Abstract

Biofluids and Microfluidics – Point-of-Use Devices for Sensing Human Stress Biomarkers

Andrew Steckl, Gieringer Professor, Ohio Eminent Scholar, University Distinguished Research Professor, University of Cincinnati

Hormones produced by glands in the endocrine system and neurotransmitters produced by the nervous system control many bodily functions. The concentrations of these molecules in the body are an indication of its state, hence the use of the term biomarker. Excess concentrations of biomarkers, such as cortisol, serotonin, epinephrine, dopamine, are released by the body in response to a variety of conditions - emotional state (euphoria, stress), disease, etc. The development of simple, low-cost modalities for point-of-use (PoU) measurements of biomarkers levels in various bodily fluids (blood, urine, sweat, saliva) as opposed to conventional hospital or lab settings is receiving increasing attention. The presentation starts with a review of the basic properties of primary stress-related biomarkers: origin in the body (produced as hormones, neurotransmitters or both), chemical composition, molecular weight (small/medium size molecules and polymers, ranging from ~100Da to ~100kDa), hydro- or lipo-philic nature. Next, a review of the published literature is presented regarding the concentration of these biomarkers found in several bodily fluids that can serve as the medium for determination of the condition of the subject: blood, urine, saliva, sweat and interstitial tissue fluid. The concentration of various biomarkers in most fluids covers a range of 5-6 orders of magnitude, from 100s of ng/mL (~1µM) down to a few pg/mL (sub 1pM). Mechanisms and materials for point-of-use biomarker sensors are summarized and key properties are reviewed. Illustrative examples from the literature are discussed for several sensor device categories, including capillary flow devices and microfluidic devices. Selected methods for detecting these biomarkers are reviewed, including antibody- and aptamer-based assays, electrochemical and optical detection. Finally, the presentation outlines key challenges of the field and provides a look ahead to future prospects.