Amount of TNF-αreleased from macrophagesreacting with polyethylene particles showeddose-dependent relationship to the totalsurface area of added particles

The immune response to ultra-high molecular weight polyethylene wear debris is thought to beone of the majorcauses of osteolysis and aseptic loosening.An in-vitro methodfor the measurement of the response is necessary in orderto priori estimate the lifespan of the implants.lt is of importance to distinguish the bioactivity of various polyethylenebiomaterials.The current research focused on the inverse culturing process,which was shown to be effective toevaluate the biological reaction of mouse macrophages and wear particles by estimating the amount of inflammatorycytokines.In this study,several improvements were carried out through trial quantification.Silicon sheet wasintroduced instead of PVC seal to remove air bubbles and to eliminate the influence of potentially-attached endotoxin.Calculations along with experiments according to Stokes'law were also performed to determine the reaction time andthe minimum particle size that can be phagocytosed by macrophages in the improved method.The authorsco-incubated mouse macrophages and polyethylene particles in different sizes,densities and molecular weights usingthe new method.The result suggests that the amount of tumour necrosis factor-α(TNF-α)generated is dosagedependent on the total surface area of particles added regardless of particle size,density and molecular weight ofpolyethylene.