Laser-programmed anisotropic hierarchical host bone interfaces for mechanotransduction-guided osseointegration

Conventional mechanical osteotomy often induces thermal and mechanical damage, which compromises the biological quality of the host bone interface and impairs subsequent osseointegration. This study aimed to develop a 9.3 μm CO₂ laser-based osteotomy strategy that integrates precise bone cutting with in situ regenerative interface engineering.

A 9.3 μm CO₂ laser osteotomy platform was developed by combining controlled pulse-overlap scanning with gas-atomized water-mist cooling. The generated osteotomy interfaces were characterized in terms of surface topography, thermal response, microstructural preservation, and local mechanical integrity. Human mesenchymal stem cell (hMSC) alignment, focal adhesion-mediated mechanotransduction, osteogenic differentiation, and osteoclast formation were evaluated in vitro. Transcriptomic and biochemical analyses were performed to investigate the underlying molecular programs. The optimized interface was further assessed in a rat femoral defect model with porous titanium scaffold implantation.

The laser osteotomy strategy generated deterministic microscale grooves and graded nanoscale roughness, forming anisotropic hierarchical micro-nano osteotomy interfaces. Compared with mechanical cutting, laser osteotomy reduced thermal accumulation, limited microstructural disruption, and better maintained local mechanical integrity. The engineered interfaces directed hMSC alignment and activated focal adhesion-mediated mechanotransduction, as indicated by enhanced pFAK activation, Lamin A/C reinforcement, and YAP nuclear translocation. These responses promoted osteogenic differentiation and suppressed osteoclast formation, with the Laser III group showing the most favorable biological response. Transcriptomic and biochemical analyses further revealed enrichment of adhesion-, cytoskeleton-, and PI3K-Akt-related osteogenic programs. In vivo, the optimized interface enhanced peri-implant bone regeneration, mineral apposition, and osseointegration.

This study provides proof-of-concept evidence that 9.3 μm CO₂ laser osteotomy may enable bone cutting to be coupled with in situ regenerative interface engineering. By reducing cutting-associated damage and actively programming the host bone interface, this approach shows translational potential for improving peri-implant bone healing and implant integration.

9.3 μm CO₂ laser-enabled osteotomy interface engineering integrates precise bone cutting with in situ programming of the host bone surface. This study reveals that laser-generated anisotropic hierarchical micro-nano interfaces can reduce cutting-associated damage, activate adhesion-mediated mechanotransduction, promote osteogenic differentiation, suppress osteoclast maturation, and enhance peri-implant osseointegration. These findings provide a regenerative osteotomy strategy for improving the biological quality of surgically created bone interfaces, which holds translational potential for orthopedic implant surgery, fracture reconstruction, and the repair of bone defects in clinical practice.