PhD Seminar - Kevin Saem, McMaster University, Chemistry
Low-cost Bench-Top Microfabrication of Nano/Microstructured Electrodes for Electrochemical Biosensing
DATE: Thursday August 15, 2019
TIME: 1:30 p.m.
LOCATION: ABB 165
SUPERVISOR: Dr. Jose Moran-Mirabal
The lack of safe drinking water, access to medical treatment and equipment, and sustainable energy are some examples of problems affecting the majority of developing nations today. While technological advances have enabled developed countries to improve the average health quality and overall life expectancy of their residents, the adoption of such technologies is cost-prohibitive for countries with small healthcare budgets. One of the obstacles in achieving low-cost and simple-to-use biotechnologies are versatile and robust fabrication methods. Therefore, there is great demand for novel and feasible biomedical device technologies that can address the current healthcare challenges of resource-limited nations.
In this thesis, a low-cost and rapid bench-top fabrication method is introduced to create nano/microstructured electrodes (NMSEs) with applications in microfluidic cell sensing, enhanced energy capture, and hemolytic agent detection. Metal deposition and shape-memory polymers were used to rapidly create tuneable wrinkled electrodes with electrochemical surface area enhancements of up to 650% and miniaturization down to 16% from the original area. These shrunken electrodes were transferred onto polydimethylsiloxane (PDMS) using a dissolvable photoresist liftoff technique. The result was a new, all PDMS-based flexible microfluidic cell sensor, capable of detecting 3T3 fibroblast cells down to 2x106 cells/ml. In a second project, biofilms of Geobacter sulfurreducens were cultured onto wrinkled NMSEs with enhanced electroactive surface area, which served as bioanodes in a microbial fuel cell. This enhanced microbial fuel cell generated twice the power output of control devices containing planar electrodes. Next, we developed a phospholipid membrane-on-a-chip platform for the electrochemical detection of membrane disrupting agents. We deposited a coating of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipids on the surface of the NMSE to electrochemically passivate the electrode. Lytic compounds were hypothesized to disrupt the coating, such that the exposed NMSE interface could transduce the signal from redox molecules in solution. We achieved limits of detection of 10 ppm and 1 ppm for sodium dodecyl sulfate (SDS) and Polymyxin-B (PmB) respectively. The addition of cholesterol to DMPC increased the supported membrane stability against SDS and PmB. We tested the cholesterol rich membranes against Pneumolysin (PLY), a hemolytic protein known to rupture cell membranes with a limit of detection of 600 ppb. All three electroanalytical devices produced using our shape-memory polymer structuring technique exemplify the potential of this versatile platform to help address the issues currently facing developing countries.