Alginate Bead Biosystem for the Determination of Lactate in Sweat Using Image Analysis.

Edilberto Ojeda,Lourdes Basabe-Desmonts,Sandra Garcia-Rey,Fernando Benito-Lopez,Udara Bimendra Gunatilake

doi:10.3390/bios11100379

Abstract

Lactate is present in sweat at high concentrations, being a metabolite of high interest in sport science and medicine. Therefore, the potential to determine lactate concentrations in physiological fluids, at the point of need with minimal invasiveness, is very valuable. In this work, the synthesis and performance of an alginate bead biosystem was investigated. Artificial sweat with different lactate concentrations was used as a proof of concept. The lactate detection was based on a colorimetric assay and an image analysis method using lactate oxidase, horseradish peroxidase and tetramethyl benzidine as the reaction mix. Lactate in artificial sweat was detected with a R² = 0.9907 in a linear range from 10 mM to 100 mM, with a limit of detection of 6.4 mM and a limit of quantification of 21.2 mM. Real sweat samples were used as a proof of concept to test the performance of the biosystem, obtaining a lactate concentration of 48 ± 3 mM. This novel sensing configuration, using alginate beads, gives a fast and reliable method for lactate sensing, which could be integrated into more complex analytical systems.

Highlights

Sweat is an aqueous solution that contains a great variety of compounds, such as NaCl, lactate [1], nitrogenous compounds, metal ions, heavy metals, immune biomarkers (e.g., IgG, IgD and interleukin-1α [7]), cortisol and stress biomarkers [8], lactoferrin [9] and xenobiotics
With the idea of being able to develop robust portable devices for the detection of lactate in sweat, in this work, we investigated the use of alginate beads as a biocompatible biosystem for the determination of lactate concentrations
The concentration of the sample was measured using a commercially available device (Lactate Plus, Nova Biomedical, Waltham, MA, USA) for the determination of lactate levels, obtaining a concentration of 56 ± 1 mM (n = 3). These results demonstrate that the biosystem developed in this work can, be used for lactate determination in real sweat samples within the physiological range, after colorimetric analysis of the alginate beads

Summary

Introduction

Sweat is an aqueous solution that contains a great variety of compounds, such as NaCl, lactate [1], nitrogenous compounds (ammonia, urea and amino acids [2,3]), metal ions (e.g., zinc and iron [4,5]), heavy metals (e.g., arsenic, cadmium, lead and mercury [6]), immune biomarkers (e.g., IgG, IgD and interleukin-1α [7]), cortisol and stress biomarkers [8], lactoferrin [9] and xenobiotics (e.g., drugs of abuse [10] and ethanol [11,12]). The main function of sweat is thermoregulation, leading to heat dissipation by water evaporation [1] in response to an increase in body core temperature. Besides the regulation of body temperature, sweat plays an important role in protecting, lubricating and waterproofing the skin. Sweat forms part of the immune system since it contains cytokines and other related molecules involved in the immune-mediated mechanisms that occur in the skin, being one of the first barriers during an immune response [13]. The high amount of physiological information contained in sweat, together with its accessibility in a non-invasive way, highlights the potential of sweat as an emerging alternative to standard blood analysis. Thereby, the analysis of sweat could provide an accurate insight into the physiological condition of the body (e.g., biomarker concentrations), and a way of measuring body dehydration [14]. Sweat is the diagnostic method for cystic fibrosis, a disease characterised by the presence of high levels of sodium and chloride in sweat [15,16]

Methods

Results

Conclusion