Thioether functionalized degradable poly(amino acids) and its calcium sulfate/calcium hydrogen phosphate composites: Reducing oxidative stress and promoting osteogenesis.

The imbalance of redox homeostasis, especially the abnormal levels of reactive oxygen species (ROS), is a key obstacle in the bone repair process. Therefore, developing materials capable of scavenging ROS and modulating the microenvironment of bone defects is crucial for promoting bone repair. In this study, to endow poly(amino acids) (PAA) and its composites with anti-oxidative stress properties and enhanced osteogenic differentiation, we designed and prepared a calcium sulfate/calcium hydrogen phosphate/poly(amino acids) (PCDM) composite material with a thioether structure (-S-) in the molecular chain of PAA matrix through situ polymerization and physical blending method. The results showed that the thioether was successfully introduced into the polymer, and the intrinsic viscosities of the poly(amino acids) ranged from 0.27 to 0.73 dL/g. PCDM materials exhibited good mechanical properties, with a compressive strength ranging from 16.28 to 33.83 MPa. The degradation performance results showed that the composite materials had a weight loss of 23.9-35.3 % after four weeks. The antioxidant stress results showed that the PCDM composite materials scavenged 67.6 %-78.3 % of DPPH radicals after 24 h and 61.4 %-93.6 % of ABTS radicals after 4 h, effectively reducing ROS levels in mouse bone mesenchymal stem cells. The cytotoxicity and osteogenic differentiation results showed that the materials had cytocompatibility and could promote alkaline phosphatase secretion and mineralized nodule formation. In conclusion, PCDM materials might broaden the application of poly(amino acids) composites in bone defect repair by regulating the ROS microenvironment and promoting the osteogenic differentiation of stem cells.