Characterization and biological properties of TiO2/PCL hybrid layers prepared via sol–gel dip coating for surface modification of titanium implants

• TiO2/PCL hybrid biomaterials synthesized by sol–gel method at various PCL percentage
• Hybrid coating of titanium substrate with dip-coating technology
• Chemical and morphological characterization of hybrids and coating
• Formation of a porous coating with low percentages of PCL
• Biocompatibility and bioactivity improvement of coated titanium

Surface modification of implants to facilitate the integration process of the biomaterials is a strategy which has been attracting increasing attention. In this work, the sol–gel method has been used to synthesize organic–inorganic nanocomposite materials consisting of an inorganic titania matrix in which different percentages of a biocompatible polymer, the poly-ε-caprolactone (PCL), have been incorporated. The synthesized materials, still in sol phase, have been used to dip-coat titanium grade 4 substrates to improve the biological properties of the surface. Fourier transform infrared spectroscopy detected the formation of H-bonds between the CO of PCL chains and the –OH groups of the sol–gel matrix. The morphological analysis of films has been performed via scanning electron microscopy (SEM) and has shown that the PCL addition allows the preparation of crack-free and porous coatings; however, uncoated areas develop if PCL is present in high percentages. Bioactivity properties of the coatings have been investigated by soaking coated substrates in a fluid simulating the human blood plasma and evaluating at a later stage the formation of a hydroxyapatite layer on the surface by means of SEM/EDX (energy dispersive X-ray). Coating biocompatibility has been studied by WST-8 assay using 3T3 cells seeded on coated and uncoated substrates.