Carbon nanotube-based surfaces: Effect on the inhibition of single- and dual-species biofilms of Escherichia coli and Enterococcus faecalis

Abstract

This study aimed to investigate the influence of multi-walled carbon nanotube (MWCNT) loading on the antibiofilm activity of MWCNT/poly(dimethylsiloxane) (PDMS) composites against single- and dual-species biofilms of Escherichia coli and Enterococcus faecalis. MWCNT/PDMS composites containing different MWCNT loadings (1, 2, and 3 wt%) were synthesized and tested for their ability to reduce biofilm formation. Surfaces were evaluated using a parallel plate flow chamber for 24 h under the hydrodynamic conditions prevailing in urinary catheters. Biofilm formation by E. coli and E. faecalis was assessed by determining the number of total, viable and culturable cells, and the biofilm architecture was analyzed by confocal laser scanning microscopy (CLSM). Results revealed that the composite with the highest MWCNT loading (3%) was the most effective against E. coli and E. faecalis biofilms. When compared with bare PDMS, it significantly reduced the number of total (63%), viable (74%), and culturable (77%) cells of E. faecalis biofilms, and the number of viable (50%) and culturable (64%) cells of E. coli biofilms. The effect of these MWCNT-based composites on the inhibition of biofilm formation was corroborated by CLSM, where reductions of up to 57% and 64% in biofilm biovolume and thickness, respectively, were observed. Even though dual-species biofilms presented lower susceptibility to the antimicrobial activity of MWCNT/PDMS composites, a reduction of 32% in the number of culturable cells was obtained with 3% MWCNT/PDMS surfaces. Taken together, these results suggest that MWCNT/PDMS composites are promising materials for developing novel antimicrobial and antifouling coatings for urinary tract devices.