Browsing by Author "Upasham, Sayali"
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Item Developing a Flexible, Affinity-based, Electrochemical Sensing Platform Towards Multiplexed Detection of Apocrine and Eccrine Sweat Based Biomarkers; SLOCK: Sensor for Circadian Clock(December 2021) Upasham, Sayali; Prasad, Shalini; Gupta, Gopal; Rodrigues, Danieli; Polk, Todd; Sirsi, ShashankChronobiology is defined as the temporal fluctuations occurring in the human physiology due to the circadian cycle. These fluctuations are good indicators of the functioning of the HypothalamicPituitary-Adrenal axis (HPA axis) and can be tracked by using biomarkers: Cortisol and Dehydroepiandrosteron (DHEA). Low volume tracking systems are beneficial for patients exposed to chronic stress, patients suffering from endocrine conditions manifested by circadian disruption and act as a lifestyle monitoring tool. An estimate of 50-70 million Americans suffer from chronic sleep disorders (NHLBI, 2003) which hinders routine functioning and has deleterious health implications including elevated cortisol levels, increased risk of hypertension, diabetes, depression, cardiac conditions, and stroke. Currently available technologies for monitoring the circadian rhythm (e.g., Polysomnography (Ambulatory monitoring of nocturnal sleep) or Actigraphy (Multiday ambulatory assessment)) do not provide an accurate estimation of the extent of circadian disruption, as they are superficial. Biomarker assays are the diagnostic gold standard techniques used for the diagnosis of circadian dysregulation caused by adrenal disorders. These assays usually rely on the use of blood or serum and take about 3-4 hours for the test results which proves to be an ineffective solution, from the point of view of developing a circadian profile for the user. Adrenal steroids like cortisol and DHEA are expressed in sweat in the nanogram range and can be used as biomarkers to facilitate self-monitoring. SLOCK is a sweat based chronobiology tracking system that works on the principles of electrochemically transduced affinity-based systems. The sensor can detect cortisol and DHEA in the physiologically relevant ranges i.e., 8-200 ng/ml and 2-131 ng/ml respectively. The sensor was also tested through human subject-based studies and is able to capture rise and fall in biomarker levels on-body. In addition to this, the use of serpentine interdigitated electrodes provides mechanical stability when exposed to oscillations caused due to a wearable form factor. Based on the cross-reactivity studies, the response for target biomarkers is highly specific to the biomarker of interest. Towards the last part of this work, the SLOCK platform was tuned for detection of a protein biomarker, interleukin-31 (IL-31) for the purpose of creating a chronic disease diagnosis and management platform. The benchmarking for this was carried out by modelling it for detection of atopic dermatitis related flares. The platform is able to sensitively detect IL-31 over the dynamic range of 50-1000 pg/mL. The platform was successfully coupled with portable electronics and was able to record biomarker fluctuations on-body through human subject-based testing. The SLOCK platforms offers highly sensitive, non-invasive monitoring of circadian related or chronic disorders in a point-of-need setting.Item Universal, Ultra-low Volume Cortisol Biosensor: From Point-of-care to Point-of-need Applications(2019-12) Upasham, Sayali; 0000-0002-3043-2010 (Upasham, SS); Prasad, ShaliniFrequent shift work by an individual causes disruption of the circadian rhythm and potentially, in the long run, result in increased health risks. Current biomarkers evaluating the presence of circadian rhythm disturbance include melatonin, cortisol, and monitoring body temperature. This requires 24- hour monitoring and as some of techniques like body temperature evaluation are indirect measures of the disturbances, they are often inconclusive. Therefore, it is imperative to design diagnostic sensors for rapid and non-invasive monitoring of biomarkers associated with circadian rhythm cycles. In this work, we have developed a hybrid flexible biosensor comprised of an aqueous and ionic interface integrated onto metallic gold microelectrodes for rapid and noninvasive monitoring of cortisol. This electrochemical sensor is calibrated for detection across multiple bio-fluids. Room temperature ionic liquid (RTIL), BMIM[BF4] (1-Butyl-3-methylimidazolium tetrafluoroborate) was used as the buffer to modulate the electrical double layer (EDL) to enhance the electrochemical signal response of the sensor. The sensor design and the surface chemistry were optimized using COMSOL simulations and FTIR (Fourier-transform infrared spectroscopy) respectively. Cortisol detection was achieved in the physiologically relevant ranges when tested in serum, blood, sweat, and, saliva using non-faradaic Electrochemical Impedance Spectroscopy (EIS) and performance parameters of the sensor were measured. The sensor’s response was tested against the only commercially available, salivary cortisol, point-of-care kit using regression analysis. Cross-reactive studies using prednisone indicated that the sensor is specific for cortisol. The sensor displayed a correlation value i.e. R2 > 0.95 between the signal response and the concentration of cortisol present in the system. Dynamic range of the sensor was across the physiologically relevant range of cortisol i.e.50-200 ng/mL for serum/blood, 1-40 ng/mL for saliva, and 10-150 ng/mL for sweat. Limit of detection for serum and sweat was 10 ng/mL and 1 ng/mL for saliva. In addition to this, we have also demonstrated that BMIM [BF4], can be used to modulate pH instability of buffers, sweat, urine, and saliva. We have observed that the sensor dynamics are conserved over the pH range of 4 through 8 in synthetic sweat, saliva, and urine. Our approach addresses the challenges associated with the variability of body buffer chemistry and its impact on monitoring cortisol.