Enhanced sinterability and in vitro bioactivity of diopside through fluoride doping
Abstract
In this work, diopside (CaMgSi2O6) was doped with fluoride at a level of 1 mol.%, without the formation of any second phase, by a wet chemical precipitation method. The sintered structure of the synthesized nanopowders was studied by X-ray diffraction, Fourier transform infrared spectroscopy and field-emission scanning electron microscopy. Also, the samples' in vitro apatite-forming ability in a simulated body fluid was comparatively evaluated by electron microscopy, inductively coupled plasma spectroscopy and Fourier transform infrared spectroscopy. According to the results, the material's sinterability was improved by fluoride doping, as realized from the further development of sintering necks. It was also found that compared to the undoped bioceramic, a higher amount of apatite was deposited on the surface of the doped sample. It is concluded that fluoride can be considered as a doping agent in magnesium-containing silicates to improve biological, particularly bioactivity, behaviors.
Summary
This paper investigates the effect of fluoride doping on the sinterability and in vitro bioactivity of diopside (CaMgSi2O6), a bioceramic material used in various biomedical applications. The authors synthesized diopside nanopowders with 1 mol.% fluoride doping using a wet chemical precipitation method. They then characterized the sintered structure using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field-emission scanning electron microscopy (FESEM). In vitro apatite-forming ability was evaluated by immersing the samples in simulated body fluid (SBF) and analyzing the surface using FESEM, inductively coupled plasma spectroscopy (ICP), and FTIR. The key findings indicate that fluoride doping enhances the sinterability of diopside, leading to more developed sintering necks between particles. Moreover, the fluoride-doped diopside exhibited improved in vitro bioactivity, demonstrated by a higher amount of apatite deposition on its surface compared to the undoped counterpart. The authors conclude that fluoride can be a beneficial doping agent for magnesium-containing silicates like diopside to improve their biological properties, especially bioactivity. This research is significant as it introduces fluoride doping as a novel approach to enhance the properties of diopside, potentially expanding its applicability in biomedical engineering by improving its bone bonding capabilities.
Key Insights
- •Fluoride doping at 1 mol.% in diopside enhances its sinterability, as evidenced by the larger mean diameter of sintering necks (500 nm for doped vs. 150 nm for undoped).
- •Fluoride doping improves the crystallinity and crystallite size of diopside after sintering at 1200°C, as indicated by sharper and more intense XRD peaks, increasing the crystallite size from 52 nm to 66 nm.
- •FTIR analysis confirms the incorporation of fluoride into the diopside structure, with the appearance of Si-F stretching bands at 800 and 930 cm-1 and a slight shift (2-5 cm-1) of Si-O vibrations to higher wavenumbers.
- •FESEM reveals that approximately 85% of the fluoride-doped diopside surface is covered by uniform leaf-like apatite precipitates after 3 days in SBF, while the undoped sample shows very little apatite formation.
- •ICP analysis shows a considerably lower amount of phosphorous in the SBF after soaking the doped sample, indicating enhanced apatite formation on the doped diopside surface.
- •The pH of SBF after immersion with the doped sample was lower (7.6) than with the undoped sample (8.3), attributed to the exchange of F- and OH- ions, promoting silanol group formation and apatite nucleation.
- •The study highlights that the chemical composition change (fluoride doping) has a greater influence on apatite-forming ability than particle size, despite smaller particle sizes generally promoting bioactivity.
Practical Implications
- •The findings suggest that fluoride-doped diopside could be used to create more bioactive coatings for biomedical implants, potentially leading to better osseointegration and implant stability.
- •This research benefits materials scientists and biomedical engineers working on bone tissue engineering, drug delivery systems, and other biomedical applications of bioceramics.
- •Practitioners can use the wet chemical precipitation method described in the paper to synthesize fluoride-doped diopside nanopowders with enhanced sinterability and bioactivity.
- •Future research should investigate the in vivo performance of fluoride-doped diopside, optimize the doping concentration, and explore the effects of fluoride doping on the mechanical properties and degradation behavior of diopside.
- •Further studies could explore the potential of combining fluoride doping with other bioactivity-enhancing strategies, such as surface modification or incorporating growth factors, to create even more advanced bioceramic materials.