Niamh Creedon

A potentiometric biosensor for rapid on-site disease diagnostics

Quantitative point-of-care (POC) devices are the next generation for serological disease diagnosis. Whilst pathogen serology is typically performed by centralized laboratories using Enzyme-Linked ImmunoSorbent Assay (ELISA), faster on-site diagnosis would infer improved disease management and treatment decisions. Using the model pathogen Bovine Herpes Virus-1 (BHV-1) this study employs an extended-gate field-effect transistor (FET) for direct potentiometric serological diagnosis. BHV-1 is a major viral pathogen of Bovine Respiratory Disease (BRD), the leading cause of economic loss (

Low-cost silver capped polystyrene nanotube arrays as super-hydrophobic substrates for SERS applications.

2 billion annually in the US only) to the cattle and dairy industry. To demonstrate the sensor capabilities as a diagnostic tool, BHV-1 viral protein gE was expressed and immobilized on the sensor surface to serve as a capture antigen for a BHV-1-specific antibody (anti-gE), produced in cattle in response to viral infection. The gE-coated immunosensor was shown to be highly sensitive and selective to anti-gE present in commercially available anti-BHV-1 antiserum and in real serum samples from cattle with results being in excellent agreement with Surface Plasmon Resonance (SPR) and ELISA. The FET sensor is significantly faster than ELISA (<10 min), a crucial factor for successful disease intervention. This sensor technology is versatile, amenable to multiplexing, easily integrated to POC devices, and has the potential to impact a wide range of human and animal diseases.

Novel Single Gold Nanowire-based Electrochemical Immunosensor for Rapid Detection of Bovine Viral Diarrhoea Antibodies in Serum

In this paper, we describe the fabrication, simulation and characterization of dense arrays of freestanding silver capped polystyrene nanotubes, and demonstrate their suitability for surface enhanced Raman scattering (SERS) applications. Substrates are fabricated in a rapid, low-cost and scalable way by melt wetting of polystyrene (PS) in an anodized alumina (AAO) template, followed by silver evaporation. Scanning electron microscopy reveals that substrates are composed of a dense array of freestanding polystyrene nanotubes topped by silver nanocaps. SERS characterization of the substrates, employing a monolayer of 4-aminothiophenol (4-ABT) as a model molecule, exhibits an enhancement factor of ∼1.6 × 10(6), in agreement with 3D finite difference time domain simulations. Contact angle measurements of the substrates revealed super-hydrophobic properties, allowing pre-concentration of target analyte into a small volume. These super-hydrophobic properties of the samples are taken advantage of for sensitive detection of the organic pollutant crystal violet, with detection down to ∼400 ppt in a 2 μl aliquot demonstrated.

Direct correlation between potentiometric and impedance biosensing of antibody-antigen interactions using an integrated system

Bovine Viral Diarrheoa (BVD) is a worldwide disease with severe financial implications for the Bovine beef and dairy industries. A key challenge to BVD eradication is that the requirement to send samples to, and receive results from, specialized laboratories slows down the diagnostic process and leads to uncontrolled spread of the virus within a herd until diagnostic confirmation is received. Consequently, rapid identification of BVD is now critical for herd protection and prevention of costly herd outbreaks and new diagnostic devices, suitable for on-farm analysis, that deliver rapid and early identification of animal disease states, are required. We report, here, an electrochemical onchip fully integrated nanowire based immunosensor device for detection of BVD in serum. The capture biomolecule, BVD virus, is covalently immobilized via a carboxylic terminated polymer firstly electrodeposited onto a single nanowire. Electrochemical characterization including faradaic electrochemical impedance spectroscopy and cyclic voltammetry is performed. Label free immunologic detection of antibodies (10 μg/mL, 20 min) is first demonstrated using a bovine serum albumin as a model antigen-antibody system. Then, the immunosensor is applied to detection of bovine viral diarrhoea antibodies (10 μg/mL, 20 min) in both buffer and serum. The sensor clearly discriminates between positive and negative infected bovine sera. This study clearly shows the potential of this chip nanowirebased electrochemical sensor for immunoassays application in serum with a view to developing portable devices for on-farm diagnosis or therapeutic monitoring in animal health applications.

Metal capped polystyrene nanotubes arrays as super-hydrophobic substrates for SERS applications

A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using ele...

Transparent polymer-based SERS substrates templated by a soda can

We present a low-cost and rapid fabrication and characterisations of polymer nanotubes based substrates inspired by a Gecko’s foot, and demonstrate its suitability for Surface Enhanced Raman Scattering (SERS) applications. Substrates are fabricated in a simple, scalable and cost efficient way by melt wetting of polystyrene (PS) in an anodised alumina (AAO) template, followed by silver or gold evaporation. Scanning electron microscopy reveals the substrates are composed of a dense array of free-standing polystyrene nanotubes topped by silver nanocaps. The gaps (electromagnetic hot spots) between adjacent nanotubes are measured to be 30nm +/-15nm. SERS characterisation of the substrates, employing a monolayer of 4-aminothiophenol (4-ABT) as a model molecule, exhibits an enhancement factor of ~1.6 × 106. This value is consistent with the one obtained from 3D-Finite Difference Time Domain (3D-FDTD) simulations of a simplified version of the sample. The contact angle of the substrates is measured to be 150°, making them super-hydrophobic. This later property renders the samples compatible to very low sample volumes and highly sensitive detection (down to 408ppt) of the environmental pollutant crystal violet in water is demonstrated.