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.