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The demand for glucose monitoring devices has witnessed continuous growth from the rising diabetic population. The traditional approach of blood glucose (BG) sensor strip testing generates only intermittent glucose readings. Interstitial fluid-based devices measure glucose dynamically, but their sensing approaches remain either minimally invasive or prone to skin irritation. Here, a sweat glucose monitoring system is presented, which completely operates under rest with no sweat stimulation and can generate real-time BG dynamics. Osmotically driven hydrogels, capillary action with paper microfluidics, and self-powered enzymatic biochemical sensor are used for simultaneous sweat extraction, transport, and glucose monitoring, respectively. The osmotic forces facilitate greater flux inflow and minimize sweat rate fluctuations compared to natural perspiration-based sampling. The epidermal platform is tested on fingertip and forearm under varying physiological conditions. Personalized calibration models are developed and validated to obtain real-time BG information from sweat. The estimated BG concentration showed a good correlation with measured BG concentration, with all values lying in the A+B region of consensus error grid (MARD = 10.56% (fingertip) and 13.17% (forearm)). Overall, the successful execution of such osmotically driven continuous BG monitoring system from passive sweat can be a useful addition to the next-generation continuous sweat glucose monitors.

Introduction A rise in tinea cruris among Thai Naval Cadets has been observed. Clotrimazole powder has been shown to be effective as an adjunct treatment for tinea cruris; however, its efficacy as a monotherapy is limited. Objectives The aim is to determine the efficacy of 1% clotrimazole cream versus 1% clotrimazole powder in treating tinea cruris. Material and Methods A randomized trial was conducted at the Thai Naval Rating School, Chonburi, Thailand. Naval rating cadets with suspected tinea cruris were randomly assigned to one of two groups: 1% clotrimazole cream or 1% clotrimazole powder, and they were instructed to apply the related medication to the affected lesion twice daily for 4 weeks. Clinical and symptomatic evaluations were carried out at 4 and 8 weeks. Results All 17 and 14 participants who received 1% clotrimazole cream and powder, respectively, were included. After 4 weeks, the clinical cure rates were 76.5% in the cream group and 85.7% in the powder group (P  = .664). All participants were clinically cured within 8 weeks. The self-evaluation of itch severity using a visual analog scale (VAS) revealed no significant difference between the two groups (P  = .343). The dermatology quality of life index decreased as clinical improvement was achieved in both the clotrimazole cream and powder groups (6.0 vs. 7.5 score reductions, respectively; P  = .765). The score for sweat reduction was higher in the 1% clotrimazole powder group compared to the cream group (5.0 vs. 4.0, respectively; P  = .006). Conclusion Monotherapy with 1% clotrimazole powder showed comparable efficacy to 1% clotrimazole cream. Furthermore, the powder treatment reduced sweat more effectively compared to the cream. [ABSTRACT FROM AUTHOR]

In this study, we conducted a literature review to deepen our understanding of the sweating response of the thermoregulatory system, focusing on the influence of individual characteristics and local body functions. Among the factors related to individual characteristics, improvement in aerobic fitness had a positive effect on the sweating response, whereas aging exerted an inhibitory effect. Short-term artificial acclimation and seasonal heat acclimatization promoted sweating, whereas long-term geographical acclimatization suppressed sweating. Male exhibited higher sweat rates than female when the metabolic heat production was high. Individuals with smaller surface area-to-mass ratios tended to have higher sweat rates than those with larger ratios. Regarding local body functions, sweat distribution in the resting state showed high regional sweat rates in the lower limbs and torso, with higher values in the lower limbs when in the supine position and higher values in the torso when in the seated position. During exercise, the regional sweat rates was high in the torso, whereas the limbs exhibited relatively low sweat rates. These differences in sweat distribution stem from the thermoregulatory potential of each body region, which aims to efficiently regulate body temperature. Local effects have only been examined in the thigh and forearm, with temperature coefficient Q10 ranging from 2 to 5. Only the forehead showed significantly high thermosensitivity among all body regions. [ABSTRACT FROM AUTHOR]

Sweat is considered the most promising candidate to replace conventional blood samples for noninvasive sensing. There are many tools and optical and electrochemical methods that can be used for detecting sweat biomarkers. Electrochemical methods are known for their simplicity and cost-effectiveness. However, they need to be optimized in terms of selectivity and catalytic activity. Therefore, electrode modifiers such as nanostructures and metal–organic frameworks (MOFs) or combinations of them were examined for boosting the performance of the electrochemical sensors. The MOF structures can be prepared by hydrothermal/solvothermal, sonochemical, microwave synthesis, mechanochemical, and electrochemical methods. Additionally, MOF nanostructures can be prepared by controlling the synthesis conditions or mixing bulk MOFs with nanoparticles (NPs). In this review, we spotlight the previously examined MOF-based nanostructures as well as promising ones for the electrochemical determination of sweat biomarkers. The presence of NPs strongly improves the electrical conductivity of MOF structures, which are known for their poor conductivity. Specifically, Cu-MOF and Co-MOF nanostructures were used for detecting sweat biomarkers with the lowest detection limits. Different electrochemical methods, such as amperometric, voltammetric, and photoelectrochemical, were used for monitoring the signal of sweat biomarkers. Overall, these materials are brilliant electrode modifiers for the determination of sweat biomarkers. [ABSTRACT FROM AUTHOR]

We report on the possibility of noninvasive diabetes monitoring through continuous analysis of sweat. The prediction of the blood glucose level in diabetic patients is possible on the basis of their sweat glucose content due to the positive correlation discovered. The ratio between the blood glucose and sweat glucose concentrations for a certain diabetic subject is stable within weeks, excluding requirements for frequent blood probing. The glucose variations in sweat display allometric (non-linear) dependence on those in blood, allowing more precise blood glucose estimation. Selective (avoiding false-positive responses) and sensitive (sweat glucose is on average 30–50 times lower) detection is possible with biosensors based on the glucose oxidase enzyme coupled with a Prussian Blue transducer. Reliable glucose detection in just secreted sweat would allow noninvasive monitoring of the glycemia level in diabetic patients. [ABSTRACT FROM AUTHOR]

