Graphene Oxide-Functionalized Membranes: The Importance of Nanosheet Surface Exposure for Biofouling Resistance

Abstract

Surface functionalization using two-dimensional (2D) graphene oxide (GO) materials is a promising technique to enhance the biofouling resistance of membranes used in water purification and reuse. However, the role of GO exposure, which is crucial for the contact-mediated toxicity mechanism, has not been well evaluated or elucidated in previous studies. Herein, we employ bioinspired polydopamine chemistry to fabricate GO-functionalized membranes through two strategies: coating and blending. The two types of GO-functionalized membranes displayed comparable roughness, hydrophilicity, water permeability, and solute retention properties but different degrees of GO nanosheet exposure on the membrane surface. When in contact with the model bacterium, Escherichia coli, the GO-coated membrane exhibited enhanced biofouling resistance compared to that of the GO-blended membrane, as evidenced by lower viable cells in static adsorption experiments, and lower water flux decline and higher flux recovery in dynamic biofouling experiments. Moreover, the development of biofilm on the GO-coated membrane was also inhibited to a greater extent than on the GO-blended membrane. Taken together, our findings indicate the paramount importance of GO exposure on the membrane surface in conferring antibacterial activity and biofouling resistance, which should be considered in the future design of antibiofouling membranes using 2D nanomaterials.

Exposure of Smaller and Oxidized Graphene on Polyurethane Surface Improves its Antimicrobial Performance

“…Increasing GNP concentration increased the chances of exposing platelets at the surface and thus the contact with bacteria. This correlates with the literature that states the importance of GBM sheets orientation, exposure and concentration on the antibacterial performance of surfaces integrating GBM [40,83]. Therefore, increasing platelets exposure increased contact with bacteria, which consequently seemed to potentiate the effects of the sharp edges and basal planes of the GNP platelets, either due to disruption of the cell membrane [36,84] or oxidative stress induction [41,85].…”

“…This affects the way GBM are deposited and oriented on the surface, thus impacting bacteria-GBM interaction and ultimately the antibacterial activity of the surfaces [40]. This relation of GBM exposure with the antibacterial activity of GBM-containing surfaces has been suggested in other studies, as recently by Cheng et al [83]. Even though antibacterial activity has been observed both when basal planes [84][85][86] or sharp edges are exposed [87], a direct contact between bacteria and the surface must occur, as reinforced by the absence of antibacterial effects both on the bacteria incubated with the composites and on bacteria collected in the supernatant with both surfaces.…”

Bioinspired Design of Graphene‐Based Materials

“…The adhesive properties of PDA coatings can also be exploited to graft graphene-based materials onto various surfaces or to secure strong interactions within a composite matrix, such as with polymers [198] or cloth. [43] Notably, this can be achieved without altering the properties of the substrate, such as the periodic-structure-dependent optical properties of photonic crystal nanoparticles when GO nanosheets are immobilized on its surface using a PDA interlayer (Figure 10a).…”

Toward the Application of Graphene for Combating Marine Biofouling

“…Hence, the exposure of GMs in the coating surface is crucial. [ 34 ] In addition, GMs have a large surface area that is beneficial when loading with other nanoparticles, which can enhance antifouling property due to the synergistic effect. [ 35 ] GMs and bacteria both have negative charges in a marine environment.…”

“…As discussed in Section 2, the exposure of GMs in the coating surface is crucial for their antifouling activity. [ 34 ] As a result, the search for new suitable matrix materials and fabrication methods may be emphasized in future studies.…”