Repetitive exposures to psychosocial stress are associated with several human diseases (e.g., cancer, drug addiction, heart disease, depression) of noteworthy public health burden. However, our progress is limited by the lack of a portable device that can enable rapid, dependable, non-invasive and continuous measurement of personal exposure to psychosocial stress in real-time, as experienced by individuals in their natural environments. Although reliable methods to assess exposure to psychosocial stress in clinical settings exist, these intermittent assessments do not accurately portray timing, duration, frequency, or intensity of exposure. Currently there are more than 3600 registered endocrinologists in the US and on an average they refer five patients per day for cortisol tests. This test is ordered by sending patient's samples to the lab. Therefore, there is a grave need to develop a rapid test for cortisol so a "No-Stress Stress Measuring Device" can be developed. In this interdisciplinary Phase II project, we propose to develop a new device called "StressSmartTM", which will house a rapid test for cortisol developed during Phase I, namely InstaCortisolTM. Cortisol is the primary steroid produced and secreted by the adrenal cortex and is used as a reliable indicator of stress. Our rapid test is based on immunoelectrochemical method where the reaction signal is measured by using dithiobissuccinimidyl propionate (DTSP) self assembled monolayer (SAM) based immunosensor for cortisol. Detection is being facilitated using impedance measuring technique. There are six specific aims of this project. First is further refining and optimizing the cortisol sensor fabrication and sensor evaluation, including sensitivity, specificity, detection limit, linearity, accuracy, dynamic range, repeatability, precision, accuracy, interference, cross-reactivity, drift, and sensor calibration. Second is the development of microfluidic architecture system.
The third aim would be the design, fabrication, integration and development of a microfluidic valves. Several such valves will be needed as parts of the three disposable cartridges. Fourth and fifth aim being the development of a reliable vacuum microfluidics pump, followed by cortisol sensor housing development as part of the device. Throughout the program, some other efforts will also include cortisol sensor clotting mitigation, cortisol sensor electronic Interface board development, cortisol sensor miniaturization efforts, clinical validation and the design integration feasibility. A virtual evaluation of cortisol sensor chip and its integration into a compact easy to use design will be carried out in parallel. A virtual evaluation of cortisol sensor chip and its integration into a compact easy to use design will also be carried out throughout the Year 2 budget period. Relevance: The InstaCortisolTM test (developed during Phase I), which will be part of StressSmartTM device during Phase II, will enable researchers to quantify personal exposure to psychosocial stress, as experienced by individuals in real-life situations. Cortisol production follows a circadian rhythm, and moreover it is affected by stimulatory events or nutrient intake, so it important to measure the trend of cortisol in a person versus taking a single measurement in one day as is done traditionally. Recent research surveys have revealed that the minimal number of samples needed in a day for an accurate assessment of cortisol is five. Our current disposable cartridge is designed to collect four measurements over 24 hours for the proof of concept. However, this device can be easily re-designed to include any other clinically relevant requirements. Availability of such a non-invasive and rapid cortisol measuring device will allow patients to be able to monitor their cortisol levels over 24 hours and professionals to be able to modify dosing regiments at multiple points throughout the day.
We are proposing to make a tool for rapid detection of cortisol, called StressSmartTM. InstaCortisolTM (a rapid cortisol test developed during Phase I), will be integrated in StressSmart device to develop a portable test for real-time measurement of personal exposure to psychosocial stress via detecting cortisol in interstitial fluid (ISF). The new minimally invasive tool will enable researchers to quantify personal exposure to psychosocial stress, as experienced by individuals in real-life situations. This device will be capable of measuring cortisol quantitatively, selectively, objectively, reliably, and securely.