Spontaneous calcification of acrylic hydrogels in abiotic calcifying media and the relevance of ionic solute effects

Polymers can undergo dystrophic calcification following their implantation in living tissues. The biomaterials-associated calcification involves the formation of calcium phosphate phases having compositions similar to that of hydroxyapatite, Ca10(PO4)6-(OH)2, but of poorer crystallinity. Calcification has a detrimental effect on the clinical success of the prosthetic devices currently in use, with the exception of orthopaedic implants where hydroxyapatite deposition is usually beneficial. Most previous calcification studies have been directed to the hydrophobic polymers, generally strong materials, either elastic or rigid. Many examples of clinical failure caused by calcification come from the field of artificial hearts and blood pumps. Here, we evaluate the precipitation of calcium phosphate from a metastable solution in the presence of a homogeneous hydrogel (a transparent PHEMA gel), and investigate the solute effects of the participating ions.