IN-VITRO MECHANICAL AND BIOLOGICAL ASSESSMENT OF HYDROXYAPATITE-REINFORCED POLYETHYLENE COMPOSITE

In vitro performance of hydroxyapatite (HA)-reinforced polyethylene (P E) composite (HAPEX(TM)) has been characterized from both mechanical a nd biological aspects. The mechanical properties of HAPEX(TM), such as tensile strength and Young's modulus, showed little change after imme rsion in a physiological solution at 37 and 70 degrees C for various p eriods. In addition, the biological response of primary human osteobla st-like (HOB) cells in vitro on HAPEX(TM) was assessed by measuring DN A synthesis and osteoblast phenotype expression. Cell proliferation ra te on HAPEX(TM) was demonstrated by an increase in DNA content with ti me. A high tritiated thymidine ([H-3]-TdR) incorporation/DNA rate was observed on day 1 for HAPEX((TM)), indicating a stimulatory effect on cell proliferation. The alkaline phosphatase (ALP) activity was expres sed earlier on HAPEX(TM) than on unfilled PE and increased with time, indicating that HOB cells had commenced differentiation. Furthermore, it was found that the HA particles in the composite provided favourabl e sites for cell attachment. It appears that the presence of HA partic les in HAPEX(TM) may have the advantage of acting as microanchors for bone bonding in vivo.