Birss Group
Biological Sensor Development & Microbial Electrolysis Cells
Bacterial Sensor Development
In one growing project, we are focused on repurposing proteins from the human immune system into electrochemical sensors. By using a class of proteins called Toll-Like Receptors (TLRs), we are developing sensors capable of responding to infectious agents that can infect humans and trigger our immune system. Using the TLRs as sensors in this manner has the dual purpose of being applicable to both medical and defense applications.
To produce these biosensors, we utilize Self-Assembled Monolayers (SAMs), which are formed on Au electrodes when small molecules such as alkanethiols adsorb onto their surfaces in an ordered fashion. The outer surface of the resultant SAM layer can then be modified in order to controllably immobilize proteins, such as the TLRs, while also providing tunable electrochemical properties. By monitoring how the modified surface layers influence electrochemical reactions and how the proteins further alter the reaction upon binding to targets of interest, we can monitor the construction and functionality of our biosensors.
Microbial Electrolysis Cells
As well as detecting infectious agents, we have recently begun working with Dr. Marc Strous (Geosciences) on a Microbial Electrolysis Cell (MEC) project. In this work, bacteria are used as catalysts to produce methane from hydrogen that is cathodically generated and from carbon dioxide in solution, all in a bioreactor. The bacteria tested in this work use the electrodes in the MEC as their terminal electron acceptors instead of oxygen (which is what humans use). By combining the bacterial metabolic pathways with the electrodes as the electron acceptors, we are capable of piggybacking on millennia of evolution to perform complex electrochemical reactions (via the bacterial cells) while still maintaining control of a typical electrochemical cell. This type of MEC could be used to convert electricity from renewable sources into conventional fuels, while also acting as a carbon dioxide conversion mechanism.
Cannabis Sensor Development
Although the police routinely test for alcohol intoxication of drivers using roadside testing devices, similar technology does not exist for other drugs, including cocaine, methamphetamines, various prescription drugs, or marijuana. We are developing a new sensor platform that can target these compounds by combining custom-designed proteins with electrochemical detection schemes. Our focus includes distinguishing the main psychoactive component of marijuana, Δ9-tetrahydrocannabinol (THC), from another medicinal cannabinoid, cannabidiol (CBD), and the two metabolites 11-nor-9-carboxy-THC (COOH-THC), and 11-hydroxy-THC (OH-THC). To date, we have focused on electrochemical characterization of THC and its metabolites on low-cost carbon electrodes, finding that the differences in structure between THC and its metabolites produce some differences in their electrochemical response. Our current efforts are also directed towards further enhancing the sensitivity and selectivity of our sensors. Also, a parallel approach for distinguishing psychoactive and inactive components of marijuana involves engineering proteins to selectively bind to THC, distinguishing it from the other cannabinoids and metabolites. This component of the project is moving forward through an ongoing collaboration with Justin MacCallum’s group, also in Chemistry at the University of Calgary.
