Testing of food and water samples for viruses and bacteria in a rapid, portable, quantitative way is of growing interest as much for government, farmers, industrials, as end-consumers. In the past two decades, many research groups were involved in the development of various paper-based devices for quantitative or semi-quantitative detection of clinically relevant analytes and in particular pathogens.

Some difficulties remain in analyzing samples with complex matrices (e.g., colored samples or muddy water), with enough sensitivity (e.g., detecting less than 10-100 cfu/mL) while minimizing culture time. Electrochemical detection can allow for rapid quantification over a wide dynamic range, with a low limit of detection, and without limitations related to presence of colors or particles in samples. Derda and co-workers validated growth of bacteria in portable paper-based culture devices [1, 2]. We added screen-printed electrodes onto those paper-based devices (Figure A-B) to allow for electrochemical detection of micro‑organisms. The presence of bacteria in the device, and particularly on the electrode, bacteria affects the characteristics of the electrode. By measuring those changes by electrochemical impedance spectroscopy, for example, we could detect the bacteria (Figure E).

The platform can be selective to bacteria by immobilizing on the electrode proximity antibodies specific to the bacteria to detect, and thus enhancing the presence of the bacteria on the electrode.

Using the paper-based portable culture device instead of metal electrodes as reported previously [3] as a support as multiple advantages: in addition to allow for an easy- sampling at the point-of-care or in-field, if the sample has a low number of bacteria (Figure C), it can be cultured in the same device and tested again once more bacteria is present (Figure D) without additional handling of the sample. The use of paper in these devices made them user-friendly, portable, light-weight, low-cost, easy to manufactured and disposed of once contaminated (e.g., burning).

References

1.    Deiss, F.; Funes-Huacca, M. E.; Bal, J.; Tjhung, K. F.; Derda, R., Antimicrobial susceptibility assays in paper-based portable culture devices. Lab on a Chip 2014,14, (1), 167.

2.    Funes-Huacca, M.; Wu, A.; Szepesvari, E.; Rajendran, P.; Kwan-Wong, N.; Razgulin, A.; Shen, Y.; Kagira, J.; Campbell, R.; Derda, R., Portable self-contained cultures for phage and bacteria made of paper and tape. Lab on a Chip 2012,12, (21), 4269.

3.    Lu, L.; Chee, G.; Yamada, K.; Jun, S., Electrochemical impedance spectroscopic technique with a functionalized microwire sensor for rapid detection of foodbornepathogens. Biosensors and Bioelectronics 2013, 42, (0), 492.