Co-reporter:Nataraja S. Yadavalli, Nikolay Borodinov, Chandan K. Choudhury, Tatiana Quiñones-Ruiz, Amine M. Laradji, Sidong Tu, Igor K. Lednev, Olga Kuksenok, Igor Luzinov, and Sergiy Minko
ACS Catalysis December 1, 2017 Volume 7(Issue 12) pp:8675-8675
Publication Date(Web):November 3, 2017
DOI:10.1021/acscatal.7b03138
Herein, we report a conjugation strategy, where we utilize a poly(ethylene oxide) cylindrical molecular brush architecture to design a self-assembled structure for thermal stabilization of enzymes. We demonstrate that the proposed architecture of the moderately stiff polymer ligand results in a significant improvement of biocatalytic activity and thermal stability of lysozyme and trypsin that retain their activity, even upon heating to 100 °C and above. The molecular brush is bound via epoxy functional groups to the amino groups of the lysine on the surface of the enzyme globule, promoting the formation of stiff and crowded cages around the enzymes and preventing the water molecules access to the enzyme and enzymes agglomeration. The molecular dynamic simulations show that the high concentration of poly(ethylene oxide) in the vicinity of the enzyme is critical for their stability. Monitoring of lysozyme–molecular brush conjugates for 6 and 12 months in lyophilized form and in solution, respectively, has shown that the conjugation does not compromise the shelf life of the enzyme.Keywords: enzyme catalysis; molecular dynamics; nanostructures; polymers; self-assembly;
Co-reporter:Maxim E. Dokukin, Hidenori Kuroki, Sergiy Minko, and Igor Sokolov
Macromolecules 2017 Volume 50(Issue 1) pp:
Publication Date(Web):December 22, 2016
DOI:10.1021/acs.macromol.6b02149
Polymers brushes (polymer chains end-tethered to a substrate) have been extensively studied with atomic force microscopy (AFM). Force–indentation curves are collected while squeezing the sample surface with the AFM probe. The analysis of these curves allows obtaining the equilibrium brush thickness and grafting density by using an appropriate model for mechanical deformation of the brush. However, this approach becomes inaccurate when the substrate is deformable, which is frequently the case. In this situation, the collected force–distance curves include information about both the brush and substrate deformations. Here we describe a method which takes into account both the brush and substrate deformations. Quantitative accuracy of the presented method is demonstrated by applying the method to measuring a poly(ethylene oxide) brush grafted to the cross-linked poly(2-vinylpyridine) substrate swollen in aqueous media of different acidity. By analyzing the AFM force curves, we simultaneously obtain the grafting density, equilibrium brush thickness, and the Young’s modulus of the substrate. The method is verified by independent measurements of the substrate Young’s modulus and direct measurements of the brush thickness using ellipsometry. The method demonstrates a very good agreement between the estimated and directly measured Young’s modulus of the substrate and molecular characteristics of the brush.
Co-reporter:Yunsang Kim;Lauren Tolbert McCoy;Eliza Lee;Hansol Lee;Raha Saremi;Corbin Feit;Ian R. Hardin;Suraj Sharma;Sudhagar Mani
Green Chemistry (1999-Present) 2017 vol. 19(Issue 17) pp:4031-4035
Publication Date(Web):2017/08/29
DOI:10.1039/C7GC01662J
We have developed a sustainable dyeing technology with nanofibrillated cellulose (NFC) fibers that would decrease the amount of water, salt and alkali used in cotton dyeing by one order of magnitude, but with comparable dyeing performance to a conventional exhaust dyeing method.
Co-reporter:Alexer Tokarev;Jeremy Yatvin;Oleksr Trotsenko;Jason Locklin
Advanced Functional Materials 2016 Volume 26( Issue 22) pp:3761-3782
Publication Date(Web):
DOI:10.1002/adfm.201504443
Magnetic field imaging in living specimens with magnetic nanoparticles as contrasting agents has attracted significant interest in the rapidly developing field of nanomedicine. Developments in this field have also stimulated research into the synthesis and design of functionalized magnetic nanoparticles that find applications in broader areas of materials science beyond contrasting for biomedical applications. This article provides a brief discussion of the methods for synthesis and surveys the surface functionalization chemistry of magnetic nanoparticles, along with various approaches for magnetic nanoparticle manipulation and assembly in uniform and nonuniform magnetic fields.
Co-reporter:Sergiy Minko
Advanced Functional Materials 2016 Volume 26( Issue 22) pp:3759-3760
Publication Date(Web):
DOI:10.1002/adfm.201601264
No abstract is available for this article.
