Project completed 2013.
Professor Liam Grover, School of Chemical Engineering
Professor Paul Murray, Insitute of Cancer and Genomic Sciencs
Professor Graham Worth, School of Chemistry
Microarray imaging now represents a core technology in translational cancer research. For example, in ~50% of patients with Hodgkin's lymphoma (HL), the Epstein-Barr virus (EBV), an oncogenic herpes virus, is present in tumour cells; microarray profiling of both HL tumours and cell lines indicates EBV infection increases the expression of the chemokine CCL20 in both primary Hodgkin and Reed-Sternberg cells and Hodgkin and Reed-Sternberg cell-derived cell lines.
A standard microarray assay for proteins is based on a 2D array of molecular sandwich structures yielding an optical image as the output: each capture molecule recognises and captures a target antigen, which is detected ("reported") by the further capture of a dye-labelled molecule. The last step (dye-labelling) is time-consuming, inefficient and highly undesirable.
This project will explore a novel strategy for label-free protein detection based on resonant optical coupling between the anchoring metal clusters and the capture antigen. Tryptophan is an amino acid which shows weak native UV fluorescence, and so could potentially allow protein arrival to be detected directly, if the signal can be amplified and red-shifted into the visible region of the spectrum.
The use of size-selected metal clusters deposited on the surface is an innovation developed by the Birmingham Nanoscale Physics group under prior EPSRC research grants. Theoretical predictions from Berlin indicate resonant photonic interactions between tryptophan residues in polypeptides/proteins and the electronic excitations of size-selected clusters in the non-scalable regime. These electronic excitations arise from the quantum nature of particles containing only a few atoms (elements such as silver), leading to fluorescent behaviour entirely absent from the corresponding bulk material. The surface-bound atomic clusters will be characterised by scanning probe techniques and optically excited by a photonic-crystal-fibre white light laser to optimise the quantum yield, and then the optical coupling to proteins chemically attached to the clusters will be measured. Shifts in fluorescence intensity and/or wavelength and/or lifetime prove the potential protein detection scheme.
The optical measurement techniques to be refined and exploited include photoluminescence (potentially time-resolved) and Near-field Scanning Optical Microscopy (NSOM), which allows confocal measurements (improving signal-to-noise) as well as a sub-wavelength lateral resolution of order 100nm. Topics of study within the EPSRC portfolio include Quantum Optics, Biophysics & Soft Matter, and Surface Science.
Link to ethesis: http://etheses.bham.ac.uk/5339/