Silicification of Genipin-Cross-Linked Polypeptide Hydrogels Toward Biohybrid Materials and Mesoporous Oxides

A simple and versatile approach is proposed to use cross-linked polypeptide hydrogels as templates for silica mineralization, allowing the synthesis of polypeptide–silica hybrid hydrogels and mesoporous silica (meso-SiO₂) by subsequent calcination. The experimental data revealed that the cross-linked polypeptide hydrogels comprised of interconnected, membranous network served as templates for the high-fidelity transcription of silica replicas spanning from nanoscale to microscale, resulting in hybrid network comprised of interpenetrated polypeptide nanodomains and silica. The mechanical properties of these as-prepared polypeptide–silica hybrid hydrogels were found to vary with polypeptide chain length and composition. The synergy between cross-link, hydrophobic interaction, and silica deposition can lead to the enhancement of their mechanical properties. The polypeptide–silica hybrid hydrogel with polypeptide and silica content as low as 1.1 wt % can achieve 114 kN/m² of compressive strength. By removing the polypeptide nanodomains, mesoporous silicas with average pore sizes ranged between 2 nm and 6 nm can be obtained, depending on polypeptide chain length and composition. The polypeptide–silica hybrid hydrogels demonstrated good cell compatibility and can support cell attachment/proliferation. With the versatility of polymer chemistry and feasibility of amine-catalyzed sol–gel chemistry, the present method is facile for the synthesis of green nanocomposites and biomaterials

Poly(l‑glutamic acid)-Decorated Hybrid Colloidal Particles from Complex Particle-Templated Silica Mineralization

We report the synthesis of polyelectrolyte complex (PEC) particles by mixing the negatively and positively charged polyelectrolytes, poly­(l-glutamic acid) (PGA) and poly­(2-(<i>N,N</i>-diethylamino) ethylmethacrylate) (PDEAEMA), and the use of negatively charged PEC particles as colloidal templates for silica mineralization under ambient conditions. The structure and property of PEC particles, as well as polypeptide chain conformation, were found to depend on the mixing weight percentage, polymer molecular weight, and solution condition. The negatively charged PEC micelles can be deposited with silica without loss colloid stability, leading to PGA-decorated hybrid particles. These hybrid particles were negatively charged at neutral and basic condition and become positively charged, accompanying the conformational changes of the grafted PGA, upon decreasing pH below isoelectric points due to the protonation/deprotonation of PGA and PDEAEMA. Functional nanoparticles such as gold NPs could be incorporated using polypeptides as the mediating agents. These hybrid particles loaded with drug exhibited noticeable pH-responsive behavior with accelerated release at acidic condition, demonstrating the potential for use as pH-responsive delivery vehicles. This type of polypeptide-decorated hybrid particles represents an interesting class of organic–inorganic hybrids in which the functional properties of polypeptides such as biocompatibility, stimuli responsiveness, and directed growth of metal nanoparticles can be incorporated

GSH/pH-Sensitive Poly(glycerol sebacate dithiodiglycolate) Nanoparticle as a Ferroptotic Inducer through Cooperation with Fe³⁺

Ferroptosis is an iron-dependent, non-apoptotic cell death induced by an overload of iron initiated through Fenton and Haber–Weiss reactions. These two reactions lead to lethal levels of intracellular reactive oxygen species (ROS) and lipid peroxidation. In contrast, glutathione (GSH) and glutathione peroxidase 4 (GPX4) suppress ferroptosis by inhibiting lipid peroxidation. Herein, the ferric ion (Fe3+) carriers, poly(glycerol sebacate dithiodiglycolate) nanoparticles (PGSDTG NPs), were prepared via nanoprecipitation. The GSH/pH-dual sensitive Fe3+/PGSDTG NPs would disintegrate via the cleavage of disulfide and ester bonds in the presence of GSH and acidic conditions. The cleaved polymer segments along with released Fe3+ rendered cancer cells showing ferroptosis characteristics including ROS production, transferrin receptor 1 (TfR1) expression, and iron accumulation after treatment with Fe3+/PGSDTG NPs. The PGSDTG NPs played an important role in ferroptosis by triggering the oxidation of intracellular GSH and reducing the GPX4 expression. An in vivo experiment also showed that Caenorhabditis elegans (C. elegans) exhibited a shortened lifespan after treatment with NPs. These results indicated that the PGSDTG NPs were potential GSH/pH-sensitive metal ion carriers for anticancer treatment by inducing ferroptosis

Alkyl-poly(l‑threonine)/Cyclodextrin Supramolecular Hydrogels with Different Molecular Assemblies and Gel Properties

We report alkyl-poly­(l-threonine)/cyclodextrin (alkyl-PLT/CD) supramolecular hydrogels with different molecular assemblies. Their properties are determined by the interplay between host–guest chemistry and hydrogen-bonding interactions. The gelation process was mainly dictated by the formation of alkyl chain/CD inclusion complex and PLT chain conformation. The dodecyl-PLT₂₀/α-CD hydrogel exhibited laminar packing due to the sheet-to-coil conformational change upon forming inclusion complex. The hexadecyl-PLT₂₀/β-CD hydrogel exhibited ribbon-like assemblies instead, because the peptide adopted mainly sheet conformation. The gel-to-sol transition occurred upon increasing temperature because of the decrease in hydrogen-bonding interactions and partly conformational change

Broadband Antireflection Coatings Based on Low Surface Energy/Refractive Index Silica/Fluorinated Polymer Nanocomposites

We demonstrated the fabrication of broadband antireflection coatings (ARCs) comprising low-surface energy/refractive index (RI) silica/polymer nanocomposites by silica mineralization of layer-by-layer (LbL) assembled poly­(2-(dimethylamino)­ethyl methacrylate)-<i>block</i>-poly­(2,2,3,3-tetrafluoropropyl methacrylate)/poly­(L-glutamic acid) (PDMA-<i>b</i>-PTFP/PGA) multilayer films without any post-treatments. The introduction of the fluorinated polymer (PTFP segments) effectively lowered not only the RI of the as-fabricated coatings but also the surface energy of the constituted pore surface, which rendered the ARCs with high transmittance and durable AR performance by preventing the absorption and capillary condensation of moisture at ambient conditions. Moreover, the formation of nanosized PDMA-<i>b</i>-PTFP vesicles can render the ARCs exhibiting small pore size, which can improve their light transmittance. The coated substrate with an average transmittance over 97.0% was obtained at the visible wavelength region. The combination of LbL assembly and silica mineralization can warrant the preparation of conformal, intact coatings with good mechanical properties. This study demonstrated a novel concept on introducing low surface energy/RI materials for fabricating broadband, moisture-repellent ARCs

Alkyl Chain-Grafted Poly(l‑lysine) Vesicles with Tunable Molecular Assembly and Membrane Permeability

The preparation of alkyl chain-grafted poly­(l-lysine) (PLL) vesicles with tunable molecular assembly in aqueous solution and the evaluation of their membrane permeability by drug release experiments have been investigated. Upon grafting long alkyl chains, polypeptides confined in the assembled nanostructures adopted ordered conformations such as α-helices or β-sheets/turns, leading to the dense packing of membranes and, consequently, the decreases in vesicular size and membrane permeability. The vesicles can also be cross-linked by genipin to form stable structures with tunable membrane permeability. Additionally, these vesicles exhibited noticeable pH-sensitive behavior, depending on the grafted alkyl chain and cross-linking