An Injectable Hydrogel Prepared Using a PEG/Vitamin E Copolymer Facilitating Aqueous-Driven Gelation

Hydrogels have been widely explored for biomedical applications, with injectable hydrogels being of particular interest for their ability to precisely deliver drugs and cells to targets. Although these hydrogels have demonstrated satisfactory properties in many cases, challenges still remain for commercialization. In this paper, we describe a simple injectable hydrogel based on poly­(ethylene glycol) (PEG) and a vitamin E (Ve) methacrylate copolymer prepared via simple free radical polymerization and delivered in a solution of low molecular weight PEG and Ve as the solvent instead of water. The hydrogel formed immediately in an aqueous environment with a controllable gelation time. The driving force for gelation is attributed to the self-assembly of hydrophobic Ve residues upon exposure to water to form a physically cross-linked polymer network via polymer chain rearrangement and subsequent phase separation, a spontaneous process with water uptake. The hydrogels can be customized to give the desired water content, mechanical strength, and drug release kinetics simply by formulating the PEGMA-<i>co</i>-Ve polymer with an appropriate solvent mixture or by varying the molecular weight of the polymer. The hydrogels exhibited no significant cytotoxicity <i>in vitro</i> using fibroblasts and good tissue compatibility in the eye and when injected subcutaneously. These polymers thus have the potential to be used in a variety of applications where injection of a drug or cell containing depot would be desirable

Injectable and Degradable Poly(Oligoethylene glycol methacrylate) Hydrogels with Tunable Charge Densities as Adhesive Peptide-Free Cell Scaffolds

Injectable, dual-responsive, and degradable poly­(oligo ethylene glycol methacrylate) (POEGMA) hydrogels are demonstrated to offer potential for cell delivery. Charged groups were incorporated into hydrazide and aldehyde-functionalized thermoresponsive POEGMA gel precursor polymers via the copolymerization of N,<i>N</i>′-dimethylaminoethyl methacrylate (DMAEMA) or acrylic acid (AA) to create dual-temperature/pH-responsive in situ gelling hydrogels that can be injected via narrow gauge needles. The incorporation of charge significantly broadens the swelling, degradation, and rheological profiles achievable with injectable POEGMA hydrogels without significantly increasing nonspecific protein adsorption or chronic inflammatory responses following in vivo subcutaneous injection. However, significantly different cell responses are observed upon charge incorporation, with charged gels significantly improving 3T3 mouse fibroblast cell adhesion in 2D and successfully delivering viable and proliferating ARPE-19 human retinal epithelial cells via an “all-synthetic” matrix that does not require the incorporation of cell-adhesive peptides