Development of an electrochemical surface-enhanced Raman spectroscopy DNA aptamer biosensor for rapid detection of protein biomarkers of disease

Abstract

Electrochemical surface-enhanced Raman spectroscopy (EC-SERS) is a vibrational spectroscopic method involving detection of a target molecule at a metal nanostructured surface to which a potential has been applied. EC-SERS can lower limits of detection, even relative to SERS, which is itself an improvement over conventional Raman spectroscopy. DNA aptamers are oligonucleotides engineered to bind a target molecule with high specificity and high affinity. Advantages of using aptamers instead of antibodies to bind a target molecule include time and temperature stability, in vitro synthesis, ease of handling and storage, and low cost. Thiolated DNA aptamers are immobilised onto Ag nanoparticles (AgNP) by the formation of a Ag-S bond. The aptamer-modified AgNP electrodes are then used for detection of target proteins: immunoglobulin E (IgE), cytochrome c (cyt c) and catalase-peroxidase (KatG), which are all biomarkers indicative of various health conditions. IgE is produced as a response to various allergens. Cyt c is a biomarker for diseases of the liver and kidney, and KatG is a biomarker for tuberculosis. This project uses EC-SERS of aptamer-modified AgNP electrodes for detection of these biomarker proteins. The overall goal is the eventual development of a low-cost and portable point of care diagnostic device that can be used in developing nation settings, such as South Africa.