Electrocatalytic Nanoparticle Based Sensing for Diagnostics

Abstract

An early and accurate diagnosis is the key to the effective and ultimately successful treatment of a large number of diseases, and only sensitive detection methods allow an early diagnosis. Current methods, employed in the clinical area, are often time-consuming, expensive, and require advanced instrumentation and high skilled professionals. Thus, more cost effective methods requiring user-friendly instrumentation that can provide an adequate sensitivity and accuracy would be ideal, and the most important challenge in biosensing is to combine the advances in nanomaterials and molecular biology, with new diagnosis methods in order to overcome the diagnosis difficulties Electrochemical biosensors can fulfil these requirements once they gather the selective biochemical recognition with the high sensitivity of electrochemical detection plus, they can be easily integrated in fluidic systems that enhance their overall manageability. To improve the electrochemical assay sensitivity and to achieve a better and more reliable analysis there is a great demand for labels with higher specific activity. The most used labels for electrochemical sensors up to date have been enzymes as well as small molecules like electro-active indicators. Nanoparticles can provide a novel platform for improving the specific activity of a label as well as its affinity to the tracer biomolecules (DNA probes, proteins and other biomolecules). They are within the same size range as biomolecules and in solution they present a similar behaviour. Therefore they can be used as electrochemical labels allowing more assay-flexibility, faster binding kinetics, high sensitivity and high reaction rates for many types of assays, ranging from protein immunoassays to DNA and cell analysis. The main objective of this thesis is the development of novel and improved electrochemical sensing systems for biomarker detection, using the electrocatalytic effects of nanoparticles. Several approaches were developed using gold nanoparticles as electrocatalytic labels in immunosensor and cell sensing systems, for the detection of proteins and cells with interest for the detection of biomarkers.