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UV sterilisation device being tested for use on human skin

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Prototype of the UVC LED irradiation system with 118 LEDs. The inset shows a detail of the LED array (©FBH/P. Immerz)

An LED irradiation system has been developed at the Ferdinand-Braun-Institut in Berlin that aims to kill microorganisms with ultra-short wave UV light. The researchers anticipate that the UV light emitted from their device will not be harmful to human skin.

A prototype is now going through trials in Germany to determine whether the device is safe to use on human skin, but also to test how effectively it can kill MDR pathogens at 230nm compared to UV lamps at 254nm and 222nm

According to the Robert Koch Institute, 400,000 to 600,000 infections with hospital germs occur in Germany every year – about 10,000 to 20,000 people die from them. Since multidrug resistant (MDR) pathogens often cannot be treated with antibiotics, alternative approaches are required.

One promising physical principle is irradiation with UVC light, which can be used to destroy microorganisms without allowing resistances to develop. Within the joint lab GaN Optoelectronics, the Ferdinand-Braun-Institut (FBH) and Technische Universität Berlin (TUB) have developed LEDs emitting in the far ultraviolet (UV) spectral range. The LEDs emit at wavelengths around 230nm and provide more than one milliwatt output power. 

Such UVC LEDs are not yet commercially available worldwide due to technological challenges of the material used in the system, aluminum-gallium nitride (AlGaN). Their light does not penetrate into the living layers of the skin because of the high degree of absorption. The researchers therefore expect that the skin – in contrast to long-wave UVC radiation as emitted by mercury vapour lamps, for example – will not be harmed at all or will be damaged so little that the natural repair mechanisms compensate for the effect. The researchers hope that this will help to kill MDR pathogens without any long-term side effects.

 

                                         Related story: Scrutinising craze for UV Covid-19 disinfection      

 

Within the framework of the VIMRE project (prevention of infection with multidrug resistant pathogens via in-vivo UVC irradiation), FBH has developed and produced an irradiation system comprising an array of 118 of these LEDs on an area of 8cm x 8cm. It achieves a maximum irradiation power of 0.2mW/cm2, with more than 90 per cent uniformity over an area of 6cm x 6cm. The first prototype has been delivered to the Department of Dermatology at Charité – Universitätsmedizin Berlin for skin examinations. Another device will soon be delivered to the Institute for Hygiene and Environmental Medicine of the University Medicine Center Greifswald to clarify the microbicidal effectiveness.

Tests carried out by the two project partners with these devices aim to show that UVC irradiation is suitable for killing microorganisms, especially MDR pathogens. At the same time, the trials will need to demonstrate that the UV light exposure is harmless to humans as long as specific irradiation doses are maintained. This will be verified using tissue samples of human skin as well as skin and mucosa models, since the preferred habitat of microorganisms such as MDR pathogens is the anterior nasal cavity and the pharynx. For this purpose, the Charité conducts dose-dependent investigations of possible DNA damage to irradiated skin.

The University Medicine Center Greifswald will determine how effectively the UV LED emitters kill MDR pathogens at 230nm and compare the results with those of UV lamps with emission at 254nm and 222nm.

Further applications

The UV LED irradiation system is to be further developed so that pathogens can be eliminated in places that are difficult to access. The device might also be interesting for corona viruses, as they can also be inactivated by short-wave UVC light. Since Sars-Cov-2 replicates in the pharynx in the first phase, it seems plausible to use such light sources in this part of the body to prevent a Covid-19 disease.

VIMRE is funded by the German Federal Ministry of Education and Research (BMBF) as part of the consortium 'Advanced UV for Life' within the Twenty20 programme.

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