donor, were electrospun to generate fibers ranging from 100−3000 nm in diameter capable of releasing NO upon immersion in aqueous solutions under physiological conditions (pH 7.4, 37 °C), with kinetics depending on polymer composition and fiber diameter. The NO release half-life for PROLI/NO-doped electrospun fibers was 2−200 times longer than that of PROLI/NO alone. The influence of polymer concentration, applied voltage, capillary diameter, solution conductivity, flow rate, and additives on fiber properties are reported and discussed with respect to potential applications.Keywords (keywords): biomaterials; controlled release; electrospinning; microfibers; nitric oxide; PROLI/NO
Co-reporter:Peter N. Coneski and Mark H. Schoenfisch
Polymer Chemistry 2011 vol. 2(Issue 4) pp:906-913
Publication Date(Web):16 Feb 2011
DOI:10.1039/C0PY00269K
Nitric oxide (NO)-releasing polyurethanes capable of releasing up to 0.20 μmol NO cm−2 were synthesized by incorporating active S-nitrosothiol functionalities into hard and soft segment domains using thiol group protection and post-polymerization modifications, respectively. The nitrosothiol position within the hard and soft segment domains of the polyurethanes impacted both the total NO release and NO release kinetics. The NO storage and release properties were correlated to both chain extender modification and ensuing phase miscibility of the polyurethanes. Thorough material characterization is provided to examine the effects of hard and soft segment modifications on the resultant polyurethane properties.
Co-reporter:Scott P. Nichols, Nga N. Le, Bruce Klitzman, and Mark H. Schoenfisch
Analytical Chemistry 2011 Volume 83(Issue 4) pp:1180
Publication Date(Web):January 14, 2011
DOI:10.1021/ac103070t
The in vivo glucose recovery of subcutaneously implanted nitric oxide (NO)-releasing microdialysis probes was evaluated in a rat model using saturated NO solutions to steadily release NO. Such methodology resulted in a constant NO flux of 162 pmol cm−2 s−1 from the probe membrane over 8 h of perfusion daily. The in vivo effects of enhanced localized NO were evaluated by monitoring glucose recovery over a 14 day period, with histological analysis thereafter. A difference in glucose recovery was observed starting at 7 days for probes releasing NO relative to controls. Histological analysis at 14 days revealed lessened inflammatory cell density at the probe surface and decreased capsule thickness. Collectively, the results suggest that intermittent sustained NO release from implant surfaces may improve glucose diffusion for subcutaneously implanted sensors by mitigating the foreign body reaction.
Co-reporter:Benjamin J. Privett, Jonghae Youn, Sung A. Hong, Jiyeon Lee, Junhee Han, Jae Ho Shin, and Mark H. Schoenfisch
Langmuir 2011 Volume 27(Issue 15) pp:9597-9601
Publication Date(Web):June 30, 2011
DOI:10.1021/la201801e
A superhydrophobic xerogel coating synthesized from a mixture of nanostructured fluorinated silica colloids, fluoroalkoxysilane, and a backbone silane is reported. The resulting fluorinated surface was characterized using contact angle goniometry, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Quantitative bacterial adhesion studies performed using a parallel plate flow cell demonstrated that the adhesion of Staphylococcus aureus and Pseudomonas aeruginosa was reduced by 2.08 ± 0.25 and 1.76 ± 0.12 log over controls, respectively. This simple superhydrophobic coating synthesis may be applied to any surface, regardless of geometry, and does not require harsh synthesis or processing conditions, making it an ideal candidate as a biopassivation strategy.
Co-reporter:Ahyeon Koh, Daniel A. Riccio, Bin Sun, Alexis W. Carpenter, Scott P. Nichols, Mark H. Schoenfisch
Biosensors and Bioelectronics 2011 Volume 28(Issue 1) pp:17-24
Publication Date(Web):15 October 2011
DOI:10.1016/j.bios.2011.06.005
Despite clear evidence that polymeric nitric oxide (NO) release coatings reduce the foreign body response (FBR) and may thus improve the analytical performance of in vivo continuous glucose monitoring devices when used as sensor membranes, the compatibility of the NO release chemistry with that required for enzymatic glucose sensing remains unclear. Herein, we describe the fabrication and characterization of NO-releasing polyurethane sensor membranes using NO donor-modified silica vehicles embedded within the polymer. In addition to demonstrating tunable NO release as a function of the NO donor silica scaffold and polymer compositions and concentrations, we describe the impact of the NO release vehicle and its release kinetics on glucose sensor performance.
