Smartphone screen technology used to trick harmful bacteria
Conducting plastics found in smartphone screens can be used to trick the metabolism of pathogenic bacteria.
When bacteria attach to a surface they grow quickly into a thick film known as a biofilm. These biofilms frequently occur in our surroundings but are especially dangerous in hospitals where they can cause life threatening infections. Researchers have now aimed to address this problem by producing coatings for medical devices made from a cheap conducting plastic called PEDOT, which is what makes smartphone screens respond to touch. By applying a small voltage, the PEDOT surface was either flooded with electrons or left almost empty, which in turn affected the growth of Salmonella bacteria.
“When the bacteria land on a surface full of electrons, they cannot replicate”, explains principal investigator Agneta Richter-Dahlfors, Professor at Karolinska Institutet’s Department of Neuroscience and Director of the Swedish Medical Nanoscience Center. “They have nowhere to deposit their own electrons which they need to do in order to respire.”
On the other hand, if the bacteria encountered an empty PEDOT surface, the opposite happened, as they grew to a thick biofilm.
“With the electrons being continually sucked out of the surface, bacteria could continually deposit their own electrons, giving them the energy they needed to grow quickly”, says Professor Richter-Dahlfors.
Read the paper: http://go.nature.com/2fofrAw
Biofouling is a major problem caused by bacteria colonizing abiotic surfaces, such as medical devices. Biofilms are formed as the bacterial metabolism adapts to an attached growth state. We studied whether bacterial metabolism, hence biofilm formation, can be modulated in electrochemically active surfaces using the conducting conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT). We fabricated composites of PEDOT doped with either heparin, dodecyl benzene sulfonate or chloride, and identified the fabrication parameters so that the electrochemical redox state is the main distinct factor influencing biofilm growth. PEDOT surfaces fitted into a custom-designed culturing device allowed for redox switching in Salmonella cultures, leading to oxidized or reduced electrodes. Similarly large biofilm growth was found on the oxidized anodes and on conventional polyester. In contrast, biofilm was significantly decreased (52–58%) on the reduced cathodes. Quantification of electrochromism in unswitched conducting polymer surfaces revealed a bacteria-driven electrochemical reduction of PEDOT. As a result, unswitched PEDOT acquired an analogous electrochemical state to the externally reduced cathode, explaining the similarly decreased biofilm growth on reduced cathodes and unswitched surfaces. Collectively, our findings reveal two opposing effects affecting biofilm formation. While the oxidized PEDOT anode constitutes a renewable electron sink that promotes biofilm growth, reduction of PEDOT by a power source or by bacteria largely suppresses biofilm formation. Modulating bacterial metabolism using the redox state of electroactive surfaces constitutes an unexplored method with applications spanning from antifouling coatings and microbial fuel cells to the study of the role of bacterial respiration during infection.
Salvador Gomez-Carretero, Ben Libberton, Mikael Rhen, and Agneta Richter-Dahlfors. “Redox-active conducting polymers modulate Salmonella biofilm formation by controlling availability of electron acceptors”. npj Biofilms and Microbiome, online 4 September 2017. doi:10.1038/s41522-017-0027-0