Objective To investigate the differential sweat metabolites and related pathways in patients with atopic dermatitis (AD) characterized by heart fire and spleen deficiency syndrome. Methods Twenty-two AD patients with heart fire and spleen deficiency syndrome and 22 healthy volunteers were recruited. Extensive targeted metabolomics analysis was conducted on collected sweat samples, and differential metabolites were identified through multivariate statistical analysis. The KEGG databases and HMDB were utilized to analyze the related pathways and associated diseases of the differential metabolites. Results A total of 115 differential metabolites were identified between the two groups of sweat samples. According to the KEGG database annotation analysis, these metabolites were involved in 15 different pathways. The HMDB's disease association analysis suggested a close relationship with digestive system diseases, including colorectal cancer, eosinophilic esophagitis, Crohn's disease, and ulcerative colitis. Conclusion There are numerous differential metabolites between AD patients with heart fire and spleen deficiency syndrome and the healthy control group, which may provide clues for the early warning of comorbidities in clinical practice. [ABSTRACT FROM AUTHOR]

Abstract Electrochemical analysis of glucose monitoring without painful blood collection provides a new noninvasive route for monitoring glucose levels. Thus, in this study, biobased cellulosic papers (methylated and phosphorylated one) based glucose monitoring sensor is developed. To achieve high hydrophilicity, microfibrillated cellulose (MFC) were functionalized using hexokinase mediated phosphorylation (–OH to – $$\text{SO}_{3}^{2-}$$ ). The instinctive increased surface charge density from 36.2 ± 3.4 to 118.4 ± 1.2 µmol/g and decrease contact angle (45°–22°) confirms the increased hydrophilicity of paper. Furthermore, functionalized phos-MFC paper increase the capillary flow of sweat, required low quantity (1 µl) of sweat for accurate analysis of glucose level. Additionally, chemically induced methyl groups (–CH3) make the sensor more barrier to other chemicals. In addition, a multilayer patch design combined with sensor miniaturization was used to lead to an increase in the efficiency of the sweat collection and sensing processes. Besides, this paper sensor integrated with artificial transdermal drug delivery unit (agarose gel as skin) for monitoring glucose levels in sweat. The patch monitoring system increase the accuracy of sensing with fluctuation in sweat vol. (1–4 µl), temperature (20–70 °C), and pH (4.0–7.0). In addition, temperature dependency artificial transdermal delivery (within agarose gel) of drug metformin agrees the measurement accuracy of sensor, called “switch system” without any error. As a result, the reported MFC paper based multi-patch disposable sensing system provides a novel closed-loop solution for the noninvasive sweat-based management of diabetes mellitus.

The quantification of protein biomarkers in blood at picomolar-level sensitivity requires labour-intensive incubation and washing steps. Sensing proteins in sweat, which would allow for point-of-care monitoring, is hindered by the typically large interpersonal and intrapersonal variations in its composition. Here we report the design and performance of a wearable and wireless patch for the real-time electrochemical detection of the inflammatory biomarker C-reactive (CRP) protein in sweat. The device integrates iontophoretic sweat extraction, microfluidic channels for sweat sampling and for reagent routing and replacement, and a graphene-based sensor array for quantifying CRP (via an electrode functionalized with anti-CRP capture antibodies-conjugated gold nanoparticles), ionic strength, pH and temperature for the real-time calibration of the CRP sensor. In patients with chronic obstructive pulmonary disease, with active or past infections or who had heart failure, the elevated concentrations of CRP measured via the patch correlated well with the protein's levels in serum. Wearable biosensors for the real-time sensitive analysis of inflammatory proteins in sweat may facilitate the management of chronic diseases.

Abstract Female development includes significant morphological changes across the breast. Yet, whether differences in breast surface area (BrSA) modify sweat gland density and output remains unclear. The present study investigated the relationship between BrSA and sweat gland density and output in 22 young to middle‐aged women (28±10 years) of varying breast sizes (BrSA range: 147–561 cm2) during a submaximal run in a warm environment (32 ±0.6°C; 53 ±1.7% relative humidity). Local sweat gland density and local sweat rate (LSR) above and below the nipple and at the bra triangle were measured. Expired gases were monitored for the estimation of evaporative requirements for heat balance (Ereq, in W/m2). Associations between BrSA and (i) sweat gland density; (ii) LSR; and (iii) sweat output per gland for the breast sites were determined via correlation and regression analyses. Our results indicated that breast sweat gland density decreased linearly as BrSA increased (r = −0.76, P

Electrodermal activity (EDA) is a widely used psychophysiological measurement in laboratory-based studies. In recent times, these measurements have seen a transfer from the laboratory to wearable devices due to the simplicity of EDA measurement as well as modern electronics. However, proper conditions for EDA measurement are recommended once wearable devices are used, and the ambient conditions may influence such measurements. It is not completely known how different types of ambient noise impact EDA measurement and how this translates to wearable EDA measurement. Therefore, this study explored the effects of various noise disturbances on the generation of EDA responses using a system for the simultaneous recording of all measures of EDA, i.e., skin conductance responses (SCRs), skin susceptance responses (SSRs), and skin potential responses (SPRs), at the same skin site. The SCRs, SSRs, and SPRs due to five types of noise stimuli at different sound pressure levels (70, 75, 80, 85, and 90 dB) were measured from 40 participants. The obtained results showed that EDA responses were generated at all levels and that the EDA response magnitudes were significantly (p < 0.001) influenced by the increasing noise levels. Different types of environmental noise may elicit EDA responses and influence wearable recordings outside the laboratory, where such noises are more likely than in standardized laboratory tests. Depending on the application, it is recommended to prevent these types of unwanted variation, presenting a challenge for the quality of wearable EDA measurement in real-world conditions. Future developments to shorten the quality gap between standardized laboratory-based and wearable EDA measurements may include adding microphone sensors and algorithms to detect, classify, and process the noise-related EDA. [ABSTRACT FROM AUTHOR]