Co-reporter:Alexis W. Carpenter, Danielle L. Slomberg, Kavitha S. Rao, and Mark H. Schoenfisch
ACS Nano 2011 Volume 5(Issue 9) pp:7235
Publication Date(Web):August 15, 2011
DOI:10.1021/nn202054f
A reverse microemulsion synthesis was used to prepare amine-functionalized silica nanoparticles of three distinct sizes (i.e., 50, 100, and 200 nm) with similar amine content. The resulting hybrid nanoparticles, consisting of N-(6-aminohexyl)aminopropyltrimethoxysilane and tetraethoxysilane, were highly monodisperse in size. N-Diazeniumdiolate nitric oxide (NO) donors were subsequently formed on secondary amines while controlling reaction conditions to keep the total amount of NO released constant for each particle size. The bactericidal efficacy of the NO-releasing nanoparticles against Pseudomonas aeruginosa increased with decreasing particle size. Additionally, smaller diameter nanoparticles were found to associate with the bacteria at a faster rate and to a greater extent than larger particles. Neither control (non-NO-releasing) nor NO-releasing particles exhibited toxicity toward L929 mouse fibroblasts at concentrations above their respective minimum bactericidal concentrations. This study represents the first investigation of the bactericidal efficacy of NO-releasing silica nanoparticles as a function of particle size.Keywords: antibacterial; bactericidal; nitric oxide; reverse microemulsion; silica nanoparticle; size dependent
Co-reporter:Benjamin J. Privett, Jae Ho Shin and Mark H. Schoenfisch
Chemical Society Reviews 2010 vol. 39(Issue 6) pp:1925-1935
Publication Date(Web):11 Mar 2010
DOI:10.1039/B701906H
The important biological roles of nitric oxide (NO) have prompted the development of analytical techniques capable of sensitive and selective detection of NO. Electrochemical sensing, more than any other NO detection method, embodies the parameters necessary for quantifying NO in challenging physiological environments such as blood and the brain. In this tutorial review, we provide a broad overview of the field of electrochemical NO sensors, including design, fabrication, and analytical performance characteristics. Both electrochemical sensors and biological applications are detailed.
Co-reporter:Benjamin J. Privett, Susan M. Deupree, Christopher J. Backlund, Kavitha S. Rao, C. Bryce Johnson, Peter N. Coneski, and Mark H. Schoenfisch
Molecular Pharmaceutics 2010 Volume 7(Issue 6) pp:2289-2296
Publication Date(Web):October 12, 2010
DOI:10.1021/mp100248e
The synergistic activity between nitric oxide (NO) released from diazeniumdiolate-modified proline (PROLI/NO) and silver(I) sulfadiazine (AgSD) was evaluated against Escherichia coli, Enterococcus faecalis, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis using a modified broth microdilution technique and a checkerboard-type assay. The combination of NO and AgSD was defined as synergistic when the fractional bactericidal concentration (FBC) was calculated to be <0.5. Gram-negative species were generally more susceptible to the individual antimicrobial agents than the Gram-positive bacteria, while Gram-positive bacteria were more susceptible to combination therapy. The in vitro synergistic activity of AgSD and NO observed against a range of pathogens strongly supports future investigation of this therapeutic combination, particularly for its potential use in the treatment of burns and chronic wounds.Keywords: Antimicrobial; combination therapy; nitric oxide; silver sulfadiazine; synergy; topical;
Co-reporter:Ellen V. Stevens, Alexis W. Carpenter, Jae Ho Shin, Jinsong Liu, Channing J. Der and Mark H. Schoenfisch
Molecular Pharmaceutics 2010 Volume 7(Issue 3) pp:775-785
Publication Date(Web):March 5, 2010
DOI:10.1021/mp9002865
