Combating Multidrug-Resistant Organisms with UV Light

Multidrug-resistant organisms (MDROs) are a major challenge in everyday medical practice, as they often cannot be treated with antibiotics. According to the Robert Koch Institute, there are 400,000 to 600,000 infections with hospital germs in Germany every year – around 10,000 to 20,000 people die from them. Alternative treatment options are therefore needed.

Light-emitting diodes (LEDs) from the Ferdinand-Braun-Institut (FBH), which emit light in the far-ultraviolet (UV) spectral range, are opening up new opportunities. The far-UVC wavelength range below 235 nanometers (nm) is highly interesting for medical applications. Due to the high absorption at these wavelengths, the light does not penetrate the living layers of the skin and therefore causes less damage than a sunburn. Far-UVC LEDs thus achieve what antibiotics do not always succeed in doing: killing harmful microorganisms, especially MDROs – experts refer to this as eradication – without developing resistance. 

Vision nasopharyngeal irradiation system – to combat pathogens where they appear
However, these irradiation systems only reach affected areas on the outer skin. That is why the vision of the medical professionals was even more ambitious during the tests at the time. “Small LED irradiation sources with an output power of around one milliwatt that we can insert directly into the nose or throat would be ideal,” says Prof. Dr. Martina Meinke, head of the Center for Skin Physiology at Charité's Department of Dermatology, Venereology, and Allergology. 

235 nm UVC LEDs with international record values – for medicine and sensor technology
Far-UVC LEDs are technologically demanding due to the aluminum gallium nitride (AlGaN) material system used – yet they have not delivered the performance required for commercial applications. Driven primarily by the work of Dr. Jens Rass, the FBH has now succeeded for the first time in exceeding the important threshold of 1 milliwatt output power with far-UVC light in continuous wave (CW) operation from a single fiber – an international record that was recently presented at a conference. This milestone opens up applications in antiseptics and sensor technology. 

The breakthrough was achieved using 235 nm UV micro-LEDs arranged in a dense array. This allows five times more light to be coupled into the fiber than with conventional far-UVC LEDs. The micro-LEDs themselves, of which up to 125,000 are arranged on a chip measuring one square millimeter, are extremely compact with diameters of only around 1.5 micrometers. This not only allows more light to be coupled out of the individual chip, but also makes it more directional – and therefore very precise. Thanks to their compact design and high performance, such fiber-coupled light sources would be ideal for eradicating multi-resistant germs and for disinfection in body cavities. The vision of a light source for disinfecting the nasopharyngeal cavity is thus within reach.