This dissertation focuses on electrochemical approaches to address several biomedical sciences, environment, and health associated challenges. The first part of this work describes an electrochemical method to remove biofilm from stainless steel surfaces by applying potential pulses. Biofilm contaminated surfaces can cause food contamination, metal surfaces corrosion and water pipe blockage. Therefore, it is important to have effective biofilm removal processes, in order to reduce biofilm contamination. While there are number of existing methods for removing biofilms from surfaces, they require the use of bactericides and hazardous chemicals. These chemicals are harmful to the environment and humans. In order to overcome this, an electropolishing method was developed for removing biofilm from a stainless steel surface without using any hazardous chemicals. This process is achieved using the simple electrolyte sodium chloride, by applying electrochemical anodic and cathodic potential pulses to the stainless steel covered biofilm. The involvement of an anodic potential pulse/ reverse cathodic pulse can eliminate the use of any hazardous strong acid mixtures as electrolytes in conventional electropolishing.

The second part of the dissertation describes a silver band counter electrode- microfluidic sensing platform for Escherichia coli (E. coli) detection. Point-of-use sensing devices are already available for environmental monitoring, food safety applications, and health recovery monitoring. Many of these sensors require an instrument to interpret the sensing results. Although these sensors are simple, easy-to-use and are portable devices, they are not suitable for the design of a disposable point-of-use sensor. A sensing design with a visual signal readout that can be measured directly by the naked-eye provides an advantage over portable sensors development even for point-of-care sensing. The sensing concept introduced in this dissertation uses a longitudinally oriented silver band, there by visualizing the sensing signal as the length of the silver band on the sensing device without using any data processing system. The sensing principle of the device is based on the electrochemical oxidation of the silver band counter electrode within the microchannel, when the sensing reduction reaction occurs on the working electrode. For detection purposes, the working electrode was modified using horseradish peroxidase enzyme-linked immunosorbent assay (ELISA) combined with the tetramethylbenzidine redox cycle to detect E. coli concentration. In this dissertation, the sensing platform was validated for E. coli sensing in both a three-electrode configuration using potentiostat and a two-electrode configuration using battery power. This silver band naked-eye signaling sensing platform design could be used as a simple, portable biosensing application.

The third section describes a single step electrochemical aptamer-based sensing method for digoxin. Digoxin has a narrow therapeutic level which is used for congestive heart failure treatment. Due to the low therapeutic range, it is required to monitor the blood serum level of digoxin. In clinical laboratories, digoxin detection is traditionally carried out using immunosorbent assay method combined with analytical techniques. This requires special sample preparation with several steps and skilled users to operate instruments. Since the digoxin monitoring is often required and used frequently, a point-of-care device development could be more useful for the physician’s office to measure the digoxin level in blood serum before prescribing the dose and it is even important for the emergency room in case of a digoxin drug overdose. Electrochemical aptamer-based sensors have been developed as a single step, reagentless and structure switching detection method for biological molecule analysis. And it is important to note this aptamer-based sensing provides a direct signal upon binding with the digoxin. Therefore, the electrochemical aptamer-based sensing mechanism was applied for digoxin sensing using a digoxin-specific DNA oligonucleotide sequence. The sensing mechanism is based on the target induced conformational change of the digoxin specific DNA aptamer sequence. The electroactive reporter tag attached to one end of the aptamer generates the electrochemical signal depending on the conformational change of DNA, while the other end of the aptamer is connected to the sensing electrode. Digoxin electrochemical detection using an aptamer provides a voltammogram as a signal by direct immersion of the DNA modified electrode into the solution without washing steps and without using any reagent as in other electrochemical detection methods. Thus, this method could be developed as a simple, convenient point-of-care applications for sensing biomolecules in a narrow therapeutic range.