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Ingestible pH sensing device for gastrointestinal health monitoring based on thread-based electrochemical sensors

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Abstract

There exists a strong correlation between the pH levels of the gastrointestinal (GI) tract and GI diseases such as inflammatory bowel disease (IBS), ulcerative colitis, and pancreatis. Existing methods for diagnosing many GI diseases predominantly rely on invasive, expensive, and time-consuming techniques such as colonoscopy and endoscopy. In this study, an autonomous ingestible smart biosensing system in a pill format with integrated pH sensors is reported. The smart sensing pills will measure the pH profile as they transit through the GI tract. The data is then downloaded from the pills after they are collected from the feces. The sensor is based on electrodeposited PANI on carbon-coated conductive threads providing high pH sensitivity. Engineering innovations allowed integration of thread-based sensors on 3D-printed pill surfaces with front-end readout electronics, memory, and microcontroller assembled on mm-size circular printed circuit boards. The entire smart sensing pill possesses an overall length of 22.1 mm and an outer diameter of 9 mm. The modular biosensing system allows integration of thread-based biosensors to monitor other biomarkers in GI tract that mitigates the complex sensor fabrication process as well as overall pill assembly.

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Abbreviations

PCB::

Printed circuit board

FIR::

Finite-impulse response

DSP::

Digital signal processing

FTIR::

Fourier-transform infrared

PANI::

Polyaniline

GI::

Gastrointestinal

IBS::

Inflammatory bowel disease

GERD::

Gastroesophageal reflux disease

ISFET::

Ion-sensitive field-effect transistor

IPA::

Isopropyl alcohol

PU::

Polyurethane

CC::

Carbon-coated

PVB::

Polyvinyl butyral

WE::

Working electrode

RE::

Reference electrode

CE::

Counter electrode

CV::

Cyclic voltammetry

OCV::

Open-circuit voltage

EEPROM::

Electrically-erasable programmable read-only memory

SPI::

Serial peripheral interface

ADC::

Analog to digital converter

NMOS::

N-type metal oxide semiconductor

PMOS::

P-type metal oxide semiconductor

SLA::

Stereolithography

FDA :

Food and drug administration

SEM::

Scanning electron microscope

EB::

Emeraldine base

ES::

Emeraldine salt

LE::

Leucoemeraldine

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Acknowledgements

We acknowledge the support of the National Institute of Health (NIH) under the grant R21AI144521 and R21DK132314. S. Sonkusale would also like to acknowledge DoD DURIP and Massachusetts Life Sciences Center (MLSC) for equipment support.

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Authors and Affiliations

  1. Department of Electrical and Computer Engineering, Tufts University, 161 College Ave, Medford, 02155, MA, USA

    Cihan Asci, Atul Sharma, Ruben Del-Rio-Ruiz & Sameer Sonkusale

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  1. Cihan Asci
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Correspondence to Sameer Sonkusale.

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Asci, C., Sharma, A., Del-Rio-Ruiz, R. et al. Ingestible pH sensing device for gastrointestinal health monitoring based on thread-based electrochemical sensors. Microchim Acta 190, 385 (2023). https://doi.org/10.1007/s00604-023-05946-1

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