Sweat Diagnostics

Sweat diagnostics is an emerging non-invasive technique used to provide insights to the health of the human body. Common sweat diagnostic tests include testing for cystic fibrosis[1] and illicit drugs.[2] Most testing of human sweat is in reference to the eccrine sweat gland which in contrast to the apocrine sweat gland, has a lower composition of oils.[3]

Although sweat is mostly water,[3] there are many solutes which are found in sweat that have at least some relation to biomarkers found in blood. These include: sodium (Na+), chloride (Cl-), potassium (K+), ammonium (NH4+), alcohols, lactate, peptides & proteins.[4][5] Development of devices, sensing techniques and biomarker identification in sweat continues to be an expanding field for medical diagnostics and athletics applications.

History

Some of the earliest, published studies[6] on sweat composition date back to the 19th century. Further studies[7][8][9] in the 20th century began to solidify understanding of the physiology and pharmacology of the eccrine sweat gland. In-vivo and in-vitro studies from this time period, and even those continuing today, have identified numerous structural nuances and new molecules present within sweat. The first commercially adopted use for sweat diagnostics included testing of sodium and chloride levels in children for the diagnosis of cystic fibrosis. Today, one of the most popular devices for this testing is the Macroduct Sweat Collection System from ELITechGroup.[10]

General evidence

More recently, numerous studies have identified the plausibility of sweat as an alternative to blood analysis.[11][12] The potential substitution for sweat versus blood analysis has many potential benefits. For example, sweat can be: extracted in a non-invasive manner via iontophoresis; extracted with little-to-no pain; and monitored continuously.[13] There are downfalls to the technology, however. For example, demonstration of successful and reliable sweat extraction and analysis on a cohesive device has yet to be demonstrated. Furthermore, although some biomarker partitioning mechanisms are well-understood and well-studied, partitioning of other useful biomarkers (cytokines, peptides, etc.) are less understood.[4]

Current research

Portable devices

Patches

Patches have been demonstrated to be a promising detection platform for sweat diagnostics.[14][15][16] Simple, long-term collection devices which check for drugs of abuse or alcohol are already on the market and operate on the following principle: a user applies the patch which then collects sweat over a period of hours or days, then the patch is analyzed utilizing techniques such as GC-MS which are accurate but the suffer the drawback in lack of continuous measurements and high costs. For example, drugs of abuse and alcohol sweat testing are provided by PharmChem and AlcoPro, respectively.

More recently, several startup companies such as have begun developing products targeted towards the consumer, healthcare and athletics market for sweat diagnostics. Ultimately, it is the hope that these devices will have the ability to detect changes in human physiology within minutes without the need for repeated sample collection and analysis.[17]

Temporary tattoos

Temporary tattoo-based sweat diagnostic tools[18] have been demonstrated by Dr. Joseph Wang's group from University of California, San Diego. Their work includes sweat diagnostics for sodium, lactate, ammonium, pH and biofuel opportunities.[19]

