Effectiveness of multivariate parameters on medical device disinfection using simultaneously-coupled triadic wavelength UV-LEDS

Abstract

Ultraviolet light emitting diodes (UV-LEDs) have shown a great potential to replace traditional UV lamps for microorganisms disinfection. Most research is focused on water and food disinfection applications whereas the utilization of UVLEDs for healthcare disinfection is not fully understood due to limited exploration on this area. This study presented a comprehensive work on UV-LEDs solitary and coupled wavelength combinations in the context of inactivation, photoreactivation and morphological characteristics which is of significance to expand UV-LEDs scope beyond water applications, specifically to be adopted in healthcare disinfection system. In this study, UV-LEDs with peak emission at 276, 311 and 364 nm were studied for the inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Under the solitary wavelength, the effectiveness of each LED was studied separately and the effects of varied exposure times as well as UV doses were investigated for the inactivation of E. coli and S. aureus. It was found that the 276 nm LED produced the highest inactivation efficiency as compared to the 311 and 364 nm LEDs which required significantly lower exposure time and UV dose to achieve maximum inactivation of both bacteria. In the focus of investigating the effects of coupled wavelengths, simultaneously, the coupled triadic wavelength (SCTW) 276|311|364 nm UV-LEDs enhanced the inactivation effects and was able to produce the highest inactivation of E. coli (98.42%) and S. aureus (99.34%). The combination of 276|311 nm achieved the second best results on E. coli (97.36%) and S. aureus (98.63%), followed by the 276, 276|364, 311, 311|364 and 364 nm, respectively. For both, the solitary and the coupled wavelengths, a relatively higher inactivation of S. aureus was found in comparison with E. coli, indicating that S. aureus was more sensitive to UV irradiation. Moreover, the evaluation of morphological images of E. coli and S. aureus showed that all UV treated samples caused significant damage and deterioration of cellular membranes. However, the most pronounced damages such as membrane transparency, pore formation, blebs protrusion and lysis were seen when both bacteria were treated with the SCTW 276|311|364 nm UV-LEDs. The results also showed that the SCTW 276|311|364 nm UV-LEDs was the most effective combination in providing better persistence against the photoreactivation of E. coli (1.75%) and S. aureus (4.29%) as compared to the 276 nm which projected the photoreactivation of 2.14% on E. coli and 8.92% on S. aureus. These results are of significance for future applications in healthcare.