Female development includes significant morphological changes across the breast. Yet, whether differences in breast surface area (BrSA) modify sweat gland density and output remains unclear. The present study investigated the relationship between BrSA and sweat gland density and output in 22 young to middle‐aged women (28±$\ \pm \ $10 years) of varying breast sizes (BrSA range: 147–561 cm2) during a submaximal run in a warm environment (32 ±$ \pm \ $0.6°C; 53 ±$ \pm \ $1.7% relative humidity). Local sweat gland density and local sweat rate (LSR) above and below the nipple and at the bra triangle were measured. Expired gases were monitored for the estimation of evaporative requirements for heat balance (Ereq, in W/m2). Associations between BrSA and (i) sweat gland density; (ii) LSR; and (iii) sweat output per gland for the breast sites were determined via correlation and regression analyses. Our results indicated that breast sweat gland density decreased linearly as BrSA increased (r = −0.76, P < 0.001), whereas sweat output per gland remained constant irrespective of BrSA (r = 0.29, P = 0.28). This resulted in LSR decreasing linearly as BrSA increased (r = −0.62, P = 0.01). Compared to the bra triangle, the breast had a 64% lower sweat gland density (P < 0.001), 83% lower LSR (P < 0.001) and 53% lower output per gland (P < 0.001). BrSA (R2 = 0.33, P = 0.015) explained a greater proportion of variance in LSR than Ereq (in W/m2) (R2 = 0.07, P = 0.538). These novel findings extend the known relationship between body morphology and sweat gland density and LSR, to the female breast. This knowledge could innovate user‐centred design of sports bras by accommodating breast size‐specific needs for sweat management, skin wetness perception and comfort. What is the central question of this study?How do differences in breast surface area impact sweat gland density and output across the breast of healthy women during running in the heat?What is the main finding and its importance?There was a novel relationship between breast morphology and sweat gland density and output such that gland density and local sweat rates decreased linearly as breast surface area increased. Furthermore, the breast had lower sweat gland density and output than the bra triangle. This knowledge could inform user‐centred design of sports bras through a better understanding of breast size‐specific thermal needs. [ABSTRACT FROM AUTHOR]

Summary: Obstructive sleep apnea (OSA) is a sleep disorder that has been associated with the incidence of other pathologies. Diagnosis is mainly based on the apnea–hypopnea index (AHI) obviating other repercussions such as intermittent hypoxemia, which has been found to be associated to cardiovascular complications. Blood‐based samples and urine have been the most utilised biofluids in metabolomics studies related to OSA, while sweat could be an alternative due to its non‐invasive and accessible sampling, its reduced complexity, and comparability with other biofluids. Therefore, this research aimed to evaluate metabolic overnight changes in sweat collected from patients with OSA classified according to the AHI and oxygen desaturation index (ODI), looking for potential cardiovascular repercussions. Pre‐ and post‐sleeping sweat samples from all individuals (n = 61) were analysed by gas chromatography coupled to high‐resolution mass spectrometry after appropriate sample preparation to detect as many metabolites as possible. Permanent significant alterations in the sweat were reported for pyruvate, serine, lactose, and hydroxybutyrate. The most relevant overnight metabolic alterations in sweat were reported for lactose, succinate, urea, and oxoproline, which presented significantly different effects on factors such as the AHI and ODI for OSA severity classification. Overall metabolic alterations mainly affected energy production‐related processes, nitrogen metabolism, and oxidative stress. In conclusion, this research demonstrated the applicability of sweat for evaluation of OSA diagnosis and severity supported by the detected metabolic changes during sleep. [ABSTRACT FROM AUTHOR]

Wearable sweat sensors can noninvasively, in real time, and continuously monitor various physiological markers in sweat at the molecular level, which has a wide range of application prospects in the fields of health management, healthcare, and clinical diagnosis. However, effective sweat sampling remains a great challenge. Here, we prepared Janus fabric sweat glucose sensors, which were made by electrospinning hydrophobic polyurethane (PU) on a super hydrophilic gauze that can unidirectionally transport sweat from the skin (hydrophobic side) to the electrode (hydrophilic side). The screen-printed electrode modified by glucose oxidase has a good linear response to glucose. On-body experiments show that the sensor can detect glucose levels in sweat in real-time. The Janus fabric glucose sensor with its in situ monitoring capability and unidirectional liquid transport, and requires very low production costs, is expected to facilitate the development of smart textile sensors, opening new possibilities for exploring precise and controllable platforms for body fluid collection and sensing. [ABSTRACT FROM AUTHOR]

Horses that sweat during exercise lose considerable amounts of water and electrolytes, such as sodium (Na), potassium (K) and chloride (Cl). Significant sweat losses between 7–10L can occur even during moderate exercise in leisure horses (500–600kg body mass); significantly higher sweat losses can be observed in endurance riding or in Three-day eventing competitions. Numerous studies have shown that most leisure and sport horses cannot compensate their increased Na and Cl requirements via a salt lick, whereas the K supply can be covered by an adequate roughage intake, even under situations with a high K requirement. The oral supplementation of electrolytes, especially Na and Cl, is a useful strategy in order to replace electrolytes that are lost by sweating in leisure and in sport horses. Although there are numerous electrolyte supplements on the market, commercial products are usually not well formulated, so that salt supplementation (e.g., table salt without fluorine and iodine) is recommended in the nutritional management of hoses. Adding electrolytes into the diet, sufficient water must be always freely available in order (i) to compensate water losses through sweating; (ii) promoting electrolyte absorption in the gastrointestinal tract; and (iii) counteracting the risks of salt overdosing, as renal elimination is dependent on water supply. Horses should be adapted to the oral supplementation of electrolytes/salt e.g., in combination with palatable feed. The application of electrolytes via the drinking water is often not recommended, as the palatability of saline solutions in horses is low and can individually vary from horse to horse. [ABSTRACT FROM AUTHOR]

