Co-reporter:Metin Uz, Anup D. Sharma, Pratish Adhikari, Donald S. Sakaguchi, Surya K. Mallapragada
Acta Biomaterialia 2017 Volume 56(Volume 56) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.actbio.2016.09.039
In this study, a poly(lactic acid) (PLLA) porous film with longitudinal surface micropatterns was fabricated by a dry phase inversion technique to be used as potential conduit material for peripheral nerve regeneration applications. The presence of a nerve growth factor (NGF) gradient on the patterned film surface and protein loaded, surface-eroding, biodegradable, and amphiphilic polyanhydride (PA) microparticles within the film matrix, enabled co-delivery of neurotrophic factors with controlled release properties and enhanced neurite outgrowth from PC12 cells. The protein loading capacity of PA particles was increased up to 80% using the spray drying technique, while the surface loading of NGF reached 300 ng/cm2 through ester-amine interactions. The NGF surface gradient provided initial fast release from the film surface and facilitated directional neurite outgrowth along with the longitudinal micropatterns. Furthermore, the variable backbone chemistry and surface eroding nature of protein-loaded PA microparticles within the film matrix ensured protein stability and enabled controlled protein release. This novel co-delivery strategy yielded tunable diffusion coefficients varying between 6 × 10−14 and 1.67 × 10−10 cm2/min and dissolution constants ranging from 1 × 10−4 to 1 × 10−3 min−1 with released amounts of ∼100–300 ng/mL. This strategy promoted guided neurite extension from PC12 cells of up to 10 μm total neurite length per cell in 2 days. Overall, this unique strategy can potentially be extended for individually programmed delivery of multiple growth factors through the use of PA microparticle cocktails and can further be investigated for in vivo performance as potential conduit material for peripheral nerve regeneration applications.Statement of SignificanceThis manuscript focuses on the development of multifunctional degradable polymer films that provide topographic cues for guided growth, surface gradients of growth factors as well as nanoparticles in the films for tunable release of growth factors to enable peripheral nerve regeneration. The combination of cues was designed to overcome limitations of current strategies to facilitate peripheral nerve regeneration. These multifunctional films successfully provided high protein loading capacities while persevering activity, protein gradients on the surface, and tunable release of bioactive nerve growth factor that promoted directional and guided neurite extension of PC12 cells of up to 10 μm in 2 days. These multifunctional films can be made into conduits for peripheral nerve regeneration.Download high-res image (338KB)Download full-size image
Co-reporter:Metin Uz, Melda Büyüköz, Anup D. Sharma, Donald S. Sakaguchi, ... Surya K. Mallapragada
Acta Biomaterialia 2017 Volume 53(Volume 53) pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.actbio.2017.02.018
In this study, gelatin-based 3D conduits with three different microstructures (nanofibrous, macroporous and ladder-like) were fabricated for the first time via combined molding and thermally induced phase separation (TIPS) technique for peripheral nerve regeneration. The effects of conduit microstructure and mechanical properties on the transdifferentiation of bone marrow-derived mesenchymal stem cells (MSCs) into Schwann cell (SC) like phenotypes were examined to help facilitate neuroregeneration and understand material-cell interfaces. Results indicated that 3D macroporous and ladder-like structures enhanced MSC attachment, proliferation and spreading, creating interconnected cellular networks with large numbers of viable cells compared to nanofibrous and 2D-tissue culture plate counterparts. 3D-ladder-like conduit structure with complex modulus of ∼0.4 × 106 Pa and pore size of ∼150 μm provided the most favorable microenvironment for MSC transdifferentiation leading to ∼85% immunolabeling of all SC markers. On the other hand, the macroporous conduits with complex modulus of ∼4 × 106 Pa and pore size of ∼100 μm showed slightly lower (∼65% for p75, ∼75% for S100 and ∼85% for S100β markers) immunolabeling. Transdifferentiated MSCs within 3D-ladder-like conduits secreted significant amounts (∼2.5 pg/mL NGF and ∼0.7 pg/mL GDNF per cell) of neurotrophic factors, while MSCs in macroporous conduits released slightly lower (∼1.5 pg/mL NGF and 0.7 pg/mL GDNF per cell) levels. PC12 cells displayed enhanced neurite outgrowth in media conditioned by conduits with transdifferentiated MSCs. Overall, conduits with macroporous and ladder-like 3D structures are promising platforms in transdifferentiation of MSCs for neuroregeneration and should be further tested in vivo.Statement of SignificanceThis manuscript focuses on the effect of microstructure and mechanical properties of gelatin-based 3D conduits on the transdifferentiation of mesenchymal stem cells to Schwann cell-like phenotypes. This work builds on our recently accepted manuscript in Acta Biomaterialia focused on multifunctional 2D films, and focuses on 3D microstructured conduits designed to overcome limitations of current strategies to facilitate peripheral nerve regeneration. The comparison between conduits fabricated with nanofibrous, macroporous and ladder-like microstructures showed that the ladder-like conduits showed the most favorable environment for MSC transdifferentiation to Schwann-cell like phenotypes, as seen by both immunolabeling as well as secretion of neurotrophic factors. This work demonstrates the importance of controlling the 3D microstructure to facilitate tissue engineering strategies involving stem cells that can serve as promising approaches for peripheral nerve regeneration.Download high-res image (102KB)Download full-size image
Co-reporter:Srikanth Nayak, Honghu Zhang, Xunpei Liu, Shuren Feng, Pierre Palo, Marit Nilsen-Hamilton, Mufit Akinc and Surya Mallapragada
RSC Advances 2016 vol. 6(Issue 62) pp:57048-57056
Publication Date(Web):07 Jun 2016
DOI:10.1039/C6RA07662A
Controlling the morphology of magnetic nanoparticles and their spatial arrangement is crucial for manipulating their functional properties. The commonly available inorganic processes for the synthesis of uniform magnetic nanoparticles typically require extreme reaction conditions such as high temperatures or harsh reagents, rendering them unsuitable for making functionalized magnetic nanoparticles with tunable properties controlled by biomolecules. Biomimetic procedures, inspired by the production of uniform magnetite and greigite crystals in magnetotactic bacteria, provide an alternative method, which can allow synthesis and spatial arrangement under ambient conditions. Mms6, an amphiphilic protein found in magnetosome membranes in Magnetospirillum magneticum strain AMB-1, can control the morphology of magnetite nanoparticles, both in vivo and in vitro. In this work, we have demonstrated the patterning of Mms6 and the formation of patterns of magnetic nanoparticles on selective regions of surfaces by directed self-assembly and control over surface chemistry, enabling facile spatial control in applications such as high density data storage and biosensors. Using microcontact printing we have obtained various patterns of 1-octadecane thiol (ODT) and protein resistant poly(ethylene glycol)methyl ether thiol (PEG) layers on gold surfaces. Atomic force microscopy (AFM) and fluorescence microscopy studies show the patterning of Mms6 on the ODT patterns and not on the PEG regions. Magnetic nanoparticles were grown on these surfaces by a co-precipitation method over immobilized protein. AFM and scanning electron microscopy (SEM) results show the localized growth of magnetic nanocrystals selectively on the Mms6 template, which in turn was determined by the ODT regions. Magnetic force measurements were conducted to assess the localization of magnetic nanoparticles on the pattern.
