Morphological Evolution Effect on the Performance of Spray Pyrolysis-Based Synthesis of Fluorapatite Thin Films for Bioimplant Applications

To correlate fluorapatite thin films’ morphology to their stability and bioactivity for temporary bioimplant applications, fluorapatite is ultrasonically spray-deposited on different substrates using chemical precursors. Mechanical agitation in phosphate-buffered saline solution is used to investigate the stability of the films aided with X-ray diffraction and electron microscopy for films’ morphology and thickness. For bioactivity, the cell adhesion to the fluorapatite thin films is evaluated by growing HaCaT cells on the film surface. The films deposited on titanium are pure and polycrystalline. Agitation in solution leads to a thickness reduction of 18.3%, and 30.5% for the films deposited on alumina. However, the persistence of the films after agitation suggests partial degradability. The improved stability of fluorapatite on titanium is attributed to the layer plus island-like morphology that offers a reduced contact area with the surrounding solution compared with the island-like morphology of fluorapatite on alumina. These different morphologies can be understood in the context of a smaller lattice mismatch between the substrate and the film which results in the layer plus island-like morphology. HaCaT cell adhesion on Ti-fluorapatite film surfaces is better than the titanium reference and alumina-fluorapatite suggesting its bioactivity and the promise of spray-deposited FAP for orthopedic applications.