Opto-Electronically Active Materials for Infection Detection and Control

This talk will present how our merger of organic bioelectronics and bacterial infection biology has opened exciting, new opportunities for <i>in vitro</i> studies in the lab as well as for infection diagnostics and control. Our approach takes advantage of the electro-catalytical properties of conductive polymers for mutual communication between bioactive surfaces and bacterial cells growing in liquid culture and as biofilms. Biofilm forms when free-living planktonic bacteria undergo a phenotypic transition, producing dense bacterial aggregates embedded in extracellular matrix. We take advantage of the dual organic-conductive nature of electrically conducting oligomers and polymers to develop novel materials and strategies to control biofilm formation and diagnose infections. Based on the conducting polymer poly(3,4-ethylenedioxythiophene (PEDOT), we show how PEDOT can be used for rapid and sensitive potentiometric sensing of bacteria in liquid cultures via their secreted redox active compounds, and how an organic electrochemical transistor (OECT) can be used to monitor growth of <i>Salmonella</i> cultures in real-time. We also show that PEDOT can act as an electron mediator for bacterial metabolism, demonstrating how growth of <i>Salmonella</i> biofilm can be modulated by the electrochemical state of the polymer. By functionalizing PEDOT with biocide agents, the material showed efficient antimicrobial activity as a surface coating. This was illustrated in PEDOT functionalized with silver nanoparticles (AgNP), where a synergistic effect of AgNP and the electrical input nearly completely prevented growth of <i>Staphylococcus aureus</i>. To overcome the lack of methods for specific reporting of the biofilm lifestyle, we developed methods for specific detection of extracellular matrix components. Utilising the opto-electronic nature of conjugated oligothiophenes, we established ‘optotracing’ as a non-toxic, fluorescence-based method for identification of ECM components, such as amyloid curli fibers and cellulose, in liquid cultures as well as when biofilm forms at the air-solid interface in real-time. Optotracing was further applied in a culture-independent diagnostic assay for biofilm-related urinary tract infection caused by uropathogenic <i>E.</i> <i>coli</i>, and as an algorithm-based optical sensing method specific for <i>Staphylococcus aureus</i>. We are now extending the applicability of optotracing technology for automated biofilm diagnostics and point-of-care bacteria identification.