Co-reporter:Oleksandr Trotsenko, Roland Koestner, Yuri Roiter, Alexander Tokarev, Sergiy Minko
Polymer 2016 Volume 102() pp:396-403
Publication Date(Web):12 October 2016
DOI:10.1016/j.polymer.2015.11.021
•Atomic force microscopy (AFM) is used for quantitative analysis of a composite rough surface.•Chemical contrast is obtained for Pt/Nafion fuel cell electrode surface.•PeakForce QNM and TUNA modes provide 50 nm lateral resolution for Pt and Nafion.Optimizing Nafion loading and surface distribution of Nafion in the fuel cell electrode is critical for the fuel cell performance for minimizing ohmic and mass transport overpotentials. An atomic force microscopy method is used here for a qualitative and a quantitative discrimination between the ionomer and Pt in the fuel cell electrode. This work describes a methodology for the analysis of complex composite surface of fuel cell electrodes and discrimination of different materials on the electrode surface. The reported methodology could be extended for imaging composite rough surfaces when contrast is based on mechanical properties, adhesion and electrical conductivity.
Co-reporter:Amine M. Laradji, Christopher D. McNitt, Nataraja S. Yadavalli, Vladimir V. Popik, and Sergiy Minko
Macromolecules 2016 Volume 49(Issue 20) pp:7625-7631
Publication Date(Web):October 10, 2016
DOI:10.1021/acs.macromol.6b01573
Herein we report a robust, highly selective, and efficient method to prepare dense poly(ethylene glycol) (PEG) polymer brushes on silicon substrates via solvent-free, catalyst-free, strain-promoted acetylene–azide cycloaddition (SPAAC) reaction. First, poly(glycidyl methacrylate) was grafted to the silicon substrate as an anchoring layer to immobilize cyclopropenone-caged dibenzocyclooctyne-amine (photo-DIBO-amine) via an epoxy ring-opening reaction providing protected, stable, and functionalized substrates. Next, three synthesized α-methoxy-ω-azido-PEGs of different molecular weights (5, 10, and 20 kg/mol) were successfully grafted to the photo-DIBO-modified silicon substrates from melt after the deprotection of DIBO with UV-irradiation. PEG molecular weight, reaction temperature, and reaction time were all used to control the grafting reaction for targeted brush thicknesses and grafting densities. The highest grafting density obtained was close to 1.2 chains/nm2 and was achieved for 5 kg/mol PEG. The prepared PEG polymer brushes displayed efficient antifouling properties and stability in PBS buffer aqueous media for a period of at least two months.
Co-reporter:Alexer Tokarev;Oleksr Trotsenko;Ian M. Griffiths;Howard A. Stone
Advanced Materials 2015 Volume 27( Issue 23) pp:3560-3565
Publication Date(Web):
DOI:10.1002/adma.201500374
Co-reporter:Alexer Tokarev;Darya Asheghali;Ian M. Griffiths;Oleksr Trotsenko;Alexey Gruzd;Xin Lin;Howard A. Stone
Advanced Materials 2015 Volume 27( Issue 41) pp:6526-6532
Publication Date(Web):
DOI:10.1002/adma.201502768
Co-reporter:Oleksandr Trotsenko, Alexander Tokarev, Alexey Gruzd, Timothy Enright and Sergiy Minko
Nanoscale 2015 vol. 7(Issue 16) pp:7155-7161
Publication Date(Web):19 Mar 2015
DOI:10.1039/C5NR00154D
Magnetic field assisted assembly is used to fabricate aligned single nanowire mesh-like nanostructured films. Inhomogeneous magnetic field is applied to translocate high aspect ratio silver nanowires from suspensions to the surface of solid supports. The tangential component of the magnetic field vector is rotated in two consecutive steps to arrange the rectangular mesh-like structure of orthogonally oriented nanowires with minimal fractions of loops and bent structures. This work demonstrates highly ordered nanowire films with superior properties to randomly deposited structures- specifically one order of magnitude greater conductivity and more than ten percent higher transparency. This method is simple, scalable and can be used for the directed assembly of magnetic and nonmagnetic highly ordered, percolated structures.