Co-reporter:Kathleen Ross, Justin Adams, Hyelee Loyd, Shaheen Ahmed, Anthony Sambol, Scott Broderick, Krishna Rajan, Marian Kohut, Tatiana Bronich, Michael J. Wannemuehler, Susan Carpenter, Surya Mallapragada, and Balaji Narasimhan
ACS Biomaterials Science & Engineering 2016 Volume 2(Issue 3) pp:368
Publication Date(Web):January 27, 2016
DOI:10.1021/acsbiomaterials.5b00477
H5N1 influenza virus has the potential to become a significant global health threat, and next generation vaccine technologies are needed. In this work, the combined efficacy of two nanoadjuvant platforms (polyanhydride nanoparticles and pentablock copolymer-based hydrogels) to induce protective immunity against H5N1 influenza virus was examined. Mice received two subcutaneous vaccinations (day 0 and 21) containing 10 μg of H5 hemagglutinin trimer alone or in combination with the nanovaccine platforms. Nanovaccine immunization induced high neutralizing antibody titers that were sustained through 70 days postimmunization. Finally, mice were intranasally challenged with A/H5N1 VNH5N1-PR8CDC-RG virus and monitored for 14 days. Animals receiving the combination nanovaccine had lower viral loads in the lung and weight loss after challenge in comparison to animals vaccinated with each platform alone. These data demonstrate the synergy between polyanhydride nanoparticles and pentablock copolymer-based hydrogels as adjuvants in the design of a more efficacious influenza vaccine.Keywords: combination nanovaccine; H5 hemagglutinin; hydrogel; influenza; nanoparticle; PDEAEM; polyanhydride
Co-reporter:Gourapura J. Renukaradhya, Balaji Narasimhan, Surya K. Mallapragada
Journal of Controlled Release 2015 Volume 219() pp:622-631
Publication Date(Web):10 December 2015
DOI:10.1016/j.jconrel.2015.09.047
Vaccine development has had a huge impact on human health. However, there is a significant need to develop efficacious vaccines for several existing as well as emerging respiratory infectious diseases. Several challenges need to be overcome to develop efficacious vaccines with translational potential. This review focuses on two aspects to overcome some barriers — 1) the development of nanoparticle-based vaccines, and 2) the choice of suitable animal models for respiratory infectious diseases that will allow for translation. Nanoparticle-based vaccines, including subunit vaccines involving synthetic and/or natural polymeric adjuvants and carriers, as well as those based on virus-like particles offer several key advantages to help overcome the barriers to effective vaccine development. These include the ability to deliver combinations of antigens, target the vaccine formulation to specific immune cells, enable cross-protection against divergent strains, act as adjuvants or immunomodulators, allow for sustained release of antigen, enable single dose delivery, and potentially obviate the cold chain. While mouse models have provided several important insights into the mechanisms of infectious diseases, they are often a limiting step in translation of new vaccines to the clinic. An overview of different animal models involved in vaccine research for respiratory infections, with advantages and disadvantages of each model, is discussed. Taken together, advances in nanotechnology, combined with the right animal models for evaluating vaccine efficacy, has the potential to revolutionize vaccine development for respiratory infections.
Co-reporter:Justin R. Adams, Shannon L. Haughney, Surya K. Mallapragada
Acta Biomaterialia 2015 Volume 14() pp:104-114
Publication Date(Web):1 March 2015
DOI:10.1016/j.actbio.2014.11.050
Abstract
We have synthesized thermogelling cationic amphiphilic pentablock copolymers that have the potential to act as injectable vaccine carriers and adjuvants that can simultaneously provide sustained delivery and enhance the immunogenicity of released antigen. While these pentablock copolymers have shown efficacy in DNA delivery in past studies, the ability to deliver both DNA and protein for subunit vaccines using the same polymeric carrier can provide greater flexibility and efficacy. We demonstrate the ability of these pentablock copolymers, and the parent triblock Pluronic copolymers to slowly release structurally intact and antigenically stable protein antigens in vitro, create an antigen depot through long-term injection-site persistence and enhance the in vivo immune response to these antigens. We show release of the model protein antigen ovalbumin in vitro from the thermogelling block copolymers with the primary, secondary and tertiary structures of the released protein unchanged compared to the native protein, and its antigenicity preserved upon release. The block copolymers form a gel at physiological temperatures that serves as an antigenic depot and persists in vivo at the site of injection for over 50 days. The pentablock copolymers show a significant fivefold enhancement in the immune response compared to soluble protein alone, even 6 weeks after the administration, based on measurement of antibody titers. These results demonstrate the potential of these block copolymers hydrogels to persist for several weeks and sustain the release of antigen with minimal effects on protein stability and antigenicity; and their ability to be used simultaneously as a sustained delivery device as well as a subunit vaccine adjuvant platform.
Co-reporter:Xunpei Liu, Honghu Zhang, Srikanth Nayak, German Parada, James Anderegg, Shuren Feng, Marit Nilsen-Hamilton, Mufit Akinc, and Surya K. Mallapragada
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 42) pp:10284-10292
Publication Date(Web):August 13, 2015
DOI:10.1021/acs.iecr.5b01413
Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated gold surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic N-terminal domain into the hydrophobic lipid bilayer environment of the magnetosome membrane, exposing the hydrophilic C-terminal domain that promotes biomineralization. Supporting this hypothesis, the larger and well-formed magnetite nanoparticles were found to be preferentially located on ODT surfaces covered with Mms6 as compared to control samples, as characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy studies. A C-terminal domain mutant of this protein did not form the same network structure as wild-type Mms6, suggesting that the network structure is important for the magnetite nanocrystal formation. This study provides valuable insights into the role of surface hydrophilicity on the action of the biomineralization protein Mms6 to synthesize magnetic nanocrystals and provides a facile route to controlling bioinspired nanocrystal synthesis in vitro.
