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

• Author / Creator

  MacKay, Scott A

• 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).

• Subjects / Keywords

  • Impedance Spectroscopy
  • Biosensors
  • Gold Nanoparticles

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3CJ88061

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.