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Journal of the Royal Society, Interface Oct 2019The state-of-the-art in wearable flexible sensors (WFSs) for sweat analyte detection was investigated. Recent advances show the development of integrated, mechanically... (Review)
Review
The state-of-the-art in wearable flexible sensors (WFSs) for sweat analyte detection was investigated. Recent advances show the development of integrated, mechanically flexible and multiplexed sensor systems with on-site circuitry for signal processing and wireless data transmission. When compared with single-analyte sensors, such devices provide an opportunity to more accurately analyse analytes that are dependent on other parameters (such as sweat rate and pH) by improving calibration from real-time analysis, while maintaining a lightweight and wearable design. Important health conditions can be monitored and on-demand regulating drugs can be delivered using integrated wearable systems but require correlation verification between sweat and blood measurements using validation tests before any clinical application can be considered. Improvements are necessary for device sensitivity, accuracy and repeatability to provide more reliable and personalized continuous measurements. With rapid recent development, it can be concluded that non-invasive WFSs for sweat analysis have only skimmed the surface of their health monitoring potential and further significant advancement is sure to be made in the medical field.
Topics: Humans; Monitoring, Physiologic; Signal Processing, Computer-Assisted; Sweat; Wearable Electronic Devices
PubMed: 31594525
DOI: 10.1098/rsif.2019.0217 -
The Japanese Journal of Physiology 1993
Review
Topics: Acclimatization; Adrenergic Fibers; Body Temperature Regulation; Exercise; Humans; Pulsatile Flow; Regression Analysis; Sweat Glands; Sweating
PubMed: 8230848
DOI: 10.2170/jjphysiol.43.275 -
Sensors (Basel, Switzerland) Oct 2022Sweat analysis offers non-invasive real-time on-body measurement for wearable sensors. However, there are still gaps in current developed sweat-sensing devices (SSDs)... (Review)
Review
Sweat analysis offers non-invasive real-time on-body measurement for wearable sensors. However, there are still gaps in current developed sweat-sensing devices (SSDs) regarding the concerns of mixing fresh and old sweat and real-time measurement, which are the requirements to ensure accurate the measurement of wearable devices. This review paper discusses these limitations by aiding model designs, features, performance, and the device operation for exploring the SSDs used in different sweat collection tools, focusing on continuous and non-continuous flow sweat analysis. In addition, the paper also comprehensively presents various sweat biomarkers that have been explored by earlier works in order to broaden the use of non-invasive sweat samples in healthcare and related applications. This work also discusses the target analyte's response mechanism for different sweat compositions, categories of sweat collection devices, and recent advances in SSDs regarding optimal design, functionality, and performance.
Topics: Biomarkers; Biosensing Techniques; Monitoring, Physiologic; Sweat; Wearable Electronic Devices
PubMed: 36236769
DOI: 10.3390/s22197670 -
Journal of Applied Physiology... Jul 2009Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytic approaches vary, and no...
Sweating threshold temperature and sweating sensitivity responses are measured to evaluate thermoregulatory control. However, analytic approaches vary, and no standardized methodology has been validated. This study validated a simple and standardized method, segmented linear regression (SReg), for determination of sweating threshold temperature and sensitivity. Archived data were extracted for analysis from studies in which local arm sweat rate (m(sw); ventilated dew-point temperature sensor) and esophageal temperature (T(es)) were measured under a variety of conditions. The relationship m(sw)/T(es) from 16 experiments was analyzed by seven experienced raters (Rater), using a variety of empirical methods, and compared against SReg for the determination of sweating threshold temperature and sweating sensitivity values. Individual interrater differences (n = 324 comparisons) and differences between Rater and SReg (n = 110 comparisons) were evaluated within the context of biologically important limits of magnitude (LOM) via a modified Bland-Altman approach. The average Rater and SReg outputs for threshold temperature and sensitivity were compared (n = 16) using inferential statistics. Rater employed a very diverse set of criteria to determine the sweating threshold temperature and sweating sensitivity for the 16 data sets, but interrater differences were within the LOM for 95% (threshold) and 73% (sensitivity) of observations, respectively. Differences between mean Rater and SReg were within the LOM 90% (threshold) and 83% (sensitivity) of the time, respectively. Rater and SReg were not different by conventional t-test (P > 0.05). SReg provides a simple, valid, and standardized way to determine sweating threshold temperature and sweating sensitivity values for thermoregulatory studies.