Co-reporter:Feng Jia, Surya K. Mallapragada, and Balaji Narasimhan
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 42) pp:10212-10220
Publication Date(Web):August 13, 2015
DOI:10.1021/acs.iecr.5b01423
Multienzyme complexes (MECs) in nature exhibit highly efficient catalytic mechanisms in reaction cascades. Different strategies have been developed to colocalize enzymes on nanocarriers to improve multienzyme catalytic efficiency by mimicking MEC structure and function. Numerous studies have indicated that the spatial arrangement and orientation of multiple enzymes in confined spaces are critical in facilitating cooperative enzymatic activity in multienzyme colocalization. Biomolecule scaffolds based on DNA hybridization have attracted great attention because of their unique effective control of the relative positions of different enzymes in multienzyme colocalization. To demonstrate this concept, glucose oxidase (GOX) and horseradish peroxidase (HRP) were colocalized onto polystyrene nanoparticles via specific DNA hybridization. Colocalization of GOX and HRP was evidenced by Förster resonance energy transfer studies of the dyes labeling the two tag DNAs. Finally, it was observed that colocalization of GOX and HRP via DNA hybridization significantly improved both the overall reaction efficiency and the storage shelf life compared with those of the single enzyme immobilization mixture control. In summary, DNA-directed colocalization of multiple enzymes on nanoparticles is an effective way to control the relative positioning of enzymes to mimic MECs and enhance catalytic activity.
Co-reporter:Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, Klaus Schmidt-Rohr, Mufit Akinc, Marit Nilsen-Hamilton, David Vaknin, and Surya Mallapragada
Langmuir 2015 Volume 31(Issue 9) pp:2818-2825
Publication Date(Web):February 10, 2015
DOI:10.1021/la5044377
Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core–corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.
Co-reporter:Surya K. Mallapragada, Timothy M. Brenza, JoEllyn M. McMillan, Balaji Narasimhan, Donald S. Sakaguchi, Anup D. Sharma, Svitlana Zbarska, Howard E. Gendelman
Nanomedicine: Nanotechnology, Biology and Medicine 2015 Volume 11(Issue 3) pp:715-729
Publication Date(Web):April 2015
DOI:10.1016/j.nano.2014.12.013
Co-reporter:J. R. Adams, M. Goswami, N. L. B. Pohl and S. K. Mallapragada
RSC Advances 2014 vol. 4(Issue 30) pp:15655-15663
Publication Date(Web):18 Mar 2014
DOI:10.1039/C3RA47687A
We report the synthesis of a family of amphiphilic pentablock polymers with different cationic blocks and with controlled architectures as potential vaccine carriers for subunit vaccines. The temperature and pH-dependent micellization and gelation of these pentablock copolymers can provide a depot for sustained protein and gene delivery. The amphiphilic central triblock promotes cellular endocytosis, good gene delivery and has been used effectively as a vaccine adjuvant. The pentablock copolymer outer blocks condense DNA spontaneously as a result of electrostatic interactions for sustained combinational therapy. This family of polymers with different cationic groups was evaluated based on DNA complexation-ability and cytotoxicity to select promising candidates as DNA-based subunit vaccine adjuvants. Modification of other polymer systems with carbohydrates like mannose has been shown to enhance immunogenicity by activating pattern recognition receptors on antigen presenting cells and increasing uptake in these cells. Here, we report the synthesis of a virus-mimicking pentablock copolymer vaccine platform by successful functionalization of these polymers with mannose through an azide–alkyne Huisgen cycloaddition. The synthesis of a mannoside with the alkyne linker was achieved by a recently reported bismuth(V)-mediated activation of a thioglycoside that proved to leave the alkyne intact. The carbohydrate modification was shown not to interfere with the ability of these virus-mimicking block copolymers to complex DNA, thereby making this family of modified materials promising candidates for DNA-based vaccine delivery.
Co-reporter:Justin R. Adams
Macromolecular Chemistry and Physics 2013 Volume 214( Issue 12) pp:1321-1325
Publication Date(Web):
DOI:10.1002/macp.201300034
Co-reporter:Tanya Prozorov, Dennis A. Bazylinski, Surya K. Mallapragada, Ruslan Prozorov
Materials Science and Engineering: R: Reports 2013 Volume 74(Issue 5) pp:133-172
Publication Date(Web):May 2013
DOI:10.1016/j.mser.2013.04.002
Magnetotactic bacteria, known to produce magnetic nanocrystals with uniform shapes and sizes at physiological conditions, serve as an inspiration and source of a number of biological macromolecules used for the biomimetic synthesis of a variety of magnetic nanomaterials. This review discusses the current state of understanding of magnetosome biomineralization in magnetotactic bacteria, as well as the ways in which iron biomineralization processes can be utilized for tailored in vivo formation of complex magnetic nanomaterials, not occurring in magnetotactic bacteria naturally. The review assesses the current efforts on in vitro synthesis of a variety of magnetic nanoparticles using bioinspired approaches by utilizing mineralization proteins from magnetotactic bacteria, and surveys biomimetic strategies for the rational synthesis of various magnetic nanomaterials under ambient conditions. Finally, this review presents magnetic characterization of nanoparticles, highlighting differences in magnetic behavior between magnetic nanoparticles produced using bioinspired in vivo and in vitro strategies, compared to those produced using conventional methods. This in turn impacts their utility in a wide range of applications for magnetic nanoparticles, which are examined in detail, where bioinspired synthesis methods have potentially provided added advantages.
Co-reporter:Kathryn E. Schlichting, Trishelle M. Copeland-Johnson, Matthew Goodman, Robert J. Lipert, Tanya Prozorov, Xunpei Liu, Todd O. McKinley, Zhiqun Lin, James A. Martin, Surya K. Mallapragada
Acta Biomaterialia 2011 Volume 7(Issue 8) pp:3094-3100
Publication Date(Web):August 2011
DOI:10.1016/j.actbio.2011.04.010
Abstract
Intra-articular fractures initiate a cascade of pathobiological and pathomechanical events that culminate in post-traumatic osteoarthritis (PTOA). Hallmark features of PTOA include destruction of the cartilage matrix in combination with loss of chondrocytes and acute mechanical damage (AMD). Currently, treatment of intra-articular fractures essentially focuses completely on restoration of the macroanatomy of the joint. However, current treatment ignores AMD sustained by cartilage at the time of injury. We are exploring aggressive biomaterial-based interventions designed to treat the primary pathological components of AMD. This study describes the development of a novel injectable co-polymer solution that forms a gel at physiological temperatures that can be photocrosslinked, and can form a nanocomposite gel in situ through mineralization. The injectable co-polymer solution will allow the material to fill cracks in the cartilage after trauma. The mechanical properties of the nanocomposite are similar to those of native cartilage, as measured by compressive and shear testing. It thereby has the potential to mechanically stabilize and restore local structural integrity to acutely injured cartilage. Additionally, in situ mineralization ensures good adhesion between the biomaterial and cartilage at the interface, as measured through tensile and shear testing. Thus we have successfully developed a new injectable co-polymer which forms a nanocomposite in situ with mechanical properties similar to those of native cartilage, and which can bond well to native cartilage. This material has the potential to stabilize injured cartilage and prevent PTOA.
Co-reporter:Bingqi Zhang, Surya Mallapragada
Acta Biomaterialia 2011 Volume 7(Issue 4) pp:1570-1579
Publication Date(Web):April 2011
DOI:10.1016/j.actbio.2010.11.032
Abstract
Poly(diethylaminoethylmethacrylate) (PDEAEM) and Pluronic F127 based pentablock copolymer vectors with the ability to transfect cancer cells selectively over normal cells in in vitro cultures were developed, as described in a previous report. Understanding the mechanism of this selectivity will enable better polymeric vectors to be designed, with inherent selectivity for specific cell types based on intracellular differences and not on the use of targeting ligands, which have shown variable success, depending on the system. It is assumed that the selectivity was due to different intracellular barriers to transfection in the different cell types. Part I focuses on investigating whether cellular entry is one of the barriers to transfection, through conjugation of epidermal growth factor (EGF) to the pentablock copolymer vector. Results indicate that EGF conjugation increased transfection efficiency the most when conjugated to the outer surface of polyplexes, with minimal disruption to DNA packaging and maximal accessibility to receptors. The overall resulting enhancement in transfection, however, was a moderate three- to five-fold increase compared with the condition with no EGF involved, implying that the addition of EGF fails to overcome the intracellular barrier to transfection, which probably involves some step other than cellular uptake in pentablock copolymer system. Therefore, the differences observed in the selectivity of transfection between cancer and normal cell lines is probably not controlled by differences in cellular entry, and the intracellular barriers to transfection in this system are likely to be endosomal escape or nuclear entry, as investigated in Part II, the companion paper to this work.
Co-reporter:Bingqi Zhang, Surya Mallapragada
Acta Biomaterialia 2011 Volume 7(Issue 4) pp:1580-1587
Publication Date(Web):April 2011
DOI:10.1016/j.actbio.2010.11.033
Abstract
Transfection efficiencies of non-viral gene delivery vectors commonly vary with cell type, owing to differences in proliferation rates and intracellular characteristics. Previous work demonstrated that the poly(diethylaminoethylmethacrylate) (PDEAEM)/Pluronic F127 pentablock copolymers exhibit transfection in vitro selectively in cancer cell lines as opposed to non-cancerous cell lines. This study continues the investigation of intracellular barriers to transfection using this vector in “normal” and cancer cell lines to understand the underlying mechanisms of the selectivity. Results from Part I of this investigation showed, using conjugated epidermal growth factor, that cellular uptake of these polyplexes is not a major barrier in these systems. Part II of this work continues the investigation into the other potential intracellular barriers, endosomal escape and nuclear entry, using a lysosomotropic agent chloroquine (CLQ), and a nuclear localization signal (NLS) SV40, respectively. Lack of effectiveness of NLS peptide in improving the transfection efficiency suggests that nuclear uptake might not be the major intracellular barrier using the pentablock copolymer vectors, or that the nuclear transport might not be primarily achieved through nuclear pores. However, inclusion of CLQ led to a dramatic enhancement in the level of gene expression, with an almost two orders of magnitude increase in expression seen in normal cell lines, compared with that the increase observed in cancer cell lines. The different lysosomal pH values in normal vs cancer cells was believed to cause the pentablock copolymer vectors to behave distinctly during transport through endocytic pathways, with greater loss of functional DNA occurring in normal cells containing more acidic endocytic vesicles in contrast to cancer cells with less acidic vesicles. Interestingly, CLQ introduced almost no enhancement in the transfection with the control vector ExGen which lacked selectivity of transfection. Exploiting intracellular differences between normal and cancer cells for gene delivery vector design offers a new paradigm to achieve transfection selectivity based on intracellular differences rather than conventional approaches involving vector modification using specific ligands for targeted delivery.
Co-reporter:Melissa A. Ver Meer, Balaji Narasimhan, Brent H. Shanks and Surya K. Mallapragada
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 1) pp:41
Publication Date(Web):December 16, 2009
DOI:10.1021/am900540x
In this study, mesoporous or colloidal silica particles were incorporated into polystyrene matrices via melt blending or by styrene polymerization initiated from the particle surface. The relationships between the surface morphology of filler particles in polymer composites and their thermomechanical properties were investigated. High molecular weight polystyrene−silica hybrids were generated by modifying the surfaces of monodisperse colloidal silica and templated mesoporous silica nanoparticles. The functionalized silica surfaces were grafted with alkyl halide initiators for atom transfer radical polymerization. Polymerization was conducted without free initiator present. The physical properties of these composites were studied by dynamic mechanical analysis, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscopy. Results indicate that colloidal and mesoporous silica polymer composites generated by atom transfer radical polymerization have similar grafted polymer characteristics, indicating that polymer growth from the surface of the particle does not allow for significant polymer chain growth in the interior of the mesoporous silica particles.Keywords: atom transfer radical polymerization; colloidal silica; melt blending; mesoporous silica; polymer composites
Co-reporter:Carlos Atico Ariza;Kyle P. McHugh;Steven J. White;Donald S. Sakaguchi
Journal of Biomedical Materials Research Part A 2010 Volume 94A( Issue 3) pp:816-824
Publication Date(Web):
DOI:10.1002/jbm.a.32741
Abstract
To control the differentiation of neural progenitor cells (NPCs), the synergistic influence of topography, extracellular matrix (ECM) proteins, and soluble factors were investigated. Previously, in our laboratory, astrocyte-derived soluble factors were found to promote differentiation of adult hippocampal progenitor cells (AHPCs) into neurons when grown on a laminin substrate (Oh et al., J Biomed Mater Res A 2009;91:575–585). Here, we determined that the ECM protein on which AHPCs are cultured does not seem to alter this neurogenic effect or the differentiation of AHPCs when grown alone. However, AHPCs cultured on ECL (a combination of entactin, collagen, and laminin) in the presence of soluble factors from hippocampal astrocytes, differentiated into a significantly greater percentage of oligodendrocytes (∼34% on ECL vs. ∼19% on laminin). Furthermore, a concomitant decrease in the percentage of proliferating cells was observed on the ECL (∼38% on ECL vs. ∼55% on laminin). In addition, the increase in AHPC differentiation into oligodendrocytes on ECL occurred only in the presence of soluble factors from astrocytes, and not when AHPCs were cultured alone. Finally, we demonstrated that micro-scale topography did not influence the phenotypic differentiation in all conditions tested. These results show that a combination of astrocyte-derived soluble factors and ECM can dramatically affect the differentiation and proliferation of NPCs. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010
Co-reporter:Carlos Atico Ariza;Asha T. Fleury;Christian J. Tormos
Stem Cell Reviews and Reports 2010 Volume 6( Issue 4) pp:585-600
Publication Date(Web):2010 December
DOI:10.1007/s12015-010-9171-0
The differentiation and proliferation of neural stem/progenitor cells (NPCs) depend on various in vivo environmental factors or cues, which may include an endogenous electrical field (EF), as observed during nervous system development and repair. In this study, we investigate the morphologic, phenotypic, and mitotic alterations of adult hippocampal NPCs that occur when exposed to two EFs of estimated endogenous strengths. NPCs treated with a 437 mV/mm direct current (DC) EF aligned perpendicularly to the EF vector and had a greater tendency to differentiate into neurons, but not into oligodendrocytes or astrocytes, compared to controls. Furthermore, NPC process growth was promoted perpendicularly and inhibited anodally in the 437 mV/mm DC EF. Yet fewer cells were observed in the DC EF, which in part was due to a decrease in cell viability. The other EF applied was a 46 mV/mm alternating current (AC) EF. However, the 46 mV/mm AC EF showed no major differences in alignment or differentiation, compared to control conditions. For both EF treatments, the percent of mitotic cells during the last 14 h of the experiment were statistically similar to controls. Reported here, to our knowledge, is the first evidence of adult NPC differentiation affected in an EF in vitro. Further investigation and application of EFs on stem cells is warranted to elucidate the utility of EFs to control phenotypic behavior. With progress, the use of EFs may be engineered to control differentiation and target the growth of transplanted cells in a stem cell-based therapy to treat nervous system disorders.
