Semiquantitative Performance and Mechanism Evaluation of Carbon Nanomaterials as Cathode Coatings for Microbial Fouling Reduction

Abstract

In this study, we examine bacterial attachment and survival on a titanium (Ti) cathode coated with various carbon nanomaterials (CNM): pristine carbon nanotubes (CNT), oxidized carbon nanotubes (O-CNT), oxidized-annealed carbon nanotubes (OA-CNT), carbon black (CB), and reduced graphene oxide (rGO). The carbon nanomaterials were dispersed in an isopropyl alcoholNafion solution and were then used to dip-coat a Ti substrate. Pseudomonas fluorescens was selected as the representative bacterium for environmental biofouling. Experiments in the absence of an electric potential indicate that increased nanoscale surface roughness and decreased hydrophobicity of the CNM coating decreased bacterial adhesion. The loss of bacterial viability on the noncharged CNM coatings ranged from 22% for CB to 67% for OA-CNT and was dependent on the CNM dimensions and surface chemistry. For electrochemical experiments, the total density and percentage of inactivation of the adherent bacteria were analyzed semiquantitatively as functions of electrode potential, current density, and hydrogen peroxide generation. Electrode potential and hydrogen peroxide generation were the dominant factors with regard to short-term (3-h) bacterial attachment and inactivation, respectively. Extended-time electrochemical experiments (12 h) indicated that in all cases, the density of total deposited bacteria increased almost linearly with time and that the rate of bacterial adhesion was decreased 8-to 10-fold when an electric potential was applied. In summary, this study provides a fundamental rationale for the selection of CNM as cathode coatings and electric potential to reduce microbial fouling. Biofilm formation is ubiquitous in aquatic environments and is undesirable for industrial systems, such as heat exchangers and ship hulls (1), as well as for engineered environmental systems, such as membrane filters (2) and water distribution pipelines. A critical initial stage of biofouling involves microorganism adhesion and formation of the primary slime layer that allows for continued biofilm development (3, 4). Thus, if initial microorganism adhesion is reduced, continued biofilm development may be slowed as well.Continuous research efforts have been devoted to microbial fouling control, from the development of antimicrobial surfaces (5) to the disturbance of bacterial biofilm ecology by quorum sensing (6, 7). With regard to antimicrobial surfaces, the interfacial energy between a surface and water has been identified as a key factor in microbial adhesion, and hydrophilic surfaces generally hinder protein adsorption and, in turn, reduce biofouling (8). A highly charged cationic surface has also been demonstrated to kill bacteria and reduce fouling (9). However, since microbes have a complex and species-dependent surface chemistry, a permanently modified surface will not reduce biofouling for all microbes, and decreased antifouling performance is often observed in complex environments. One solution may be active biofouling reduction that can be tuned in situ ...

Antimicrobial and anti-adhesive properties of carbon nanotube-based surfaces for medical applications: a systematic review

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Cell Transport Prompts the Performance of Low-Voltage Electroporation for Cell Inactivation

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