[Fabrication and evaluation of composite hydroxyapatite coating on ordered micro-/nanotextured titanium surface]

Medical implants often face challenges in integrating with surrounding bone tissue. Surface modification techniques aim to enhance osteogenic activity. Prior research has shown that titanium surfaces with micro- or nanostructures can influence cell behavior. However, the combined effect of these structures with hydroxyapatite coatings remains unclear. This gap motivated researchers to explore composite coatings. The role of hydroxyapatite in promoting bone cell adhesion is well-documented. Yet, its performance on micro/nanotextured surfaces is less understood. This study addresses the need to evaluate such composite surfaces for improved bone integration.

This study aimed to assess the osteogenic potential of a composite hydroxyapatite coating on micro/nanotextured titanium. The motivation stems from the need to improve implant integration with bone tissue. Researchers focused on a specific fabrication method for hydroxyapatite deposition. The goal was to determine if this coating enhances cell adhesion and differentiation. Bone marrow mesenchymal stem cells were used as the model system. The study compared three surface types: control, micro/nanotextured, and hydroxyapatite-coated. The hypothesis was that the composite surface would outperform others in promoting osteogenesis. The specific problem addressed is the limited understanding of combined surface features in bone regeneration.

Researchers first created an ordered micro/nanotextured titanium surface. They then applied hydroxyapatite using an alternative loop immersion method. Scanning electron microscopy was used to analyze surface morphology. Bone marrow mesenchymal stem cells were seeded onto three different surfaces. Cell adhesion was assessed using 4',6-diamidino-2-phenylindole staining. Cell proliferation was measured with a cell counting kit-8 assay. Extracellular matrix mineralization was evaluated using alizarin red staining. Gene expression was analyzed via real-time quantitative PCR. Each experiment included three samples per group to ensure statistical reliability.

Hydroxyapatite deposition preserved the microholes on the micro/nanotextured surface. The hydroxyapatite formed a uniform petal-like structure on the nanotubes. Bone marrow mesenchymal stem cells on the hydroxyapatite surface showed elongated morphology. Cell adhesion was significantly higher on the hydroxyapatite surface at all time points. On day 1, cell proliferation on hydroxyapatite was higher than on the control and micro/nanotextured surfaces. By day 3, cell proliferation on hydroxyapatite decreased compared to the control and micro/nanotextured surfaces. On day 7, hydroxyapatite showed lower proliferation than micro/nanotextured surfaces but not the control. Extracellular matrix mineralization was highest on the hydroxyapatite surface with a value of 0.607±0.011.

The hydroxyapatite coating on micro/nanotextured titanium supports early cell adhesion and osteogenic differentiation. The surface promotes extracellular matrix mineralization more than the control and micro/nanotextured surfaces. The study suggests that hydroxyapatite enhances the osteogenic activity of titanium implants. The findings indicate that this composite surface may improve bone regeneration outcomes. The researchers propose that the coating’s structure contributes to its effectiveness. No prior work had resolved the specific role of hydroxyapatite on such surfaces. The results align with the hypothesis that composite coatings enhance osteogenesis. The authors suggest further investigation into long-term implant performance.