Commensal microflora coating endows implants with biofilm-repellent, immunomodulatory and osteogenic properties

Bacteria often form biofilms on biomaterials, and these biomaterial-associated infections then become highly resistant to antibiotics and the host immune system. Biofilm-driven implant failures underscore the urgent need for surface modifications that can concurrently prevent microbial colonization, modulate immune responses, and stimulate bone formation. Considering the competitive and osteo-immunomodulatory properties of commensal microflora, we developed Commensal Hybrid Materials (CHMs) by heat-anchoring multilayer assemblies of beneficial microbes onto titanium surfaces. A firmly adherent, carbon- and phosphorus-rich coating with micro-roughness and near-hydrophobic wettability (θ≈90°) suppressed Porphyromonas gingivalis biofilm formation on implant surfaces ‒ even after human-saliva conditioning. The coating did not release antimicrobial agents or alter bacterial gene expression, thereby avoiding selective pressure for antimicrobial resistance. The coated surfaces were cytocompatible with murine cells, did not elicit an inflammatory response, and skewed macrophages toward an M1-like phenotype with increased reactive oxygen species (ROS) production. Furthermore, CHMs first induced macrophages toward a balanced immune response by promoting pro-inflammatory M1 polarization with elevated TNF-α for infection control, followed by an IL-10-rich anti-inflammatory M2 phenotype that supports tissue repair. This polarization significantly upregulated expression of the osteoinductive factor oncostatin M (OSM), and conditioned media from CHM-stimulated macrophages upregulated type I collagen (Col1) expression in osteoblasts. Coated surfaces supported osteogenic potential in osteoblasts by increasing alkaline phosphatase activity and matrix mineralization. Although forthcoming in vivo studies will further validate performance, these findings position commensal microflora as a single, drug-free coating that integrates biofilm resistance, pro-host immune modulation, and osteogenic support to improve long-term implant outcomes. STATEMENT OF SIGNIFICANCE: Biomaterial-associated infections resist antibiotics and evade host immunity. We engineered commensal hybrid materials (CHMs) by heat-anchoring commensal microflora onto titanium, yielding a drug-free coating that repels biofilms without releasing antimicrobials or perturbing pathogen gene expression, thereby limiting resistance pressure. CHMs modulate macrophages‒eliciting an early M1/TNF-α phenotype for pathogen control followed by an IL-10-rich M2 phase that restores homeostasis. They also increase macrophage oncostatin M (OSM) and enhance osteoblast alkaline phosphatase activity and mineralization, promoting osteogenesis. By uniting biofilm resistance, immune modulation, and osteogenic support on a single surface, CHMs offer a promising route to extend implant longevity in orthopaedics and dentistry.