Multifunctional Strontium-Substituted Hydroxyapatite/Polydopamine Photothermal Coating for Enhancing Antibacterial Activity and Osteoblast Response of Porous Tantalum Implants

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.