Towards electro-chemical characterisation of paper-based sensors and usage perspectives

Point-of-care biosensors have the potential to revolutionize health care and disease prevention in both developing and developed countries. Indeed, rapid and relatively inexpensive disposable tests are powerful tools for accessible and adequate health control on the one hand and for environmental quality monitoring on the other hand. The project that led to this master’s thesis aims to create a point-of-care paper-based electrical screening device suitable for detection of bacteria in water. This affordable, portable and sensitive biosensor creates opportunities in applications that need frequent and rapid pathogen detection; such as the detection of E. Coli in drinking water or Legionella in cooled industrial water. Through appropriate modification, our sensor could meet the need for detection of various viruses as well, which may prove particularly useful in the light of the recent COVID-19 pandemic. This work focuses on the electro-chemical detection of bacteria with interdigital electrodes (IDE) through impedance spectroscopy. These bacteria are captured in a nitrocellulose membrane through bio-functionalisation, thus altering the permittivity and conductivity of the sensed medium. The conducted study adds two innovations to the field of impedimetric sensing with IDE, which already has a wide variety applications. First, the electrodes are directly deposited on nitrocellulose. Second, we aim at sensing the whole nitrocellulose membrane volume rather than the IDE surface, which is commonly targeted. In the present thesis, the whole system is characterised from scratch. An analytical model is established and validated between 10^2 and 10^9 Hz. A proof of concept is substantiated: 10^8 CFU/ml of Bacillus thuringiensis are detected in DI water. Phage endolysin is used for specific capture of these bacteria on the nitrocellulose membrane. The protoyping of our biosensor is framed by a responsible design approach. In this work, an innovative study evaluates the societal impacts of the information generated by the sensor, using a relevant water economy approach as developed in academic research. It proposes a configuration of an information system focusing on tap water, which relies on citizens and anticipates the problems associated with their inclusion in a water quality monitoring system. Two case studies, in Belgium and in the Philipines, are established to validate the approach.