Although the potent antitumor activity of nitric oxide (NO) supports its promise as an antineoplastic agent, effective and selective delivery and action on tumor and not normal cells remains a limiting factor. Nanoparticle-based delivery of NO has been considered as one approach to overcome these limitations. Therefore, we determined the utility of NO delivery using silica nanoparticles and evaluated their antitumor efficacy against human ovarian tumor and nontumor cells. The NO-releasing nanoparticles exhibited enhanced growth inhibition of ovarian tumor cells when compared to both control nanoparticles and a previously reported small molecule NO donor, PYRRO/NO. In addition, the NO-releasing nanoparticles showed greater inhibition of the anchorage-independent growth of tumor-derived and Ras-transformed ovarian cells. Confocal microscopy analysis revealed that fluorescently labeled NO-releasing nanoparticles entered the cytosol of the cell and localized to late endosomes and lysosomes. Furthermore, we observed a nanoparticle size dependency on efficacy against normal versus transformed ovarian cells. Our study provides the first application of nanoparticle-derived NO as an antitumor therapy and merits future studies examining nanoparticle formulation for in vivo applications.Keywords: Nanoparticle; nitric oxide; ovarian cancer; Ras; silica;
Co-reporter:Laurel E. Averett and Mark H. Schoenfisch
Analyst 2010 vol. 135(Issue 6) pp:1201-1209
Publication Date(Web):30 Mar 2010
DOI:10.1039/B924814E
Since its invention in 1986 by Binnig, Quate, and Gerber, the atomic force microscope (AFM) has proven to be an extremely useful tool for examining the interactions of proteins with surfaces. Fibrinogen in particular has been used as a model protein to demonstrate new methodologies for studying protein behavior with AFM due to its unique size, shape, and function. Indeed, fibrinogen's central role in both blood coagulation and blood-based infections has made it the primary protein used to interrogate the biocompatibility of surfaces. The goal of this review is to provide an analytical perspective on the utility of AFM for investigating the interaction of fibrinogen with surfaces.
Co-reporter:Peter N. Coneski, Kavitha S. Rao, and Mark H. Schoenfisch
Biomacromolecules 2010 Volume 11(Issue 11) pp:
Publication Date(Web):October 18, 2010
DOI:10.1021/bm1006823
The synthesis of diverse nitric oxide (NO)-releasing network polyesters is described. The melt phase condensation of polyols with a calculated excess of diacid followed by thermal curing generates cross-linked polyesters containing acid end groups. Varying the composition and curing temperatures of the polyesters resulted in materials with tunable thermal and degradation properties. Glass transition temperatures for the synthesized materials range from −25.5 to 3.2 °C, while complete degradation of these polyesters occurs within a minimum of nine weeks under physiological conditions (pH 7.4, 37 °C). Post-polymerization coupling of aminothiols to terminal carboxylic acids generate thiol-containing polyesters, with thermal and degradation characteristics similar to those of the parent polyesters. After nitrosation, these materials are capable of releasing up to 0.81 μmol NO cm−2 for up to 6 d. The utility of the polyesters as antibacterial biomaterials was indicated by an 80% reduction of Pseudomonas aeruginosa adhesion compared to unmodified controls.
Co-reporter:Laurel E. Averett, Boris B. Akhremitchev, Mark H. Schoenfisch, and Oleg V. Gorkun
Langmuir 2010 Volume 26(Issue 18) pp:14716-14722
Publication Date(Web):August 23, 2010
DOI:10.1021/la1017664
The interactions between the constituent monomers of fibrin, the polymerized protein network that provides the structural stability of blood clots, are frequently under stress because of the dynamic nature of blood flow. Herein, the calcium dependence of the structural unfolding linked to the forced dissociation of the “A−a” knob−hole bond between fibrin monomers is reported. The presence of calcium was shown to influence the incidence of the last event in the unfolding pattern characteristic of “A−a” rupture. This effect, attributed to the function of the γ1 calcium-binding site, was found to be reversible and specific. Our results indicate that binding of calcium at the γ1 site has no effect on the strength of the knob−hole bond prior to unfolding of the hole-containing γ module. Rather, calcium bound at the γ1 site makes the structure of the hole more resilient to such forced unfolding, leading to survival of the “A−a” knob−hole bond during larger extensions of the fibrinogen molecule but at the cost of rupture of the bond at lower forces.
