Biological Response of J774.2 macrophages grown on diatom frustules (a) LDH release measuring cytotoxicity after 24 hrs, (b) cell proliferation, solid bars represent 24 h and hatched bars represent 72 h in culture, Error bars indicate ±1 SD, N = 3 for a and b. (c to f) fluorescence microscopy images of live/dead stained J774 cells (green = live; red = dead) after 24 hrs in culture, (c) cells (d) Diatom (e) Diatom Amine (f) Diatom Thiol (g) quantitative J774 cell viability determined from image analysis. Error bars indicate ±1 SD. N = 6/image × N 3 replicate wells.