Sweat production is vital for human survival as its evaporation eases heat dissipation. Nevertheless, excessive perspiration or hyperhidrosis causes stress and discomfort affecting people’s quality of life. Persistent hyperhidrosis treatments during long time periods with classical antiperspirants, anticholinergic medications or botulinum toxin injections produce diverse side effects that limit their clinical use. Inspired in anticholinergic compounds, we used an in silico molecular modelling approach to design novel peptides targeting sweat induction signaling cascade initiated by M3 activation and coupling to Gq- αβγ in order to treat hyperhidrosis conditions. We selected 8 designed peptides that inhibited acetylcholine-induced M3 activation in CHO cells. The most potent peptides were lipopeptides including palmitoyl and myristoyl groups pLI1-3, pLI1-3-n6.1, pLI1-3-n6.2 and mLI2-1 as corroborated by their IC50 value. Noteworthy, local acute and chronic administration of the most potent pLI1-3 peptide significantly decreased pilocarpine-induced sweating in an in vivo rat model. Taken together, our in silico approximation produced active peptides able to attenuate excessive sweating by halting M3 activation-induced sweat production signaling cascade, and proposed pLI1-3 peptide as a potential new anti-hyperhidrosis candidate for clinical development. [ABSTRACT FROM AUTHOR]

Recently, continuous glucose monitoring has gained global importance in diabetes management, leading to increased interest in noninvasive technologies as more convenient alternatives to traditional finger-pricking methods for frequent glucose monitoring. Sweat has emerged as a promising alternative, although challenges persist regarding the stability of disposable biosensors and the reliability of enzymes for detecting glucose concentration in human sweat. This study focuses on synthesizing Ti3C2Tx/polyaniline (PANI; MXP2; 1% Ti3C2Tx) ratios as electrocatalysts for enzyme-free glucose sensing, aiming to address these issues in noninvasive glucose detection. Furthermore, the parent Ti3C2Tx, PANI, and MXP2 were drop-coated over disposable screen-printed carbon electrodes (SPCE) to enable reliable, rapid, and easy glucose detection. The resulting MXP2, exhibiting semiconductor properties (Eg = −2.79 eV), showed excellent redox performance facilitated by its large active surface area, leading to enhanced electrocatalytic glucose oxidation. Modified PANI/SPCE, Ti3C2Tx/SPCE, and MXP2/SPCE sensors demonstrated excellent sensitivity values of 576.9, 687.44, and 1241.57 μA mM–1 cm–2, respectively, along with low detection limits of 25 nM, 18 nM, and 17 nM (considered S/N = 3). These sensitivities were observed in the linear dynamic range of 1–350 μM within the potential window of −0.5 V to +0.5 V. Furthermore, the MXP2/SPCE sensor exhibited repeatability with an RSD of 0.632% under artificial sweat conditions. Real glucose detection in human sweat was performed using the fast walking task. Overall, the MXP2/SPCE sensor shows promise as a stable, reliable, disposable, and cost-effective noninvasive enzyme-free device for wearable bioelectronics. [ABSTRACT FROM AUTHOR]

Electrophysiological signals are commonly used to assess health performance, providing valuable information on body status. However, stable signal acquisition by commercial Ag/AgCl gel or metal electrodes is susceptible to electrode/skin interface interferences due to perspiration and motion during exercise. To address this challenge, herein a sweat absorbing skin electrode (SAE) is designed, which can not only become softer and more adhesive but also enhance conductivity after sweat during exercise. The resulting stable interface between SAE/skin after sweat enables accurate and continuous electrophysiological measurement during exercise. SAE is demonstrated by assembly of MXene (Ti3C2TX) aerogel and zwitterionic polymer, where Ti3C2TX aerogel works as conductive skeleton and zwitterionic polymer endows skin conformability as well as expediting interfacial charge transfer by the inherent ions. SAE can monitor a variety of electrophysiological signals during exercise. As an example, electromyogram (EMG) signals are acquired to assess muscle fatigue, which is impossible by commercial gel electrodes. Via machine learning, the correlation between EMG and physiological markers (body fat percentage (BF) and body mass index (BMI)) are constructed. The research shows that sweat‐absorbing SAEs can reliably monitor electrophysiological signals during exercise, such as muscle status, leading to evidence‐based scientific guidelines for sports and rehabilitation training. [ABSTRACT FROM AUTHOR]

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Abstract The demand for glucose monitoring devices has witnessed continuous growth from the rising diabetic population. The traditional approach of blood glucose (BG) sensor strip testing generates only intermittent glucose readings. Interstitial fluid‐based devices measure glucose dynamically, but their sensing approaches remain either minimally invasive or prone to skin irritation. Here, a sweat glucose monitoring system is presented, which completely operates under rest with no sweat stimulation and can generate real‐time BG dynamics. Osmotically driven hydrogels, capillary action with paper microfluidics, and self‐powered enzymatic biochemical sensor are used for simultaneous sweat extraction, transport, and glucose monitoring, respectively. The osmotic forces facilitate greater flux inflow and minimize sweat rate fluctuations compared to natural perspiration‐based sampling. The epidermal platform is tested on fingertip and forearm under varying physiological conditions. Personalized calibration models are developed and validated to obtain real‐time BG information from sweat. The estimated BG concentration showed a good correlation with measured BG concentration, with all values lying in the A+B region of consensus error grid (MARD = 10.56% (fingertip) and 13.17% (forearm)). Overall, the successful execution of such osmotically driven continuous BG monitoring system from passive sweat can be a useful addition to the next‐generation continuous sweat glucose monitors.

Wearable sensors hold great potential in empowering personalized health monitoring, predictive analytics, and timely intervention toward personalized healthcare. Advances in flexible electronics, materials science, and electrochemistry have spurred the development of wearable sweat sensors that enable the continuous and noninvasive screening of analytes indicative of health status. Existing major challenges in wearable sensors include: improving the sweat extraction and sweat sensing capabilities, improving the form factor of the wearable device for minimal discomfort and reliable measurements when worn, and understanding the clinical value of sweat analytes toward biomarker discovery. This review provides a comprehensive review of wearable sweat sensors and outlines state-of-the-art technologies and research that strive to bridge these gaps. The physiology of sweat, materials, biosensing mechanisms and advances, and approaches for sweat induction and sampling are introduced. Additionally, design considerations for the system-level development of wearable sweat sensing devices, spanning from strategies for prolonged sweat extraction to efficient powering of wearables, are discussed. Furthermore, the applications, data analytics, commercialization efforts, challenges, and prospects of wearable sweat sensors for precision medicine are discussed.