Co-reporter:Peter N. Coneski and Mark H. Schoenfisch
Organic Letters 2009 Volume 11(Issue 23) pp:5462-5465
Publication Date(Web):November 9, 2009
DOI:10.1021/ol902282y
Reactions of amines with nitric oxide (NO) at high pressures form diverse NO donor species, highly dependent on the precursor structure. While monoamine precursors favor the formation of N-diazeniumdiolates in high yield, polyamines exhibit competitive formation of N-nitrosamines and diazeniumdiolates, resulting in mixed products containing significant percentages of undesired N-nitroso compounds.
Co-reporter:Susan M. Deupree, Mark H. Schoenfisch
Acta Biomaterialia 2009 Volume 5(Issue 5) pp:1405-1415
Publication Date(Web):June 2009
DOI:10.1016/j.actbio.2009.01.025
Abstract
Atomic force microscopy (AFM) was used to study the morphological changes of two Gram-negative pathogens, Pseudomonas aeruginosa and Escherichia coli, after exposure to nitric oxide (NO). The time-dependent effects of NO released from a xerogel coating and the concentration-dependent effects rendered by a small molecule that releases NO in a bolus were examined and compared. Bacteria exhibited irregular and degraded exteriors. With NO-releasing surfaces, an increase in surface debris and disorganized adhesion patterns were observed compared to controls. Analysis of cell surface topography revealed that increasing membrane roughness correlated with higher doses of NO. At a lower total dose, NO delivered via a bolus resulted in greater membrane roughness than NO released from a surface via a sustained flux. At sub-inhibitory levels, treatment with amoxicillin, an antibiotic known to compromise the integrity of the cell wall, led to morphologies resembling those resulting from NO treatment. Our observations indicate that cell envelope deterioration is a visible consequence of NO-exposure for both Gram-negative species studied.
Co-reporter:Jae Ho Shin and Mark H. Schoenfisch
Chemistry of Materials 2008 Volume 20(Issue 1) pp:239
Publication Date(Web):December 11, 2007
DOI:10.1021/cm702526q
The preparation and characterization of nitric oxide (NO)-releasing silica particles formed following the synthesis of N-diazeniumdiolate-modified aminoalkoxysilanes are reported. Briefly, an aminoalkoxysilane solution was prepared by dissolution of an appropriate amount of aminoalkoxysilane in a mixture of ethanol, methanol, and sodium methoxide (NaOMe) base. The silane solution was reacted with NO (5 atm) to form N-diazeniumdiolate NO donor moieties on the aminoalkoxysilanes. Tetraethoxy- or tetramethoxysilane (TEOS or TMOS) was then mixed with different ratios of N-diazeniumdiolate-modified aminoalkoxysilane (10–75 mol %, balance TEOS or TMOS). Finally, the silane mixture was added into ethanol in the presence of an ammonia catalyst to form NO donor silica nanoparticles via a sol–gel process. This synthetic approach allows for the preparation of NO delivery silica scaffolds with remarkably improved NO storage and release properties, surpassing all macromolecular NO donor systems reported to date with respect to NO payload (11.26 µmol·mg−1), maximum NO release amount (357 000 ppb·mg−1), NO release half-life (253 min), and NO release duration (101 h). The N-diazeniumdiolate-modified silane monomers and the resulting silica nanoparticles were characterized by 29Si nuclear magnetic resonance (NMR) spectroscopy, UV–vis spectroscopy, chemiluminescence, atomic force microscopy (AFM), gas adsorption–desorption isotherms, and elemental analysis.
