Background: Selective laser melting (SLM) titanium is an ideal option to manufacture customized implants with suitable surface modification to improve its bioactivity. The peri-implant soft tissues form a protective tissue barrier for the underlying osseointegration. Therefore, original microrough SLM surfaces should be treated for favorable attachment of surrounding soft tissues. Material and methods: In this study, anodic oxidation (AO) was applied on the microrough SLM titanium substrate to form TiO2 nanotube arrays. After that, calcium phosphate (CaP) nanoparticles were embedded into the nanotubes or the interval of nanotubes by electrochemical deposition (AOC). These two samples were compared to untreated (SLM) samples and accepted mechanically polished (MP) SLM titanium samples. Scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, surface roughness, and water contact angle measurements were used for surface characterization. The primary human gingival epithelial cells (HGECs) and human gingival fibroblasts (HGFs) were cultured for cell assays to determine adhesion, proliferation, and adhesion-related gene expressions. Results: For HGECs, AOC samples showed significantly higher adhesion, proliferation, and adhesion-related gene expressions than AO and SLM samples (P<0.05) and similar exceptional ability in above aspects to MP samples. At the same time, AOC samples showed the highest adhesion, proliferation, and adhesion-related gene expressions for HGFs (P<0.05). Conclusion: By comparison between each sample, we could confirm that both anodic oxidation and CaP nanoparticles had improved bioactivity, and their combined utilization may likely be superior to mechanical polishing, which is most commonly used and widely accepted. Our results indicated that creating appropriate micro-/nano-topographies can be an effective method to affect cell behavior and increase the stability of the peri-implant mucosal barrier on SLM titanium surfaces, which contributes to its application in dental and other biomedical implants.

Background: Micro/nano-textured hierarchical titanium topography is more bioactive and biomimetic than smooth, micro-textured or nano-textured titanium topographies. Bone marrow mesenchymal stem cells (BMSCs) and exosomes derived from BMSCs play important roles in the osseointegration of titanium implants, but the effects and mechanisms of titanium topography on BMSCs-derived exosome secretion are still unclear. This study determined whether the secretion behavior of exosomes derived from BMSCs is differently affected by different titanium topographies both in vitro and in vivo. Results: We found that both micro/nanonet-textured hierarchical titanium topography and micro/nanotube-textured hierarchical titanium topography showed favorable roughness and hydrophilicity. These two micro/nano-textured hierarchical titanium topographies enhanced the spreading areas of BMSCs on the titanium surface with stronger promotion of BMSCs proliferation in vitro. Compared to micro-textured titanium topography, micro/nano-textured hierarchical titanium topography significantly enhanced osseointegration in vivo and promoted BMSCs to synthesize and transport exosomes and then release these exosomes into the extracellular environment both in vitro and in vivo. Moreover, micro/nanonet-textured hierarchical titanium topography promoted exosome secretion by upregulating RAB27B and SMPD3 gene expression and micro/nanotube-textured hierarchical titanium topography promoted exosome secretion due to the strongest enhancement in cell proliferation. Conclusions: These findings provide evidence that micro/nano-textured hierarchical titanium topography promotes exosome biogenesis and extracellular secretion for enhanced osseointegration. Our findings also highlight that the optimized titanium topography can increase exosome secretion from BMSCs, which may promote osseointegration of titanium implants.

Implant surface topography has been proven to determine the fate of adhered macrophage polarization, which is closely related to the cytoskeletal arrangement during adhesion. Our purpose was to establish a topography that is favourable to M2 macrophage switching by regulating macrophage cytoskeleton distribution. Two micro/nano-net structures with different pore sizes were generated by alkali bathing at medium (SAM) or high (SAH) temperature based on the micro-level surface. Their surface characteristics, in vitro macrophage polarization and impact on endothelial cells were analysed. The in vivo macrophage response and osseointegration were also tested. The results showed that the micro/nano-net has high hydrophilicity and moderate roughness. In the SAH and SAM groups, macrophages exhibited an elongated cytoskeleton with tiny protrusions and had a high M2/M1 polarization ratio with enhanced angiogenic ability, and in vivo studies also showed faster angiogenesis and bone formation in these groups. SAH showed even better results than SAM. For cytoskeleton related pathway explanation, ROCK expression was upregulated and Src expression was downregulated at the early or late adhesion stage in both the SAH and SAM groups. These results indicated that the micro/nano-net structure guides elongated macrophage adhesion states via Src–ROCK signalling and switches macrophages towards the M2 phenotype, which provides a cytoskeleton-oriented topography design for an ideal immune response.