References

  1. ↑ Mishra, A.; Greaves, R. & Massie, J. "The relevance of sweat testing for the diagnosis of cystic fibrosis in the genomic era." The Clinical biochemist. Reviews/Australian Association of Clinical Biochemists. 26, 135-153 (2005). PMID 16648884
  2. ↑ De Giovanni, N. & Fucci, N. "The current status of sweat testing for drugs of abuse: A review." Current Medicinal Chemistry 20, 545-561 (2013). PMID 23244520
  3. 1 2 Wilke, K.; Martin, A.; Terstegen, L. & Biel, S. S. "A short history of sweat gland biology." International Journal of Cosmetic Science 29, 169-179 (2007). DOI: 10.1111/j.1467-2494.2007.00387.x
  4. 1 2 Sonner, Z.; Wilder, E.; Heikenfeld, J.; Kasting, G.; Beyette, F.; Swaile, D.; Sherman, F.; Joyce, J.; Hagen, J. & Kelley-Loughnane, N. "The microfluidics of the eccrine sweat gland, including biomarker partitioning, transport, and biosensing implications." Biomicrofluidics 9, 031301 (2015). DOI: 10.1063/1.4921039
  5. ↑ Sato, K.; Kang, W. H.; Saga, K. & Sato, K. T. "Biology of sweat glands and their disorders. I. Normal sweat gland function". Journal of the American Academy of Dermatology 20, 537-563 (1989). DOI: 10.1016/S0190-9622(89)70063-3
  6. ↑ Hoelscher, J. H. "A STUDY IN PERSPIRATION.: ORIGINAL RESEARCH IN ONE HUNDRED AND THIRTEEN CASES." Journal of the American Medical Association (JAMA) 32, 1352-1360 (1899). DOI:10.1001/jama.1899.92450510001003
  7. ↑ Nyman, E. & Palmlöv, A. "The elimination of ethyl alcohol in sweat." Skandinavisches Archiv für Physiologie 74, 155-159 (1936). DOI: 10.1111/j.1748-1716.1936.tb01150.x
  8. ↑ Schwartz, I. L. & Thaysen, J. H. "Excretion of sodium and potassium in human sweat." Journal of Clinical Investigation 35, 114-120 (1956). DOI: 10.1172/JCI103245
  9. ↑ Sato, K. "The physiology, pharmacology, and biochemistry of the eccrine sweat gland." in Reviews of Physiology, Biochemistry and Pharmacology Vol. 79 51-131 (Springer, 1977). DOI: 10.1007/BFb0037089
  10. ↑ Pullan, N. J.; Thurston, V. & Barber, S. "Evaluation of an inductively coupled plasma mass spectrometry method for the analysis of sweat chloride and sodium for use in the diagnosis of cystic fibrosis." Annals of clinical biochemistry 50.3 (2013): 267-270. DOI: 10.1177/0004563212474565
  11. ↑ Czarnowski, D.; Górski, J.; Jóźwiuk, J. & Boroń-Kaczmarska, A. "Plasma ammonia is the principal source of ammonia in sweat". European Journal of Applied Physiology and Occupational Physiology 65, 135-137 (1992). DOI: 10.1007/BF00705070
  12. ↑ Cizza, G.; Marques, A. H.; Eskandari, F.; Christie, I. C.; Torvik, S.; Silverman, M. N.; Phillips, T. M. & Sternberg, E. M. for the POWER Study Group. "Elevated neuroimmune biomarkers in sweat patches and plasma of premenopausal women with major depressive disorder in remission: the POWER study". Biological Psychiatry 64, 907-911 (2008). DOI: 10.1016/j.biopsych.2008.05.035
  13. ↑ Banga, A. K. & Chien, Y. W. "Iontophoretic delivery of drugs: fundamentals, developments and biomedical applications". Journal of Controlled Release 7, 1-24 (1988). DOI: 10.1016/0168-3659(88)90075-2
  14. ↑ Susan Scutti in "Measuring Your Sweat, A Health Monitor And Diagnostic Device Is The Future Of Wearable Technology" from Medical Daily (29 Oct 2014).
  15. ↑ Rudy Fenner in "CoreSyte Selected as Worldwide Athletics Partner by Eccrine Systems" from Business Wire (08 May 2015).
  16. ↑ Rose Begonia in "Kenzen Wearable Optimizes Athletic Performance with Real-Time Hydration, Lactic Acid and Glucose Analysis" from PR Newswire (05 Dec 2014).
  17. ↑ Heikenfeld, J. "Sweat Sensors Will Change How Wearables Track Your Health." in IEEE Spectrum (22 Oct 2014).
  18. ↑ Kathryn Free in "A Temporary Tattoo to Track Your Workout and Charge Your Phone" from Popular Mechanics (13 Aug 2014).
  19. ↑ Bandodkar, A. J.; Jia, W. & Wang, J. "Tattoo-Based Wearable Electrochemical Devices: A Review." Electroanalysis 27, 562-572 (2015). DOI: 10.1002/elan.201400537
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