Co-reporter:Yan-Yan Hu, Yusuf Yusufoglu, Mathumai Kanapathipillai, Chu-Ya Yang, YaQiao Wu, Papannan Thiyagarajan, Timothy Deming, Mufit Akinc, Klaus Schmidt-Rohr and Surya Mallapragada
Soft Matter 2009 vol. 5(Issue 21) pp:4311-4320
Publication Date(Web):09 Sep 2009
DOI:10.1039/B904440J
Polylysine and polyleucine based block copolypeptides (K170L30) that form gels at very low concentrations in aqueous media are used as templates for forming self-assembled calcium phosphate nanocomposites. The synthesis method allows for simultaneous formation of the self-assembled block copolypeptide gel and of the inorganic phase, providing inorganic contents of over 50 wt% in the nanocomposite, approaching the inorganic content in bone. The self-assembled nanocomposites are characterized by thermogravimetric analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, solid state nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The nanocomposites formed in the presence of the block copolypeptide templates exhibit very different nanoparticle morphologies than those formed in the absence of the organic phase. Multinuclear solid state NMR methods are used to prove nanocomposite formation and characterize the secondary structure and mobility of the block copolypeptide template. The data from XRD, FTIR, and 31P NMR consistently show that the inorganic phase present in the nanocomposite is carbonated hydroxyapatite of nano-scale dimensions, with an elongated plate-like morphology, observed by TEM and SAXS, similar to the mineral phase of natural bone. Overall, this approach allows a bioinspired bottom-up approach to self-assembled hydroxyapatite nanocomposites using block copolypeptide templates, which could have applications in tissue repair.
Co-reporter:Jisun Oh;Jennifer B. Recknor;Justin C. Recknor;Donald S. Sakaguchi
Journal of Biomedical Materials Research Part A 2009 Volume 91A( Issue 2) pp:575-585
Publication Date(Web):
DOI:10.1002/jbm.a.32242
Abstract
Rat adult hippocampal progenitor cells (AHPCs) are self-renewing, multipotent neural progenitors that have the ability to differentiate into neurons and glia. Previously, we demonstrated that coculture of AHPCs with postnatal day 2, type 1 cortical astrocytes on laminin-coated micropatterned polymer substrates facilitates selective neuronal differentiation of the AHPCs (Recknor et al., Biomaterials 2006;27:4098–4108). Under this condition, multidimensional cell–cell and/or cell–extracellular matrix interactions, as well as possible soluble factors released from astrocytes provided spatial and temporal control selectively enhancing neuronal differentiation and neurite alignment on topographically different regions of the same substrate. To investigate the potential role of astrocyte-derived soluble factors as cues involved in neuronal differentiation, a noncontact coculture system was used. Under control conditions, ∼14% of the AHPCs were immunoreactive (IR) for the neuronal marker, class III β-tubulin (TUJ1-IR). When cocultured in physical contact with astrocytes, neuronal differentiation increased significantly to about 25%, consistent with our previous results. Moreover, under noncontact coculture conditions using Transwell® insert cultures, neuronal differentiation was dramatically increased to ∼64%. Furthermore, neurite outgrowth from neuronal cell bodies was considerably greater on the patterned substrate when compared with the nonpatterned planar substrate under noncontact coculture conditions. Taken together, our results demonstrate that astrocyte-derived soluble factors provide cues for specific neuronal differentiation of AHPCs cultured on micropatterned substrates. In addition, a suppressive influence on neuronal differentiation appears to be mediated by contact with cocultured astrocytes. These results provide important insights into mechanisms for controlling neural progenitor/stem cell differentiation and facilitate development of strategies for CNS repair. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
Co-reporter:Bingqi Zhang;Mathumai Kanapathipillai;Paul Bisso
Pharmaceutical Research 2009 Volume 26( Issue 3) pp:
Publication Date(Web):2009 March
DOI:10.1007/s11095-008-9813-y
In this study, the novel poly(diethylaminoethylmethacrylate) (PDEAEM)/Pluronic F127 pentablock copolymers were found to be able to mediate high-efficiency transfection of human epithelial ovarian carcinoma (SKOV3) cell line while showing significantly lower efficacy in human epithelial retinal (ARPE-19) cell line and Swiss Mouse Fibroblast (3T3) cell line.The intracellular routes of polyplexes were investigated by confocal microscopy after appropriately labeling the polymer and DNA.It was found that lesser nuclear entry in the ARPE-19 cells may result in the lower efficiency of transfection. Since the SKOV3 proliferation rate was found to be much higher than that of the ARPE-19 cells, the nuclear entry of polyplexes was assumed to be correlated with the proliferation rate, and it was hypothesized that the novel pentablock copolymers could mediate gene delivery selectively in fast growing cells. The different intracellular barriers to gene transfer may also account for the observed difference of transfection efficacy.Although the validity of the hypothesis that our pentablock copolymer could selectively transfect hyperproliferative cells needs further examination, this present work provides a new perspective to design targeting vectors for cancer therapies based on different characteristics among specific cell types.
