Antibacterial activity and cytotoxicity of multi-walled carbon nanotubes decorated with silver nanoparticles

Abstract

Recently, various nanoscale materials, including silver (Ag) nanoparticles, have been actively studied for their capacity to effectively prevent bacterial growth. A critical challenge is to enhance the antibacterial properties of nanomaterials while maintaining their biocompatibility. The conjugation of multiple nanomaterials with different dimensions, such as spherical nanoparticles and high-aspect-ratio nanotubes, may increase the target-specific antibacterial capacity of the consequent nanostructure while retaining an optimal biocompatibility. In this study, multi-walled carbon nanotubes (MWCNTs) were treated with a mixture of acids and decorated with Ag nanoparticles via a chemical reduction of Ag cations by ethanol solution. The synthesized Ag-MWCNT complexes were characterized by transmission electron microscopy, X-ray diffractometry, and energy-dispersive X-ray spectroscopy. The antibacterial function of Ag-MWCNTs was evaluated against Methylobacterium spp. and Sphingomonas spp. In addition, the biocompatibility of Ag-MWCNTs was evaluated using both mouse liver hepatocytes (AML 12) and human peripheral blood mononuclear cells. Finally, we determined the minimum amount of Ag-MWCNTs required for a biocompatible yet effective antibacterial treatment modality. We report that 30 μg/mL of Ag-MWCNTs confers antibacterial functionality while maintaining minimal cytotoxicity toward both human and animal cells. The results reported herein would be beneficial for researchers interested in the efficient preparation of hybrid nanostructures and in determining the minimum amount of Ag-MWCNTs necessary to effectively hinder the growth of bacteria.

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

“… Sphingomonas spp. Ag-MWCNT (40 or 50 μg/mL) completely inhibited bacterial growth ( Seo et al., 2014 ) Silver and copper nanoparticles MWCNT Medical devices E. coli Ag-MWCNT and Cu-MWCNT exhibited 97% and 89% growth inhibition against E. coli , respectively ( Mohan et al., 2011 ) Copper nanoparticles MWCNT Nonspecified Gram-positive and -negative bacteria; Fungi Cu-MWCNT showed an enhanced inhibitory effect when compared with MWCNT ( Yallappa et al., 2016 ) Titanium oxide-gold (TiO 2 -Au) MWCNT Drug delivery A broad range of Gram-positive and -negative bacteria More than 90% biofilm inhibition was observed in the presence of TiO2-Au-MWCNT ( Karthika et al., 2018 ) Titanium dioxide (TiO 2 ) MWCNT Antimicrobial agents E. coli S. aureus TiO 2 -MWCNT displayed high antimicrobial activity against both bacteria, as demonstrated by the diameter of inhibition zones (≥18 mm) ( Sukkar et al., 2019 ) Cadmium quantum dots (CdS) MWCNT Antimicrobial agents E. coli P. aeruginosa S. aureus The bacteria-killing ability of f-MWCNT-CdS was 87.2% ± 4.1%, 68.9% ± 2.5%, and 46.7% ± 1.4% against E. coli , P. aeruginosa, and S. aureus , respectively ( Neelgund et al., 2012 ) Polymers: Amphiphilic poly(propyleneimine) Dendrimer (APPI) MWCNT Drug delivery Bioimaging Medical devices B. subtilis E. coli S. aureus MWCNTs-APPI hybrid inhibited bacterial growth by 96.6% ± 0.3%, 96.5% ± 0.2%, and 87% ± 0.5% for B. subtilis , S. aureus , and E. coli , respectively ( Murugan and Vimala, 2011 ) O...…”

“…and Sphingomonas spp. after treatment with silver nanoparticle (AgNP)-decorated carboxylated MWCNTs ( Seo et al., 2014 ), the literature reports high inactivation rates of E. coli, B. subtilis, and S. aureus (> 90%) after cell incubation with AgNP-deposited MWCNTs functionalized with an amphiphilic poly(propyleneimine) dendrimer ( Murugan and Vimala, 2011 ). Likewise, more than 90% biofilm inhibition was observed after incubation of Shigella dysenteriae , Proteus vulgaris , K. pneumoniae , Streptococcus pneumoniae , B. subtilis , S. aureus , and C. albicans with titanium oxide-gold ( Karthika et al., 2018 ).…”

“…Based on the reviewed studies, the conjugation of CNTs with silver or titanium plays an important role in decreasing CNTs' toxicity ( Subbiah et al., 2011 ; Seo et al., 2014 ; Karthika et al., 2018 ; Chaudhari et al., 2019 ). Likewise, the incorporation of CNTs into polymeric matrices was also effective in suppressing its toxicity ( Subbiah et al., 2011 ; Nie et al., 2017 ; Sharmeen et al., 2018 ).…”

Application of a silver coating on plastic biliary stents to prevent biofilm formation: an experimental study using electron microscopy

“…Specific metal ions such as silver or zinc ions possess antibacterial properties and can be considered as antibacterial substances. Silver ions are well known to have excellent antimicrobial activity against a wide range of microorganisms 9 , which is why silver-based nanomaterials are being used for its bactericidal activity 10 11 . Interestingly, several studies have shown that silver demonstrates a more potent bactericidal activity against gram-negative bacteria compared to gram-positive bacteria 12 13 .…”

Current Approaches for Exploration of Nanoparticles as Antibacterial Agents

“…In addition to the above-mentioned metallic and polymeric nanoparticles, carbon-based nanostructures have shown antibacterial effects. For instance, the antibacterial activity of fullerene [67] and carbon nanotubes [68,69] ( single-walled or multi-walled) derivatives have been observed. However, the antibacterial mechanism of carbon-based nanostructures is still under debate and has not received particular attention, possibly due to the difficulties of their dispersion in water, especially in case of the carbon nanotubes [70].…”