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Christchurch, New Zealand

Billinge E.R.,Loughborough University | Broom M.,Izon Science Ltd. | Platt M.,Loughborough University
Analytical Chemistry | Year: 2014

Aptamers are short single-stranded pieces of DNA or RNA capable of binding to analytes with specificity and high affinity. Due to their comparable selectivity, stability, and cost, over the last two decades, aptamers have started to challenge antibodies in their use on many technology platforms. The binding event often leads to changes in the aptamer's secondary and tertiary structure; monitoring such changes has led to the creation of many new analytical sensors. Here, we demonstrate the use of a tunable resistive pulse sensing (TRPS) technology to monitor the interaction between several DNA aptamers and their target, thrombin. We immobilized the aptamers onto the surface of superparamagnetic beads, prior to their incubation with the thrombin protein. The protein binding to the aptamer caused a conformational change resulting in the shielding of the polyanion backbone; this was monitored by a change in the translocation time and pulse frequency of the particles traversing the pore. This signal was sensitive enough to allow the tagless detection of thrombin down to nanomolar levels. We further demonstrate the power of TRPS by performing real time detection and characterization of the aptamer-target interaction and measuring the association rates of the thrombin protein to the aptamer sequences. © 2013 American Chemical Society. Source

Adela Booth M.,University of Auckland | Adela Booth M.,Institute of Environmental Science & Research Ltd. ESR | Vogel R.,Izon Science Ltd. | Vogel R.,University of Queensland | And 4 more authors.
Biosensors and Bioelectronics | Year: 2013

Despite the plethora of DNA sensor platforms available, a portable, sensitive, selective and economic sensor able to rival current fluorescence-based techniques would find use in many applications. In this research, probe oligonucleotide-grafted particles are used to detect target DNA in solution through a resistive pulse nanopore detection technique. Using carbodiimide chemistry, functionalised probe DNA strands are attached to carboxylated dextran-based magnetic particles. Subsequent incubation with complementary target DNA yields a change in surface properties as the two DNA strands hybridize. Particle-by-particle analysis with resistive pulse sensing is performed to detect these changes. A variable pressure method allows identification of changes in the surface charge of particles. As proof-of-principle, we demonstrate that target hybridization is selectively detected at micromolar concentrations (nanomoles of target) using resistive pulse sensing, confirmed by fluorescence and phase analysis light scattering as complementary techniques. The advantages, feasibility and limitations of using resistive pulse sensing for sample analysis are discussed. © 2013 Elsevier B.V. Source

A method is provided for detecting, measuring or controlling particles and/or electromagnetic radiation, comprising providing a deformable material containing a deformable aperture defining a path for particles or radiation, adjusting the deformable aperture to a prescribed geometry and/or size by deforming the deformable material to change at least one of the parameters of the path defined by the deformable aperture, and causing the particle or radiation to be detected, measured or controlled to enter the deformable aperture. The method includes the step of monitoring the geometry and/or size of the deformable aperture and controlling the adjustment of the size of the deformable aperture in response to such monitoring. The required apparatus is easily fabricated from inexpensive materials. Furthermore the deformable aperture can be tuned to the appropriate geometry post fabrication, and the ability to adjust the aperture geometry renders it capable of discriminating a plurality of differently sized particles.

IZON SCIENCE Ltd | Date: 2011-01-26

The flow of particles (

Willmott G.R.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Vogel R.,University of Queensland | Yu S.S.C.,Izon Science Ltd. | Groenewegen L.G.,Izon Science Ltd. | And 4 more authors.
Journal of Physics Condensed Matter | Year: 2010

Tunable nanopores fabricated in elastomeric membranes have been used to study the dependence of ionic current blockade rate on the concentration and electrophoretic mobility of particles in aqueous suspensions. A range of nanoparticle sizes, materials and surface functionalities has been tested. Using pressure-driven flow through a pore, the blockade rate for 100 nm carboxylated polystyrene particles was found to be linearly proportional to both transmembrane pressure (between 0 and 1.8 kPa) and particle concentration (between 7 × 108 and 4.5 × 1010 ml -1). This result can be accurately modelled using Nernst-Planck transport theory, enabling measurement of particle concentrations. Using only an applied potential across a pore, the blockade rates for carboxylic acid and amine coated 500 and 200 nm silica particles were found to correspond to changes in their mobility as a function of the solution pH. Scanning electron microscopy and confocal microscopy have been used to visualize changes in the tunable nanopore geometry in three dimensions as a function of applied mechanical strain. The pores were conical in shape, and changes in pore size were consistent with ionic current measurements. A zone of inelastic deformation adjacent to the pore has been identified as important in the tuning process. © 2010 IOP Publishing Ltd. Source

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