Sterilization effect of power airborn ultrasound combined with ultraviolet radiation on bacteria

Controlling acute respiratory infections involves rapidly eradicating bacteria and viruses, which holds great significance. This study examined the effectiveness of combining power airborne ultrasound (US) with ultraviolet (UV) light to eradicate aerosolized pathogenic bacteria. This study evaluated the sterilization efficacy of a custom-built device that simultaneously delivers 40 W airborne ultrasound at 20-30 kHz and 275 nm ultraviolet light emitted by six 0.6 W LEDs. In the experiment, aerosol-encapsulated Escherichia coli was treated using both power airborne US and UV light. The bactericidal efficiency of this combined approach was evaluated, and the underlying mechanisms were explored. The results indicated substantial alterations in both the internal and external structures of the bacteria following gas-mediated, medium-to-high intensity US treatment. The ultrasonic cavitation effect significantly damaged the bacterial surface structure, while the microstreaming effect disrupted the cytoplasmic matrix. A marked increase in conductivity and β-galactosidase activity indicated bacterial wall disruption. Intracellular components, such as soluble proteins and adenosine triphosphate (ATP) content, showed a marked decrease, suggesting intracellular substance leakage. Exposure to airborne, medium-to-high intensity US resulted in a significant reduction in ATPase activity, implying interference with bacterial energy metabolism. The combined airborne ultrasound and UV treatment demonstrated superior bactericidal efficiency. It achieved over 95 % bacterial reduction within 120 s. Viable colonies decreased from 930 ± 156.986 CFU in untreated controls to 56.667 ± 15.965 CFU. Significant efficacy emerged within 15 s, reducing colonies to 442.778 ± 66.879 CFU. This performance substantially exceeded standalone UV or ultrasound treatments across all exposure durations. This work offers an efficient and rapid sterilization method with substantial application value for controlling disease transmission.