Near-IR-induced dissociation of thermally-sensitive star polymers.

Responsive systems sensitive to near-infrared (NIR) light are promising for triggered release due to efficient deep tissue penetration of NIR irradiation relative to higher energy sources (e.g., UV), allowing for spatiotemporal control over triggering events with minimal potential for tissue damage. Herein, we report star polymers containing thermally-labile azo linkages that dissociate during conventional heating or during localized heating via the photothermal effect upon NIR irradiation. Controlled release during conventional heating was investigated for the star polymers loaded with a model dye, with negligible release being observed at 25 °C and >80% release at 90 °C. Star polymers co-loaded with NIR-responsive indocyanine green showed rapid dye release upon NIR irradiation (λ ≥ 715 nm) due to the photothermally-induced degradation of azo linkages within the cores of the star polymers. This approach provides access to a new class of delivery and release systems that can be triggered by noninvasive external stimulation.

Side-chain amino acid based cationic polymer induced actin polymerization.

Actin filament dynamics is important for proper cellular functions and is controlled by hundreds of actin binding proteins inside the cells. There are several natural and synthetic compounds that are able to bind actin and alter the actin filament dynamics. Since the actin dynamics changes due to nonspecific electrostatic interactions between negatively charged actin and positively charged proteins, and natural or synthetic compounds, herein we report the synthesis of poly(tert-butyl carbamate (Boc)-l-alanine methacryloyloxyethyl ester) (P(Boc-Ala-HEMA)) homopolymer in a controlled fashion by the reversible addition-fragmentation chain transfer (RAFT) polymerization. Subsequent deprotection of the Boc groups in the homopolymer under acidic conditions resulted in a positively charged polymer with primary amine moieties at the side chains. This cationic polymer (P(NH3 +-Ala-HEMA)), is able to nucleate actin in vitro. The cationic polymer and corresponding partially fluorescence tagged polymer are able to nucleate actin filament in vivo. These polymers are nontoxic to the cultured cells and also stabilize the filamentous actin in vitro.

Water soluble polyperoxides from 2-(2-methoxyethoxy)ethyl methacrylate: influence of molecular oxygen on thermoresponsive properties and thermal degradation.

The 2-(2-methoxyethoxy)ethyl methacrylate and molecular oxygen react at 50 °C under high pressure in the presence of a radical initiator to give water soluble, thermoresponsive poly(2-(2-methoxyethoxy)ethyl methacrylate) peroxide (PMEO(2)MAP), which degrades highly exothermically. The polymer structure has been confirmed by spectroscopy, elemental analysis, calorimetry and mass spectrometry.

Biodegradation and in vitro biocompatibility of polyperoxides: alternating co-polymers of vinyl monomers and molecular oxygen.

Vinyl polyperoxides, alternating co-polymers of vinyl monomers and molecular oxygen, are a small but important class of polymers with unique properties, such as highly exothermic degradation in contrast to common polymers, which generally show endothermic degradation. Enzymatic degradation and in vitro biocompatibility have been studied for the vinyl polyperoxides polystyrene peroxide (PSP), poly(α- methylstyrene) peroxide (PAMSP) and poly(methyl methacrylate) peroxide (PMMAP). Enzymatic degradation of polyperoxides has been carried out using horseradish peroxidase enzyme at room temperature. The rate of the enzyme-catalyzed degradation depends on enzyme concentrations. The cytotoxicity study shows that the polyperoxide has good biocompatibility with no obvious inhibition effect on HeLa cell growth up to 120 µg/ml PSP and PAMSP and up to 60 µg/ml PMMAP. Fluorescence microscopic studies established the cellular viability of HeLa cells in the presence of polyperoxides.