A Comprehensive Kinetic Model of Free‐Radical‐Mediated Interfacial Polymerization

Shenoy, Raveesh; Bowman, Christopher N.

doi:10.1002/mats.201200062

Cited by 5 publications

(6 citation statements)

References 33 publications

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“…Because bulk photopolymerization proceeds through drastically different initiation conditions than a typical surface-initiated system, the crosslinking profiles generated are inherently different. 32 Further, polymer diffusivities are typically measured with a polymer geometries that are several micrometers thick when hydrated, which is a much larger length scale than the thin films generated in this work. 16,33 Thus, direct measurement of diffusivities of films on cellular substrates would result in a more representative characterization of transport in the cellular microenvironment.…”

Section: Resultsmentioning

confidence: 99%

Characterization of Molecular Transport in Ultrathin Hydrogel Coatings for Cellular Immunoprotection

Lilly

Romero

et al. 2015

Biomacromolecules

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PEG hydrogels are routinely used in immunoprotection applications to hide foreign cells from a host immune system. Size dependent transport is typically exploited in these systems to prevent access by macromolecular elements of the immune system while allowing the transport of low molecular weight nutrients. This work studies a nanoscale hydrogel coating for improved transport of beneficial low molecular weight materials across thicker hydrogel coatings while completely blocking transport of undesired larger molecular weight materials. Coatings composed of PEG diacrylate of molecular weight 575 Da and 3500 Da were studied by tracking the transport of fluorescently-labeled dextrans across the coatings. The molecular weight of dextran at which the transport is blocked by these coatings are consistent with cutoff values in analogous bulk PEG materials. Additionally, the diffusion constants of 4 kDa dextrans across PEG 575 coatings (9.5×10−10 – 2.0×10−9 cm2/s) was lower than across PEG 3500 coatings (5.9 – 9.8×10−9 cm2/s), and these trends and magnitudes agree with bulk scale models. Overall, these nanoscale thin PEG diacrylate films offer the same size selective transport behavior of bulk PEG diacrylate materials, while the lower thickness translates directly to increased flux of beneficial low molecular weight materials.

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Section: Resultsmentioning

confidence: 99%

Characterization of Molecular Transport in Ultrathin Hydrogel Coatings for Cellular Immunoprotection

Lilly

Romero

et al. 2015

Biomacromolecules

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“…To improve the surface coverage of the coating on GFTV samples further, we increased the concentrations of glucose oxidase (Figure J–L) and glucose (Figure M–O). Previous studies have shown that increasing glucose oxidase concentration increases the rate of reaction, whereas increases in glucose concentration were previously reported to increase the coating thickness but not rate of reaction. , In the present study on GFVT samples, we observed greater surface coverage for the same reaction time by increasing the glucose oxidase concentration 10-fold. There was no clearly observable increase in thickness due to this increase, although quantitative data is needed.…”

Section: Discussionmentioning

confidence: 99%

“…In groups with low glucose oxidase, one problem contributing to the low surface coverage may have been the delocalization of the radical initiation reaction. In previous studies, it was reported that the reaction rate of glucose with glucose oxidase (and downstream, hydrogen peroxide with iron) must be sufficiently fast to prevent delocalization of the radical initiation. , Similarly, this delocalized polymerization may have resulted in the reduced coating coverage seen in low GOx GFVT. By increasing the glucose oxidase concentration, the formation of radicals was more effectively confined to the surface to be coated, resulting in more surface coverage in the high GOx GFVT samples.…”

Section: Discussionmentioning

confidence: 99%

Interfacial Coating Method for Amine-Rich Surfaces using Poly(ethylene glycol) Diacrylate Applied to Bioprosthetic Valve Tissue Models

Roseen

Fahrenholtz

Connell

et al. 2020

ACS Appl. Bio Mater.

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Bioprosthetic heart valve implants are beset by calcification and failure due to the interactions between the body and the transplant. Hydrogels can be used as biological blank slates that may help to shield implants from these interactions; however, traditional light-based hydrogel polymerization is impeded by tissue opacity and topography. Therefore, new methods must be created to bind hydrogel to implant tissues. To address these complications, a two-step surface-coating method for bioprosthetic valves was developed. A previously developed bioprosthetic valve model (VM) was used to investigate and optimize the coating method. Generally, this coating is achieved by first reacting surface amine groups with an NHS-PEG-acrylate while also allowing glucose to absorb into the bulk. Then, glucose oxidase, poly(ethylene glycol) diacrylate (PEGDA), and iron ions are added to the system to initiate free-radical polymerization that bonds the PEGDA hydrogel to the acrylates sites on the surface. Results showed a thin (∼8 μm), continuous coating on VM samples that is capable of repelling protein adhesion (2% surface fouling versus 20% on uncoated samples) and does not significantly affect the surface mechanical properties. Based on this success, the coating method was translated to glutaraldehyde-fixed valve tissue samples. Results showed noncontinuous but evident coating on the surface, which was further improved by adjusting the coating solution. These results demonstrate the feasibility of the proposed two-step surface coating method for modifying the surface of bioprosthetic valve replacements.

