Screening for SARS-CoV-2 persistence in Long COVID patients using sniffer dogs and scents from axillary sweats samples

Objectives: Dogs can be trained to identify several substances not detected by humans, corresponding to specific volatile organic compounds (VOCs). The presence of VOCs, triggered by SARS-CoV-2 infection, was tested in sweat from Long COVID patients. Patients and methods: An axillary sweat sample of Long COVID patients and of COVID-19 negative, asymptomatic individuals was taken at home to avoid any hospital contact. Swabs were randomly placed in olfaction detection cones, and the material sniffed by at least 2 trained dogs. Results: Forty-five Long COVID patients, mean age 45 (6-71), 73.3% female, with prolonged symptoms evolving for a mean of 15.2 months (5-22) were tested. Dogs discriminated in a positive way 23/45 (51.1%) Long COVID patients versus 0/188 (0%) control individuals (p<.0001). Conclusion:This study suggests the persistence of a viral infection in some Long COVID patients and the possibility of providing a simple, highly sensitive, non-invasive test to detect viral presence, during acute and extended phases of COVID-19.

PANI-Based Wearable Electrochemical Sensor for pH Sweat Monitoring

Nowadays, we are assisting in the exceptional growth in research relating to the development of wearable devices for sweat analysis. Sweat is a biofluid that contains useful health information and allows a non-invasive, continuous and comfortable collection. For this reason, it is an excellent biofluid for the detection of different analytes. In this work, electrochemical sensors based on polyaniline thin films deposited on the flexible substrate polyethylene terephthalate coated with indium tin oxide were studied. Polyaniline thin films were abstained by the potentiostatic deposition technique, applying a potential of +2 V vs. SCE for 90 s. To improve the sensor performance, the electronic substrate was modified with reduced graphene oxide, obtained at a constant potential of −0.8 V vs. SCE for 200 s, and then polyaniline thin films were electrodeposited on top of the as-deposited substrate. All samples were characterized by XRD, SEM, EDS, static contact angle and FT-IR/ATR analysis to correlate the physical-chemical features with the performance of the sensors. The obtained electrodes were tested as pH sensors in the range from 2 to 8, showing good behavior, with a sensitivity of 62.3 mV/pH, very close to a Nernstian response, and a reproducibility of 3.8%. Interference tests, in the presence of competing ions, aimed to verify the selectivity, were also performed. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance.

Can the detection dog alert on COVID-19 positive persons by sniffing axillary sweat samples? A proof-of-concept study

The aim of this proof-of-concept study was to evaluate if trained dogs could discriminate between sweat samples from symptomatic COVID-19 positive individuals (SARS-CoV-2 PCR positive) and those from asymptomatic COVID-19 negative individuals. The study was conducted at 2 sites (Paris, France, and Beirut, Lebanon), followed the same training and testing protocols, and involved six detection dogs (three explosive detection dogs, one search and rescue dog, and two colon cancer detection dogs). A total of 177 individuals were recruited for the study (95 symptomatic COVID-19 positive and 82 asymptomatic COVID-19 negative individuals) from five hospitals, and one underarm sweat sample per individual was collected. The dog training sessions lasted between one and three weeks. Once trained, the dog had to mark the COVID-19 positive sample randomly placed behind one of three or four olfactory cones (the other cones contained at least one COVID-19 negative sample and between zero and two mocks). During the testing session, a COVID-19 positive sample could be used up to a maximum of three times for one dog. The dog and its handler were both blinded to the COVID-positive sample location. The success rate per dog (i.e., the number of correct indications divided by the number of trials) ranged from 76% to 100%. The lower bound of the 95% confidence interval of the estimated success rate was most of the time higher than the success rate obtained by chance after removing the number of mocks from calculations. These results provide some evidence that detection dogs may be able to discriminate between sweat samples from symptomatic COVID-19 individuals and those from asymptomatic COVID-19 negative individuals. However, due to the limitations of this proof-of-concept study (including using some COVID-19 samples more than once and potential confounding biases), these results must be confirmed in validation studies.

