Development of poly(propylene fumarate) (PPF), vinyl phosphonic acid (VPA) and vinyl phosphonic acid di-ethyl ester (VPES) based scaffolds for bone tissue engineering

Autologous and allogenous bone grafts or permanent prosthetic implants are used in treatment of bone damages. The limitations and disadvantages of these techniques led to find other ways of healing the damaged bones. A biodegradable material which acts as a structural support to the damaged area and as a scaffold that guides bone formation is one desirable solution. Biodegradable materials have the advantage of enhancing the regeneration of the damaged area. Polypropylene fumarate (PPF) is an unsaturated polyester. PPF can be copolymerized with a vinyl monomer to give a biocompatible and biodegradable thermoset. Recently, N-vinyl pyrrolidone (VP) is widely used as a co-monomer with PPF in different weight ratios in order to support the damaged area of a bone. In addition, it is observed that the resulting biomaterial also acts as a scaffold that guides the bone formation. Moreover, composites of PPF/VP biomaterial (containing organic additives) gave promising results as bone tissue engineering scaffolds. In this study, the PPF polymer was synthesized via polycondensation of excess propylene glycol and fumaric acid. The PPF pre-polymer was then thermally cured with vinylphosphonic acid (VPA) and diethyl vinylphosphonate (VPES) in the presence of benzoyl peroxide initiator, via radical polymerization at changing co-monomer and initiator weight ratios. Additionally synthesized PPF was cured via UV light in the presence of phenylbis(2,4,6-trimethylnbenzoyl)phosphine oxide with the same co-monomers. Effect of co-monomer contents on thermal transitions, thermomechanical properties, compressive properties, biodegradability and hydrophilicity of the resulting biomaterials were evaluated. Biocompatability of the resulting materials with the use of VPA and VPES was analysed by the MTS assay. Results of von kossa, alkaline phosphatase and osteocalcin activities were evaluated in order to observe the osteoblast activity.