Co-reporter:Hidenori Kuroki, Crescent Islam, Igor Tokarev, Heng Hu, Guojun Liu, and Sergiy Minko
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 19) pp:10401
Publication Date(Web):April 27, 2015
DOI:10.1021/acsami.5b01416
The concept of a responsive nanoporous thin-film gel membranes whose pores could be tuned to a desired size by a specific “molecular signal” and whose pore geometry becomes “memorized” by the gel is reported. The ∼100 nm thick membranes were prepared by dip-coating from a solution mixture of a random copolymer comprising responsive and photo-cross-linkable units and monodisperse latex nanoparticles used as a sacrificial colloidal template. After stabilization of the films by photo-cross-linking the latex template was removed, yielding nanoporous structures with a narrow pore size distribution and a high porosity. The thin-film membranes could be transferred onto porous supports to serve as tunable size-selective barriers in various colloids separation applications. The pore dimensions and hence the membrane’s colloidal-particle-size cutoff were reversibly regulated by swelling–shrinking of the polymer network with a specially selected low-molar-mass compound. The attained pore shape was “memorized” in aqueous media and “erased” by treatment in special solvents reverting the membrane to the original state.Keywords: nanostructure; pore memory; responsive membrane; size-selective filtration; template;
Co-reporter:Igor Tokarev, Venkateshwarlu Gopishetty, and Sergiy Minko
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 23) pp:12463
Publication Date(Web):January 22, 2015
DOI:10.1021/am5076327
The article describes a novel polymer blend system that yields thin films with unique porous nanoscale morphologies and environmentally responsive properties. The blend consists of sodium alginate and amine end-terminated PEG, which undergoes phase separation during film deposition. The blend films can be readily converted into highly porous membranes using facile treatment with a solution containing divalent ions. The resulting membranes are primarily comprised of alginate hydrogel, whereas the PEG phase is removed from the films during exposure to the saline solution, yielding nanometer-sized pores. The alginate gel phase forms a three-dimensional nanostructure which can be best described as a filament or fibrous network. Because such network geometry is untypical of polymer blends in thin films, possible reasons for the observed phase morphology are discussed. Because of ionizable carboxyl groups, the hydrogel membranes demonstrate responsive behavior, in particular a drastic change in their porosity between a highly porous state and a state with completely closed pores in response to changes in the solution pH. The pore-size tunability can be explored in multiple applications where the regulation of material’s permeability is needed.Keywords: alginate; membrane; nanostructured thin film; polymer blend; porous material;
Co-reporter:Dr. Alexer Tokarev;Dr. Oleksr Trotsenko;Darya Asheghali;Dr. Ian M. Griffiths; Howard A. Stone; Sergiy Minko
Angewandte Chemie International Edition 2015 Volume 54( Issue 46) pp:13613-13616
Publication Date(Web):
DOI:10.1002/anie.201506796
Abstract
Reactive spinning of nano- and microfibers that involves very fast chemical reactions and ion exchange is a challenge for the common methods for nanofiber formation. Herein, we introduce the reactive magnetospinning method. This procedure is based on the magnetic-field-directed collision of ferrofluid droplets with liquid droplets that contain complementary reactants. The collision, start of the chemical reaction, and the fiber drawing are self-synchronized. The method is used to synthesize, cross-link, and chemically modify fiber-forming polymers in the stage of fiber formation. The method provides new opportunities for the fabrication of nanofibers for biomedical applications.
Co-reporter:Dr. Alexer Tokarev;Dr. Oleksr Trotsenko;Darya Asheghali;Dr. Ian M. Griffiths; Howard A. Stone; Sergiy Minko
Angewandte Chemie 2015 Volume 127( Issue 46) pp:13817-13820
Publication Date(Web):
DOI:10.1002/ange.201506796
Abstract
Reactive spinning of nano- and microfibers that involves very fast chemical reactions and ion exchange is a challenge for the common methods for nanofiber formation. Herein, we introduce the reactive magnetospinning method. This procedure is based on the magnetic-field-directed collision of ferrofluid droplets with liquid droplets that contain complementary reactants. The collision, start of the chemical reaction, and the fiber drawing are self-synchronized. The method is used to synthesize, cross-link, and chemically modify fiber-forming polymers in the stage of fiber formation. The method provides new opportunities for the fabrication of nanofibers for biomedical applications.
Co-reporter:Alexer Tokarev;Yu Gu;Andrey Zakharchenko;Oleksr Trotsenko;Igor Luzinov;Konstantin G. Kornev
Advanced Functional Materials 2014 Volume 24( Issue 30) pp:4738-4745
Publication Date(Web):
DOI:10.1002/adfm.201303358
A method for the generation of remotely reconfigurable anisotropic coatings is developed. To form these coatings, locking magnetic nanoparticles (LMNPs) made of a superparamagnetic core and a two-component polymer shell are employed. Two different polymers form phase-separated coaxial shells. The outer shell provides repulsive interactions between the LMNPs while the inner shell exerts attractive forces between the particles. Applying a non-uniform magnetic field, one gathers the particles together, pushing them to come in contact when the internal shells could effectively hold the particles together. When the magnetic field is turned off, the particles remain locked due to these strong interactions between internal shells. The shells are thus made stimuli-responsive, so this locking can be made reversible and the chains can be disintegrated on demand. In a non-uniform magnetic field, the assembled chains translocate, bind to the solid substrate and form anisotropic coatings with a “locked” anisotropic structure. The coatings can be constructed, aligned, realigned, degraded, and generated again on demand by changing the magnetic field and particle environment. The mechanism of the coating formation is explained using experimental observations and a theoretical model.
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