Effects of solvent-free amine functionalization of graphene oxide and nanodiamond on bacterial growth

Abstract

We studied the effect of covalent functionalization of graphene oxide (GO) and nanodiamond (ND) with octadecylamine (ODA) on bacterial growth (a series of experiments was performed also with pristine single-walled carbon nanotubes [SWNTs] for comparison). The bacteria tested were Escherichia coli and Staphylococcus aureus, which represent Gram-positive and Gram-negative types, respectively, and are of importance for the environment and human health. We found that pristine GO is the most toxic nanomaterial in both bacteria species, which exhibits a dose-dependent behavior. SWNTs show toxicity only against S. aureus at the higher concentrations of 1.0 and 10 mg/mL. Pristine ND, as expected, was found to be the least toxic against both species of bacteria, and in the experiments with S. aureus it even showed a viability amplifier activity at 10 mg/mL concentration. The use of ODA-functionalized nanomaterials generally changed the toxicity behavior, neutralizing the antibacterial effect of GO (for both S. aureus and E. coli), but making ODA-functionalized ND more toxic as compared to pristine material (with respect to S. aureus).