Owusu, E;
MacRobert, AJ;
Naasani, I;
Parkin, IP;
Allan, E;
Yaghini, E;
(2019)
Photoactivable Polymers Embedded with Cadmium-free Quantum Dots and Crystal Violet: Efficient Bactericidal Activity against Clinical Strains of Antibiotic-Resistant Bacteria.
ACS Applied Materials and Interfaces
, 11
(13)
pp. 12367-12378.
10.1021/acsami.9b02109.
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Abstract
The rising incidence of antibiotic-resistant infections from contaminated surfaces in hospitals or implanted medical devices has led to increasing interest in new antibacterial surfaces. Photoactivatable surfaces that can generate cytotoxic reactive oxygen species under exposure to ambient light is a promising approach to inactivation of surface-borne microorganisms. There is growing interest in the use of quantum dots (QDs) as light-harvesting agents for photobactericidal applications but the cadmium in commonly used QDs will restrict clinical application. Herein, the photobactericidal activity of novel polyurethane substrates containing cadmium-free quantum dots was tested against clinical multi-drug resistant Gram-positive and Gram-negative bacterial strains: methicillin-resistant Staphylococcus aureus (MRSA) and a carbapenemase-producing strain of Escherichia coli (E. coli). To enhance the capacity for reactive oxygen species generation, QDs were incorporated into the polymer with a photosensitising dye, crystal violet. Close proximity between the QD and dye enables electron and energy transfer processes leading to generation of cytotoxic singlet oxygen and superoxide radicals. A QD solution in cyclohexane was premixed with a solution of CV in the more polar solvent, dichloromethane, to promote the formation of QD-CV nanocomposite complexes via CV adsorption. This solution was then used to embed the quantum dots and crystal violet into medical grade polyurethane via swell-encapsulation. The combination of QD and CV elicited significant synergistic antibacterial activity under visible light against MRSA within 1 h (99.98% reduction) and E. coli within 4 h (99.96% reduction). Photoluminescence lifetime and singlet oxygen phosphorescence measurements demonstrated interaction between the quantum dots and the crystal violet occurs within the polymer that can lead to enhanced generation of reactive oxygen species. Strong inhibition of kill was observed using the superoxide scavenger, superoxide dismutase. The efficacy of these QD-CV polymer substrates that can harvest light across the visible spectrum, against multi-drug resistant bacteria demonstrates the feasibility of this approach.
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