Biocompatible nanocrystalline octacalcium phosphate thin films obtained by pulsed laser deposition

We extended for the first time pulsed laser ablation to the deposition of octacalcium phosphate Ca₈H₂(PO₄) ₆·5H₂O (OCP) thin films. The depositions were performed with a pulsed UV laser source (λ=248nm, τ≥20ns) in a flux of hot water vapors. The targets were sintered from crystalline OCP powder and the laser ablation fluence was set at values of 1.5-2J/cm². During depositions the collectors, Si or Ti substrates, were maintained at a constant temperature within the range 20-200°C. The resulting structures were submitted to heat treatment in hot water vapors for up to 6h. The best results were obtained at a substrate temperature of 150°C during both deposition and post-deposition treatment. High-resolution electron microscopy and XRD at grazing incidence indicated that the coatings obtained were made of nanocrystalline OCP. Cross-section TEM investigations showed that the coatings contained droplets stacked on Ti substrates as well as distributed across the entire thickness of the arborescence-like structure layers. The results of WST-1 assay, cell adherence, DNA replication, and caspase-1 activity confirmed the good biocompatibility of the coatings.