Interactions of Microorganisms with Polymer Nanocomposites Containing Different Loadings of Oxidized Single and Multi-walled Carbon Nanotubes
David G. Goodwin , Kris M. Marsh, Iruhany B. Sosa, Julianne B. Payne, Justin M. Gorham, Edward J. Bouwer, D H. Fairbrother
The environmental fate and impact of polymer nanocomposites (PNCs) containing carbon nanotubes (CNTs) will depend upon their interactions with microorganisms, with implications for the antimicrobial properties and long term persistence of PNCs. Using oxidized single-walled (O-SWCNT) and multi-walled CNTs (O-MWCNT), we have explored the influence that CNT loading (mass fraction ≤ 0.1% - 10%) and type have on the initial interactions of Pseudomonas aeruginosa with CNT/polyvinyl alcohol (PVOH) nanocomposites containing well-dispersed CNTs. LIVE/DEAD staining revealed that both O-SWCNTs and O-MWCNTs cause the PNC surfaces to exhibit antimicrobial properties. The fraction of living cells deposited on both O-SWCNT and O-MWCNT/PNC surfaces decreased exponentially with increasing CNT loading, with O-SWCNTs being approximately three times more cytotoxic on a % w/w basis. The cytotoxicity of the CNT/PNC surfaces appears to scale with the total contact area that exists between the microorganisms and CNTs, although each interaction between a CNT and an attached microorganism does not necessarily lead to cell death. However, the dependence of the antimicrobial properties on direct CNT contact with the microorganisms eventually led to biofilm formation of living cells on top of the dead cells in contact with the CNTs when nanocomposites were exposed to Pseudomonas aeruginosa for sufficiently long time periods (> 6 h).