Biomarkers: Implications from Discovery and the development of Microscale Electrochemical Sensing Techniques for Their Detection

Abstract

The majority of scientific advancement is facilitated by curiosity, determination, and tools to measure and analyze the subject and environment in question. Discovery at the biorelevant level of microns and nanometers requires tools with exceptional sensitivity, selectivity, and repeatability. Among the available methodologies, electrochemical sensing techniques occupy a unique place given their well-understood fundamental principles, relatively low cost, and use of electrons and ions to interact with the target in question. Although the principles of electrochemistry are established and their use as a sensing platform is widespread, there is still a great deal of room for innovation in the packaging, fabrication, and application of electrochemical sensing in next generation devices. The present study reports on questions from two major scientific fields—biochemistry and molecular biology—and addresses them in part by developing and applying a novel sensing approach using an electrochemical setup. The first is with regard to the biochemical mechanisms involved in microbial metal respiration and was carried out in association with the DiChristina Lab at the Georgia Institute of Technology, School of Biology. Metal respiration is a topic of interest because of its role in biogeochemical cycling and it is the basis of some bioremediation strategies for contamination cleanup by the United States Department of Energy. In the course of this study an in-gel redox protein detection system was developed using scanning electrochemical microscopy. The identified proteins helped to postulate a mechanism for anaerobic dissimilatory iron respiration by Shewanella oneidensis MR-1. An additional finding during this study is the identification of a large outer membrane protein that mediates adhesion of the bacterium to iron oxide particles and may localize itself to the cell surface via Type V protein secretion. The second question, which relates to molecular biology, is with regard to the epigenetic mechanisms associated with aging. This work was carried out in association with the Wang lab at the University of Louisville, School of Medicine. In this study a review of known epigenetic factors that influence aging or age-related disease was conducted. Following that, a long-lived model was used to identify microRNAs that may influence midlife decline, which occurs in a large portion of a population in their fifties and sixties and is a phenomenon ascribed to the onset of disruptions to physiological homeostasis that snowball into rapid aging and increased incidence of age-related disease. The major interest in finding epigenetic factors and particularly microRNAs is that the damage is potentially reversible if detected in time. In other words, microRNA profiles provide an instantaneous snapshot of the cell, tissue, or organism’s response to environmental queues and may provide information in time to reverse the damage by quenching the insult before permanent damage sets in. Current methods to detect and validate microRNA activity require both nucleic acid and biochemical assays that are tedious, expensive, and timeconsuming. The desire to develop a sensing device that could carry out all of the necessary work on a single, low-cost and rapid platform led to the design and fabrication of the microelectrode array sensor reported here.