Co-reporter:Jae Ho Shin, Benjamin J. Privett, Justin M. Kita, R. Mark Wightman and Mark H. Schoenfisch
Analytical Chemistry 2008 Volume 80(Issue 18) pp:6850
Publication Date(Web):August 20, 2008
DOI:10.1021/ac800185x
An amperometric fluorinated xerogel-derived nitric oxide (NO) microelectrode is described. A range of fluorine-modified xerogel polymers were synthesized via the cohydrolysis and condensation of alkylalkoxy- and fluoroalkoxysilanes. Such polymers were evaluated as NO sensor membranes to identify the optimum composition for maximizing NO permeability while providing sufficient selectivity for NO in the presence of common interfering species. By taking advantage of both the versatility of sol−gel chemistry and the “poly(tetrafluoroethylene)-like” high NO permselective properties of the xerogels, the performance of the fluorinated xerogel-derived sensors was excellent, surpassing all miniaturized NO sensors reported to date. In contrast to previous electrochemical NO sensor designs, xerogel-based NO microsensors were fabricated using a simple, reliable dip-coating procedure. An optimal permselective membrane was achieved by synthesizing xerogels of methyltrimethoxysilane (MTMOS) and 20% (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (17FTMS, balance MTMOS) under acid-catalyzed conditions. The resulting NO microelectrode had a conical tip of ∼20 μm in diameter and ∼55 μm in length and exhibited sensitivities of 7.91 pA·nM−1 from 0.2 to 3.0 nM (R2 = 0.9947) and 7.60 nA·μM−1 from 0.5 to 4.0 μM (R2 = 0.9999), detection limit of 83 pM (S/N = 3), response time (t95%) of <3 s, and selectivity (log KNO,jamp) of −5.74, <−6, <−6, <−6, <−6, −5.84, and −1.33 for j = nitrite, ascorbic acid, uric acid, acetaminophen, dopamine, ammonia/ammonium, and carbon monoxide. In addition, the sensor proved functional up to 20 d, maintaining ≥90% of the sensor’s initial sensitivity without serious deterioration in selectivity.
Co-reporter:Evan M. Hetrick, Jae Ho Shin, Nathan A. Stasko, C. Bryce Johnson, Daniel A. Wespe, Ekhson Holmuhamedov, Mark H. Schoenfisch
ACS Nano 2008 Volume 2(Issue 2) pp:235
Publication Date(Web):January 16, 2008
DOI:10.1021/nn700191f
The utility of nitric oxide (NO)-releasing silica nanoparticles as novel antibacterial agents is demonstrated against Pseudomonas aeruginosa. Nitric oxide-releasing nanoparticles were prepared via co-condensation of tetraalkoxysilane with aminoalkoxysilane modified with diazeniumdiolate NO donors, allowing for the storage of large NO payloads. Comparison of the bactericidal efficacy of the NO-releasing nanoparticles to 1-[2-(carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate (PROLI/NO), a small molecule NO donor, demonstrated enhanced bactericidal efficacy of nanoparticle-derived NO and reduced cytotoxicity to healthy cells (mammalian fibroblasts). Confocal microscopy revealed that fluorescently labeled NO-releasing nanoparticles associated with the bacterial cells, providing rationale for the enhanced bactericidal efficacy of the nanoparticles. Intracellular NO concentrations were measurable when the NO was delivered from nanoparticles as opposed to PROLI/NO. Collectively, these results demonstrate the advantage of delivering NO via nanoparticles for antimicrobial applications.Keywords: antibacterial; bactericidal; cytotoxicity; nitric oxide; reactive nitrogen species; reactive oxygen species; silica nanoparticle
Co-reporter:Nathan A. Stasko, Thomas H. Fischer and Mark H. Schoenfisch
Biomacromolecules 2008 Volume 9(Issue 3) pp:
Publication Date(Web):February 5, 2008
DOI:10.1021/bm7011746
The synthesis and characterization of two generation-4 polyamidoamine (PAMAM) dendrimers with S-nitrosothiol exteriors are reported. The hyperbranched macromolecules were modified with either N-acetyl-d,l-penicillamine (NAP) or N-acetyl-l-cysteine (NACys) and analyzed via 1H and 13C NMR, UV absorption spectroscopy, MALDI-TOF mass spectrometry, and size exclusion chromatography. Treatment of the dendritic thiols with nitrite solutions yielded the corresponding S-nitrosothiol nitric oxide (NO) donors (G4-SNAP, G4-NACysNO). Chemiluminescent NO detection demonstrated that the dendrimers were capable of storing ∼2 µmol NO·mg−1 when exposed to triggers of S-nitrosothiol decomposition (e.g., light and copper). The kinetics of NO release were found to be highly dependent on the structure of the nitrosothiol (i.e., tertiary vs primary) and exhibited similar NO release characteristics to classical small molecule nitrosothiols reported in the literature. As a demonstration of utility, the ability of G4-SNAP to inhibit thrombin-mediated platelet aggregation was assayed. At equivalent nitrosothiol concentrations (25 µM), the G4-SNAP dendrimer resulted in a 62% inhibition of platelet aggregation, compared to only 17% for the small molecule NO donor. The multivalent NO storage, the dendritic effects exerted on nitrosothiol stability and reactivity, and the utility of dendrimers as drug delivery vehicles highlight the potential of these constructs as clinically useful S-nitrosothiol-based therapeutics.
