Immunosensors

Biosensors and Biointerfaces Group - Research Projects

Immunosensors for pesticide detection in environmental analysis (with CSIRO)

This project is based on the Blocked Electrochemical Sensor Technology (BEST) concept we have developed. The BEST concept involves using molecules as wires to allow electrochemical communication with an otherwise passivated electrode. The advantages of this strategy are electroactive interferences are negated and the electrode can be modified such that nonspecific adsorption of proteins to the electrode surface are restricted. The aim of this study is to develop a label free immunosensor for the detection of small molecules such as pesticides and drugs or proteins that bind to the immunosensing surface. The immunosensor is fabricated by modifying an electrode surface with a molecular wire and an insulator component as depicted. To the end of the molecular wire is attached a redox probe and an antigen. An antibody for this antigen will specifically bind to the electrode surface. When this happens the electrochemistry from the redox probe is suppressed. If the sensor is exposed to a sample containing the antigen, the antibody will dissociate from the surface to bind with the antigen in solution and give an increase in current. Initial proof of concept studies have been very promising with the detection of pesticides in the environment, drugs in dairy samples and proteins in whole blood. The fabrication of the biosensor has been greatly simplified using nanoparticles in place of the molecular wire. This work is funded by an ARC Linkage grant and our commercial partners.

label free immunosensor for small analytes such as pesticides and drugs

Above - the label free immunosensor for small analytes such as pesticides and drugs. The BEST interface comprises a passivation of oligo(ethyleneglycol) terminated molecules, that resist protein adsorption and block access to the electrode, and molecular wires which penetrate the insulator layer and allow electrical communication to the underlying electrode. In the immunosensor, a redox active molecule is attached to the end of the molecular wire. Also attached to the redox active species is an analogue of the antigen, the analyte of interest. Complexation of the antibody to this surface bound antigen encases the redox active species into a protein environment with a concomitant loss in electrochemistry. Exposure of this sensor to a solution that contains the analogue, results in a competition for the antibodies between solution and surface bound antigen. Some of the antigen dissociates from the surface with a resulting increase in electrochemical current.

For further information on this system see:

G.Z. Liu, M.N. Paddon-Row, J.J. Gooding, Protein Modulation of Electrochemical Signals:  Application to Immunobiosensing for Detecting Small Molecules, Chem. Comm. 3870-3872 (2008).

S.M. Khor, G.Z. Liu, J.R. Peterson, S.G. Iyengar, J.J. Gooding, A Label-Free Electrochemical Immuno-Biosensor for Analysis of Veterinary Drug Residue in Dairy and Water Samples, Electroanalysis 23 1797-1804 (2011).

G.Z. Liu, S. Iyengar, J.J. Gooding, An Amperometric Immunosensor based on Gold Nanoparticle-Diazonium Salt Modified Sensing Interface for Detection of HbA1c in Human Blood, Electroanalysis 25 881-887 (2013).