Synthesis and characterization of porous hydroxyapatite coatings deposited on titanium by flame spraying

Applying a porous hydroxyapatite (HA) coating on a titanium substrate is a widely used method to increase the biocompatibility and osteogenic potential of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. Thermal spraying is one of the most prevalent methods used to coat HA on titanium substrates due to its ease in processing and ability to produce coatings with good adherence, which affect positively the surface topography and coating performance. The objective of this work is to enhance the biocompatibility and osteogenic potential of HA coatings on titanium substrates. HA was first synthesized and then coated onto a titanium substrate by two distinct methods, i.e., the dry coating method and the wet coating method. The phase content was evaluated by X-ray diffraction (XRD). The particle morphology was observed by scanning electron microscopy (SEM). HEPM pre-osteoblasts were used to test the cell-material interaction in vitro, and thereafter, an alkaline phosphatase (ALP) test was conducted. The wet coating method enhanced the specific surface area, which in turn increased the cell proliferation on HA-coated titanium substrates. The in vitro test demonstrated that wet coatings resulted in enhanced cell attachment and ALP activity. This study shows that spraying HA using the wet coating method is a technique that can produce potentially bioactive bone-regeneration implants.