Composite biocompatible hydroxyapatite–silk fibroin coatings for medical implants obtained by Matrix Assisted Pulsed Laser Evaporation

Abstract

The aim of this study was to obtain biomimetic inorganic–organic thin films as coatings for metallic medical implants. These contain hydroxyapatite, the inorganic component of the bony tissues, and a natural biopolymer – silk fibroin – added in view to induce the surface functionalization. Hydroxyapatite (HA), silk fibroin (FIB) and composite HA–FIB films were obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE) in order to compare their physical and biological performances as coatings on metallic prostheses. We used an excimer laser source (KrF*, λ = 248 nm, τ = 25 ns) operated at 10 Hz repetition rate. Coatings were deposited on quartz, Si and Ti substrates and then subjected to physical (FTIR, XRD, AFM, SEM) analyses, correlated with the results of the cytocompatibility in vitro tests. The hybrid films were synthesized from frozen targets of aqueous suspensions with 3:2 or 3:4 weight ratio of HA:FIB. An appropriate stoichiometric and functional transfer was obtained for 0.4–0.5 J/cm2 laser fluence. FTIR spectra of FIB and HA–FIB films exhibited distinctive absorption maxima, in specific positions of FIB random coil form: 1540 cm−1 amide II, 1654 cm−1 amide I, 1243 cm−1 amide III, while the peak from 1027 cm−1 appeared only for HA and composite films. Osteosarcoma SaOs2 cells cultured 72 h on FIB and HA–FIB films showed increased viability, good spreading and normal cell morphology. The well-elongated, flattened cells are a sign of an appropriate interaction with the MAPLE FIB and composite HA–FIB coatings.