Co-reporter:Carri B. Geer, Nathan A. Stasko, Ioana A. Rus, Susan T. Lord and Mark H. Schoenfisch
Biomacromolecules 2008 Volume 9(Issue 7) pp:
Publication Date(Web):June 21, 2008
DOI:10.1021/bm800146j
A complex relationship exists between reduced, oxidized, and nitrosated glutathione (GSH, GSSG, and GSNO, respectively). Although previous studies have demonstrated S-nitrosoglutathione (GSNO) has potent antiplatelet efficacy, little work has examined the role of GSNO and related species on subsequent aspects of coagulation (e.g., fibrin polymerization). Herein, the effects of GSH, GSSG, and GSNO on the entire process of fibrin polymerization are described. Relative to normal fibrinogen, the addition of GSH, GSSG, or GSNO leads to prolonged lag times, slower rates of protofibril lateral aggregation and the formation of clots with lower final turbidities. Dose-dependent studies indicate the influence of GSH on fibrin formation is a function of both GSH and fibrinogen concentration. Studies with Aα251 recombinant fibrinogen (lacking αC regions) showed GSH had no influence on its polymerization, suggesting the glutathione species interact within the αC region of fibrinogen.
Co-reporter:Evan M. Hetrick, Heather L. Prichard, Bruce Klitzman, Mark H. Schoenfisch
Biomaterials 2007 Volume 28(Issue 31) pp:4571-4580
Publication Date(Web):November 2007
DOI:10.1016/j.biomaterials.2007.06.036
The tissue response to nitric oxide (NO)-releasing subcutaneous implants is presented. Model implants were created by coating silicone elastomer with diazeniumdiolate-modified xerogel polymers capable of releasing NO. The host tissue response to such implants was evaluated at 1, 3, and 6 weeks and compared to that of uncoated silicone elastomer blanks and xerogel-coated controls incapable of releasing NO. Delivery of NO (∼1.35 μmol/cm2 of implant surface area) reduced foreign body collagen capsule (“scar tissue”) thickness by >50% compared to uncoated silicone elastomer after 3 weeks. The chronic inflammatory response at the tissue/implant interface was also reduced by >30% at NO-releasing implants after 3 and 6 weeks. Additionally, CD-31 immunohistochemical staining revealed ∼77% more blood vessels in proximity to NO-releasing implants after 1 week compared to controls. These findings suggest that conferring NO release to subcutaneous implants may promote effective device integration into healthy vascularized tissue, diminish foreign body capsule formation, and improve the performance of indwelling medical devices that require constant mass transport of analytes (e.g., implantable sensors).
