Chelating agents in biological systems.

Chelation enables metals to be transported to or from vulnerable target sites, and to hinder or facilitate their carcinogenic potential. In the reverse sense, metals are capable of ligand scavenging via complexation or mixed complex formation--the latter being the result of interaction with binary complexes. Consequently, metal complexes can be utilized for the transport of selected organic chemotherapeutic drugs to target organs, or for the decorporation of those toxic organic compounds which are able, before or after metabolic activation, of reacting with metals or 1:1 metal complexes. It is emphasized that the degree to which metal ions interact in vivo should employ the conditional constants which take into account competition from other ions, especially Ca2+, H+, and OH-. The genotoxic consequences of the various chemical factors involved in chelation, along with examples: kinetics, stabilization of oxoidation states, lipophilicity, and mixed ligand formation, are discussed.