Development and assessment of a rapid biosensor for pathogenic bacteria detection in water.

Thesis Abstract

Waterborne pathogenic bacteria pose significant public health risks, particularly in regions where traditional microbial detection methods are labor-intensive, time-consuming, and often lack sensitivity. These limitations hinder timely intervention and effective water quality management, increasing the likelihood of disease outbreaks linked to contaminated water sources. In response to these challenges, this study aims to develop and rigorously evaluate a rapid, highly sensitive biosensor designed for the detection of critical pathogenic bacteria—namely Escherichia coli, Salmonella spp., and Vibrio cholerae—in water samples. The overarching goal is to provide an affordable, portable, and real-time diagnostic tool that can be integrated into water monitoring systems, thereby supporting public health initiatives. The specific objectives are to (1) design a biosensor leveraging nanomaterial-enhanced biorecognition elements and electrochemical detection techniques; (2) optimize biosensor fabrication parameters to maximize sensitivity and specificity; (3) validate the biosensor’s performance against standard microbiological culture and PCR methods using natural water samples; and (4) assess the biosensor’s operational stability, repeatability, and user-friendliness under field conditions. The research adopts a quantitative methodological approach, employing an experimental design to compare biosensor outputs with conventional gold-standard tests, thereby establishing the biosensor's analytical validity. The study population consists of 150 water samples collected from various sources, including municipal water supplies, river systems, and wells within an urban environment. A purposive sampling technique ensures diverse contamination profiles. Data collection involves the preparation of the biosensor prototype, utilizing gold nanoparticles to functionalize electrodes with specific aptamers or antibodies targeting the targeted bacteria. Electrochemical impedance spectroscopy and cyclic voltammetry serve as the primary analytical techniques to detect and quantify bacterial presence. Validation involves parallel testing with standard culture techniques, PCR amplification, and quantitative analysis, with the collection of triplicate measurements for each sample to ensure reproducibility. Analysis of the data will employ descriptive statistics for initial data characterization, followed by regression analysis to assess correlation between biosensor readings and conventional methods, and Bland-Altman plots to evaluate agreement. Sensitivity, specificity, positive predictive value, and negative predictive value of the biosensor will be computed using receiver operating characteristic (ROC) curves. Additionally, stability and repeatability metrics will be analyzed via ANOVA and coefficient of variation calculations. The study also explores the application of the Transactional Model of Technology Adoption to evaluate the likelihood of field implementation. Expected findings indicate that the biosensor will detect pathogenic bacteria at concentrations as low as 10^2 CFU/mL within less than 30 minutes, outperforming traditional methods in terms of speed and cost-effectiveness. The biosensor is anticipated to demonstrate high sensitivity (above 95%) and specificity (above 98%), with stable performance under field conditions over a three-month period. The results aim to establish the biosensor as a viable point-of-use diagnostic tool capable of facilitating real-time water quality assessment, greatly reducing surveillance lag. This research will contribute to existing knowledge by advancing biosensor technology specific to waterborne pathogen detection, filling critical gaps in rapid diagnostics, and informing regulatory standards and public health policies for water safety. The study's innovation lies in integrating nanotechnology and electrochemical sensing with portable device design, providing a scalable solution adaptable to diverse environmental contexts. Based on the findings, recommendations include the development of standardized protocols for biosensor deployment, training of local personnel in operational procedures, and further refinement for broader pathogen multiplexing. Future research should explore integration with data transmission systems for remote monitoring, extend testing to other microbiological contaminants, and evaluate long-term field durability.