Preparation of paper-based devices for reagentless electrochemical (bio)sensor strips

Abstract

Despite substantial advances in sensing technologies, the development, preparation, and use of self-testing devices is still confined to specialist laboratories and users. Decentralized analytical devices will enormously impact daily lives, enabling people to analyze diverse clinical, environmental, and food samples, evaluate them and make predictions to improve quality of life, particularly in remote, resource-scarce areas. In recent years, paper-based analytical tools have attracted a great deal of attention; the well-known properties of paper, such as abundance, affordability, lightness, and biodegradability, combined with features of printed electrochemical sensors, have enabled the development of sustainable devices that drive (bio)sensors beyond the state of the art. Their blindness toward colored/turbid matrices (i.e., blood, soil), their portability, and the capacity of paper to autonomously filter/purge/react with target species make such devices powerful in establishing point-of-need tools for use by non-specialists. This protocol describes the preparation of a voltammetric phosphate sensor and an amperometric nerve agent biosensor; both platforms produce quantitative measurements with currents in the range of microamperes. These printed strips comprise three electrodes (graphite for working and counter electrodes and silver/silver chloride (Ag/AgCl) for the reference electrode) and nanomodifiers (carbon black and Prussian blue) to improve their performance and specificity. Depending on analytical need, different types of paper (filter, office) and configurations (1D, 2D, 3D) can be adopted. The protocol, based on the use of cost-effective manufacturing techniques such as drop casting (to chemically modify the substrate surface) and wax/screen printing (for creating the channels and electrodes), can be completed in <1 h.

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Fig. 1: Configuration of a paper-based electrochemical device.
Fig. 2: Manufacture of a paper-based electrochemical sensor.
Fig. 3: Enhancing the electrochemical properties of the paper-based devices.
Fig. 4: Making the paper-based electrochemical device reagentless.
Fig. 5: Photographs of the end products, expected results, and troubleshooting interventions.

Data availability

The data generated or analyzed during this study are included in this published article and its Supplementary Information files.

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Acknowledgements

S.C. thanks Fondazione Umberto Veronesi for a postdoctoral fellowship in 2018.

Author information

S.C. conceived and designed the protocol. S.C., D.M., and F.A. designed, performed, and analyzed the experiments reported in the ‘Anticipated results’ section.

Correspondence to Stefano Cinti or Fabiana Arduini.

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Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Protocols thanks W.K.T. Coltro, Conor F. Hogan, and other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Related links

Key references using this protocol

Cinti, S., Talarico, D., Palleschi, G., Moscone, D., & Arduini, F. Anal. Chim. Acta 919, 78–84 (2016): https://doi.org/10.1016/j.aca.2016.03.011

Cinti, S., Minotti, C., Moscone, D., Palleschi, G., & Arduini, F. Biosens. Bioelectron. 93, 46–51 (2017): https://doi.org/10.1016/j.bios.2016.10.091

Cinti, S., Proietti, E., Casotto, F., Moscone, D., & Arduini, F. Anal. Chem. 90, 13680–13686 (2018): https://doi.org/10.1021/acs.analchem.8b04052

Integrated supplementary information

Supplementary Fig. 1. Diffusion of analyte at different paper-based electrodes.

Difference in diffusion of analytes at a filter paper-based electrode (top) and at an office paper-based electrode (bottom). In the case of filter paper, the analyte must diffuse within the cellulose matrix of paper prior to arrive at the working electrode surface. It causes a lowering of diffusion, thus a lowering of the recorded current (sensitivity). In the case of office paper, the analyte does not encounter the paper while diffusing towards the working electrode area. Diffusion is not limited by the paper and the recorded current is higher than that one recorded with a filter paper-based electrode.

Supplementary Fig. 2. Wax-patterning design.

Several example patterns and channels that have been drawn with Adobe Illustrator, prior to being wax printed.

Supplementary Fig. 3. Electrodes’ stencil design.

Electrodes’ patterns that have been drawn with Adobe Illustrator. These patterns are used to obtain stencils to screen-print conductive inks onto the chosen paper-based substrates.

Supplementary information

Supplementary Information

Supplementary Figures 1–3

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