Piperazine-based polyurethane-ureas with controllable degradation as potential bone scaffolds

Piperazine-based polyurethane ureas (P-PUUs) with piperazine (PP) units as the functional ingredients have been designed to explore a novel polymeric biomaterial with the controllable degradation for bone repair in this study. P-PUUs were prepared upon the chain-growth polymerization of poly (d, l -lactic acid) diol (PDLLA diol), 1, 6-hexamethylene diisocyanate (HDI) where PP functioned as the chain extender. The investigation of in vitro degradation of P-PUUs was performed and the mechanical properties of P-PUUs during degradation were calculated. The results revealed that manipulating the ratio of PDLLA diol: HDI: PP could obtain the precise number of PP units (Num(pp)) in P-PUUs which may significantly impact the degradation stability and the degradation rate of P-PUUs. The negative linear correlation between the degradation rate and the Num(pp) of P-PUUs has been proved, suggesting the P-PUUs were endowed with controllable degradation. Such a linear correlation is expected to be applied to bone repair where the specific degradation rate of P-PUUs for the specific bone defect can be precisely predicted once the Num(pp) and the bone repairing period are known. Additionally, P-PUUs with higher Num(pp) exhibited remarkable mechanical properties during degradation which allowed polymers to provide more persistent mechanical support to bone repair.