Bioenhanced Rapid Redox Initiation for RAFT Polymerization in the Air.

A well-controlled bioenhanced reversible addition-fragmentation chain transfer (RAFT) in the presence of air is carried out by using glucose oxidase (GOx), glucose, ascorbic acid (Asc acid), and ppm level of hemin. The catalytic concentration of hemin is employed to enhance hydrogen peroxide (H2 O2 )/Asc acid redox initiation, achieving rapid RAFT polymerization. Narrow molecular weight distributions and high monomer conversion (Ð as low as 1.09 at >95% conversion) are achieved within tens of minutes. Several kinds of monomers are used to verify the universal implication of the presented method. The influences of the pH and feed ratio of each component on the polymerization rate are assessed. Besides, a polymerization rate regulation is realized by managing Asc acid addition. This work significantly increases the rate of redox-initiated GOx-deoxygen RAFT polymerization by using simple and green reactants, facilitating the application of RAFT polymerization in areas such as biomedical applications.

Oxygen-Tolerant RAFT Polymerization Catalyzed by a Recyclable Biomimetic Mineralization Enhanced Biological Cascade System.

An enzyme cascade system including glucose oxidase (GOx) and iron porphyrin (DhHP-6) is encapsulated in a metal-organic framework called zeolitic imidazolate framework-8 (ZIF-8) through one-step facile synthesis. The composite (GOx&DhHP-6@ZIF-8) is then used to initiate oxygen-tolerant reversible addition-fragmentation chain-transfer polymerization for different methacrylate monomers, such as 2-diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, and poly(ethylene glycol) methyl ether methacrylate (Mn = 500 g mol-1 ). The composite shows the robustness toward solvent and temperatures, all polymerizations using above monomers and catalyzing by GOx&DhHP-6@ZIF-8 exhibits high monomer conversion (>85%) and narrow molar mass dispersity (<1.3). Besides, acrylic and acrylamide monomers such as 2-hydroxyethyl acrylate and N,N-dimethylacrylamide are also carried to demonstrate the broad applicability. Proton nuclear magnetic resonance characterization and chain extension experiments confirm the retaining end groups of the resultant polymers, which is a significant feature of living polymerization. More importantly, the process of recycling the composite through a centrifuge is simplistic, and the composite still maintains similar activity compared to the original composites after five times. This low-cost and easily separated composite catalyst represents a versatile strategy to synthesize well-defined functional polymers suitable for industrial-scale production.

Glucose oxidase and Fe3O4/TiO2/Ag3PO4 co-embedded biomimetic mineralization hydrogels as controllable ROS generators for accelerating diabetic wound healing.

The hyperglycemic environment and the presence of bacterial infections delay the healing of diabetic wounds. Herein, glucose oxidase (GOx) and Fe3O4/TiO2/Ag3PO4 were embedded in a polyacrylic acid-calcium phosphate (PAA-CaPs@Nps@GOx) hydrogel through an in situ biomimetic mineralization approach. The GOx encapsulation efficiency was 96.75% and exhibited exceptional enzyme activity stability. Moreover, the co-immobilization of GOx and Fe3O4/TiO2/Ag3PO4 nanoparticles generated a simple and multifunctional antibacterial platform with the advantages of decreasing blood glucose concentration and efficiently producing reactive oxygen species (ROS). In addition, the degradation rate of the hydrogel was controlled by regulating the concentration of phosphate thus controlling the release of Fe3O4/TiO2/Ag3PO4 and GOx. As a result, both the potential toxicity and oxidative stress associated with the antimicrobial biomaterial can be controlled within the body therefore potentially preventing detriment. In vivo results indicated that the PAA-CaPs@Nps@GOx hydrogel effectively promoted diabetic wound healing and showed great potential for clinical applications of chronic wound management.

A conductive polyacrylamide hydrogel enabled by dispersion-enhanced MXene@chitosan assembly for highly stretchable and sensitive wearable skin.

MXene is recognized as an ideal material for sensitive wearable strain sensors because of its unique advantages of conductivity, hydrophilicity and mechanical properties. However, conventional hydrogel sensors utilizing MXene as a conductive material inevitably encounter the excessive accumulation of MXene nanosheets during the process of synthesis, which limits the electron transmission, reduces the conductivity, and concurrently weakens the mechanical capability and sensitivity of sensors. Herein, we construct a dispersion-enhanced MXene hydrogel (DEMH) through a chitosan-induced self-assembly strategy for the first time. Charge transfer is carried out through the flow of a material or a collection of material microstructures, and thus the highly interconnected 3D MXene@Chitosan network provides fast transport channels for electrons, and the DEMH exhibits excellent conductivity and sensibility simultaneously. Besides, the electrostatic self-assembly between MXene and chitosan, and the supramolecular interactions between MXene, chitosan and polyacrylamide chain segment result in excellent mechanical strength (of up to 1900%) and flexibility of DEMH. Furthermore, the introduction of chitosan which possesses a high density of positively charged groups and MXene with semiconducting properties also endows sensor versatility, such as self-adhesion properties and antibacterial activity. This work develops a simple and cut-price strategy for combining MXene unaggregated into a hydrogel as a sensor with high conductivity, sensibility and flexibility. A simple and inexpensive strategy for avoiding self-stacking of two-dimensional conductive materials is proposed, which paves the way for a broad range of applications in electronic skin, human motion detection and intelligent devices.