Abstract
Ultraviolet (UV) irradiation is an effective bacterial inactivation technique with broad applications in environmental disinfection. However, biomedical applications are limited due to the low selectivity, undesired inactivation of beneficial bacteria and damage of healthy tissue. New approaches are needed for the protection of biological cells from UV radiation for the development of controlled treatment and improved biosensors. Aluminum plasmonics offers attractive opportunities for the control of light-matter interactions in the UV range, which have not yet been explored in microbiology. Here, we investigate the effects of aluminum nanoparticles (Al NPs) prepared by sonication of aluminum foil on the UVC inactivation of E. coli bacteria and demonstrate a new radiation protection mechanism via plasmonic nanoshielding. We observe direct interaction of the bacterial cells with Al NPs and elucidate the nanoshielding mechanism via UV plasmonic resonance and nanotailing effects. Concentration and wavelength dependence studies reveal the role and range of control parameters for regulating the radiation dosage to achieve effective UVC protection. Our results provide a step towards developing improved radiation-based bacterial treatments.
Highlights
Bacterial inactivation has recently received much attention due to the rising concern of antibiotic resistance[1]
Scanning electron microscopy (SEM) images show aluminum nanoparticles (Al NPs) (Fig. 3a) and E. coli shielded by Al NPs (Fig. 4a)
Energy-dispersive spectroscopy (EDS) analysis was performed to confirm the elemental composition of the Al NPs attached to the bacteria
Summary
Bacterial inactivation has recently received much attention due to the rising concern of antibiotic resistance[1]. Many alternative bacterial inactivation techniques have been developed, including the promising light-induced photo-inactivation methods such as photodynamic[2,3,4,5,6] and photothermal[7,8,9,10,11] treatments The former relies on the interaction of light at frequencies typically in the visible and near-infrared range with photosensitizers which produce reactive species. The latter is based on the local heat generated using visible or near-infrared light interacting with plasmonic nanostructures made of Ag, Au and other metals The advantages of these techniques are high efficiencies, robustness to bacterial resistance, and localized treatments. We investigate the effects of aluminum nanoparticles (Al NPs) on the UV inactivation of Escherichia coli (E. coli) K12 bacteria and demonstrate a new UV protection mechanism via plasmonic nanoshielding. Our results show that UV nanoshielding has no effect on the freely-suspended bacteria and is primarily achieved due to the direct interaction between E. coli and Al NPs
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