Biocompatible composite films and fibers based on Poly(Vinyl alcohol) and powders of calcium salts

A method for obtaining composite biodegradable materials in the form of films and fibers, based on hydrophilic poly(vinyl alcohol) matrix and synthetic nanopowders of calcium salts containing phosphate and/or carbonate anions, was proposed. The phase composition of fillers previously synthesized from Ca(CH3COO)2·H2O, (NH4)2HPO4 and/or (NH4)2CO3 aqueous solutions at a chosen ratio of components was represented by hydroxyapatite (Ca10(PO4)6(OH)2), brushite (CaHPO4·2H2O), as well as calcite and vaterite polymorphs (CaCO3), all of which are known to be compatible with biological cells. Filled poly(vinyl alcohol)-based nanofibers with the wide thickness range of approximately 190–530 ​nm were manufactured from composite suspensions by bottom-up type of electrospinning. The addition of calcium carbonate to the suspension with a particle filling degree of 20% showed a significant reduction in operating voltages (from 42 ​kV to 28 ​kV) during electrospinning process and, as a result, facilitated stable fiber formation. According to the microscopy data, the average size of inorganic inclusions did not exceed 5 ​μm for fibrous materials, while the particle size of calcium phosphate fillers in films obtained by casting into polystyrene molds, was characterized by larger values (up to 40 ​μm) due to intensive crystallization process on film surfaces. The biocompatible phase composition and structural features, including surface roughness and special particle morphology, ensures a potential application of the studied materials as filled scaffolds for the multipotent stromal cells cultivation in bone tissue engineering.