The phagocytosis and transforming activity of crystalline metal sulfide particles are related to their negative surface charge

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Abstract
Crystalline nickel sulfide (.alpha.NiS) and cobalt sulfide (CoS2) particles can cause greater [carcinogenic] cell transformation and cellular toxicity than the respective amorphous metal sulfide particles. Cultured mammalian cells phagocytose the crystalline metal sulfide particles more readily than the amorphous ones. In the case of the nickel sulfides, the crystalline metal sulfide particles had negatively charged surfaces, in contrast to the amorphous particles which were positively charged X-ray photoelectron spectroscopy analysis of amorphous and crystalline NiS particles revealed that the outermost surface of the 2 particles had striking differences in Ni/S ratios and in their S oxidation states. Rendering particles'' surfaces more negative by reduction with lithium aluminum hydride enhanced their phagocytosis and, in the case of amorphous NiS chemical reduction, resulted in an incidence of morphological transformation of Syrian hamster embryo cells comparable to that observed with untreated crystalline .alpha.NiS.