Topics: Anaerobic Threshold; Body Temperature; Body Temperature Regulation; Exercise Test; Humans; Male; Oxygen Consumption; Reproducibility of Results; Sweating; Young Adult
PubMed: 19423839
DOI: 10.1152/japplphysiol.00250.2009 -
The Journal of Physiological Sciences :... Nov 2012This review provides a critical overview of the literature published in the area of lactate in human sweat between 1934 and the present. The first section summarizes the... (Review)
Review
This review provides a critical overview of the literature published in the area of lactate in human sweat between 1934 and the present. The first section summarizes the relevant pieces of literature, the second evaluates the literature across a range of topics and the third presents potential applications for sweat lactate measurements. Key factors that may affect sweat lactate are discussed in detail in the second section of this review. Both acetylcholine and catecholamine hormonal signals can trigger sweating independently of one another; differences in sweat output and lactate concentrations are compared. The primary triggers for sweating, exercise and heat are also compared, with exercise-induced sweating being further examined with respect to the exercise intensity. This review examines the significant variations in sweat lactate between bodily sites as well the relationship to physiological parameters such as gender, age and physical fitness, along with the effect of climate adaptation on sweat lactate concentrations.
Topics: Adaptation, Physiological; Climate; Humans; Lactic Acid; Sweat; Sweating
PubMed: 22678934
DOI: 10.1007/s12576-012-0213-z -
Journal of Nanobiotechnology Nov 2023The rapid advancement of wearable biosensors has revolutionized healthcare monitoring by screening in a non-invasive and continuous manner. Among various sensing... (Review)
Review
The rapid advancement of wearable biosensors has revolutionized healthcare monitoring by screening in a non-invasive and continuous manner. Among various sensing techniques, field-effect transistor (FET)-based wearable biosensors attract increasing attention due to their advantages such as label-free detection, fast response, easy operation, and capability of integration. This review explores the innovative developments and applications of FET-based wearable biosensors for healthcare monitoring. Beginning with an introduction to the significance of wearable biosensors, the paper gives an overview of structural and operational principles of FETs, providing insights into their diverse classifications. Next, the paper discusses the fabrication methods, semiconductor surface modification techniques and gate surface functionalization strategies. This background lays the foundation for exploring specific FET-based biosensor designs, including enzyme, antibody and nanobody, aptamer, as well as ion-sensitive membrane sensors. Subsequently, the paper investigates the incorporation of FET-based biosensors in monitoring biomarkers present in physiological fluids such as sweat, tears, saliva, and skin interstitial fluid (ISF). Finally, we address challenges, technical issues, and opportunities related to FET-based biosensor applications. This comprehensive review underscores the transformative potential of FET-based wearable biosensors in healthcare monitoring. By offering a multidimensional perspective on device design, fabrication, functionalization and applications, this paper aims to serve as a valuable resource for researchers in the field of biosensing technology and personalized healthcare.
Topics: Biosensing Techniques; Sweat; Saliva; Biomarkers; Wearable Electronic Devices
PubMed: 37936115
DOI: 10.1186/s12951-023-02153-1 -
Clinical Autonomic Research : Official... Apr 2009Sudomotor dysfunction is common in many subtypes of neuropathy but is one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathy.... (Review)
Review
Sudomotor dysfunction is common in many subtypes of neuropathy but is one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathy. Clinical assessments of sudomotor function include thermoregulatory sweat testing (TST), quantitative sudomotor axon reflex testing (QSART), silicone impressions, the sympathetic skin response (SSR), the acetylcholine sweat-spot test and quantitative direct and indirect axon reflex testing (QDIRT). These testing techniques, when used in combination, can detect and localize pre- and postganglionic lesions, can provide early diagnosis of sudomotor dysfunction and can monitor disease progression or disease recovery. In this article, we describe many of the common clinical tests available for evaluation of sudomotor function with focus on the testing methodology and limitations while providing concrete examples of test results.
