Multifunctional Strontium-Substituted Hydroxyapatite/Polydopamine Photothermal Coating for Enhancing Antibacterial...

Infection associated with orthopedic implants and insufficient biological integration remain important clinical challenges. In this study, strontium-substituted hydroxyapatite (SrHA) was prepared by a chemical co-precipitation method, and a SrHA/polydopamine (SrHA@PDA) composite coating was constructed on porous tantalum (Ta) through the self-polymerization of polydopamine (PDA). The coating exhibited a photothermal conversion efficiency of 63.79% under 808 nm near-infrared (NIR) irradiation, with the temperature increasing to 62.7 °C within 10 min. The antibacterial activity was primarily attributed to PDA-mediated photothermal heating. After NIR irradiation, pronounced antibacterial effects were observed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), while Sr²⁺ release remained controlled during the investigated period. In addition, the SrHA@PDA coating supported MC3T3-E1 osteoblast proliferation, indicating a favorable cellular response. Cross-sectional observations demonstrated the formation of a dense and continuous SrHA-containing coating on the porous Ta scaffold, and biomimetic mineralization further indicated favorable surface bioactivity. Overall, the SrHA@PDA coating integrates controlled Sr²⁺ release, favorable osteoblast response, and PDA-mediated photothermal antibacterial activity within a single surface modification strategy. This multifunctional approach provides a promising platform for improving the biological and antibacterial performance of porous tantalum implants for bone repair applications.