Medium-Dependent Antibacterial Properties and Bacterial Filtration Ability of Reduced Graphene Oxide.

Alexander Gusev,Denis V Kuznetsov,Evgeny Kolesnikov,Aleš Lapanje,Dmitry S Muratov,Mamun Sarker,Iaroslav Rybkin,Olga Zakharova,Nataliia S Vorobeva,Daniil Bratashov,Alexander Sinitskii

doi:10.3390/nano9101454

Abstract

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little effect on the behavior of E. coli in a physiological saline solution. The observed effects of rGO on E. coli in different media could be at least partially rationalized through the adsorption of bacteria and nutrients on the dispersed rGO sheets, which is likely mediated via hydrogen bonding. We also found that the interaction between rGO and E. coli is medium-dependent, and in physiological saline solutions they form stable flocculate structures that were not observed in nutrition media. Furthermore, the aggregation of rGO and E. coli in saline media was observed regardless of whether the bacteria were alive or dead. Filtration of the aggregate suspensions led to nearly complete removal of bacteria from filtered liquids, which highlights the potential of rGO for the filtration and separation of biological contaminants, regardless of whether they include live or dead microorganisms.

Highlights

Graphene and related materials are widely recognized for their potential for a multitude of biomedical applications, which include biosensing, bioimaging, anti-cancer therapy, cell growth, tissue engineering and antibacterial agents among others [1,2,3]
We show that in the experiments involving the same dispersions of reduced graphene oxide (rGO) and same recombinant Escherichia coli (E. coli) bacteria expressing green fluorescent protein (GFP) the outcome of the nanotoxicity experiment strongly depends on the culture medium
While previous studies showed that the toxic effects associated with rGO depend on a large number of factors, which include the flake size, surface functionalization and concentration among other parameters, here we demonstrate that the type of culture medium is an important factor that could affect the outcome of a nanotoxicity experiment

Summary

Introduction

Graphene and related materials are widely recognized for their potential for a multitude of biomedical applications, which include biosensing, bioimaging, anti-cancer therapy, cell growth, tissue engineering and antibacterial agents among others [1,2,3]. While GO, rGO and other graphene-based materials have been widely used in biomedical research [1,2,3,4,5], there are different views on their nanotoxicity [5]. There was a considerable amount of in vitro and in vivo research on toxic effects associated with graphene-based materials [4,5]. Other authors argue that graphene-based materials do not exhibit inhibitory effects on bacteria [11,12,13,14]

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Conclusion