Development of micro-electrode arrays as biosensors for immunoassays in clinical diagnostics

The diagnosis and monitoring of complex human diseases using biomarkers coupled with in vitro clinical diagnostic devices is becoming pivotal in a society placing increasing importance on disease prevention and individualised patient care. The inherent complexity of chronic diseases such as cancer and heart disease suggest that useful clinical diagnosis will rely on panels of biomarkers, requiring methods of multiplexed analysis. Initially introduced as miniaturised DNA assemblies on microscope slides, the microarray field has expanded, creating a trend towards multiplexing and miniaturisation in many types of biological assays. Antibodies have proven to be a paradigm for the design of high-affinity, protein-based binding reagents and remain the gold standard affinity reagents in clinical diagnostics. Antibody microarrays have been successfully used for the identification of differentially expressed biomarker proteins in a range of samples including serum. The serum proteome is estimated to contain 10,000 proteins ranging over 10 orders of magnitude in abundance. Biomarkers may be present at or below the picomolar range and potentially masked by the profusion of a few high abundance proteins. The development of highly sensitive detection systems in assay platforms is required to facilitate biomarker detection in a clinical setting. Electrochemical biosensors have undergone intensified development to become coupled successfully with protein microarray technology. Electrochemical biosensors offer the advantage of label-free detection in real-time on a platform with the potential for high spatial resolution. Such devices may evolve as miniaturised platforms for rapid and sensitive analyte detection required for point-of-care clinical diagnostics. The proposed studentship will develop label-free high-density biosensor arrays for the multiplexed detection of low abundance biomarkers in complex biological fluids. The biosensors will be based on our proven electrochemical impedance spectroscopy platform and on Abbott's large range of validated reagents. The aim of this project will be to expand our previous studies (see e.g. D. Evans et al, J Biol 7:3-11, 2008) by refining sensor performance and determining the applicability of micro-electrode arrays as a clinical diagnostics platform using benchmark reagents. The commercial partner, Abbott Diagnostics Division (ADD) is a global leader in the development and manufacture of immunoassays for clinical diagnostics. The ADD ARCHITECT range is a family of automated immunochemistry platforms with an extensive menu of FDA-approved and CE-marked assays in a range of disease areas. The components of ARCHITECT assays are highly characterised benchmark rare reagents (antibodies-antigen pairs) and are ideal for direct comparison between an existing high-performance diagnostics platform with emerging biosensor-array technologies. The proposed research project will compare the performance of ADD reagents on micro-electrode arrays with the ARCHITECT platform using key diagnostic assays. Troponin I (cTnI), a marker of cardiac disease, has been selected as a model assay as tests are performed both on high-throughput analysers such as ARCHITECT and on point-of-care diagnostics, which require rapid, highly sensitive assays. Overall the programme will aim to evaluate and develop the sensor technology to assess utility as diagnostic platform through the use of high pedigree biological rare reagents with established performance benchmarks in current immunoassay formats as used in clinical settings. As such it will form a bridge between established biological knowledge, the chemistry of functionalising gold surfaces and the underlying physics of the sensor technology. The interdisciplinary nature of the proposed project will promote the acquisition of a wide range of skills and diverse future opportunities in both academia and industry for a prospective PhD candidate.