A new insight into in vitro behaviour of poly(ε-caprolactone)/bioactive glass composites in biologically related fluids

In the present work, the role of content, size and chemical composition of gel-derived bioactive glass particles from the SiO₂–CaO–P₂O₅ system in modulating the in vitro bioactivity, osteoinductive properties and long-term (up to 15 months) degradation behaviour of poly(ε-caprolactone)-based composite films was investigated. Bioactivity was assessed in simulated body fluid (SBF) and HEPES-free Dulbecco’s modified Eagle medium (DMEM) supplemented with 10% foetal bovine serum (FBS), while hydrolytic degradation tests were performed in phosphate buffer saline. Obtained composite films showed excellent calcium phosphate (CaP) layer forming ability in both SBF and DMEM-10% FBS. However, kinetics of bioactivity process strongly depended on the type of medium used. The layer of amino acids and proteins, derived from cell culture medium, on the surfaces of composites created barrier that inhibited release of the ions on the one hand, while increasing nucleation density of calcium phosphates, affecting the morphology of formed CaP layers on the other. The presence of bioactive glass fillers was shown to impart osteoinductive properties to obtained films, supporting osteoblast attachment and proliferation, as well as stimulating cell differentiation and also matrix mineralization process in vitro. We showed that kinetics of bioactivity process and also osteoinductive properties of composite films could be easily modulated with the use of different contents and chemical compositions of fillers. The results showed that modification of PCL matrix with bioactive glass particles accelerated its degradation. We proved that the degradation rate of composites could be controlled and optimized for bone regeneration, in particular by using bioactive fillers causing different calcium phosphate layer forming ability on the surfaces of composites, depending on particle size and chemical composition. We have presented new opportunities to design and obtain multifunctional composites with tunable degradation and bioactivity kinetics, as well as biological properties that can meet complex requirements of bone tissue engineering.