Photoluminescent biodegradable polyorganophosphazene: A promising scaffold material for <i>in vivo</i> application to promote bone regeneration.

Abstract

Tissue engineering scaffolds made of conventional aliphatic polyesters are inherently non-fluorescent, which results in their <i>in vivo</i> degradation hard to be visualized. Photoluminescent biodegradable polyorganophosphazenes (PPOPs) are synthesized by introducing fluorophores onto the polyphosphazene backbone via nucleophilic substitution reaction. In this study, a fluorophore (termed as TPCA), derived from citric acid and 2-aminoethanethiol, was co-substituted with alanine ethyl ester onto the polyphosphazene backbone to obtain a photoluminescent biodegradable POPP (termed as PTA). The scaffolds made of PTA demonstrated non-cytotoxicity and cell affinity, particularly, capacity in promoting osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs). <i>In vivo</i> evaluations using the rat calvarial defect model confirmed its strong potential in enhancing osteogenesis, more importantly, the <i>in vivo</i> degradation of the PTA scaffold could be monitored via its fluorescence intensity alongside implantation time.