Besides, the toxic potential of FeCoNiCuZn was assessed against Gram-negative bacterium E. 17 coli using the agar-well diffusion method, with the antibiotic ciprofloxacin as the positive control 18 and PBS as the negative control. As seen in Fig. , ciprofloxacin significantly inhibits the proliferation of E. coli to an average diameter of 15 mm. On the other hand, there are no apparent ). It is observed that irrespective of the type of 14 pharmaceutical compound, their percentage decomposition over the as-developed FeCoNiCuZn 1 HEA is several orders of magnitude higher than metal oxide nanoparticles and their composites,