Antioxidant Properties of 2-Hydroxyethyl Methacrylate-Based Copolymers with Incorporated Sterically Hindered Amine

Straightforward synthesis of complex polymeric architectures with ultra-high chain density

Synthesis of complex polymeric architectures (CPAs) via reversible-deactivation radical polymerization (RDRP) currently relies on the rather inefficient attachment of monofunctional initiation/transfer sites onto CPA precursors. This drawback seriously limits the overall functionality of the resulting (macro)initiators and, consequently, also the total number of installable polymeric chains, which represents a significant bottleneck in the design of new polymeric materials. Here, we show that the (macro)initiator functionality can be substantially amplified by using trichloroacetyl isocyanate as a highly efficient vehicle for the rapid and clean introduction of trichloroacetyl groups (TAGs) into diverse precursors. Through extensive screening of polymerization conditions and comprehensive NMR and triple-detection SEC studies, we demonstrate that TAGs function as universal trifunctional initiators of copper-mediated RDRP of different monomer classes, affording low-dispersity polymers in a wide molecular weight range. We thus unlock access to a whole new group of ultra-high chain density CPAs previously inaccessible via simple RDRP protocols. We highlight new opportunities in CPA synthesis through numerous examples, including the de novo one-pot synthesis of a novel "star-on-star" CPA, the preparation of β-cyclodextrin-based 45-arm star polymers, and facile grafting from otherwise problematic cellulose substrates both in solution and from surface, obtaining effortlessly ultra-dense, ultra-high-molecular weight bottle-brush copolymers and thick spatially-controlled polymeric coatings, respectively.

Nitroxide-Containing Amphiphilic Random Terpolymers for Marine Antifouling and Fouling-Release Coatings

Two types of amphiphilic random terpolymers, poly(ethylene glycol methyl ether methacrylate)-ran-poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate)-ran-poly(polydimethyl siloxane methacrylate) (PEGMEMA-r-PTMA-r-PDMSMA), were synthesized and evaluated for antifouling (AF) and fouling-release (FR) properties using diverse marine fouling organisms. In the first stage of production, the two respective precursor amine terpolymers containing (2,2,6,6-tetramethyl-4-piperidyl methacrylate) units (PEGMEMA-r-PTMPM-r-PDMSMA) were synthesized by atom transfer radical polymerization using various comonomer ratios and two initiators: alkyl halide and fluoroalkyl halide. In the second stage, these were selectively oxidized to introduce nitroxide radical functionalities. Finally, the terpolymers were incorporated into a PDMS host matrix to create coatings. AF and FR properties were examined using the alga Ulva linza, the barnacle Balanus improvisus, and the tubeworm Ficopomatus enigmaticus. The effects of comonomer ratios on surface properties and fouling assay results for each set of coatings are discussed in detail. There were marked differences in the effectiveness of these systems against the different fouling organisms. The terpolymers had distinct advantages over monopolymeric systems across the different organisms, and the nonfluorinated PEG and nitroxide combination was identified as the most effective formulation against B. improvisus and F. enigmaticus.

SHARP hydrogel for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a relapsing and remitting inflammatory disease affecting millions of people worldwide. The active phase of IBD is characterized by excessive formation of reactive oxygen species (ROS) in the intestinal mucosa, which further accelerates the inflammatory process. A feasible strategy for the IBD treatment is thus breaking the oxidation-inflammation vicious circle by scavenging excessive ROS with the use of a suitable antioxidant. Herein, we have developed a novel hydrogel system for oral administration utilizing sterically hindered amine-based redox polymer (SHARP) incorporating covalently bound antioxidant SHA groups. SHARP was prepared via free-radical polymerization by covalent crosslinking of 2-hydroxyethyl methacrylate (HEMA), poly(ethylene oxide) methyl ether methacrylate (PEGMA) and a SHA-based monomer, N-(2,2,6,6-tetramethyl-piperidin-4-yl)-methacrylamide. The SHARP hydrogel was resistant to hydrolysis and swelled considerably (∼90% water content) under the simulated gastrointestinal tract (GIT) conditions, and exhibited concentration-dependent antioxidant properties in vitro against different ROS. Further, the SHARP hydrogel was found to be non-genotoxic, non-cytotoxic, non-irritating, and non-absorbable from the gastrointestinal tract. Most importantly, SHARP hydrogel exhibited a statistically significant, dose-dependent therapeutic effect in the mice model of dextran sodium sulfate (DSS)-induced acute colitis. Altogether, the obtained results suggest that the SHARP hydrogel strategy holds a great promise with respect to IBD treatment.

Development of Poly(2-Methacryloyloxyethyl Phosphorylcholine)-Functionalized Hydrogels for Reducing Protein and Bacterial Adsorption

A series of hydrogels with intrinsic antifouling properties was prepared via surface-functionalization of poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based hydrogels with the biomembrane-mimicking zwitterionic polymer, poly(2-methacryloyloxyethyl phosphorylcholine) [p(MPC)]. The p(MPC)-modified hydrogels have enhanced surface wettability, high water content retention (61.0%-68.3%), and good transmittance (>90%). Notably, the presence of zwitterionic MPC moieties at the hydrogel surfaces lowered the adsorption of proteins such as lysozyme and bovine serum albumin (BSA) by 73%-74% and 59%-66%, respectively, and reduced bacterial adsorption by approximately 10%-73% relative to the unmodified control. The anti-biofouling properties of the p(MPC)-functionalized hydrogels are largely attributed to the dense hydration layer formed at the hydrogel surfaces by the zwitterionic moieties. Overall, the results demonstrate that biocompatible and antifouling hydrogels based on p(HEMA)-p(MPC) structures have promising potential for application in biomedical materials.

Carbohydrate-modified magnetic nanoparticles for radical scavenging

Maghemite (gamma-Fe2O3) nanoparticles, 12 nm in size, were prepared by co-precipitation of Fe(II) and Fe(III) chlorides with ammonium hydroxide and oxidation with hydrogen peroxide. To achieve stability and biocompatibility, obtained particles were coated with silica, to which glucose and ascorbic acid were bound by different mechanisms. The composite particles were thoroughly characterized by transmission electron microscopy, dynamic light scattering, elemental analysis, and FT-Raman and fluorescence spectroscopy to determine composition, morphology, size and its distribution, zeta-potential, and scavenging of peroxyl and hydroxyl radicals. As the particles showed promising antioxidative properties, they may have a possible application as a stable magnetically controlled scavenger of reactive oxygen species.