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1.
Aims Bioengineering ; 9(2):93-101, 2022.
Article in English | Web of Science | ID: covidwho-1798847

ABSTRACT

The spread of infections, as in the coronavirus pandemic, leads to the desire to perform disinfection measures even in the presence of humans. UVC radiation is known for its strong antimicrobial effect, but it is also harmful to humans. Visible light, on the other hand, does not affect humans and laboratory experiments have already demonstrated that intense visible violet and blue light has a reducing effect on bacteria and viruses. This raises the question of whether the development of pathogen-reducing illumination is feasible for everyday applications. For this purpose, a lighting device with white and violet LEDs is set up to illuminate a work surface with 2,400 lux of white light and additionally with up to 2.5 mW/cm2 of violet light (405 nm). Staphylococci are evenly distributed on the work surface and the decrease in staphylococci concentration is observed over a period of 46 hours. In fact, the staphylococci concentration decreases, but with the white illumination, a 90% reduction occurs only after 34 hours;with the additional violet illumination the necessary irradiation time is shortened to approx. 3.5 hours. Increasing the violet component probably increases the disinfection effect, but the color impression moves further away from white and the low disinfection durations of UVC radiation can nevertheless not be achieved, even with very high violet emissions.

2.
Current Directions in Biomedical Engineering ; 7(2):315-318, 2021.
Article in English | Scopus | ID: covidwho-1594912

ABSTRACT

The ongoing coronavirus pandemic spreads through airborne transmission and is therefore difficult to contain. However, coronaviruses are highly sensitive to UVC, so UVC air disinfection systems should be able to inactivate the virus. Unfortunately, so far there are only few possibilities to test the reduction of airborne viruses or other pathogens. A special test rig, which mainly consisted of a nebulizer and an airflow system, was developed to determine the antiviral and antibacterial efficiency of UVC air disinfection systems. In the assessment of such an UVC air disinfection system with nebulized Staphylococcus carnosus and a sampling period of 30 minutes, a mean bactericidal reduction of 3.70 log10 (99.98 %) was determined. For antiviral irradiation of the coronavirus surrogate phi6 a mean viral load reduction of 1.18 log10 (93.40 %) was observed after a sampling period of 10 minutes. Therefore, mobile UVC air disinfection systems could be applied in hospitals, retirement and nursing homes. © 2021 by Walter de Gruyter Berlin/Boston.

3.
Current Directions in Biomedical Engineering ; 7(2):239-242, 2021.
Article in English | Scopus | ID: covidwho-1598102

ABSTRACT

Artificial respiration is saving lives especially in the COVID-19 pandemic, but it also carries the risk to cause ventilator-Associated pneumonia (VAP). VAP is one of the most common and severe nosocomial infections, often leading to death and adding a major economic burden to the healthcare system. To prevent a proliferation of microbial pathogens that cause VAP, an endotracheal tube (ETT) equipped with blue LEDs (LED-ETT) was developed. This blue wavelength exhibits antimicrobial properties but may also harm human tracheal cells at higher irradiances. Therefore, the aim of this study was to find the minimal required irradiance for microbial reduction of 1 log level in 24 h by applying LED-ETTs. A LED-ETT with 48 blue LEDs (450 nm) was fixed in a glass tube, which served as a trachea model. The investigation was carried out with irradiations of 4.2, 6.6 and 13.4 mW/cm² at 37 °C for 24 h. The experiments were performed with Acinetobacter kookii as a surrogate of Acinetobacter baumannii, which is classified as critical by the WHO. Samples of A. kookii suspensions were taken every 4 h during irradiation from the trachea model. Bacteria concentrations were quantified by determining colony forming units (CFU)/ml. A homogeneous irradiance of only 4.2 mW/cm² generated by the blue LEDs, at a LED forward current of 3.125 mA, is sufficient to achieve a 1 log reduction of A. kookii within 24 h. The total irradiation dose within this period was 360 J/cm2. Human cells survive this dose without cellular damage. Previous studies revealed that the pathogen A. baumannii is even more sensitive to blue light than A. kookii. Therefore, blue LED-ETTs are expected to reduce A. baumannii without harming human tracheal cells. © 2021 by Walter de Gruyter Berlin/Boston.

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