MONITORING CIRCULATING METABOLIC
MARKERS THROUGH MICRONEEDLE ARRAYS
FOR ANIMAL WELFARE

L Gautier, I Sorrentino, S Brulais, Florence Gondret, C Verplanck, I Texier

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L Gautier, I Sorrentino, S Brulais, Florence Gondret, C Verplanck, et al. MONITORING CIRCULATING METABOLIC MARKERS THROUGH MICRONEEDLE ARRAYS FOR ANIMAL WELFARE. WISED (Wearable and Implantable Sensors and Electrochemical Devices), Nov 2024, Lyon, France. hal-04904808

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Submitted on 21 Jan 2025

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# MONITORING CIRCULATING METABOLIC MARKERS THROUGH MICRONEEDLE ARRAYS FOR ANIMAL WELFARE

L. Gautier<fnref n="1" />, I. Sorrentino<fnref n="1" />, S. Brulais<fnref n="1" />, F. Gondret², C. Verplanck<fnref n="1" />, I. Texier<fnref n="1" />

**Keywords:** Microneedles, conductivity, skin perforation, animal welfare

## Abstract

The analysis of the dermal interstitial fluid (ISF), which is representative of blood in terms of circulating markers but is more accessible, could provide an interesting alternative to traditional blood sampling tests. Real-time measurements of circulating markers to follow the kinetics of variations in response to nutritional or environmental changes could be very useful to check adaptive physiology in a non-invasive way to assess health and well-being of livestock animals, particularly when facing heat stress due to climate change. Microneedles (MNs) with micropoints of 400-1500 µm height (for human), are able to perforate the skin and can give an easy access to ISF. Integrated with optical or electrochemical sensors to design wearable devices, MN arrays offer a minimally invasive and painless solution for the analysis of circulating metabolites or physiological integrative proxies [1-3]. The ambition of the project is to design MN-based electrochemical wearable sensors to monitor markers of animal well-being in real time. We focused on conductivity measurements that are indicative of variations in electrolytes content in intracellular fluids and monitor the metabolism of water and ions and therefore the animal dehydration.

For that purpose, wearable devices were designed where the microneedles themselves served as the measurement electrodes. A poly(lactic-co-glycolic) microneedles array was prepared by a hot-molding process and used as a template, then coated with different thin metallic layers. Metal-coated MNs were then screened for conductivity measurement performance in pure chemical solutions and in different skin models. Stability and ageing tests were performed to evaluate the robustness of the system to perform long lasting measurements. Finally, a complete packaged system was developed and tested on living pigs subjected to heat stress (32°C) during 7 days.

## Acknowledgements

The WAIT4 project is funded by Agence Nationale de la Recherche under the France 2030 program with the reference ANR-22-PEAE-0008.

## References:

[1] J. Li, M. Wei, B. Gao, « A Review of Recent Advances in Microneedle-Based Sensing within the Dermal ISF That Could Transform Medical Testing », ACS Sens., vol. 9, no 3, p. 1149-1161, mars 2024, doi: 10.1021/acssensors.4c00142.

[2] J. Li et al., « High-Performance Flexible Microneedle Array as a Low-Impedance Surface Biopotential Dry Electrode for Wearable Electrophysiological Recording and Polysomnography », Nano-Micro Lett., vol. 14, no 1, p. 132, juin 2022, doi: 10.1007/s40820-022-00870-0.

[3] S. A. N. Gowers et al., « Development of a Minimally Invasive Microneedle-Based Sensor for Continuous Monitoring of β-Lactam Antibiotic Concentrations in Vivo », ACS Sens., vol. 4, no 4, p. 1072-1080, avr. 2019, doi: 10.1021/acssensors.9b00288.

<footnote n="1">¹Université Grenoble Alpes, CEA, LETI-DTIS, F-38054 Grenoble, France (corresponding author : laurabelle.gautier@cea.fr) ; ²PEGASE, INRAE, Institut Agro, F-35590 Saint-Gilles, France</footnote>