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Title: Detection of disease related enzymes by peptide functionalised nanoparticles
Author: Dick, John Alexander Gordon
ISNI:       0000 0004 2714 7141
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Colloidal nanoparticles stabilised in an aqueous mixture were used for the rapid detection of disease biomarkers at high levels of sensitivity. Peptide substrates were used to functionalise the nanoparticle surfaces for targeted interaction with specific enzymes related to breast cancer and other maladies. These systems have potential clinical applications for disease detection and high-throughput drug screening. Semiconductor nanoparticles or quantum dots (QDs) were functionalised by a synthetic peptide substrate for the detection of the protease breast cancer biomarker urokinase plasminogen activator (uPA). A non-radiative energy pathway was created through the conjugation of the peptide to a 1.4 nm gold nanoparticle. The enzymatic dispersion of this system was quantified by fluorescence spectroscopy and used to determine the enzyme concentration. A materials-based characterisation of the uPA system was conducted using small angle X-ray scattering at the Australian Synchrotron. Results were used to determine the maximum number of peptide conjugates that could bind to the QD and how they spatially arranged themselves around the surface. Application of these results can be used in the design of new QD-based biosensors. The uPA detection assay was combined with a Förster resonance energy transfer based QD detection assay for the kinase breast cancer biomarker, human epidermal growth factor receptor - 2 (Her2). Multiplexed detection of the two enzymes was successfully shown in a proof-of-concept experiment. This assay demonstrates the potential for accurate biosensing by nanoparticles in a complex biological environment. A highly sensitive peptide assembled gold nanoparticle based assay for the detection of proteolytic enzymes was designed for use with absorbance spectroscopy and surface enhanced Raman spectroscopy (SERS). The protease thermolysin was detected at a concentration of 0.01 nM using SERS. The assay illustrated the usefulness of SERS for enzyme detection for the investigation of protein-peptide interactions.
Supervisor: Stevens, Molly Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral