MgAl and ZnAl-Hydrotalcites as Materials for Cosmetic and Pharmaceutical Formulations: Study of Their Cytotoxicity on Different Cell Lines

The knowledge about the effect of hydrotalcites (HTlcs), largely used in pharmaceutics, on non-malignant cell lines is limited. The effect of MgAl-HTlc-and ZnAl-HTlc- (NO(3−)/Cl(−)/CO(3)(2−)) on the cell viability of HaCat, fibroblasts and HepG2 was studied by MTT assay. Cells were incubated either with HTlc suspensions in the culture media and with the supernatant obtained from the suspension being centrifuged. MgAl-HTlcs suspensions resulted in being cytotoxic. As SEM and TEM analyses showed the presence of sub-micrometric particles in all the MgAl-HTlc examined, it could be hypothesized that this fraction can be internalized into cells reducing the viability. MgAl-HTlc-NO(3) is the most cytotoxic probably due to the additional effect of NO(3)(−) anions. ZnAl-HTlcs are cytotoxic, especially for HaCat and HepG2 cells (viability <60% at all the concentrations assayed). The effect is attributable both to the sub-micrometric fraction (identified by TEM) and to the high Zn(2+) levels found in the culture medium by ICP-OES analysis, suggesting that ZnAl-HTlcs are less stable than MgAl-HTlc in the used media. The obtained results suggest that it is very important to perform ad hoc studies in order to evaluate HTlc safety before to be introduced in a formulation.