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

Abstract

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.

In vitro model alveoli from photodegradable microsphere templates

“…From this plot, an estimate of the particle diffusion coefficient was calculated as previously published, and used to determine the light dose needed to reach the gel to sol transition. 49–51 …”

Multistructured Nanogel‐Based Networks Formed from Interfacial Redox Polymerizations for Modulating Small Molecule Release

“…We first examined the ability of these nanogels to form a crosslinked coating on a bulk polymer gel. Based on previous reports, we hypothesized that the diffusion of TEMED from the bulk gel would undergo a redox reaction with APS in solution to generate free radicals at the gel surface as diagrammed in Figure . This surface‐mediated initiation would in turn constrain the nanogel crosslinking to occur immediately around the gel.…”

Facile One‐Step Micropatterning Using Photodegradable Gelatin Hydrogels for Improved Cardiomyocyte Organization and Alignment

“…[12] Recently photodegradable hydrogels were used as a platform to evaluate the mechanical dosing effect on human mesenchymal stem cell (hMSC) behavior, [13] and as a means to trigger the release of bioactive molecules or encapsulated compounds from the gel. [14] …”