Development of a model for bioresorbability of bioceramic microparticles

Over the past decade, numerous studies have implicated wear particle debris, generated by everyday wear or ceramic implants, as the essential contributors to implant failure [3,4,5,6,7]. We investigated the interactions of ceramic particles (TCP and HA) on cell viability, cell damage, and respiratory burst in a macrophage cell line (RAW 264.7) for a duration of 24, 48, and 72 hours. The results show that cellular protein levels ranged between 0.20-0.3 mg/ml for the duration of the experiment, and there was no difference detected between or among the groups (P < 0.05). Differences in MDA levels (the amount of lipid peroxides formed at the cellular membrane) were not detected at the early time points (24-48 hours). However, with time in culture there is an increase in MDA levels in all groups. There were no differences detected in nitric oxide production between TCP and the control at all phases. The amount of nitric oxide produced by cells treated with Ha decreased slightly at 24 hours. In contrast, at 48 and 72 hours there was a significant increase when compared to the control. Morphological evaluation revealed that cells treated with TCP contained irregular membrane boundaries, and appeared to have cytoplasmic extensions. Many of the macrophages consisted of large vacuoles containing TCP particles. Cells treated with HA also contained irregular cytoplasmic borders with an increase in vacuolization. At 48 hours, the morphology of all groups remained the same, and at 72 hours, many of the cells treated with TCP and HA began to lyse. Overall, RAW 264.7 macrophage cells are capable of ingesting particles of TCP and HA, and after three days in culture the cells begin to show the effects of increased retention of ceramic particles. The results of this investigation can be used as a model for the assessment of the resorbability rate of implantable devices.