Co-reporter:Ankit Agarwal, Rita Vilensky, Anne Stockdale, Yeshayahu Talmon, Robert C. Unfer, Surya K. Mallapragada
Journal of Controlled Release 2007 Volume 121(1–2) pp:28-37
Publication Date(Web):16 August 2007
DOI:10.1016/j.jconrel.2007.05.008
Novel cationic pentablock copolymers based on poly(2-diethylaminoethylmethacrylate) (PDEAEM) and Pluronic F127 were evaluated as non-viral gene delivery vectors from a physiochemical point of view for stability and transfection efficiency in complete growth media. A novel strategy was introduced to sterically stabilize the polyplexes of such Pluronic-based cationic polymers against aggregation with serum proteins. As cationic pentablock copolymers condense plasmid DNA into nanoplexes of 100–150 nm diameter, unmodified Pluronic added to the formulation self-assemble with the pentablock copolymers on the surface of polyplexes and shield the cationic PDEAEM chains of pentablock copolymers sterically with its long poly(ethyleneoxide) chains. These coated polyplexes formed colloidally stable dispersions of 150–250 nm diameter in serum-supplemented buffers. Cryo-TEM micrographs also showed that coating polyplexes with unmodified Pluronic reduced aggregation in serum proteins. Pentablock copolymers preserved the integrity of plasmid DNA condensed inside the polyplexes and provided efficient resistance to its degradation by nucleases. Though the total amount of DNA retained by ExGen 500® polyplexes after nuclease digestion was more than that retained by pentablock copolymers, the amount of plasmid retained in supercoiled form was not significantly different. Polyplexes coated with unmodified Pluronic provided efficient transfection in SKOV3 cells in complete growth media, comparable to that provided by ExGen 500® in terms of number of cells transfected, and one order less in terms of total transgene protein expressed. These sterically shielded polyplexes also exhibited much lower cytotoxicities than uncoated polyplexes of pentablock copolymers, and significantly lower than the cytotoxicity of ExGen 500® at relevant concentrations. This colloidally stable, versatile, multi-component gene delivery system also forms thermo-reversible injectable hydrogels like Pluronics at physiological temperatures that can be used for sustained delivery of polyplexes, and is promising for systemic applications.
Co-reporter:Ankit Agarwal;Robert Unfer
Journal of Biomedical Materials Research Part A 2007 Volume 81A(Issue 1) pp:24-39
Publication Date(Web):15 NOV 2006
DOI:10.1002/jbm.a.30920
Novel pentablock copolymers of poly(diethylaminoethylmethacrylate) (PDEAEM), poly(ethylene oxide) (PEO), and poly(propylene oxide) (PPO), (PDEAEM-b-PEO-b-PPO-b-PEO-b-PDEAEM), were synthesized as vectors for gene delivery, and were tested for their biocompatibility on SKOV3 (human ovarian carcinoma) and A431 (human epidermoid cancer) cell lines under different in vitro conditions using various assays to elucidate the mechanism of cell death. These copolymers form micelles in aqueous solutions and can be tuned for their cytotoxicity by tailoring the weight percentage of their cationic component, PDEAEM. Copolymers with higher PDEAEM content were found to be more cytotoxic, though their polyplexes were less toxic than the polycations alone. Pentablock copolymers displayed higher cell viability than commercially available ExGen 500® at similar N:P ratios. While cell death with ExGen was found to be accompanied by an early loss of cell membrane integrity, pentablock copolymers caused very little membrane leakage. Caspase-3/7 assay confirmed that none of these polymers induced apoptosis in the cells. These pentablock copolymers form thermo-reversible gels at physiological temperatures, thereby enabling controlled gene delivery. Toxicity of the polymer gels was tested using an agarose-matrix, simulating an in vivo tumor model where injected polyplex gels would dissolve to release polyplexes, diffusing through tumor mass to reach the target cells. Twenty five weight percent of copolymer gels were found to be nontoxic or mildly cytotoxic after 24 h incubation. Transfection efficiency of the copolymers was found to be critically correlated to cytotoxicity and depended on DNA dose, polymer concentration, and N:P ratios. Transgene expression obtained was comparable to that of ExGen, but ExGen exhibited greater cell death. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Co-reporter:James P. Cox;Michael D. Determan
Journal of Biomedical Materials Research Part A 2007 Volume 81A(Issue 2) pp:326-333
Publication Date(Web):21 NOV 2006
DOI:10.1002/jbm.a.30991
A novel pH-dependent injectable sustained delivery system was developed by utilizing a cationic pentablock copolymer that exhibits a thermoreversible sol-gel transition. Aqueous solutions of the pentablock copolymer, consisting of poly(2-diethylaminoethyl-methyl methacrylate)-poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-poly(2-diethylaminoethyl-methyl methacrylate) (PDEAEM25-PEO100-PPO65-PEO100-PDEAEM25) exhibit temperature and pH dependent micellization due to the lower critical solution temperature of the PPO blocks and the polyelectrolyte character of the PDEAEM blocks, respectively. Aqueous solutions of the copolymers above 12 wt % are free flowing liquids at room temperature and form elastic physical hydrogels reversibly above 37°C. Hydrophobic probe absorbance studies indicate that pentablock copolymer micelles increase the solubility of sparingly soluble drugs. Solutions of the pentablock copolymer that form gels at body temperature exhibit sustained zero-order release in in vitro experiments. The release rates of model drugs and proteins were significantly influenced by the pH of the release media, thereby making these polymers ideal candidates for modulated drug delivery. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 2007
Co-reporter:Sim-Siong Wong;Sacide Alsoy Altinkaya
Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 8) pp:930-935
Publication Date(Web):1 MAR 2007
DOI:10.1002/polb.21101
Crystallization of semicrystalline polymer films during drying has a significant effect on the rate of solvent removal. Understanding and controlling the crystallization kinetics is important in controlling residual solvent levels and drying kinetics. The degree of crystallinity of the poly(vinyl alcohol) films during multicomponent drying was investigated using Fourier transform infrared spectroscopy (FTIR). The 1141 cm−1 band is sensitive to the degree of crystallinity of the polymer and the growth of intensity of this band was monitored as drying progressed. The results from the FTIR studies were comparable to the results obtained from differential scanning calorimetry. Studies were conducted to test the effect of initial solvent composition (water–methanol mixture), drying temperature, and polymer molecular weight on the rate of crystallization and the final crystallinity of the films. An increase in initial methanol composition increased the crystallization rate but did not affect the final degree of crystallinity. An increase in drying temperature and decrease in polymer molecular weight increased the rate of crystallization as well as the final degree of crystallinity. Based on the experimental data, rate constants for crystallization kinetics were extracted from our previously developed model based on free volume theory. The experimental data and the simulation results showed good agreement. The ability of the free volume theory to illustrate the crystallization behavior validated the model and improved its capability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 930–935, 2007
