Impacts of strontium-incorporated micro-nano structured titanium surfaces on osseointegration through mediating...

Titanium implants require surface modifications to overcome biological inertia and enhance osteointegration. Macrophage polarization is critical in regulating osteogenesis which affects inflammation and tissue repair. Strontium has been shown to enhance bone formation, and Sr²⁺ ions have also been found to influence immune responses and inflammation, suggesting potential applications in bone repair and regeneration. Our research utilized phase-transited lysozyme (PTL) surface modification to immobilize Sr²⁺ ions within the PTL coating, thereby obtaining two distinct morphological coatings: Sr-incorporation PTL-nanofilm (PSR-nanofilm) and Sr-incorporation PTL-coating (PSR-coating). Through a combination of in vitro and in vivo experimental approaches, this study demonstrated that PSR-coating implants with rough titanium surfaces enhance osteogenesis compared to PSR-nanofilm implants. This effect is attributed to their ability to polarize macrophages into the pro-inflammatory M1 phenotype during the early stage of implantation, followed by a transition to the anti-inflammatory M2 phenotype at a later stage via the sustained release of Sr²⁺.