Detection of Total Bacterial Load in Water Samples Using a Disposable Impedimetric Sensor

Detection of bacterial colonies in water is a pressing issue in recent times owing to its implications on human health, leading to an urgent need for low cost, disposable sensors. In this work, we report a disposable impedimetric sensor for detection of total bacterial colonies present in water samples. The sensor consists of a polyaniline coated filter paper functionalized with a homo-bi functional crosslinker, glutaraldehyde. Prior to the functionalization step, two Ag electrodes are deposited on the filter paper using conductive silver paste. The aldehyde groups of glutaraldehyde bind with the amine functional groups present on bacterial cell wall resulting in a change in dielectric constant, and consequently, the capacitive effect between the two Ag electrodes. Also, bacterial metabolism affects the medium conductivity and in turn, the medium resistance changes. The combined effect of changes in capacitive effect as well as resistance is reflected as a change in AC impedance measured using a frequency response analyzer (FRA). E. coli and Pseudomonas aeruginosa bacteria are detected in PBS buffer up to ~ 500 cfu/mL. Testing is also carried out by spiking tap water and grey water with known concentrations of bacteria samples. The detection limits obtained are 500 - 1000 cfu/mL with a response time of ~ 20 minutes. The developed sensor provides rapid, moderately sensitive, cost-effective solution for detecting total bacterial load in water samples.