Antibacterial effect of graphene oxide (GO) nano-particles against Pseudomonas putida biofilm of variable age.

Hussam Fallatah,Mohamad Elhaneid,Tim W Overton,Hanene Ali-Boucetta,Konstantinos Gkatzionis,Hani El Kadri

doi:10.1007/s11356-019-05688-9

Abstract

Graphene oxide (GO) has been reported to possess antibacterial activity; therefore, its accumulation in the environment could affect microbial communities such as biofilms. The susceptibility of biofilms to antimicrobials is known to depend on the stage of biofilm maturity. The aim of this study was to investigate the effect of GO nano-particles on Pseudomonas putida KT2440 biofilm of variable age. FT-IR, UV-vis, and Raman spectroscopy confirmed the oxidation of graphene while XPS confirmed the high purity of the synthesised GO over 6 months. Biofilms varying in maturity (24, 48, and 72 h) were formed using a CDC reactor and were treated with GO (85 μg/mL or 8.5 μg/mL). The viability of P. putida was monitored by culture on media and the bacterial membrane integrity was assessed using flow cytometry. P. putida cells were observed using confocal microscopy and SEM. The results showed that GO significantly reduced the viability of 48-h biofilm and detached biofilm cells associated with membrane damage while the viability was not affected in 24- and 72-h biofilms and detached biofilm cells. The results showed that susceptibility of P. putida biofilm to GO varied according to age which may be due to changes in the physiological state of cells during maturation. Graphical abstract Electronic supplementary materialThe online version of this article (10.1007/s11356-019-05688-9) contains supplementary material, which is available to authorized users.

Highlights

Graphene is a two-dimensional material and a single layer of monocrystalline graphite with sp2 hybridised carbon atoms (Jamialahmadi et al 2018)
In 24- and 72-h biofilms, the percentage of PIpositive cells was similar in the control and after graphene oxide (GO) treatment, but in the 48-h biofilm, the percentage of propidium iodide (PI)-positive cells was 4-fold higher after GO treatment compared with the control. These results indicate that the antibacterial activity of GO on P. putida depends on the maturity stage of the biofilm
Antibacterial activity of GO against biofilms was observed and this activity only occurred at a specific stage of biofilm maturity

Summary

Introduction

Graphene is a two-dimensional material and a single layer of monocrystalline graphite with sp hybridised carbon atoms (Jamialahmadi et al 2018). Environ Sci Pollut Res (2019) 26:25057–25070 properties and relatively low manufacturing cost. These have shown promising applications in various areas in industry used as metal free catalysts for degradation of organic matters in water and can be used in polymer membranes for water purification and medical cloths for wound disinfection, and coating of silicon tubes of catheters to prevent biofilm formation (Wang et al 2013; Zheng et al 2018) Such applications may increase the release of non-biodegradable GO into the environment posing risks of biological toxicity (Guo and Mei 2014)

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Conclusion