Chemical and biological reactivity of insoluble nickel compounds and the bioinorganic chemistry of nickel.

The basic concepts describing the surface properties of binary metal compounds at solid-solution interfaces are reviewed. For hydrated surfaces, the development of surface charge is dependent on pH and the extent of specific adsorption of cations and anions. It is concluded from data on haemolysis of human erythrocytes, and surface adsorption of proteins and cations that surface passivity (external smoothness/crystallinity, low surface charge) combined with low to moderate body fluid solubility correlate with published carcinogenicities. In a review of the coordination chemistry of Ni2+, the following chemical properties are identified as determinants of biological reactivity: size, stereochemistry, binding preferences, complex stability, kinetic lability, and redox properties. New developments in the association of Ni2+ with proteins suggest: a role for the Ni3+/Ni2+ redox couple in bacterial proteins; the involvement of the primary copper/nickel binding site of human serum albumin in antigen recognition by antibodies with nickel-related specificity; and that Ni2+ can act as an antagonist of essential metal ions. It is concluded that there is considerable scope for work elucidating the surface properties of binary nickel compounds, and that the in vivo displacement of Mg2+, Ca2+, Zn2+ and perhaps other ions by Ni2+ constitutes a useful mechanistic concept in nickel toxicology.