Co-reporter:Tanya Prozorov, Pierre Palo, Lijun Wang, Marit Nilsen-Hamilton, DeAnna Jones, Daniel Orr, Surya K. Mallapragada, Balaji Narasimhan, Paul C. Canfield and Ruslan Prozorov
ACS Nano 2007 Volume 1(Issue 3) pp:228
Publication Date(Web):October 31, 2007
DOI:10.1021/nn700194h
Magnetotactic bacteria produce exquisitely ordered chains of uniform magnetite (Fe3O4) nanocrystals, and the use of the bacterial mms6 protein allows for the shape-selective synthesis of Fe3O4 nanocrystals. Cobalt ferrite (CoFe2O4) nanoparticles, on the other hand, are not known to occur in living organisms. Here we report on the use of the recombinant mms6 protein in a templated synthesis of CoFe2O4 nanocrystals in vitro. We have covalently attached the full-length mms6 protein and a synthetic C-terminal domain of mms6 protein to self-assembling polymers in order to template hierarchical CoFe2O4 nanostructures. This new synthesis pathway enables facile room-temperature shape-specific synthesis of complex magnetic crystalline nanomaterials with particle sizes in the range of 40–100 nm that are difficult to produce using conventional techniques.Keywords: bioinspired synthesis; biomineralization protein; cobalt ferrite nanocrystals; magnetic nanocrystals; superparamagnetism; templating
Co-reporter:María P. Torres;Bron M. Vogel;Balaji Narasimhan;María P. Torres;Bron M. Vogel;Balaji Narasimhan
Journal of Biomedical Materials Research Part A 2006 Volume 76A(Issue 1) pp:102-110
Publication Date(Web):1 SEP 2005
DOI:10.1002/jbm.a.30510
We have designed a new synthesis route to create polyanhydrides based on monomers that contain hydrophilic entities within highly hydrophobic backbones. The method results in polyanhydrides that can be easily processed into drug-containing tablets. The synthesis, characterization, and erosion studies of polyanhydride copolymers based on 1,6-bis(p-carboxyphenoxy)hexane (CPH), which is highly hydrophobic, and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG), which has hydrophilic oligomeric ethylene glycol segments in the monomer unit, was performed using a combination of molecular spectroscopy, thermal analysis, gravimetry, and scanning electron microscopy. The studies demonstrate that by increasing the CPH content in the CPTEG:CPH copolymers, the erosion of the system can be tailored from bulk-eroding to surface-eroding mechanism. These systems have promise as protein carriers. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Co-reporter:Jennifer B. Recknor, Donald S. Sakaguchi, Surya K. Mallapragada
Biomaterials 2006 Volume 27(Issue 22) pp:4098-4108
Publication Date(Web):August 2006
DOI:10.1016/j.biomaterials.2006.03.029
Directional growth and differentiation of adult rat hippocampal progenitor cells (AHPCs) were investigated on micropatterned polymer substrates in vitro. Astrocytes or AHPCs cultured on micropatterned polystyrene substrates chemically modified with laminin exhibited over 75% alignment in the groove direction. AHPCs co-cultured with astrocytes preferentially acquired neuronal morphology, with nearly double the percentage of cells expressing class III β-tubulin on the micropatterned half of the substrate, as opposed to the planar half of the substrate, or compared to those growing in the absence of astrocytes. This indicates that substrate three-dimensional topography, in synergy with chemical (laminin) and biological (astrocytes) guidance cues, facilitates neuronal differentiation of the AHPCs. Through multi-dimensional cell–cell interactions, this environment provides spatial control selectively enhancing neuronal differentiation and neurite alignment on topographically different regions of the same substrate. Integrating these cues is important in understanding and controlling neural stem cell differentiation and designing scaffolds for guided nerve regeneration.
Co-reporter:Ankit Agarwal, Robert Unfer, Surya K. Mallapragada
Journal of Controlled Release 2005 Volume 103(Issue 1) pp:245-258
Publication Date(Web):2 March 2005
DOI:10.1016/j.jconrel.2004.11.022
New cationic pentablock copolymers of poly(diethylaminoethylmethacrylate) (PDEAEM), poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO)—PDEAEM-b-PEO-b-PPO-b-PEO-b-PDEAEM—synthesized in our laboratory were investigated for their potential as non-viral vectors for gene therapy. Agarose gel studies showed that the copolymers effectively condensed plasmid DNA to form polyplexes, and also protected plasmids against nuclease degradation. Light scattering and transmission electron microscopy were used to analyze the apparent size, molecular weight and morphology of these polyplexes. Lactate dehydrogenase assay was employed to find the cytotoxicity limits of the polymers and polyplexes on a human ovarian cancer cell line. The polymers showed much less cytotoxicity than commercially available ExGen 500 (linear polyethyleneimine). By changing the relative lengths of the blocks in the copolymers, it was found that the cytotoxicity of these copolymers could be tailored. The micellar structures of these copolymers in aqueous solutions and their pH-sensitive protonation were added advantages. In vitro transfection efficiencies of the polymers using green fluorescent protein (pEGFP-N1) and luciferase (pRL-CMV) reporter genes were found comparable to ExGen 500. Besides, aqueous solutions of these pentablock copolymers have been shown to exhibit thermodynamic phase transitions and thermoreversible gelation, a quality that could allow subcutaneous/intramuscular injections of these polymers for controlled gene delivery over time.
Co-reporter:Sim-Siong Wong;Sacide Alsoy Altinkaya
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 22) pp:3191-3204
Publication Date(Web):27 SEP 2005
DOI:10.1002/polb.20615
The effect of glassy skin formation on the drying of semicrystalline polymers was investigated with a comprehensive mathematical model developed for multicomponent systems. Polymers with high glass-transition temperatures can become rubbery at room temperature under the influence of solvents. As the solvents are removed from the polymer, a glassy skin can form and continue to develop. The model takes into account the effects of diffusion-induced polymer crystallization as well as glassy–rubbery transitions on the overall solvent content and polymer crystallinity. A Vrentas–Duda free-volume-based diffusion scheme and crystallization kinetics were used in our model. The polymer–solvent system chosen was a poly(vinyl alcohol) (PVA)–water–methanol system. The drying kinetics of PVA films were obtained by gravimetric methods with swollen films with known water/methanol concentrations. The overall drying behaviors of the polymer system determined by our model and experimental methods were compared and found to match well. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3191–3204, 2005
Co-reporter:Bron M. Vogel;Balaji Narasimhan
Macromolecular Rapid Communications 2004 Volume 25(Issue 1) pp:330-333
Publication Date(Web):19 DEC 2003
DOI:10.1002/marc.200300156
Summary: Polyanhydrides were synthesized from aliphatic and aromatic diacids using microwave radiation without vacuum at significantly reduced reaction times when compared to conventional melt polycondensation. Reaction conditions, such as duration of polymerization, equivalents of acetic anhydride, and choice of starting species, were studied. In addition, copolymers were synthesized and monomer sequence lengths were calculated using dyad conditional probabilities. The results are in good agreement with monomer sequence lengths from conventional copolymerization.