Co-reporter:
Science 1921 Vol 53(1367) pp:231
Publication Date(Web):11 Mar 1921
DOI:10.1126/science.53.1367.231
Co-reporter:Scott P. Nichols, Wesley L. Storm, Ahyeon Koh, Mark H. Schoenfisch
Advanced Drug Delivery Reviews (September 2012) Volume 64(Issue 12) pp:1177-1188
Publication Date(Web):1 September 2012
DOI:10.1016/j.addr.2012.03.002
Non-invasive treatment of injuries and disorders affecting bone and connective tissue remains a significant challenge facing the medical community. A treatment route that has recently been proposed is nitric oxide (NO) therapy. Nitric oxide plays several important roles in physiology with many conditions lacking adequate levels of NO. As NO is a radical, localized delivery via NO donors is essential to promoting biological activity. Herein, we review current literature related to therapeutic NO delivery in the treatment of bone, skin and tendon repair.Download high-res image (86KB)Download full-size image
Co-reporter:Benjamin J. Privett, Angela D. Broadnax, Susanne J. Bauman, Daniel A. Riccio, Mark H. Schoenfisch
Nitric Oxide (31 March 2012) Volume 26(Issue 3) pp:169-173
Publication Date(Web):31 March 2012
DOI:10.1016/j.niox.2012.02.002
While much research has been directed to harnessing the antimicrobial properties of exogenous NO, the possibility of bacteria developing resistance to such therapy has not been thoroughly studied. Herein, we evaluate potential NO resistance using spontaneous and serial passage mutagenesis assays. Specifically, Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa were systematically exposed to NO-releasing 75 mol% MPTMS-TEOS nitrosothiol particles at or below minimum inhibitory concentration (MIC) levels. In the spontaneous mutagenesis assay, bacteria that survived exposure to lethal concentrations of NO showed no increase in MIC. Similarly, no increase in MIC was observed in the serial passage mutagenesis assay after exposure of these species to sub-inhibitory concentrations of NO through 20 d.Graphical abstractDownload full-size imageHighlights► We evaluate the ability of bacteria to develop a resistance to exogenous NO. ► Nitrosothiol nanoparticles were utilized as an exogenous antimicrobial model. ► Prolonged exposure to sub-therapeutic NO did not result in increased resistance. ► Single-dose exposure to bactericidal NO did not result in increased resistance. ► These assays may serve as a blueprint for future NO resistance studies.
Co-reporter:Timothy A. Johnson, Nathan A. Stasko, Jessica L. Matthews, Wayne E. Cascio, Ekhson L. Holmuhamedov, C. Bryce Johnson, Mark H. Schoenfisch
Nitric Oxide (1 January 2010) Volume 22(Issue 1) pp:30-36
Publication Date(Web):1 January 2010
DOI:10.1016/j.niox.2009.11.002
We report the therapeutic potential of S-nitroso-N-acetylpenicillamine-derivatized generation-4 polyamidoamine dendrimers (G4-SNAP) for reducing ischemia/reperfusion (I/R) injury in an isolated, perfused rat heart. The use of this dendrimer scaffold to deliver the nitrosothiol therapeutic did not inhibit NO donor activity as the required dose of G4-SNAP to minimize I/R injury (31 nM corresponding to 2 μM SNAP) was consistent with the optimum concentration of small molecule SNAP alone. An exploration of G4-SNAP NO release kinetics in the presence of physiologically relevant concentrations of glutathione (GSH) indicated enhanced NO release (t[NO] = 1.28 μM NO/mg) at 500 μM GSH. Reperfusion experiments conducted with 500 μM GSH further lowered the optimal therapeutic G4-SNAP dose to 230 pM (i.e., 15 nM SNAP). The unique combination of G4-SNAP dendrimer and glutathione trigger represents a novel strategy with possible clinical relevance toward salvaging ischemic tissue.
Co-reporter:Benjamin J. Privett, Jae Ho Shin and Mark H. Schoenfisch
Chemical Society Reviews 2010 - vol. 39(Issue 6) pp:NaN1935-1935
Publication Date(Web):2010/03/11
DOI:10.1039/B701906H
The important biological roles of nitric oxide (NO) have prompted the development of analytical techniques capable of sensitive and selective detection of NO. Electrochemical sensing, more than any other NO detection method, embodies the parameters necessary for quantifying NO in challenging physiological environments such as blood and the brain. In this tutorial review, we provide a broad overview of the field of electrochemical NO sensors, including design, fabrication, and analytical performance characteristics. Both electrochemical sensors and biological applications are detailed.
Co-reporter:Peter N. Coneski and Mark H. Schoenfisch
Chemical Society Reviews 2012 - vol. 41(Issue 10) pp:NaN3758-3758
Publication Date(Web):2012/02/24
DOI:10.1039/C2CS15271A
Nitric oxide's expansive physiological and regulatory roles have driven the development of therapies for human disease that would benefit from exogenous NO administration. Already a number of therapies utilizing gaseous NO or NO donors capable of storing and delivering NO have been proposed and designed to exploit NO's influence on the cardiovascular system, cancer biology, the immune response, and wound healing. As described in Nitric oxide release: Part I. Macromolecular scaffolds and Part II. Therapeutic applications, the preparation of new NO-release strategies/formulations and the study of their therapeutic utility are increasing rapidly. However, comparison of such studies remains difficult due to the diversity of scaffolds, NO measurement strategies, and reporting methods employed across disciplines. This tutorial review highlights useful analytical techniques for the detection and measurement of NO. We also stress the importance of reporting NO delivery characteristics to allow appropriate comparison of NO between studies as a function of material and intended application.
