Binary-ternary Cd(II)-(hydroxycarboxylic acid)-(aromatic chelator) systems exhibit in vitro cytotoxic selectivity in a tissue-specific manner

Abstract

Cadmium is a metallotoxin, amply encountered in the environment and derived through physical and anthropogenic activities. Its entry in various organisms leads through water and the food chain to humans, thereby inducing a plethora of pathophysiologies. Delineation of the interactive role of cadmium with physiological and physiologically relevant substrates, requires well-defined forms of cadmium arising from such interactions along with the ensuing chemical reactivity amounting to toxic manifestations and health aberrations. To implement such efforts, low molecular mass substrate metal ion binders are needed, forming species with enhanced solubility and bioavailability. To that end, α-hydroxy isobutyric acid (HIBAH2) was used in pH-specific synthetic efforts involving bulky aromatic chelators 2,2′-bipyridine (2,2′-bipy) and 1,10-phenanthroline (phen), thus leading to new crystalline materials [Cd(C4H7O3)2]n(1), [Cd(C4H7O3)2(H2O)2](2), [{Cd2(C4H7O3)2(C10H8N2)2(H2O)2}(NO3)2]n·nH2O(3), and [{Cd2(C4H7O3)2(C12H8N2)2(H2O)2}(NO3)2]n·2nH2O(4), which were physicochemically characterized (elemental analysis, FT-IR, NMR, ESI-MS, and X-ray crystallography) in the solid state and solution. Their physicochemical characteristics led to their employment in tissue-specific biological toxicity studies in three different cell lines. Their toxicity profile (cell viability, morphology, chemotacticity) was correlated through genetic biomarkers to apoptotic-necrotic processes, thereby shedding light on cadmium cellular toxicity processes. Finally, the cytoprotective action of specific chelators was examined, lending credence to the notion that appropriately structured chelators and antioxidants may be used as effective deterrent to cadmium toxicity. Collectively, structure-specificity linked to tissue-specific toxicity profiling in well-defined binary-ternary Cd(II)-HIBAH2 systems exemplifies that metal ion's aberrant interactions in the cellular milieu, meriting further probing into the development of efficient chelators in cadmium detoxification.