Light against bacteria

The Czech Republic is the world’s leading country in nanotechnology, which is used in many types of industries including healthcare, cleaning water, food industry, or electronics. One of the more interesting fields of research is healthcare, where polymeric nanofibers are investigated for picking up pathogens and pollutants from the environment.

Nanofibers are super thin fibers of a diameter 1000 times less than a human hair. Nanomembranes are created by putting these nanofibers together, which can resemble a dense spider web even though each fiber is only visible by an electron microscope. This membrane, much like a spider web, can pick up different objects such as bacteria or pollutants of the environment. Moreover, it can be adjusted for a specific application.

Demonstration of antibacterial properties of prepared nanofibrous membrane – on the left is a membrane with incubated bacteria E. coli at 37 °C in the dark E), on the right is a membrane with E. coli after blue light illumination (10 minutes) and consequent incubation (F), source: the original article

The authors of the article have been investigating a nanofibrous membrane from a polyurethane-based polymer. They have put molecules of photosensitizer tetraphenylporphyrin and magnetic nanoparticles of Fe₂O₃ to the structure of the nanofibers. Photosensitizers are molecules able to generate an active form of oxygen (so-called singlet oxygen) after being irradiated by light. The singlet oxygen has a strong antibacterial effect even against antibiotic-resistant bacteria. Scientists have used an innovative way which consists of combination of photodisinfective properties of singlet oxygen, magnetic, and even thermic effects of metal nanoparticles.

Multifunctional nanofibrous membranes with mentioned properties have been tested on Escherichia Coli bacteria. The test consisted in putting bacteria on the surface of the membrane and consequently illuminating the surface with blue light for the duration of 10 minutes. It was shown, that over 99 % of bacteria were killed in that short time. Moreover, the effect of metal nanoparticles caused heating of the membrane and a mild production of hydrogen peroxide, which is another antibacterial substance besides the singlet oxygen. Both phenomena have a positive effect on the antibacterial efficiency of the prepared membrane.

Demonstration of magnetic properties of prepared water suspension of Fe₂O₃ metal nanoparticles (1-4) and photoactive nanofibrous membrane (silver cylinder is permanent magnet) (5-8), source: the original article

This conclusion of scientists can lead to a preparation of multipurpose nanofibrous membranes, which have not only antibacterial effect, but can also be manipulated from a distance by the magnetic field and actively pick up pollutants and bacteria from contaminated environment without direct physical presence. Considering the rapid growth of the nanotechnology industry, we can expect results of this study in practical use in the near future. Such contribution in this field confirms the great place of the Czech Republic and our scientists in the world of nanotechnology.

Liška, V., Kubát, P., Křtěnová, P., Mosinger, J. Magnetically Separable Photoactive Nanofiber Membranes for Photocatalytic and Antibacterial Applications. ACS Omega. 2022, 7, 51, 47986–47995.

Robert Willimetz