With this work we propose a guideline for the development of efficient and effective UVC surface disinfection systems for SARS-CoV-2 based on LED technology. The work analyzes the optical and electrical characteristics of state of the art UVC LEDs. From the most recent scientific literature, optical simulations, and laboratory experiments we propose guidelines for the design of high efficiency LED based antiviral system for the treatment of contaminated surfaces. To validate the guidelines two different UVC-LED irradiation systems, for spherical and flat surfaces, have been designed, manufactured and tested. Results indicate a log-4 inactivation of SARS-CoV-2 in few minutes.
Pseudomonas aeruginosa may be isolated from skin wounds of burn patients, bedsore and diabetic ulcers. The healing of wounds is often impaired by the intrinsic antibiotic resistance, the tolerance to many antimicrobials and the ability to form biofilm of this opportunistic pathogen. Finding new topical treatments to combine with antibiotics is thus essential. Among natural products, the antimicrobial properties of honeys have been known for millennia. In this study honey and visible light have been combined to control the growth of P. aeruginosa PAO1. The irradiation by a broad spectrum light source of bacteria inoculated onto 2 % w/v fir and forest honeydew (HD) honeys caused a killing effect that the honeys alone or the light alone did not show. This antimicrobial activity was light energy-dose and honey-concentration dependent. Among the tested honeys, the fir and forest HD honeys were the most efficient ones. In particular, the irradiation by blue LED (λmax = 466 nm) yielded good rates of killing, that were significantly higher in comparison to irradiation alone and honey alone. Interestingly, a similar effect was obtained by plating bacteria on blue LED pre-irradiated HD honeys. The combined use of honey and blue light was also successful in inhibiting the biofilm formation of P. aeruginosa. The blue LED irradiation of PAO1 administered with 10 % w/v forest HD honey significantly enhanced the inhibition of biofilm formation in comparison to dark incubated honey.
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