Topics: Acetylcholine; Diagnostic Techniques, Neurological; Humans; Peripheral Nervous System Diseases; Reflex; Sweat; Sweating
PubMed: 18989618
DOI: 10.1007/s10286-008-0506-8 -
Allergology International : Official... Jan 2021Cholinergic urticaria (CholU) manifests small, itchy and/or painful wheals occurring upon perspiration and mechanically involving acetylcholine (Ach). Although a... (Review)
Review
Cholinergic urticaria (CholU) manifests small, itchy and/or painful wheals occurring upon perspiration and mechanically involving acetylcholine (Ach). Although a considerable number of studies have been conducted, the pathomechanisms underlying perspiration-associated release of histamine remain to be elucidated. We have proposed that CholU can be categorized into two major subtypes: Ach-indirectly induced, sweat allergic type and Ach-directly induced, depressed sweating type. In the former type, Ach evokes perspiration, and some sweat antigen(s) leaking from the sweat ducts to the dermis may stimulate mast cells to release histamine. In this scenario, the ducts might be damaged or obstructed for sweat leakage, and patients frequently exhibit positive autologous sweat skin test, representing "sweat allergy (hypersensitivity)". On the other hand, the latter Ach-mast cell directly interacting type, typically seen as "CholU with anhidrosis and/or hypohidrosis (CUAH)", eccrine sweat gland epithelial cells lack cholinergic receptor M3 expression. The expression of cholinergic receptors is completely absent in the anhidrotic areas and only slightly expressed in the hypohidrotic areas. In the hypohidrotic area, where pinpoint wheal occurs, it is hypothesized that released Ach cannot be completely trapped by cholinergic receptors of eccrine glands and overflows to the adjacent mast cells, leading to wheal formation. Thus, sweat allergy is not a requirement in this depressed sweating type. Although some additional complications, such as angioedema, anaphylaxis, and cold urticaria, have been documented, these two types represent the modes of action of Ach in this enigmatic urticaria.
Topics: Acetylcholine; Allergens; Biomarkers; Disease Susceptibility; Gene Expression Regulation; Histamine; Histamine Release; Humans; Immunoglobulin E; Mast Cells; Receptors, Cholinergic; Skin Tests; Sweat; Urticaria
PubMed: 32565175
DOI: 10.1016/j.alit.2020.05.006 -
Physiology & Behavior Oct 2023Humans produce odorous secretions from multiple body sites according to the microbiomic profile of each area and the types of secretory glands present. Because the... (Review)
Review
Humans produce odorous secretions from multiple body sites according to the microbiomic profile of each area and the types of secretory glands present. Because the axilla is an active, odor-producing region that mediates social communication via the sense of smell, this article focuses on the biological mechanisms underlying the creation of axillary odor, as well as the intrinsic and extrinsic factors likely to impact the odor and determine individual differences. The list of intrinsic factors discussed includes sex, age, ethnicity, emotions, and personality, and extrinsic factors include dietary choices, diseases, climate, and hygienic habits. In addition, we also draw attention to gaps in our understanding of each factor, including, for example, topical areas such as the effect of climate on body odor variation. Fundamental challenges and emerging research opportunities are further outlined in the discussion. Finally, we suggest guidelines and best practices based on the factors reviewed herein for preparatory protocols of sweat collection, data analysis, and interpretation.
Topics: Humans; Odorants; Sweat; Smell; Sweating; Axilla
PubMed: 37516230
DOI: 10.1016/j.physbeh.2023.114307 -
Molecules (Basel, Switzerland) Jun 2023Sweat, a biofluid secreted naturally from the eccrine glands of the human body, is rich in several electrolytes, metabolites, biomolecules, and even xenobiotics that... (Review)
Review
Sweat, a biofluid secreted naturally from the eccrine glands of the human body, is rich in several electrolytes, metabolites, biomolecules, and even xenobiotics that enter the body through other means. Recent studies indicate a high correlation between the analytes' concentrations in the sweat and the blood, opening up sweat as a medium for disease diagnosis and other general health monitoring applications. However, low concentration of analytes in sweat is a significant limitation, requiring high-performing sensors for this application. Electrochemical sensors, due to their high sensitivity, low cost, and miniaturization, play a crucial role in realizing the potential of sweat as a key sensing medium. MXenes, recently developed anisotropic two-dimensional atomic-layered nanomaterials composed of early transition metal carbides or nitrides, are currently being explored as a material of choice for electrochemical sensors. Their large surface area, tunable electrical properties, excellent mechanical strength, good dispersibility, and biocompatibility make them attractive for bio-electrochemical sensing platforms. This review presents the recent progress made in MXene-based bio-electrochemical sensors such as wearable, implantable, and microfluidic sensors and their applications in disease diagnosis and developing point-of-care sensing platforms. Finally, the paper discusses the challenges and limitations of MXenes as a material of choice in bio-electrochemical sensors and future perspectives on this exciting material for sweat-sensing applications.
Topics: Humans; Wearable Electronic Devices; Sweat; Biosensing Techniques; Nanostructures
PubMed: 37375172
DOI: 10.3390/molecules28124617