Co-reporter:Jennifer B. Recknor, Justin C. Recknor, Donald S. Sakaguchi, Surya K. Mallapragada
Biomaterials 2004 Volume 25(Issue 14) pp:2753-2767
Publication Date(Web):June 2004
DOI:10.1016/j.biomaterials.2003.11.045
In an effort to develop a permissive environment for neural stem cell differentiation, directional growth of astrocytes has been achieved on polymer substrates in vitro. Manipulating a combination of physical and chemical cues, astrocyte adhesion and alignment in vitro were examined. To provide physical guidance, micropatterned polymer substrates of polystyrene (PS) were fabricated. Laminin was selectively adsorbed onto the grooves of the patterned surface. Rat type-1 astrocytes were seeded onto the micropatterned PS substrates, and the effects of substrate topography and the adsorption of laminin to the PS substrates on the behavior and morphology of the astrocytes were explored. The astrocytes were found to align parallel to the micropatterned grooves at initial seeding densities of approximately 7500, 13,000, and 20,000 cells/cm2 due to the effects of the physical and chemical guidance mechanisms. Adsorbing laminin in the microgrooves of the micropatterned PS substrates improved cell adhesion and spreading of cytoskeletal filaments significantly. At these initial seeding densities, over 85% astrocyte alignment in the direction of the grooves was achieved on the micropatterned PS substrates with laminin adsorbed in the grooves. This combination of guidance cues has the potential to provide a permissive substrate for in vivo regeneration within the central nervous system.
Co-reporter:Brian C. Anderson;Suzan M. Cox;Amar V. Ambardekar
Journal of Pharmaceutical Sciences 2002 Volume 91(Issue 1) pp:180-188
Publication Date(Web):26 DEC 2001
DOI:10.1002/jps.10037
Studies were performed to examine the effect of ionic salts on phase transitions, dissolution rates, and diffusion coefficients of water in gels of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) with polymer concentrations ranging from 22 to 32% w/w and salt concentrations ranging from 0 to 1.5% w/w. Salts tested include Na3PO4, Na2SO4, Na2HPO4, NaH2PO4, NaCH3CO2, NaCl, and KI. Micellization transition temperatures were obtained using differential scanning calorimetry. The dissolution rates were obtained by measurement of the surface erosion rates, and diffusion coefficients were obtained by using a method to analyze the intrusion of water into the aqueous gels. It was found that salts had no effect on the dissolution rate of the polymer gels into deionized water. However, when the salt concentration in the aqueous dissolution media was adjusted to match the concentration in the gels, the dissolution rate of the polymer gel decreased with increasing salt concentration. The salts also had a profound effect on the critical micellization temperature (CMT) and the diffusion coefficient of water within the gel. The diffusion coefficient and CMT decreased in the presence of salts. The magnitude of these effects was comparable to their placement on the Hofmeister, or lyotropic series for salts. The effects of polymer and salt concentrations on the CMT were quantified, and a single correlation was proposed to predict the micellization temperatures for a wide range of salt and polymer concentrations. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:180–188, 2002
Co-reporter:Surya K. Mallapragada, Balaji Narasimhan
Biomaterials 2002 Volume 23(Issue 22) pp:4305
Publication Date(Web):November 2002
DOI:10.1016/S0142-9612(02)00172-2
Co-reporter:Brian C. Anderson, Surya K. Mallapragada
Biomaterials 2002 Volume 23(Issue 22) pp:4345-4352
Publication Date(Web):November 2002
DOI:10.1016/S0142-9612(02)00173-4
Several homopolymers and copolymers of 2-(diethylamino)ethyl methacrylate (DEAEM) and poly(ethylene glycol) methyl ether methacrylate (PEGMEM) were synthesized using anionic polymerization initiated by potassium t-butoxide. The polymers were characterized by average molecular weight, polydispersity and monomeric unit composition. A very narrow molecular weight distribution was achieved with a well-controlled composition. The glass transition temperatures and compositions of the copolymers followed a Gordon–Taylor relationship. The water solubility and biocompatibility of the copolymers was compared to their parent homopolymers to determine if the addition of a poly(ethylene glycol) group was sufficient to solubilize the polymers in aqueous buffer solutions and to increase the biocompatibility of the polymers. These water-soluble, injectable cationic copolymers have potential applications in gene delivery as well as other biomaterial applications.
Co-reporter:Brian C Anderson, Nita K Pandit, Surya K Mallapragada
Journal of Controlled Release 2001 Volume 70(1–2) pp:157-167
Publication Date(Web):29 January 2001
DOI:10.1016/S0168-3659(00)00341-2
Experimental and mathematical studies were performed to understand the release mechanism of small molecular weight compounds from poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer gels (trademarked Pluronic® by BASF Corp.) of various concentrations. Studies of the diffusion coefficient of solutes in the polymer gels were performed using a novel technique to predict movement of drugs within the gel as release occurs. Studies were also performed to determine the diffusion coefficient of water in the polymer gel, as it is this parameter that controls the dissolution rate of the polymer, and in turn, the drug release rate. A model was formulated and solved numerically to determine the controlling release mechanism. By parameter modification, this algorithm for determining the overall mass of drug released from a drug loaded gel can be used for a number of drugs and for a wide range of initial polymer concentrations. Drug release data were obtained with a novel experimental setup and were used to verify the accuracy of the overall solution of the model. The results of the model indicate that although the rate of polymer dissolution ultimately controls the drug release, about 5% of the release is due to diffusion at the gel/liquid interface, giving rise to a slightly non-linear release. It was also found that agitation speed greatly affects the dissolution rates of these polymer gels.
Co-reporter:Howard E. Gendelman, Vellareddy Anantharam, Tatiana Bronich, Shivani Ghaisas, Huajun Jin, Anumantha G. Kanthasamy, Xinming Liu, JoEllyn McMillan, R. Lee Mosley, Balaji Narasimhan, Surya K. Mallapragada
Nanomedicine: Nanotechnology, Biology and Medicine (April 2015) Volume 11(Issue 3) pp:751-767
Publication Date(Web):1 April 2015
DOI:10.1016/j.nano.2014.12.014
Interest in nanoneuromedicine has grown rapidly due to the immediate need for improved biomarkers and therapies for psychiatric, developmental, traumatic, inflammatory, infectious and degenerative nervous system disorders. These, in whole or in part, are a significant societal burden due to growth in numbers of affected people and in disease severity. Lost productivity of the patient and his or her caregiver, and the emotional and financial burden cannot be overstated. The need for improved health care, treatment and diagnostics is immediate. A means to such an end is nanotechnology. Indeed, recent developments of health-care enabling nanotechnologies and nanomedicines range from biomarker discovery including neuroimaging to therapeutic applications for degenerative, inflammatory and infectious disorders of the nervous system. This review focuses on the current and future potential of the field to positively affect clinical outcomes.From the Clinical EditorMany nervous system disorders remain unresolved clinical problems. In many cases, drug agents simply cannot cross the blood-brain barrier (BBB) into the nervous system. The advent of nanomedicines can enhance the delivery of biologically active molecules for targeted therapy and imaging. This review focused on the use of nanotechnology for degenerative, inflammatory, and infectious diseases in the nervous system.
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