A dual-functional strontium-decorated titanium implants that guides the immune response for osseointegration of osteoporotic rats

Due to the dynamic imbalance between osteogenesis and osteoclasis and the abnormal inflammatory microenvironment in situ, osteoporosis hampers the early osseointegration between implants and bones. To improve osseointegration with the osteoporosis, we first coated the titanium implants (Ti) with polydopamine (PDA) coating (Ti-PDA), followed by modification with strontium (Sr) to prepare the Ti-PDA-Sr implants. An osteoporotic rat model with femoral bone defect was verified to estimate the osseointegration of the implants. The TiPDA-Sr implants exhibited good biocompatibility with continuous release of Sr ions for up to 21 days. Ti-PDA-Sr implants promoted the osteogenesis of BMSCs and the polarization of BMMs to M2 phenotype compared to that of Ti and Ti-PDA implants, revealing the double-regulated effects in bone induction and immune regulation. According to the Micro-CT and histopathology results, Ti-PDA-Sr implants exhibited the most stable osseointegration between bone tissues and implants. According to the immunohistochemistry results, the Ti-PDA-Sr implants differentiated the BMMs to M2 phenotype, alleviating the abnormal inflammation in osteoporosis and preventing the consistent bone destruction between the implants and bone tissues. This study provides a practical and effective strategy in preparing bi-functional implants that can promote osseointegration with osteoporosis.