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Design of an Impedance-based, Gold Nanoparticle Enhanced Biosensor System Open Access


Other title
Gold Nanoparticles
Impedance Spectroscopy
Type of item
Degree grantor
University of Alberta
Author or creator
MacKay, Scott A
Supervisor and department
Chen, Jie (Electrical and Computer Engineering)
Examining committee member and department
Mandal, Mrinal (Electrical and Computer Engineering)
Barlage, Doug (Electrical and Computer Engineering)
Zhang, Jin (Chemical and Biochemical Engineering)
Sit, Jeremy (Electrical and Computer Engineering)
Brett, Michael (Electrical and Computer Engineering)
Department of Electrical and Computer Engineering
Biomedical Engineering
Date accepted
Graduation date
2017-11:Fall 2017
Doctor of Philosophy
Degree level
The detection of biological molecules is a useful tool for diagnostics, research, and general health monitoring. By measuring concentrations of certain key components of biological samples, vital information can be gained as to the condition of the entire biological system. Diseases such as cancer can be detected by monitoring changes in concentrations of certain biomarkers for example. The more accessible and versatile biological sensing becomes, the more good it can do for more people. To this end, a biosensor system has been designed with a focus on simplicity, low cost, versatility, and accessibility. The system consists of a portable impedance sensor, microfabricated interdigitated gold electrodes, and modified gold nanoparticles. Detection of biological components using this sensor is based on electrical impedance changes in interdigitated electrodes caused by the binding of modified gold nanoparticles to those electrodes. Molecular recognition elements, such as antibodies or aptamers, bind specifically to target biomolecules and facilitate the binding of nanoparticles which change the measured impedance. Because this change does not depend on the biomolecule itself, the system is very versatile. Several generations of interdigitated electrodes have been made over the course of this research. The electrical properties of different designs have been simulated, and processes in making electrodes have been refined to create smaller electrodes (reducing cost), with smaller dimensions (increasing sensor sensitivity). The newest generation of electrode chips used for testing consist of eight gold electrode pairs with interlocking digits on silicon dioxide substrates. The surfaces of the electrodes can be modified with molecular recognition elements for detecting specific metabolites. Methods have been developed for modifying the surface of the electrode chips with molecular recognition elements (such as antibodies) as well as modifying gold nanoparticles with similar molecules. Tests have been completed on direct chemical bonding of gold nanoparticles onto electrodes and measuring the resulting impedance change. Using antibodies, proteins have been detected (using a secondary antibody to bind gold nanoparticles) at concentrations that have been found to be relevant for clinical diagnosis. Work is continuing focusing on quantitative detection of metabolites and other biomarkers. The impedance sensor circuit is an Arduino-based system on a printed circuit board with Bluetooth connectivity. The device connects to the sensor electrodes, and is controlled using a smartphone app. The app controls the settings for impedance measurement, calculates values and interprets incoming data, and displays and saves the resulting data. The circuit is capable of measuring impedances over a range of frequencies (1 kHz to1 MHz), and can track changes in impedance over time. The results from the circuit are comparable to much larger and more expensive systems (within ±2% error). The circuit is handheld and has a total cost (without a smartphone) of around $60 (compared to $15000 for more complex tabletop electrochemical stations).
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