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Updated: Jul 18, 2026

Rapid Mix Preparation of Bioinspired Nanoscale Hydroxyapatite for Biomedical Applications
Published on: February 23, 2017
Yongsheng Wang1, Sam Zhang, Xianting Zeng
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
This study investigated how adding fluoride to hydroxyapatite coatings affects their stability and ability to support bone cell growth. Researchers used a sol-gel method to apply coatings with varying fluoride levels onto titanium alloy substrates. They found that coatings with 0.8-1.1M fluoride had the lowest solubility, meaning they were more durable. In vitro tests with MG63 cells showed these coatings also promoted better cell growth and differentiation. The improved cell response was linked to the combined release of calcium, phosphorus, and fluoride ions. The study recommends using this fluoride concentration range for optimal performance in implant applications.
Area of Science:
Background:
Research into implant surfaces has identified a need to improve osseointegration while maintaining material stability. Prior studies have shown that hydroxyapatite coatings can support bone cell attachment, but their solubility and long-term performance remain unclear. No prior work had resolved how fluoride incorporation affects both the structural and biological properties of these coatings. This gap motivated the investigation of fluoridated hydroxyapatite as a potential improvement over traditional formulations. It was already known that fluoride can alter the solubility of calcium phosphates, but the extent of this effect in a sol-gel dip-coating context was not established. The role of fluoride concentration in influencing cell behavior was also uncertain. This study aimed to clarify how varying fluoride levels impact coating stability and osteoblastic activity. Understanding these relationships could help refine implant surface design for better clinical outcomes.
Purpose Of The Study:
The goal was to assess how fluoride incorporation affects the solubility and biological performance of hydroxyapatite coatings on titanium alloys. The specific problem addressed was the lack of data on optimal fluoride concentrations for both material durability and cell response. Researchers focused on Ti6Al4V substrates, which are commonly used in orthopedic and dental implants. The motivation stemmed from the need to enhance the longevity and integration of implant surfaces. By varying fluoride levels, the study aimed to identify a balance between coating stability and cell activity. The sol-gel dip-coating method was selected for its ability to produce uniform layers with controlled composition. The researchers proposed that fluoride could reduce solubility while promoting osteoblastic function. This approach could lead to improved implant designs with enhanced osseointegration potential.
Main Methods:
The study used sol-gel dip-coating to apply fluoridated hydroxyapatite onto Ti6Al4V substrates. Fluoride ion concentrations were varied to produce different coating compositions. X-ray photoelectron spectroscopy confirmed the integration of fluoride into the hydroxyapatite lattice. Dissolution tests were conducted in Tris-buffered physiological saline to measure solubility. In vitro experiments used human osteosarcoma MG63 cells to assess cell behavior. Cell morphology, proliferation, and differentiation markers were evaluated. Alkaline phosphatase activity and osteocalcin levels were measured to gauge differentiation. The combined effects of calcium, phosphorus, and fluoride ions were analyzed to explain observed cell responses. This approach allowed the researchers to link coating composition with biological outcomes.
Main Results:
Fluoride ions were successfully incorporated into the hydroxyapatite lattice as confirmed by X-ray photoelectron spectroscopy. Dissolution tests showed that fluoridated coatings had lower solubility than pure hydroxyapatite. The lowest solubility was observed at fluoride concentrations of 0.8-1.1M. Cell morphology and viability were similar across all tested coatings. Coatings with 0.8-1.1M fluoride showed enhanced cell proliferation and differentiation. Alkaline phosphatase activity and osteocalcin levels were higher in these samples. The combined release of calcium, phosphorus, and fluoride ions was linked to improved cell activity. The recommended composition for optimal performance is Ca(10)(PO4)(6)(OH)(1.2-0.9)F(0.8-1.1).
Conclusions:
The study found that fluoride incorporation reduces hydroxyapatite solubility and enhances osteoblastic cell activity. Coatings with 0.8-1.1M fluoride showed the best balance between stability and biological performance. The researchers propose that this concentration range optimizes both dissolution resistance and cell response. The observed effects were attributed to the combined release of calcium, phosphorus, and fluoride ions. These findings suggest that fluoridated hydroxyapatite could improve implant surface design. The recommended composition supports long-term osseointegration without compromising structural integrity. The authors state that this approach may lead to better clinical outcomes for titanium-based implants. Further work is needed to confirm these results in vivo.
The study suggests 0.8-1.1M fluoride is optimal for both solubility and cell activity.
X-ray photoelectron spectroscopy confirmed fluoride integration into the HA structure.
Lower solubility improves coating durability and long-term implant performance.
Alkaline phosphatase activity and osteocalcin levels were measured.
Coatings with 0.8-1.1M fluoride showed stronger stimulation of cell proliferation.
The combined release of Ca, P, and F ions was linked to enhanced cell activity.