Abstract
A rapid photothermal bacterial inactivation technique has been developed by irradiating near-infrared (NIR) light onto bacterial cells (Escherichia coli, Bacillus subtilis, Exiguobacterium sp. AT1B) deposited on surfaces coated with a dense, random array of nanoporous gold disks (NPGDs). With the use of cell viability tests and SEM imaging results, the complete inactivation of the pathogenic and heat-resistant bacterial model strains is confirmed within ~25 s of irradiation of the NPGD substrate. In addition to irradiation control experiments to prove the efficacy of the bacterial inactivation, thermographic imaging showed an immediate averaged temperature rise above 200 °C within the irradiation spot of the NPGD substrate. The light-gated photothermal effects on the NPGD substrate offers potential applications for antimicrobial and nanotherapeutic devices due to strong light absorption in the tissue optical window, i.e., the NIR wavelengths, and robust morphological structure that can withstand high instantaneous thermal shocks.
Highlights
The risks of contracting a hospital-acquired infection has long been a real threat and the rate can be as high as 13.5% in certain countries [1, 2]
Aside from the high penetration depth of NIR light for biological material, the laser wavelength used (785 nm) provides sufficient photothermal conversion resulting to heat transfer to surrounding media due to the effective absorption of nanoporous gold disks (NPGDs) array at this broad NIR wavelength range
The NPGD substrate was tested in vitro to induce efficient bacterial inactivation using the photothermal effect within a short period of time
Summary
The risks of contracting a hospital-acquired (nosocomial) infection has long been a real threat and the rate can be as high as 13.5% in certain countries [1, 2]. With sufficient heat generated from the NPGD arrays towards the bacteria, real-time inactivation within a few seconds of irradiation can be achieved, considerably shorter than on nanoparticle arrays demonstrated in recent studies [9, 10, 20, 21] Another advantage of NPGD arrays as a reliable light-gated photothermal substrate for direct bacterial inactivation is that it does not require additional surface modifications for preventing particle aggregation in solution typical in dispersed nanoparticles. In relation to previous studies on inactivation methods using nanoparticle arrays, our results show the strong potential of NPGDs for instantaneous (~seconds) disinfection of nosocomial bacteria in situ
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