EFFECT OF CO-MONOMER COMPOSITION ON THE INTEGRITY OF BIOACTIVE GROWTH-HORMONE RELEASED FROM NOVEL PEMA BASED POLYMERS

The release of human growth hormone (hGH) from hormone loaded bone cem ent was previously shown to enhance osteoid formation. hGH is a comple x protein and its incorporation into such cements may compromise its b ioactivity. We therefore characterized the release of hGH from a serie s of methacrylate systems based upon poly(ethylmethacrylate) (PEMA). D ifferent mixtures of two monomers, hydroxyethylmethacrylate (HEMA) and n-butylmethacrylate (n-BM) were used to provide polymers with graded water uptakes. Exclusive use of only one of the monomers resulted in e nhanced cytotoxicity and also reduced release of the bioactive hormone . Combinations of the monomers improved the recovery of bioactivity fr om the polymers and reduced their cytotoxicity. hGH released from the polymer with the lowest water uptake (100% n-BM, 0% HEMA) had an excep tionally low bioactivity: immunoactivity ratio, suggesting that the bi oactive site of the hormone is particularly susceptible to disruption when it is incorporated into this matrix. (C) 1996 John Wiley & Sons, Inc.