The negative results can be attributed either to the

The negative results can be attributed either to the inability of the complexes to diffuse into the Gram-negative bacteria cell membranes and hence unable to interfere with its biological activity or they can diffuse and inactivated by unknown cellular mechanism i.e. bacterial enzymes. The positive results suggested the very diffusion of the complexes into the bacterial ARQ197 and were able to kill the bacterium as indicated by the zones of inhibition of bacterial growth [51] and [52]. These complexes also disturb the respiration process of the cell and thus block the synthesis of the proteins that restricts further growth of the organism [52] and [53].
Cell proliferation assay
In view of the biological activity of thiosemicarbazides, we firstly have evaluated the ability of the some thiosemicarbazides derivatives to inhibit cancer cell growth against hepatocellular carcinoma (HCC) [29]. In our experiments, IC50 values (compound concentration alternation of generations produces 50% of cell death) in micro molar units were calculated. For comparison purposes the cytotoxicity of Fluorouracil (5-FU) and the free ligand as well as its metal complexes has been evaluated under the same experimental conditions. It is clearly observed that complexation with metal has no synergistic effect on the cytotoxicity (Figs. 9). The comparison of cytotoxicity indicates that all complexes show much lower IC50 values for HePG2 and MCF-7 than ligand. These gratifying results are encouraging its further screening in vitro. Therefore, its further biological evaluation in vivo as well as studies of mechanism of action is necessary [54].