Wearable Electrodes for Lactate: Applications in Enzyme‐Based Sensors and Energy Biodevices

Abstract

Wearable bioelectronics is a promising next-generation technology for its versatility in personalized applications. Measuring lactate is one of the growing trends in wearable biosensing research. To achieve this goal, enzymes capable of catalyzing reactions involving lactate must be coupled with bioelectrode components, creating a variety of biodevices such as biosensors, biofuel cells, and other devices harvesting energy from wearers. This review provides a brief history of noninvasive and minimally invasive enzyme-based lactate biosensors and energy biodevices. We introduce key principles of lactate oxidase and lactate dehydrogenase, together with immobilization strategies for efficient electrical contacts between redox enzymes and electrode supports. Additionally, we discuss recent examples of advanced wearable enzymatic lactate sensors and elaborate on a collection of self-powered wearable energy biodevices (e. g., biofuel cells, triboelectric nanogenerators, and piezoelectric devices). Lastly, we finish this review with discussions on challenges in developing lactate bioelectronics and provide our outlook on the prospects and future directions of this compelling technology.

Wearable Sensor Patch with Hydrogel Microneedles for In Situ Analysis of Interstitial Fluid

“…A flow velocity ( u ) is applied to account for the body’s response to counteract the lactate injection and enhance its dissipation into the bloodstream . We developed an equation for the time-dependent lactate concentration at the sensing site ( L s ) by combining balance equations and molecule conservation By applying the boundary conditions ( L ( x 0 , 0) = L 0 δ­( x – x 0 ) and L ( x b , t ) = 0), we quantified the time-dependent concentration on the sensor surface in 3D geometry Therefore, we introduced an empirical factor β accounting for the relationship between analyte concentration and amperometric response ( L S to J conversion, and J for absolute value of current density) The parameter β indicates the efficiency of the sensor patch in detecting the particular lactate analyte and is thus linked to the sensor’s sensitivity and selectivity …”

“…We reframed the MM formalism’s validity for the electrochemical setup that we adopted: J = q N A t ez α i false[ i false] K i + [ i ] where q is the electron charge, N A is the Avogadro number, t ez is the theoretical deposited thickness of the enzyme layer, [ i ] is the analyte concentration, and K i is the MM constant. The empirical parameter α i accounts for deviations from the MM equation’s ideal formalism, incorporating (a) the fraction of enzymatic active sites contributing to analyte conversion, (b) the catalytic rate constant efficiency, and (c) the capacitor partition between generated product fluxes. − The latter process suppresses the efficiency of the overall reaction further; after being generated by the enzyme-analyte complex, only a limited fraction of product molecules approach the sensing site (electrode) to produce an amperometric response, while the remaining amount is lost in the beaker solution. We used eq to calibrate the experimental data.…”

“…62 We developed an equation for the time-dependent lactate concentration at the sensing site (L s ) by combining balance equations and molecule conservation By applying the boundary conditions (L(x 0 , 0) = L 0 δ(x − x 0 ) and L(x b , t) = 0), we quantified the time-dependent concentration on the sensor surface in 3D geometry Therefore, we introduced an empirical factor β accounting for the relationship between analyte concentration and amperometric response (L S to J conversion, and J for absolute value of current density) The parameter β indicates the efficiency of the sensor patch in detecting the particular lactate analyte and is thus linked to the sensor's sensitivity and selectivity. 59 Figure 6e demonstrates the consistency between the experimental results and the theoretical predictions. To calibrate the response outlined in eq 9, we used the red curve depicted in Figure 6d.…”

Wearable electrochemical sensors for real-time monitoring in diabetes mellitus and associated complications

“…It is important to note that oxygen serves as the physiological electron acceptor in this oxidasebased concept. First-generation biosensors have demonstrated remarkable sensitivity and are distinguished by exceedingly short response times, typically on the order of one second [104] . Nevertheless, the stoichiometric constraints of oxygen and the inherent fluctuations in its levels within biofluids may introduce inaccuracies in this initial conceptualization [105] .…”

Smartphone-Based Portable Bio-Chemical Sensors: Exploring Recent Advancements

“…So far, various overview papers have covered the utilization of smartphones in biochemical sensing; however, they tend to focus on specific domains [1][2][3], or does not explain the sensors' mechanism in detail [4,5]. Thus, this review aims to provide a comprehensive overview of recent advancements in smartphone-based sensors, covering both optical and electrochemical sensing methods.…”