Review—Electrochemical Sensors for Large and Small Molecules in Biofluids

Per the 2020 National Diabetes Statistics Report (2018 estimates), 34.2 million people of all ages (10.5% of the US population) had diabetes, and 88.0 million Americans (34.5% of all US adults) had prediabetes (an increase from 79 million in 2010). Diagnosed diabetic conditions cost the nation $327 billion in 2017, a 26% increase from the prior estimate of $245 billion in 2012. Thus, substantial health and economic burdens are placed on the nation and globally, added with the ongoing COVID-19 pandemic and its negative impacts on pre-existing health conditions (e.g., diabetic and autoimmune disorders). Our research goal is to contribute to the development of user-friendly, point-of-care sensors that would offer monitoring ultra-low clinically relevant levels of desired biomarkers by minimally invasive and non-invasive ways (e.g., picomolar serum/blood insulin, small molecules in urine, and large serum antibodies). We explored a wide range of surface chemistries and electroanalytical techniques for successfully measuring the described markers. Independent validations of our electrochemical sensors with surface plasmon resonance binding assays and commercial biological assays (although tedious and relatively more expensive than electrochemical approaches), and applications for real samples have been accomplished. Our ongoing efforts focus on new label-free point-of-care sensors for infectious disease markers.