Microbial infections remain the leading cause of increased morbidity and mortality rates of patients suffering from infectious diseases. While thousands of pathogenic bacteria have been recognized, the majority of healthcare-associated infections are caused by only a few opportunistic pathogens (e.g., Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli), which are associated with increased antibiotic resistance. The rapid detection, reliable identification and real-time monitoring of these pathogens remain not only a scientific problem but also a practical challenge of vast importance, especially in tailoring effective treatment strategies. Various approaches, such as conventional culturing, molecular methods and mass spectrometry techniques, have been employed to identify and quantify pathogenic agents. Yet, these procedures are costly, time-consuming, mostly qualitative, and are indirect detection methods. A great challenge is therefore to develop rapid and quantitative methods for the detection of microbes. As an alternative, electrochemical techniques have been explored as a means for the detection of infection-related biomarkers. This thesis presents the development and application of a robust electrochemical platform using transparent carbon ultramicroelectrode arrays (T-CUAs) for the in vitro detection of bacterial warfare toxin, pyocyanin, and other phenazine metabolites produced by P. aeruginosa. This antibiotic-resistant pathogen is commonly found in chronic wounds and the lungs of cystic fibrosis patients. During early infection stages, P. aeruginosa produces various phenazines as virulence factors, which are highly diffusible signals that are toxic to surrounding host cells and other competing microorganisms. Although phenazines play important roles in cellular functions, very little is known about how their concentrations fluctuate and influence cellular behaviors and population-dependent responses (quorum sensing) during infection and growth. Therefore, quantitative, real-time electrochemical monitoring of distinct redox-active phenazine metabolites from P. aeruginosa in simulated growth media is demonstrated using T-CUAs. Moreover, electrochemical monitoring of the influence of polymicrobial infections on P. aeruginosa phenazine production is presented. In addition to quantifying phenazine concentrations in complex environments, changes in phenazine dynamics are observed in the biosynthetic route for pyocyanin production. Finally, desorption electrospray ionization and nanoelectrospray ionization mass spectrometry are used to identify phenazines observed with our electrochemical devicesChemistr