. This study aimed to develop a paper-based glucose sensor using artificial sweat and saliva samples, a non-invasive, practical, and affordable concept for measuring glucose levels. The chosen method was the colorimetric method using the Glucose Oxidase (GOx) enzyme, Horseradish Peroxidase (HRP) enzyme, and 3,3?-diaminobenzidine (DAB) chromogen. The wax stamping method was utilized on a piece of filter paper to test the glucose sensor. The test was carried out in several stages, including testing various concentrations of reagents and wax stamping sizes, fabricating the glucose sensors, and testing multiple concentrations of glucose, artificial sweat, and artificial saliva. The RGB method was used to test the resulting color. The data obtained were then validated using UV-Vis Spectrophotometry. The GOx concentration on the glucose sensor affected the color change velocity. The HRP, DAB, and wax stamping size concentration simultaneously indicated a strong correlation with changes in the color intensity that appeared on the glucose sensor. The glucose sensor in this study could measure the glucose concentration of the artificial sweat and saliva samples, respectively, from 0-3000 and 0.9987. This study proved a strong correlation between the reagents' concentration and the color intensity on the developed glucose sensor.

Abstract Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future.

The cortisol in human body is a crucial biomarker in terms of wellness management, mental state monitoring and stress-related disorder diagnosis. Therefore, the rapid, reliable and facile measurement of cortisol concentration has attracted extensive research interest. However, traditional cortisol detection such as immunosensing requires demanding laboratory layout, lengthy procedures and high costs, which means, consequently, it is incompatible with the current goal of cortisol sensing. Given the contradiction, an electrochemical sensor based on molecularly imprinted polymer (MIP) for simple, efficient, non-invasive cortisol detection was proposed. The two-step approach employed is simple enough and allows for the mass production of devices. And the embedding of Prussian Blue (PB) within the MIP layer eliminates the need for complex external probes, thereby making the resultant sensors more suitable for integration into wearable devices. We firstly demonstrated the feasibility of the proposed strategy and characterized the successful formation of cavities specific to cortisol molecules. Thereafter, we measured the dependence of the current response on cortisol concentration in Phosphate Buffered Saline (PBS) buffer, which revealed a near-linear relationship between the logarithm of the cortisol concentration and the redox current from 10−9 mol/L to 10−5 mol/L, covering the optimal range of cortisol concentration in sweat. Subsequently, sensors with the same specifications were prepared and tested in PBS buffer, exhibiting good consistency. In artificial sweat, we further demonstrated that they have benign selectivity, interference immunity and great potential in practical applications.

Hemodialysis patients are susceptible to excess volume accumulation, particularly over the 2-day interval (long interdialytic gap), resulting in higher interdialytic weight gain (IDWG). We thought to determine whether a novel device designed to enhance fluid and salt loss by activating the eccrine sweat glands can mitigate IDWG. Patients eligible for the study were undergoing regular hemodialysis for ≥3 months, without residual renal function, and with IDWG (as a percentage of IDWG/dry body weight) ≥2.5%. Treatments were administered at the patient’s home. The primary performance endpoint was differences in weight gain over long interdialytic period with the device compared to the control period. Secondary exploratory endpoints included the need for ultrafiltration (UF) rate > 10 mL/kg/h in the post-interval dialysis. Five patients were enrolled into the pilot study (age range 26 to 69 years, 3 women). The hourly mean weight loss from sweat was 186 ± 45 g/h. The average procedure length was 4.5 h with an average fluid loss of 899 ± 283 grams per procedure. The average least-squares mean absolute difference of IDWG between the control and treatment periods was −2.0%; (95% confidence interval [CI], −2.9% to −1.2%, p

Biomarkers are crucial biological indicators in medical diagnostics and therapy. However, the process of biomarker discovery and validation is hindered by a lack of standardized protocols for analytical studies, storage and sample collection. Wearable chemical sensors provide a real-time, non-invasive alternative to typical laboratory blood analysis, and are an effective tool for exploring novel biomarkers in alternative body fluids, such as sweat, saliva, tears and interstitial fluid. These devices may enable remote at-home personalized health monitoring and substantially reduce the healthcare costs. This Review introduces criteria, strategies and technologies involved in biomarker discovery using wearable chemical sensors. Electrochemical and optical detection techniques are discussed, along with the materials and system-level considerations for wearable chemical sensors. Lastly, this Review describes how the large sets of temporal data collected by wearable sensors, coupled with modern data analysis approaches, would open the door for discovering new biomarkers towards precision medicine.

[Display omitted] Realizing an electrode that can stably monitor biosignals after multiple exposures to sweat is challenging. Utilizing a Janus electrode, which is composed of a stack of ultrathin hydrophobic microporous Au membrane and water-durable hydrophilic nanofiber layers, asymmetric wettability can be realized and maintained for 7 days. Thus, it can create spontaneous unidirectional sweat transport from the skin surface, ensuring that the skin-electrode interface remains dry, especially during sweating. The ultrathin hydrophobic membrane facilitates self-adhesion with an adhesion energy of 59.2 µJ cm−2, which creates a high conformal contact to the skin and self-adhering to the hydrophilic nanofibers. The hydrophilic nanofibers exhibit excellent durability even after continuous immersion in water for up to 1 month. Additionally, a thin translucent polyvinyl alcohol nanofibers frame assists the Janus electrode in achieving highly conformable attachment to both dry and sweaty skin. The Janus electrode also exhibits excellent breathability and high mechanical stability owing to its porous structure and fine thickness. With these properties, the Janus electrode can monitor an electrocardiogram signal after dynamic activities, including physical exercise, waking up, desk work, meals, and going out for 6 days, while maintaining a stable signal-to-noise ratio of ∼ 18.8 dB. [ABSTRACT FROM AUTHOR]

