Quantification of PVA hydrogel dissolution in water and bovine serum

Poly(vinyl alcohol) (PVA) hydrogel is a candidate biomaterial for orthopaedic applications such as cartilage resurfacing due to its viscoelastic nature, high water content, and biocompatibility. PVA is not assumed to be biodegradable; however, depending on the level of physical and/or chemical crosslinking it may illicit dissolution either during storage in water or during in vivo use when articulating against cartilage. In addition, gravimetric quantification of wear during pre-clinical wear testing of a PVA-based implant is challenging due to unpredictable changes in water content. Our aim was to develop a method to detect dissolved PVA in water and bovine serum; bovine serum is the lubricant of choice for pre-clinical wear testing of orthopaedic implants. We used iodine complexation to determine PVA concentration in solution using UV-Vis spectrophotometry. We further refined this method to determine the effects of PVA molecular weight and the presence of poly(ethylene glycol) (PEG) that may be used in the fabrication of the gel. In addition, we developed a method for determining the amount of PVA dissolved in bovine serum to quantify the extent of PVA dissolution during pre-clinical wear studies. We were able to detect PVA in solution with concentrations as low as 10−5 g/mL and created calibration curves for different solvents, i.e. water and bovine serum. Based on the calibrations, we quantified the dissolution behavior of PVA in water at 40 °C during a six month period and found that the dissolution from an untreated PVA hydrogel is 3 × 104 ppm, and could be lowered to 1 × 103 ppm by dehydration and/or annealing of the PVA hydrogel.