Synthesis of methacryloyloxyethyl phosphate copolymers and in vitro calcification capacity

Methacryloyloxyethyl phosphate is a methacrylic monomer used to modify different substrates by copolymerisation, in order to enhance hydroxyapatite deposition onto their surfaces. We report the synthesis of two copolymers series using increasing concentrations of methacryloyloxyethyl phosphate with (diethylamino) ethyl methacrylate and 1-vinyl-2-pyrrolidinone. Reactivity ratios were evaluated for the two copolymer systems. The influence of phosphate content and distribution on the capacity to form a calcium-rich layer was evaluated after immersion for 15 days in a synthetic body fluid. Corresponding homopolymers were synthesised as controls. Calcium-phosphorus globules were developed only on samples containing (diethylamino) ethyl methacrylate, and presenting a low density of phosphate groups. The amounts of calcium increased when higher concentrations of methacryloyloxyethyl phosphate were used. The use of 1-vinyl-2-pyrrolidinone was associated with greater calcium amounts, (compared to (diethylamino) ethyl methacrylate). The amine groups may favour the attraction of phosphorus, thus creating another way for the nucleation of calcium/phosphate crystals.