Primary hyperhidrosis (PH) is a relatively common chronic disorder, characterized by significant and uncontrollable sweating. The predominant areas of occurrence are hands, feet, head and armpits, and it affects both men and women equally, with a false impression of increased prevalence in women. This study aims to determine the incidence of cases of hyperhidrosis, the gender of the patients and the environment of origin and to identify the most affected age groups and the distribution of hyperhidrosis, as well as creating a curve of cases within the time interval studied and their comparison with those in the specialized literature. [ABSTRACT FROM AUTHOR]

Herein, a self-powered lactate biosensor (SPLBs) was assembled to detect lactate in sweat based on flexible textile matrix enzymatic electrodes. A porous three-dimensional electrode with high flexibility and electrical conductivity was obtained by decorating composites of reduced graphene oxide and carboxylate multiwalled carbon nanotubes onto a cellulose fabric substrate. The excellent enzyme embedding method using a gel electrolyte showed a Michaelis–Menten constant of 1.46 mM, indicating the high enzymatic activity of lactate dehydrogenase. Moreover, the assembled (SPLBs) displayed a sensitivity of 3.16 µW mM−1 cm−2 with a linear range of 0–10 mM and a detection limit of 9.49 µM. Additionally, the biosensor has good tensile flexural stability, selectivity, and long-term stability. When integrated into clothing, the (SPLBs) recovered 91.5–102.3% of lactate from real sweat, with a relative standard deviation of less than 4.16%. This biosensor is promising for sensing lactate in human sweat. [ABSTRACT FROM AUTHOR]

Alumina inorganic molecularly imprinted polymer (MIP) modified multi-walled carbon nanotubes (MWCNTs) on a glassy carbon electrode (MWCNTs-Al2O3-MIP/GCE) was firstly designed and fabricated by one-step electro deposition technique for the detection of uric acid (UA) in sweat. The UA templates were embedded within the inorganic MIP by co-deposition with Al2O3. Through the evaluation of morphology and structure by Field Emission Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM), it was verified that the specific recognition sites can be fabricated in the electrodeposited Al2O3 molecular imprinted layer. Due to the high selectivity of molecular imprinting holes, the MWCNTs-Al2O3-MIP/GCE electrode demonstrated an impressive imprinting factor of approximately 2.338 compared to the non-molecularly imprinted glassy carbon electrode (MWCNTs-Al2O3-NIP/GCE) toward uric acid detection. Moreover, it exhibited a remarkable limit of detection (LOD) of 50 nM for UA with wide detection range from 50 nM to 600 μM. The MWCNTs-Al2O3-MIP/GCE electrode also showed strong interference resistance against common substances found in sweat. These results highlight the excellent interference resistance and selectivity of MWCNTs-Al2O3-MIP/GCE sensor, positioning it as a novel sensing platform for non-invasive uric acid detection in human sweat. [ABSTRACT FROM AUTHOR]

A wearable sweat sensor chip based on surface-enhanced Raman spectroscopy (SERS) is here presented. The plasmonic core of the chip, obtained by deposition of silver nanowires on a polytetrafluoroethylene (PTFE) porous membrane, permits the direct and label-free detection of urea and lactate at physiologic concentrations in combination with the pH measurement in the range between 5 and 9. Once integrated with commercial biocompatible and adhesive tape layers, the as produced SERS-active chip provides a low-cost, flexible and wearable sensing device for rapid and reliable human sweat analysis. The chip was finally tested on real sweat samples to estimate lactate and urea during medium-intense exertions. [ABSTRACT FROM AUTHOR]

A lactic acid (LA) monitoring system aimed at sweat monitoring was fabricated and tested. The sweat LA monitoring system uses a continuous flow of phosphate buffer saline, instead of chambers or cells, for collecting and storing sweat fluid excreted at the skin surface. To facilitate the use of the sweat LA monitoring system by subjects when exercising, the fluid control system, including the sweat sampling device, was designed to be unaffected by body movements or muscle deformation. An advantage of our system is that the skin surface condition is constantly refreshed by continuous flow. A real sample test was carried out during stationary bike exercise, which showed that LA secretion increased by approximately 10 μg/cm2/min compared to the baseline levels before exercise. The LA levels recovered to baseline levels after exercise due to the effect of continuous flow. This indicates that the wristwatch sweat LA monitor has the potential to enable a detailed understanding of the LA distribution at the skin surface. [ABSTRACT FROM AUTHOR]

Wearable glucose biosensors enable noninvasive glucose monitoring, thereby enhancing blood glucose management. In this work, we present a wearable biosensor based on carbon black nanoparticles (CBNPs) for glucose detection in human sweat. The biosensor consists of CBNPs, Prussian blue (PB), glucose oxidase, chitosan, and Nafion. The fabricated biosensor has a linear range of 5 µM to 1250 µM, sensitivity of 14.64 µA mM−1 cm−2, and a low detection potential (−0.05 V, vs. Ag/AgCl). The detection limit for glucose was calculated as 4.83 µM. This reusable biosensor has good selectivity and stability and exhibits a good response to glucose in real sweat. These results demonstrate the potential of our CBNP-based biosensor for monitoring blood glucose in human sweat. [ABSTRACT FROM AUTHOR]

Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increases thermoeffector output (i.e., sweating and skin blood flow) and lowers cardiovascular strain (i.e., heart rate) during heat stress. However, the mechanisms mediating these adaptations remain understudied. Furthermore, several possible benefits of heat acclimation for other systems and functions involved in maintaining health and performance during heat stress remain to be elucidated. This review summarizes recent advances in human heat acclimation, with emphasis on recent studies that (1) advanced our understanding of the mechanisms mediating improved thermoeffector output and (2) investigated adaptations that go beyond those classically associated with heat acclimation. We highlight that these studies have contributed to a better understanding of the integrated physiological responses underlying human heat acclimation while leaving key unanswered questions that will need to be addressed in the future. What is the topic of this review?This review summarizes studies that advance our understanding of the mechanisms mediating improved thermoeffector output following heat acclimation and investigate adaptations that go beyond those classically associated with heat acclimation.What advances does it highlight?Most studies that investigated possible mechanisms mediating greater thermoeffector output following heat acclimation have focused on end‐organ responses. Some evidence suggests that heat acclimation improves cardiac function, body fluid regulatory functions, and preserves cognitive performance under heat stress. However, these conclusions are based on limited and conflicting data. [ABSTRACT FROM AUTHOR]