The lasting smell of emotions: The effects of reutilizing fear sweat samples

A growing body of research has shown that human apocrine sweat carries information about the emotional state of its donor. Exposure to sweat produced in a fear-inducing context triggers in its receivers a simulacrum of this emotional state, as evidenced by increased medial frontalis and corrugator supercilii (facial electromyography; fEMG) activity – two facial muscles involved in the display of fear facial expressions. However, despite the increased interest in the effects of emotional sweat, little is known about the properties of these chemical sweat samples. The goal of this study was to examine whether a second application of the same sweat sample would yield reliable results. Specifically, we assessed whether sweat samples collected from Portuguese males (N = 8) in fear (vs. neutral)-inducing contexts would produce similar fEMG activations (i.e., in the medial frontalis and corrugator supercilii) in female receivers (N = 60) across two independent applications (the first with Dutch and the second with Portuguese receivers). Our findings showed that exposure to fear (vs. neutral) sweat resulted in higher activation of both muscles compared with neutral odors, revealing a similar data pattern across the two applications and underlining the feasibility of reusing emotional sweat samples. The implications of these findings for properties of these sweat volatiles are discussed.

Detection of Anomalous Sodium Chloride Concentrations in Perspiration Using Microsensors

It is common knowledge that an early diagnosis of a disease improves the treatment provided to a patient. With the advent of nanotechnology, engineers and scientists are beginning to utilize these nanoscale capabilities in the hope of - early disease detection. Viral, bacterial infections and other chronic diseases seem to alter the concentrations of some compounds present in sweat [1,2]. This project attempts to detect some of these diseases by measuring the variation in salinity of sweat that differs from the commonly accepted level [2]. By creating a low-cost, reusable and portable microsensor, it can then apply the same principles to construct a nanosensor to yield even more accurate results. The electrical signals obtained by the sensor produce data that translates into diagnostic medical results for sweat-related illnesses such as cystic fibrosis [3]. For a deeper and thorough understanding of all aspects of the sensor, multiple concepts for measuring sweat using electrical signals were considered. Ultimately, the concept chosen to measure varying sweat concentrations was through a capacitor. Multiple capacitor designs were simulated to determine the best way of maximizing performance. After the sensors were constructed, they were tested using various concentrations of sodium chloride (NaCl), from 0.1 grams per liter to 5 grams per liter, dissolved in distilled water to mimic the effect of authentic human sweat [4]. The designed sensor is successfully able to determine the likelihood of a person having cystic fibrosis using a sweat sample as their sweat sodium chloride concentration will correspond to an electrical signal obtained throughout the testing process.

Nonisotonicity of simian eccrine primary sweat induced in vitro

Na+, K+, Cl-, and HCO-3 concentrations were determined in both methacholine (MCh)-induced and isoproterenol (ISO)-induced primary sweat collected directly from isolated and cannulated rhesus monkey palm eccrine secretory coils in vitro. Na+ concentration [( Na+]) of MCh-induced sweat was higher than that of the bathing medium by 4.2 mM, i.e., 155.4 vs. 151.2 mM. Sweat [Cl-] was consistently higher than that of the medium by 13.7 and 11.2 mM in both MCh- and ISO-induced primary fluid, respectively. The sweat-to-bath Cl- gradient increased as [Cl-] in the bath was lowered by substituting with less-permeable anions. In contrast sweat [HCO-3] was much lower in both MCh- and ISO-induced sweat than that of the bathing medium, i.e., approximately 6 mM in sweat vs. 25 mM in the bath. [K+] in MCh-induced primary sweat (mean of 6.63 mM) was consistently higher than that of the bathing medium (5 mM). Furthermore, [K+] tended to be the highest in the first sweat sample after MCh stimulation, reaching as high as 9 mM. In sharp contrast ISO-induced primary sweat showed [K+] that was almost always less than 5 mM with the mean of 4.03 mM. These electrolyte profiles of the primary fluid have been discussed relative to the transport model generally applied for Cl- secretory epithelia.