Bisepoxide-Jeffamine microgel synthesis and application toward heterogeneous surface morphology for differential neuronal/non-neuronal cell responses in vitro

Preparation and characterization of polysaccharide-based conductive hydrogels for nerve repair

Peripheral nerve injury is a serious medical condition, but the limited availability of autologous grafts often delays timely treatment for many patients. The implantation of functional hydrogels with good biocompatibility provides an effective solution to this challenge. In this study, a novel chitosan derivative, choline functionalized catechol carboxymethyl chitosan (CF-Catechol-CMCS), was synthesized by modifying carboxymethyl chitosan (CMCS) with choline functionalized (CF) molecule and catechol. CF-Catechol-CMCS, sodium alginate (SA), and pyrrole monomer (Py) were then combined, crosslinked with Fe3+ and Ca2+, and polymerized in situ to form polypyrrole (PPy), resulting in the CF-Catechol-CMCS/SA/PPy hydrogel. This hydrogel exhibits excellent thermal stability, with a maximum thermal degradation temperature of 580 °C. By adjusting the ratio of PPy to CF-Catechol-CMCS/SA in the hydrogel, its degradation properties, swelling behavior, mechanical properties, and electrical conductivity can be fine-tuned. Specifically, when the mass ratio of PPy to CF-Catechol-CMCS/SA is 8:10, the hydrogel achieves optimal conductivity within a safe range (1.82 × 10-3 S·cm-1). By controlling the mass ratio of CF-Catechol-CMCS to SA in the hydrogel, the acetylcholine concentration can be regulated. When the CF-Catechol-CMCS:SA ratio is 2:1, the measured Sciatic Function Index (SFI) value is -34.54, indicating that the CF-Catechol-CMCS/SA/PPy hydrogel has excellent nerve repair potential.

Leveraging Microgels Prepared from Poly(ethylene glycol) Bisepoxide and Polyetheramine for Versatile Surface Structuring of Agarose Hydrogels

We demonstrate a macromer-type bisepoxide, poly(ethylene glycol) diglycidyl ether, polymerizing readily with a trifunctional polyetheramine Jeffamine T-403 in water to facilitate the development of a series of microgels abbreviated as PMG. Simply by varying the concentration of the as-prepared thermoresponsive intermediate prepolymer from 1 to 2 and 4%, hydrodynamic sizes of the resulting P1MG, P2MG, and P4MG are easily tuned in the submicrometer to micrometer range shown by the dynamic light scattering results. Besides size difference, these microgels also deform differently, where the drying-induced deformation effect is most severe for P1MG and least prominent for P4MG. Simple evaporative deposition of PMG into multilayer packing provides versatile and green options for microgel-mediated surface structuring of agarose hydrogels. Specifically, deformabile P1MG- and P2MG-derived coatings render agarose gel microwrinkle textures by buckling against swelling-induced surface instability. Conversely, stiffer P4MG microgels lead to a patchy patterned hierarchical coating on agarose, similar to the cracking effect in drying colloidal films. The straightforward microgel-on-macrogel strategy allows integration of both wrinkle and patchy patterns to generate Janus-type agarose gels, just by rationally arranging the coating sequence. Diversifying topographic features attainable through microgel-based coatings on hydrogels could potentially make the sustainable and biocompatible material of agarose a more compelling choice for bioapplications. Brief demonstrations of the broad applicability of P1MG toward wrinkling of proteinaceous and synthetic hydrogels further highlight promising prospects of the PMG microgel-on-macrogel functionalization strategy.

Cytophilic Agarose-Epoxide-Amine Cryogels Engineered with Granulated Microstructures

Inherent cytophobicity of agarose limits its direct use for the growth of anchorage-dependent cells. Here, we report a simple strategy allowing the development of agarose-based hydrogels entailed with both cytophilicity and microstructured morphology. Through the reaction of water-soluble 1,4-butanediol diglycidyl ether (BDDE) with trifunctional polyetheramine Jeffamine T403 in agarose solution followed by cryogelation of the mixtures, a series of macroporous agarose-epoxide-amine cryogels were prepared readily. Results from fluorescent labeling and energy-dispersive X-ray elemental mapping showed the formation of granulated microstructures in the cryogels. Such features closely correlated to the phase separation of BDDE-T403 polymers within the agarose matrix. Cytophilicity of the microstructured cryogels due to the integrated amine moieties was demonstrated through the adhesion of fibroblasts. Functional enrichment of the cryogels was further highlighted by leveraging the granulates as micro-reservoirs for polyphenol proanthocyanidin to enable antioxidation and protection of fibroblasts from H₂O₂-induced cytotoxic effect in vitro.