Injectable polyphosphazene/gelatin hybrid hydrogel for biomedical applications

Injectable hydrogels are promising candidates for tissue engineering because of their easy and minimally invasive manipulation, and their ability to mimic the features of the extracellular matrix. Hydrogels developed from water-soluble polyphosphazenes are attractive due to the unique flexibility of phosphazene chemistry. In this study, a photocrosslinkable water-soluble polyphosphazene was synthesized by introducing citronellol with a double bond and hydrophilic diethylene glycol monomethyl ether as cosubstituted side groups; the corresponding hydrogel was obtained by exposing the polyphosphazene aqueous solution to ultraviolet light. Benefiting from the elastic polyphosphazene backbone and the flexible ether side group, the hydrogel exhibited excellent injectability and mechanical stability. To improve the hydrogel's mechanical and biological properties targeting biomedical applications, photocrosslinkable methacrylate gelatin and inorganic calcium phosphate were incorporated. The resulting composite hydrogels were able to retain excellent injectability, deformability and fatigue resistance, and were evaluated to be excellent for biomedical applications via in vitro cell culture and in vivo subcutaneous implantation. (C) 2018 Elsevier Ltd. All rights reserved.