Enhanced osteoblast response to a polymethylmethacrylate-hydroxyapatite composite

Hydroxyapatite (HA)-reinforced polymers have been proposed as a method of i mproving the biological properties of bone cements and implant materials. F or example, bone cements based on polymethylmethacrylate (PMMA) have long b een used to secure orthopedic implants to the skeleton. This composite coul d also be used as a polished coating on other materials or in bulk form, sh aped or molded, to custom fit a specific clinical need. However, complicati ons may occur as a result of the limited mechanical and biological properti es of PMMA. The purpose of this investigation was to determine whether the incorporation of HA in a PMMA matrix would enhance the biological propertie s of osteoblast response as compared to PMMA alone. Fetal rat calvarial ost eoblasts were plated on discs of PMMA, PMMA/HA, commercially pure titanium (CpTi) and tissue culture polystyrene (control). Osteoblast attachment and day 2 proliferation were similar on all implant materials, whereas, day 8 p roliferation on PMMA/HA was significantly higher than on PMMA and similar t o CpTi and control. Extracellular matrix production was examined by immunoh istochemistry which indicated that osteoblasts cultured on PMMA/HA showed a more distinct networked pattern of organized fibronectin. Histochemical st aining of mineralization was examined by confocal microscopy which demonstr ated a higher degree of mineralization in nodules formed on PMMA/HA as comp ared to PMMA. Together, these results indicate that the addition of HA in a PMMA matrix improves osteoblast response as compared to PMMA alone. Theref ore, the incorporation of HA into a PMMA matrix may be a useful method to p rovide PMMA materials with enhanced osteogenic properties. (C) 2001 Elsevie r Science Ltd. All rights reserved.