Dr Peter Dungel heads the photobiomodulation group at the LBI Trauma. Photobiomodulation means nothing more than “using light (photo) to influence (modulate) biological functions”. The fact that light actually interacts with cells and therefore also has an effect on the body is clearly demonstrated by sunburn. If one is too sunkissed, the high-energy UV light leaves visible and tangible marks on the body. It shows how important it is to weigh up light wavelength, dose and other parameters. The aim of photobiomodulation research is to find optimal conditions in order to utilise the positive effects of light and avoid any side effects. To do this, scientists need to understand which molecules in our body react to light and which reactions are triggered as a result. It is already known, for example, that mitochondrial respiration and the concentration of ATP, our body’s ‘energy currency’, are increased. Light therapy is practical, mobile, easy to use and extremely cost-effective compared to surgical or pharmacological interventions.

Red or green for diabetic wounds

Diabetics often suffer from slowed or completely absent wound healing. Circulatory disorders such as arterial occlusive disease mean that the wound is not supplied with sufficient oxygen and nutrients. A reduced immune defence due to impaired insulin metabolism does the rest. In the case of diabetic wound healing disorders, the first thing to do is always to ensure that the blood glucose level is correctly adjusted so that healing is possible. However, as blood vessels need a lot of time to regenerate, many other, often local therapeutic approaches are currently being tested. The need is great, as almost one in ten people in Austria suffer from diabetes.

In a project with the Viennese company Repuls, the Photobiomodulation, Soft Tissue Regeneration and Vascular Biology groups at the LBI Trauma investigated the healing of diabetic wounds treated with red, blue or green light in comparison to untreated wounds. The result depended on the wavelength, i.e. the colour of the light. While green light showed a slight improvement in wound healing, red light led to significantly faster wound closure. Both types of light promoted the formation of small blood vessels under the wound surface. The effect of red light reached particularly deep into the tissue, which may explain the better effect.

Blue light against infections

In the face of increasing antibiotic resistance, scientists have long been looking for alternatives to combat bacteria. Light itself can also have a disinfectant effect; we are familiar with the use of UV lamps. These are also used in laboratories. Once the work is done in the sterile workbench, the disinfection protocol is started up. The UV light soon makes the laboratory smell like a solarium. UV rays have a high energy density, they penetrate the genetic material of microorganisms and destroy it. The technology is also used in swimming pools and air purifiers. However, UV light would be inappropriate for use on infected wounds as it is too damaging to the skin.

PhD student Magdalena Metzger, MSc focussed on the question of whether effective disinfection can also be achieved with light of lower energy densities. Blue light has a comparatively high energy density and short wavelength in the visible spectrum, but is still much gentler than ultraviolet light. In her study, she discovered that some bacterial strains are killed by the light, while others are resistant. Particularly interesting: the strains susceptible to blue light lacked a molecule that is responsible for DNA repair. Future projects will investigate whether this repair can be blocked.

Future outlook: Light against Alzheimer’s?

Light could also help in the search for treatment options for Alzheimer’s disease. At least this is currently the aim of intensive research. At the LBI Trauma, a paper by Joachim Enengl, MSc, shed light on the theoretical foundations.

The study situation is still limited, but points in one direction: in double-blind clinical studies in the USA, the light group showed improved short-term memory compared to the respective control group and performed better in the clock test – a standard test for dementia in which patients draw a clock face. A study in which light was introduced into the cerebral arteries using a catheter showed an improvement in cerebral microcirculation and the recovery of cognitive abilities.

It should be emphasised, however, that although there is reason for hope, rejoicing is still a long way off. This is because several studies have shown that the positive effects of light therapy quickly diminish if it is not carried out regularly.

These examples show the numerous possible applications of light energy in medicine. Dr Dungel believes it is important to take light out of the voodoo and esoteric corner and use scientific methods to shed light on the underlying mechanisms of light therapy.