Wear particles and strain cause different levels of cell membrane damage in MC3T3-E1 and RAW 264.7 cells. A: Sytox green assay of membrane damage in no-treatment (N), Ti, SPS, and Ti + SPS groups. In MC3T3-E1 cells, membrane damage in the Ti + SPS group was increased compared with control and Ti groups. In RAW 264.7 cells, number of membrane-damaged cells was similar in Ti + SPS and Ti groups. B: in MC3T3-E1 and RAW 264.7 cells, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay shows similar level of metabolic activities in Ti and Ti + SPS groups. Each symbol denotes significant difference (P < 0.05); n = 5.