Although significant technological advancements have been made in the development of analytical biosensor chips for detecting bacteria, critical requirements i.e. limit of detection (LOD), fast time of response (TOR), ultra-sensitivity with high reproducibility and good shelf-life with robust sensing capability have yet to be met within a single sensor chip. In order to achieve these criteria, we present a simple label-free paper based electrically-receptive thermally-responsive (ER-TR) biosensor chip with electrode coverage area of 1.2×1.2 mmxmm for the detection of E. coli cells as a model bacterial strain. The proposed system has excellent capability to detect and monitor E. coli with LOD as low as 100 cells/mL and TOR of about 1 – 3 min depending on the range of E. coli 100 – 50000 cells/mL. Autoclave water, tap water, lake water and milk samples were used and tested with ER-TR chip with and without E. coli cells at different time intervals. A single ER-TR chip was comprised of simple filter paper used as substrate coated with composite of poly(N-isopropylacrylamide) polymer (PNIPAm) – graphene nanoplatelet (GR) followed by evaporation of Au electrodes. The biosensor chip was integrated with in-house built printed circuit board (PCB) to transmit/receive electrical signals. The interaction of E. coli cells with fibers of PNIPAm-GR resulted in a change of electrical resistance and the readout was monitored in real-time fashion wirelessly using MATLAB algorithm. Detection range of 100 – 50000 cells/mL was achieved with regression value of 0.9779, 0.9667, 0.9964 for tap water, lake water and milk samples respectively. Proposed ERPTB chip also exhibited a reproducibility of 85-97% with shelf-life of about four weeks after testing with lake water sample. Results were successfully repeated for Bacillus subtilis and Streptococcus mutans. Results reveal the high possibility of developing the paper-based multilayer sensor as a low-cost handheld bacterial sensor chip integrated with battery operated PCB which could bring new adoptability to rural and remote areas where expensive and laborious equipment are not as easily applied.

Highly Sensitive electrically-receptive thermally-responsive analytical biosensor chip for rapid detection of Bacterial cells

255th National Meeting (2018)

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