Co-reporter:Alexis W. Carpenter and Mark H. Schoenfisch
Chemical Society Reviews 2012 - vol. 41(Issue 10) pp:NaN3752-3752
Publication Date(Web):2012/02/24
DOI:10.1039/C2CS15273H
A wide range of nitric oxide (NO)-releasing materials has emerged as potential therapeutics that exploit NO's vast biological roles. Macromolecular NO-releasing scaffolds are particularly promising due to their ability to store and deliver larger NO payloads in a more controlled and effective manner compared to low molecular weight NO donors. While a variety of scaffolds (e.g., particles, dendrimers, and polymers/films) have been cleverly designed, the ultimate clinical utility of most NO-releasing macromolecules remains unrealized. Although not wholly predictive of clinical success, in vitro and in vivo investigations have enabled a preliminary evaluation of the therapeutic potential of such materials. In this tutorial review, we review the application of macromolecular NO therapies for cardiovascular disease, cancer, bacterial infections, and wound healing.
Co-reporter:Daniel A. Riccio and Mark H. Schoenfisch
Chemical Society Reviews 2012 - vol. 41(Issue 10) pp:NaN3741-3741
Publication Date(Web):2012/02/24
DOI:10.1039/C2CS15272J
The roles of nitric oxide (NO) in physiology and pathophysiology merit the use of NO as a therapeutic for certain biomedical applications. Unfortunately, limited NO payloads, too rapid NO release, and the lack of targeted NO delivery have hindered the clinical utility of NO gas and low molecular weight NO donor compounds. A wide-variety of NO-releasing macromolecular scaffolds has thus been developed to improve NO's pharmacological potential. In this tutorial review, we provide an overview of the most promising NO release scaffolds including protein, organic, inorganic, and hybrid organic-inorganic systems. The NO release vehicles selected for discussion were chosen based on their enhanced NO storage, tunable NO release characteristics, and potential as therapeutics.
Co-reporter:Scott P. Nichols and Mark H. Schoenfisch
Biomaterials Science (2013-Present) 2013 - vol. 1(Issue 11) pp:NaN1159-1159
Publication Date(Web):2013/07/17
DOI:10.1039/C3BM60130G
Nitric oxide (NO) is an endogenous antibacterial agent produced by immune cells in response to pathogens. Herein, the NO fluxes necessary to reduce bacterial adhesion of different bacteria (S. aureus, methicillin-resistant S. aureus, S. epidermidis, E. faecalis, E. coli, and P. aeruginosa) were investigated to ascertain the sensitivity of these bacteria to NO. S-Nitrosothiol NO donor-modified xerogels were selected as a model NO-release surface due to their extended NO-release kinetics relative to other NO donor systems. The xerogels were coated with poly(vinyl chloride) (PVC) to achieve consistent surface energy between NO-releasing and control substrates. Fibrinogen was pre-adsorbed to these materials to more accurately mimic conditions encountered in blood and promote bacteria adhesion. Nitric oxide fluxes ranging from 20–50 pmol cm−2 s−1 universally inhibited the bacterial adhesion by >80% for each strain studied. Maximum bacteria killing activity (reduced viability by 85–98%) was observed at the greatest NO payload (1700 nmol cm−2).
Co-reporter:Alexis W. Carpenter, Katelyn P. Reighard, Joseph E. Saavedra and Mark H. Schoenfisch
Biomaterials Science (2013-Present) 2013 - vol. 1(Issue 5) pp:NaN459-459
Publication Date(Web):2013/01/24
DOI:10.1039/C3BM00153A
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-Protected N-diazeniumdiolate-based silanes were grafted onto mesoporous silica nanoparticles to yield a scaffold with an NO payload of 2.4 μmol NO per mg and NO release half-life of 23 d. Adhesion of Streptococcus mutans to dental restorative materials doped with these NO-releasing particles was reduced by 3-log compared to controls.
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