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“…The self-limiting growth results from H 2 O 2 , generated within the core, diffusing to the moving interface between the shell and the bulk monomer solution. In order to sustain shell growth, H 2 O 2 must diffuse through the shell layer while avoiding reaction with Fe 2+ that is diffusing into the shell to generate radicals at the shell-bulk interface. , Otherwise, hydroxyl radical production occurs within the shell instead of near the desired interface, thereby contributing negligibly to shell growth.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Further, the thickness of the shell can be controlled by changing the bulk iron concentration, which acts to influence the degree of confinement of the initiation reaction. Previous work on the enzyme-mediated redox reaction mechanism has established that using higher concentrations of Fe 2+ promotes localized polymerization by confining the redox reaction between H 2 O 2 and Fe 2+ to the interface as a result of enabling a highly reactive surrounding phase. , Therefore, the concentration of iron was increased by a factor of ∼4 to enable inhibition in the bulk. However, the higher initiation rates adjacent to the interface, compared to the bulk media, allows interfacial polymerization to occur.…”

Section: Results and Discussionmentioning

confidence: 99%

Formation of Core–Shell Particles by Interfacial Radical Polymerization Initiated by a Glucose Oxidase-Mediated Redox System

et al. 2013

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A unique design paradigm to form core–shell particles based on interfacial radical polymerization is described. The interfacial initiation system is comprised of an enzymatic reaction between glucose and glucose oxidase (GOx) to generate hydrogen peroxide, which, in the presence of iron (Fe2+), generates hydroxyl radicals that initiate polymerization. Shell formation on prefabricated polymeric cores is achieved by localizing the initiation reaction to the interface of the core and a surrounding aqueous monomer formulation into which it is immersed. The interfacially confined initiation reaction is accomplished by incorporating one or more of the initiating species in the particle core and the remainder of the complementary initiating components in the surrounding media such that interactions and the resulting initiation reaction occur at the interface. This work is focused on engineering the reaction behavior and mass transport processes to promote interfacially confined polymerization, controlling the rate of shell formation, and manipulating the structure of the core–shell particle. Specifically, incorporating GOx in the precursor solution used to fabricate cores ranging from 100 to 200 μm, and the remainder of the complementary initiating components and monomer in the bulk solution prior to interfacial polymerization yielded shells whose average thickness was 20 μm after 4 min of immersion and at a bulk iron concentration of 12.5 mM. When the locations of glucose and GOx are interchanged, the average thickness of the shell was 15 or 100 μm for bulk iron concentrations of 45 and 12.5 mM, respectively. The initial locations of glucose and GOx also determine the degree of interpenetration of the core and the shell. Specifically, for a bulk iron concentration of 45 mM, the thickness of the interpenetrating layer averaged 12 μm when GOx was initially within the core, whereas no interpenetrating layer was observed when glucose was incorporated in the core. The polymeric shell formed by this technique is also demonstrated to be self-supporting following core degradation. This behavior is accomplished by fabricating the particle core hydrogel from monomers possessing degradable groups that can be irreversibly cleaved by light exposure following shell formation. When the coated particle was exposed to light, the shell remained intact while the core degraded as evidenced by a dramatic change in diffusion coefficient of fluorescent beads immobilized within the core.

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A Comprehensive Kinetic Model of Free‐Radical‐Mediated Interfacial Polymerization

Cited by 5 publications

References 33 publications

Characterization of Molecular Transport in Ultrathin Hydrogel Coatings for Cellular Immunoprotection

Characterization of Molecular Transport in Ultrathin Hydrogel Coatings for Cellular Immunoprotection

Interfacial Coating Method for Amine-Rich Surfaces using Poly(ethylene glycol) Diacrylate Applied to Bioprosthetic Valve Tissue Models

Formation of Core–Shell Particles by Interfacial Radical Polymerization Initiated by a Glucose Oxidase-Mediated Redox System

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