Elucidation of Antimicrobial Activity of Non-Covalently Dispersed Carbon Nanotubes

Abstract

Microorganisms have begun to develop resistance because of inappropriate and extensive use of antibiotics in the hospital setting. Therefore, it seems to be necessary to find a way to tackle these pathogens by developing new and effective antimicrobial agents. Carbon nanotubes (CNTs) have attracted growing attention because of their remarkable mechanical strength, electrical properties, and chemical and thermal stability for their potential applications in the field of biomedical as therapeutic and diagnostic nanotools. However, the impact of carbon nanotubes on microbial growth has not been fully investigated. The primary purpose of this research study is to investigate the antimicrobial activity of CNTs, particularly double-walled and multi-walled nanotubes on representative pathogenic strains such as Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Pseudomonas aeruginosa, Klebsiella pneumoniae, and fungal strain Candida albicans. The dispersion ability of CNT types (double-walled and multi-walled) treated with a surfactant such as sodium dodecyl-benzenesulfonate (SDBS) and their impact on the microbial growth inhibition were also examined. A stock concentration 0.2 mg/mL of both double-walled and multi-walled CNTs was prepared homogenized by dispersing in surfactant solution by using probe sonication. UV-vis absorbance, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) were used for the characterization of CNTs dispersed in the surfactant solution to study the interaction between molecules of surfactant and CNTs. Later, scanning electron microscopy (SEM) was used to investigate how CNTs interact with the microbial cells. The antimicrobial activity was determined by analyzing optical density growth curves and viable cell count. This study revealed that microbial growth inhibited by non-covalently dispersed CNTs was both depend on the concentration and treatment time. In conclusion, the binding of surfactant molecules to the surface of CNTs increases its ability to disperse in aqueous solution. Non-covalent method of CNTs dispersion preserved their structure and increased microbial growth inhibition as a result. Multi-walled CNTs exhibited higher antimicrobial activity compared to double-walled CNTs against selected pathogens.

Optimizing CNT Loading in Antimicrobial Composites for Urinary Tract Application

“…Representative CLSM images of the E. coli CECT 434 GFP biofilms developed on different surfaces (Figure 6) clearly show an effect of the BM treatment on biof Results show a further decrease in the number of culturable cells for the ball-milled samples of around 24% when compared to the same loading (3 wt%) of CNT-O. This result suggests that BM treatment increases CNT's ability to disperse in the PDMS matrix, inducing morphological changes in the CNT/PDMS composites [45], which may increase the CNT surface contact with the microbial cells, leading to cell death [44]. Moreover, the effect of ball-milled CNTs on the reduction of E. coli adhesion and its association with the degree of dispersion of CNTs were already demonstrated [24].…”

“…However, only the surface with 3 wt% CNT-O loading presented a statistically significant reduction of cell culturability (p < 0.001), being the most promising surface for the inhibition of E. coli biofilms. The lower antimicrobial activity of 4 and 5 wt% CNT-O/PDMS surfaces may be justified by the decrease of CNTs dispersion degree imposed by increased loading, once the CNTs antimicrobial activity depends on their dispersion state [44]. Since no major differences were observed in the total cell number (Figure 4b), it is possible to assume that this decrease in cell culturability is a consequence of the antimicrobial activity of CNT-O/PDMS composites (an anti-adhesive activity would lead to a higher decrease in the total cell number).…”

Is the Antibacterial Activity of Multi-Walled Carbon Nanotubes (MWCNTs) Related to Antibiotic Resistance? An Assessment in Clinical Isolates

“…Some studies have identified oxidative stress (producing bacterial membrane damage) as one of the possible causes of the antimicrobial properties of CNTs [30][31][32][33][34]. However, recent studies have shown that the mechanical interaction of carbon-based nanomaterials with bacteria, and not oxidative stress, is the main antimicrobial activity of these compounds [35][36][37][38][39]. In particular, the first evidence of the strong antimicrobial activity of CNTs was obtained by treatment of Escherichia coli with SWCNTs, which caused severe membrane damage and bacterial death [40].…”

Potentiometric Study of Carbon Nanotube/Surfactant Interactions by Ion-Selective Electrodes. Driving Forces in the Adsorption and Dispersion Processes

“…As a consequence of these properties, they show a wide range of applications. For example, they have been used in electronics, polymer composites, energy storage materials, catalysis, gas storage materials, sensors, environment and biomedicine [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. These applications are limited due to a low and poor solubility in solution because of the existence of strong Van der Waals forces and π-π stacking interactions among the tubes, which provoke their agglomeration into ropes and/or bundles [ 13 , 14 , 15 ].…”

“…They will also shed new light onto the difference between the adsorption of ionic surfactants at the CNT surfaces and the dispersion of these nanostructures by these ionic surfactants. Understanding the driving forces of both processes is important in relation to the wide range of applications of CNTs in which a good dispersion of the carbon nanotubes is essential [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ].…”