Lipid-mediated growth of SrCO3/CaCO3 hybrid films as bioactive coatings for Ti surfaces

Abstract

SrCO₃ is frequently used as Sr²⁺ source in ceramic cements, but its application as bioactive coating for metallic implants has not been explored yet. Aiming at rapid osteointegration and because of the well-known Sr²⁺ effects on bone metabolism, researchers have sought to design Sr²⁺-containing biomaterials. In this context, developing simple techniques to prepare Sr²⁺-based coatings is a must nowadays. Here, we describe the use of a bioinspired lipid-mediated approach to grow SrCO₃ hybrid films on Ti surfaces at room temperature. To obtain these coatings, we applied the Langmuir-Blodgett technique to deposit phospholipid films with high degree of organization on Ti. In this way, we expected that controlled SrCO₃ crystal growth could be templated by the array of nucleation points arising from electrostatic interaction between Sr²⁺ and the phospholipid polar heads. To control surface composition and the amount of Sr²⁺ released from the coatings, we also promoted CaCO₃ co-precipitation in the hybrid films. We characterized the hybrid coatings in terms of morphology, chemical structure, wettability, and ability to release Sr²⁺ upon immersion in biological medium. In vitro osteoblast culture on mixed SrCO₃/CaCO₃ films revealed that the osteogenic response depended on surface composition, as indicated by alkaline phosphatase activity overexpression, which is an early indicator of osteoblast differentiation. Results showed that the mixed SrCO₃/CaCO₃ hybrid film created a synergic environment for osteoblasts, and that proper Sr²⁺ release associated with a Ca²⁺-rich environment might have optimized the Sr²⁺ anabolic effect. In conclusion, we have proposed a bioinspired and versatile technique to grow hybrid films that can control surface composition and Sr²⁺ release. Our results open an opportunity to explore the use of SrCO₃-based coatings for rapid metallic implant osteointegration.

Keywords: Langmuir-Blodgett films; Osteoblasts; Strontium; Surface modification; Titanium.