Micellized α‑Cyclodextrin-Based Supramolecular Hydrogel Exhibiting pH-Responsive Sustained Release and Corresponding Oscillatory Shear Behavior Analysis

The fabrication of supramolecular hydrogels from micellized PLLA/DMAEMA/PEGMA polymers with α-CD has been explored to design injectable gel formulations for sustained drug release. The tricomponent hydrogels (5% w/v)/α-CD (10% w/v) were able to sustain protein (BSA and lysozyme) release for 60–120 h at different pH conditions (pH 3, 7 and 10). In-depth rheological analysis highlighted the role of pH in tuning hydrogel behavior upon shear at microscopic level affecting protein release profiles. Protein release involved complex interactions within the network (isoelectric point and diffusion coefficient of the protein, p<i>K</i>_a of DMAEMA, and pore size of the hydrogel). Lissajous–Bowditch curves explained the microstructural response to increasing strain which weakened the supramolecular association and collapsed the formation of the porous hydrogel. Power Law was adopted to represent both transport mechanism and drug release phenomena. The release mechanism resulted from a combination of erosion- and diffusion-controlled release (non-Fickian and super case II)

Engineering Poly(lactide)–Lignin Nanofibers with Antioxidant Activity for Biomedical Application

Biodegradable poly­(lactic acid) (PLA)–lignin composites are considered to be promising renewable plastic materials toward a sustainable world. The addition of lignin to PLA may assist to combat the oxidative stress induced by PLA as biomaterials. In this study, PLA–lignin copolymers with various contents of alkylated lignin (10–50%) were synthesized by ring-opening polymerization. The molecular weight of such copolymers ranged from 28 to 75 kDa, while the PLA chain length varied from 5 to 38. These PLA–lignin copolymers were further blended with poly­(l-lactide) (PLLA) and fabricated into nanofibrous composites by electrospinning. The PLLA/PLA–lignin nanofibers displayed uniform and bead-free nanostructures with fiber diameter of 350–500 nm, indicating the miscibility of PLLA and lignin copolymers in nanoscale. Unlike bulk materials, incorporation of PLA–lignin copolymers did not enhance the mechanical properties of the nanofibrous composites. Antioxidant assay showed that the lignin copolymers and PLLA/PLA–lignin nanofibers rendered excellent radical scavenging capacity for over 72 h. Moreover, three different types of cells (PC12, human dermal fibroblasts, and human mesenchymal stem cells) were cultured on the electrospun nanofibers to evaluate their biocompatibility. Lignin-containing nanofibers exhibited higher cell proliferation compared to neat PLLA nanofibers. PLLA/PLA-Lig20 nanofibers displayed the best biocompatibility as it achieved a balance between the antioxidant activities and the cytotoxicity. With excellent antioxidant activities and good biocompatibility, the PLLA/PLA–lignin electrospun nanofibers hold great potential to be used as biomedical materials for protecting cells from oxidative stress conditions

Cationic Lignin-Based Hyperbranched Polymers to Circumvent Drug Resistance in Pseudomonas Keratitis

The rise of antimicrobial-resistant bacteria strains has been a global public health concern due to their ability to cause increased patient morbidity and a greater burden on the healthcare system. As one of the potential solutions to overcome such bacterial infections, hyperbranched copolymers with cationic charges were developed. These copolymers were assessed for their antimicrobial efficacy and their bactericidal mechanisms. They were found to be potent against mobile colistin-resistant 1 strains, which was significant as colistin is known to be the last-resort antibiotic against Gram-negative bacteria. Furthermore, there was no sign of mutational resistance developed by E. Coli ATCC 25922 and MCR 1+ E. Coli against the copolymer even up to 20 passages. The ability to evade inducing resistance would provide invaluable insights for future antibiotic development. Our studies suggest that the bactericidal efficacy comes from the ability to target the outer membrane efficaciously. In vivo study using a Pseudomonas keratitis model showed that the copolymer was compatible with the eye and further supported that the copolymer treatment was effective for complete bacteria elimination

Transforming Polyethylene into Water-Soluble Antifungal Polymers

Petroleum-based polyolefin plastics currently possess highly unsustainable cradle-to-grave linear life cycles. Using them as a resource for the production of new functional polymers not only decreases the generated waste but also reduces our reliance on petroleum-derived monomers for traditional bottom-up synthesis of new polymeric materials. Herein, we demonstrate that polyethylene (PE), the most abundant plastic in production today, can be transformed into low-molecular-weight water-soluble antimicrobial polymers. In this proof-of-concept study, organocatalytic C–H aerobic oxidation of PE was first achieved to append reactive oxygenated and chloro functional groups onto the inert polymer chains, followed by further chemical modifications to form water-soluble amphiphilic polymers. Our first-generation polymer showed antimicrobial efficacy against opportunistic pathogenic Candida fungi without appreciable hemolysis even at high concentrations (2 mg/mL). The PE-derived antimicrobial polymer may find applications to combat the spread of fungal pathogens

Versatile and Extendable Boronate-Based Tunable Hydrogel Networks for Patterning Applications

Hydrogel patterning is an emerging area of interest and a valuable tool for studying cellular interactions. However, patterning of hydrogels is normally performed with photo-cross-linkable moieties, severely limiting the choice of materials that can be used. Dynamic covalent cross-linked systems show highly desirable properties as they can show covalent and noncovalent characteristics in response to different environmental conditions, therefore allowing for a potential switch in hydrogel properties. To expand the repertoire of materials suitable for hydrogel patterning, we report versatile pregel polymer networks comprising poly­(vinyl alcohol) cross-linked with PEG-diboronates cross-linkers at low ratios. These pregel networks are highly processable and extendable: they can be pulled up into thin strands and used for patterning of thin lines and exhibit both shear thinning and shear thickening properties. The pregels can be easily converted into a hydrogel state by pH adjustment and show clear antibacterial effects. Valuably, the pregels can be integrated into a 3D printing setup to print programmable lines and shapes and subsequently converted into patterned hydrogels. This study demonstrates that dynamic boronate networks can be tuned to exhibit different states and could offer alternate strategies and possibilities for hydrogel patterning applications