This study aimed to develop a paper-based glucose sensor using artificial sweat and saliva samples, a non-invasive, practical, and affordable concept for measuring glucose levels. The chosen method was the colorimetric method using the Glucose Oxidase (GOx) enzyme, Horseradish Peroxidase (HRP) enzyme, and 3,3′-diaminobenzidine (DAB) chromogen. The wax stamping method was utilized on a piece of filter paper to test the glucose sensor. The test was carried out in several stages, including testing various concentrations of reagents and wax stamping sizes, fabricating the glucose sensors, and testing multiple concentrations of glucose, artificial sweat, and artificial saliva. The RGB method was used to test the resulting color. The data obtained were then validated using UV-Vis Spectrophotometry. The GOx concentration on the glucose sensor affected the color change velocity. The HRP, DAB, and wax stamping size concentration simultaneously indicated a strong correlation with changes in the color intensity that appeared on the glucose sensor. The glucose sensor in this study could measure the glucose concentration of the artificial sweat and saliva samples, respectively, from 0-3000 μM with R2 = 0.9862 and 0.9987. This study proved a strong correlation between the reagents' concentration and the color intensity on the developed glucose sensor. [ABSTRACT FROM AUTHOR]

Solid-contact (SC) ion-selective electrodes (ISEs) are often employed in wearables for electrolytes detection owing to their simplicity and ease of miniaturization. However, to mitigate their inherently unstable open circuit potential signal, ISEs require long hours of conditioning and frequent calibration prior to and during operation, limiting their practicality in wearable applications. Inspired by strategies to address water crossover and flooding in polyelectrolyte fuel cells, we demonstrated a SCISE with minimal conditioning time and long-term stability by modulating the rate-limiting step between mass transfer of water and hydrated ions and redox kinetics in the conducting polymer (CP). Our strategy comprised a wearable ISE with a superhydrophobic CP, PEDOT:TFPB, which reduced water and ion fluxes within the ISE, resulting in a stable and less-swollen CP and diminished water layer formation while maintaining CP's high capacitance. Our PEDOT:TFPB based ISEs functioned after a short conditioning time of 30 min and exhibited extended stability with a reduced signal deviation of only 0.16 % per hour (0.02 mV h−1) during 48 h of continuous measurement. Through systematic studies, we showed that ISE performance could be further tuned by tailoring the thickness of the ion-selective membrane as well as the hydrophobicity and polymerization charges of the CP. Without the need for recurrent calibration, our ISEs sustain high accuracy and prolonged stability upon integration into a wearable format for on-body perspiration analysis. Our strategy allows wearable ion-selective sensors with minimal maintenance at the user-end for long-term continuous monitoring, unveiling their potential in sports, healthcare, and diagnosis fields.

Over the last decade, a significant paradigm shift has been observed towards leveraging less invasive biological fluids—such as skin interstitial fluid (ISF), sweat, tears, and saliva—for health monitoring. This evolution seeks to transcend traditional, invasive blood-based methods, offering a more accessible approach to health monitoring for non-specialized personnel. Skin ISF, with its profound resemblance to blood, emerges as a pivotal medium for the real-time, minimally invasive tracking of a broad spectrum of biomarkers, thus becoming an invaluable asset for correlating with blood-based data. Our exploration delves deeply into the development of wearable molecular biosensors, spotlighting dermal sensors for their pivotal roles across both clinical and everyday health monitoring scenarios and underscoring their contributions to the holistic One Health initiative. In bringing forward the myriad challenges that permeate this field, we also project future directions, notably the potential of skin ISF as a promising candidate for continuous health tracking.Moreover, this paper aims to catalyse further exploration and innovation by presenting a curated selection of seminal technological advancements. Amidst the saturated landscape of analytical literature on translational challenges, our approach distinctly seeks to highlight recent developments. In attracting a wider spectrum of research groups to this versatile domain, we endeavour to broaden the collective understanding of its trajectory and potential, mapping the evolution of wearable biosensor technology. This strategy not only illuminates the transformative impact of wearable biosensors in reshaping health diagnostics and personalized medicine but also fosters increased participation and progress within the field. Distinct from recent manuscripts in this domain, our review serves as a distillation of key concepts, elucidating pivotal papers that mark the latest advancements in wearable sensors. Through presenting a curated collection of landmark studies and offering our perspectives on the challenges and forward paths, this paper seeks to guide new entrants in the area. We delineate a division between wearable epidermal and subdermal sensors—focusing on the latter as the future frontier—thereby establishing a unique discourse within the ongoing narrative on wearable sensing technologies.

Advancements in wearable bioanalytical microsystems have enabled diurnal and (semi)continuous monitoring of physiologically-relevant indices that are accessible through probing sweat. To deliver an undistorted and physiologically-meaningful interpretation of these readings, tracking the sweat secretion rate is essential, because it allows for calibrating the biomarker readings against variations in sweat secretion and inferring the bodys hydration/electrolyte homeostasis status. To realize an autonomous wearable solution with intrinsically high signal-to-noise ratio sweat rate sensing capabilities, here, we devise a digitized microbubble detection mechanism-delivered by a hybrid microfluidic/electronic system with a compact footprint. This mechanism is based on the intermittent generation of microliter-scale bubbles via electrolysis and the instantaneous measurement of their time-of-flight (and thus, velocity) via impedimetric sensing. In this way, we overcome the limitations of previously proposed sweat rate sensing modalities that are inherently susceptible to non-targeted secretion characteristics (pH, conductivity, and temperature), constrained by volume, or lack system integration for autonomous on-body operation. By deploying our solution in human subject trials, we validate the utility of our solution for seamless monitoring of exercise- and iontophoretically-induced sweat secretion profiles.

