Enzymatically cross-linked hyaluronic acid/graphene oxide nanocomposite hydrogel with pH-responsive release

<div><p>Hyaluronic acid (HA) is made up of repeating disaccharide units (<i>β</i>-1,4-d-glucuronic acid and <i>β</i>-1,3-N-acetyl-d-glucosamine) and is a major constituent of the extracellular matrix. HA and its derivatives which possess excellent biocompatibility and physiochemical properties have been studied in drug delivery and tissue engineering applications. Tyramine-based HA hydrogel with good compatibility to cell and tissue has been reported recently. However, inferior mechanical property may limit the biomedical application of the HA hydrogel. In this study, HA/graphene oxide (GO) nanocomposite (NC) hydrogel was prepared through a horseradish peroxidase catalyzed <i>in situ</i> cross-linking process. As compared with pure HA hydrogels, incorporation of GO to the HA matrix could significantly enhance the mechanical properties (storage moduli 1800 Pa) of the hydrogel and prolong the release of rhodamine B (RB) as the model drug from the hydrogel (33 h) as well. In addition, due to the multiple interactions between GO and RB, the NC hydrogels showed excellent pH-responsive release behavior. The release of RB from the NC hydrogel was prolonged at low pH (pH 4.0) in the presence of GO, which could be attributed to the enhanced interactions between GO and HA as well as with RB. <i>In situ</i> three-dimensional encapsulation of mouse embryonic fibroblasts (BALB 3T3 cells) in the NC hydrogels and cytotoxicity results indicated the cytocompatibility of both the enzymatic cross-linking process and HA/GO NC hydrogels (cell viability 90.6 ± 4.25%). The enzymatically catalyzed fabrication of NC hydrogels proved to be an easy and mild approach, and had great potential in the construction of both tissue engineering scaffolds and stimuli-responsive drug release matrices.</p></div

Poly(γ-glutamic acid) modulates the properties of poly(ethylene glycol) hydrogel for biomedical applications

<p>In this paper, a series of copolymer hydrogels were fabricated from methacrylated poly(γ-glutamic acid) (mPGA) and poly(ethylene glycol) diacrylate (PEGDA). The effect of ionic strength and pH on the swelling behavior and mechanical properties of these hydrogels were studied in detail. Release of Rhodamine B as a model drug from the hydrogel was evaluated under varied pH. <i>In vitro</i> photoencapsulation of bovine cartilage chondrocytes was performed to assess the cytotoxicity of this copolymer hydrogel. The results revealed that the copolymer hydrogel is ionic- and pH-sensitive, and does not exhibit acute cytotoxicity; this copolymer hydrogel may have promising application as matrix for controlled drug release and scaffolding material in tissue engineering.</p