Antibacterial and Bone Ingrowth Properties of Iodine Ion-Releasing Titanium Implant With Gradient Pores: An in Vivo Study

Abstract

Titanium implants are widely used in orthopedics and spinal surgery, but implant-associated infections remain a major clinical challenge that often necessitates implant removal. To address this issue, we evaluated whether an iodine-loaded porous titanium implant with a gradient pore design could balance antibacterial activity and bone formation. The structure transitions from large outer pores to smaller inner pores, enhancing osseointegration while providing a greater surface area for iodine ion loading. Implants were fabricated by selective laser melting and surface-modified to incorporate iodine ions. In vivo experiments using rabbit femoral condyles demonstrated that gradient implants (Ti-D) showed bone ingrowth comparable to larger pore implants at 4 weeks. Iodine-treated implants (ITi-D) exhibited sustained ion release, strong antibacterial activity against Staphylococcus aureus and Escherichia coli, and no clear cytotoxicity in vitro. In vivo subcutaneous infection models confirmed significant antibacterial efficacy of ITi-D, while blood tests showed no systemic toxicity up to 90 days. Compared with uniformly porous implants, ITi-D achieved an optimal balance between antimicrobial performance and biocompatibility. This dual-functional approach addresses the longstanding tradeoff between infection control and osseointegration in porous titanium implants.