Wearable non-invasive biosensors for the continuous monitoring of metabolites in sweat can detect a few analytes at sufficiently high concentrations, typically during vigorous exercise so as to generate sufficient quantity of the biofluid. Here we report the design and performance of a wearable electrochemical biosensor for the continuous analysis, in sweat during physical exercise and at rest, of trace levels of multiple metabolites and nutrients, including all essential amino acids and vitamins. The biosensor consists of graphene electrodes that can be repeatedly regenerated in situ, functionalized with metabolite-specific antibody-like molecularly imprinted polymers and redox-active reporter nanoparticles, and integrated with modules for iontophoresis-based sweat induction, microfluidic sweat sampling, signal processing and calibration, and wireless communication. In volunteers, the biosensor enabled the real-time monitoring of the intake of amino acids and their levels during physical exercise, as well as the assessment of the risk of metabolic syndrome (by correlating amino acid levels in serum and sweat). The monitoring of metabolites for the early identification of abnormal health conditions could facilitate applications in precision nutrition.

Introduction/Objective. Primary focal hyperhidrosis (PFH) is an idiopathic condition where excessive sweating affects one or more body regions, including axillae, palms, soles, and/or face. Most studies on quality-of-life (QoL) focus on the period up to one year after bilateral thoracoscopic sympathectomy (BTS). This study aims to determine the 10-year trend in QoL among patients from the Republic of Serbia with palmar-plantar-axillary PFH, treated with BTS at the R3–R4 level. A secondary goal is to ascertain the existence of compensatory sweating. Methods. All patients underwent a standardized BTS in a single act, through the cutting of ganglia with ultrasonic scissors at the R3–R4 level. For data collection, patients completed the “Hyperhidrosis Quality of Life Questionnaire,” and the Hyperhidrosis Disease Severity Scale, preoperatively, postoperatively within 30 days, and 10 years after BTS. Results. The total sample consisted of 103 subjects who completed all three questionnaires. Considering the improvement in QoL from the group excellent, good, and average, the postoperative improvement was immediately postoperative in 88.4% of patients, while in the ten-year period, it was 87.4%. No statistically significant differences were found between the assessment of life satisfaction after 30 days and 10 years after BTS. Out of the total number of operated patients, two patients (1.94%) characterized their compensatory sweating as very pronounced. Conclusion. After 10 years from BTS, the QoL remains at an exceptionally high level, with an annual trend of decline of about 0.1%.

Sweat is considered the most promising candidate to replace conventional blood samples for noninvasive sensing. There are many tools and optical and electrochemical methods that can be used for detecting sweat biomarkers. Electrochemical methods are known for their simplicity and cost-effectiveness. However, they need to be optimized in terms of selectivity and catalytic activity. Therefore, electrode modifiers such as nanostructures and metal–organic frameworks (MOFs) or combinations of them were examined for boosting the performance of the electrochemical sensors. The MOF structures can be prepared by hydrothermal/solvothermal, sonochemical, microwave synthesis, mechanochemical, and electrochemical methods. Additionally, MOF nanostructures can be prepared by controlling the synthesis conditions or mixing bulk MOFs with nanoparticles (NPs). In this review, we spotlight the previously examined MOF-based nanostructures as well as promising ones for the electrochemical determination of sweat biomarkers. The presence of NPs strongly improves the electrical conductivity of MOF structures, which are known for their poor conductivity. Specifically, Cu-MOF and Co-MOF nanostructures were used for detecting sweat biomarkers with the lowest detection limits. Different electrochemical methods, such as amperometric, voltammetric, and photoelectrochemical, were used for monitoring the signal of sweat biomarkers. Overall, these materials are brilliant electrode modifiers for the determination of sweat biomarkers.

We report on the possibility of noninvasive diabetes monitoring through continuous analysis of sweat. The prediction of the blood glucose level in diabetic patients is possible on the basis of their sweat glucose content due to the positive correlation discovered. The ratio between the blood glucose and sweat glucose concentrations for a certain diabetic subject is stable within weeks, excluding requirements for frequent blood probing. The glucose variations in sweat display allometric (non-linear) dependence on those in blood, allowing more precise blood glucose estimation. Selective (avoiding false-positive responses) and sensitive (sweat glucose is on average 30–50 times lower) detection is possible with biosensors based on the glucose oxidase enzyme coupled with a Prussian Blue transducer. Reliable glucose detection in just secreted sweat would allow noninvasive monitoring of the glycemia level in diabetic patients.

Outdoor athletes often eschew using sunscreen due to perceived performance impairments, which many attribute in part to the potential for reduced thermoregulatory heat loss. Past studies examining the impact of sunscreen on thermoregulation are equivocal. The purpose of this study was to determine the effects of mineral and chemical-based sunscreens on sweating responses and critical environmental limits in hot-dry (HD) and warm-humid (WH) environments. Nine subjects (3 M/6 F; 25 ± 2 yr) were tested with 1) no sunscreen (control), 2) chemical-, and 3) mineral-based sunscreen. Subjects were exposed to progressive heat stress with either 1) constant dry-bulb temperature (Tdb) at 34℃ and increasing water vapor pressure (Pa) (WH trials) or 2) constant Pa at 12 mmHg and increasing Tdb (HD trials). Subjects walked at 4.9 ± 0.5 metabolic equivalents (METs) until an upward inflection in gastrointestinal temperature was observed (i.e., the critical environmental limit). Compared with control (39.9 ± 3.0℃), critical Tdb was not different in mineral (39.2 ± 3.5℃, P = 0.39) or chemical (39.7 ± 3.0℃, P = 0.98) sunscreen trials in HD environments. Compared with control (18.8 ± 4.0 mmHg), critical Pa was not different in mineral (18.9 ± 4.8 mmHg, P = 0.81) or chemical (19.5 ± 4.6 mmHg, P = 0.81) sunscreen trials in WH environments. Sweating rates, evaporative heat loss, skin wettedness, and sweating efficiency were not different among the three trials in the WH (all P > 0.48) or HD (all P > 0.87) environments. Critical environmental limits are unaffected by sunscreen application, suggesting sunscreen does not alter integrative thermoregulatory responses during exercise in the heat. [ABSTRACT FROM AUTHOR]