Injectable and cross-linkable polyphosphazene hydrogels for space-filling scaffolds

Low mechanical strength is a major disadvantage of injectable hydrogels. Although the mechanical properties of hydrogels can be improved by the introduction of robust materials, the use of conventional reinforcing agents limits the medical application of injectable hydrogels due to their non-biodegradable property. We synthesized and self-assembled an injectable hydrogel from biodegradable mixed-substituted polyphosphazene and the natural organic molecule alpha-cyclodextrin (alpha CD) by host-guest inclusion. Photo-crosslinking was then employed for the hydrogel to transform it into the solid state with the desired shape. By this approach, the mechanical properties and anti-water solubility of the polyphosphazene hydrogel can meet the requirements of potential applications. In addition, the surface of the cured hydrogel can be readily tuned from cell-philic to cell-phobic by changing the ratio of two side chains of substituted polyphosphazene.