29 research outputs found
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Effect of Nanoporous Gold Thin Film Morphology on Electrochemical DNA Sensing
Langmuir–Blodgett films of polyaniline for low density lipoprotein detection
Langmuir–Blodgett (LB) films of polyaniline (PANI) were utilized for the fabrication of impedimetric immunosensor for detection of human plasma low density lipoprotein (LDL) by immobilizing anti-apolipoprotein B (AAB) via EDC–NHS coupling. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. AAB/PANI–SA LB immunoelectrodes studied by EIS spectroscopy revealed detection of LDL in the wide range of 0.018 μM (6 mg/dl) to 0.39 μM (130 mg/dl), covering the physiological range in blood, with a sensitivity of 11.25 kΩ μM− 1
Effect of Nanoporous Gold Thin Film Morphology on Electrochemical DNA Sensing
Advances
in materials science and chemistry have led to the development
of a wide range of nanostructured materials for building novel electrochemical
biosensors. A systematic understanding of the challenges related to
electrode morphology involved in designing such sensors is essential
for developing effective biosensing tools. In this study, we use nanoporous
gold (np-Au) thin film electrode coatings with submicrometer thicknesses,
as a model system to investigate the influence of nanostructuring
on DNA–methylene blue (MB) interactions and their application
to DNA biosensors. The interaction of single- and double-stranded
DNA immobilized onto morphologically different np-Au films with MB
was electrochemically interrogated via square wave voltammetry (SWV).
The electrochemical signal from these electrodes in response to MB
decayed progressively with each SWV scan. The decay rate was governed
by accessibility of the electrochemically active np-Au surface by
the analyte. The optimum frequency for extracting the maximum signal
via SWV was influenced by the film morphology, where the optimum frequency
was lower for the nanoporous morphology with lower density of molecular
access points into the porous coating. Overall, the np-Au electrodes
exhibited a 10-fold enhancement in probe grafting density and approximately
10-fold higher electrochemical current upon probe-target hybridization
as compared to the planar Au electrodes. The np-Au electrodes enabled
sensitive detection with a dynamic range of 10 to 100 nM that shifts
by 1 order of magnitude for coarsened np-Au morphology due to increased
target penetration into the porous network and hence enhanced hybridization
efficiency. These findings provide insight into the influence of nanostructuring
on the transport mechanisms of small molecules and nucleic acids,
and yield an understanding of diverse sensor performance parameters
such as DNA grafting density, hybridization efficiency, sensitivity
and dynamic range
Miniature Enzyme-Based Electrodes for Detection of Hydrogen Peroxide Release from Alcohol-Injured Hepatocytes
Alcohol insult to the liver sets off a complex sequence
of inflammatory
and fibrogenic responses. There is increasing evidence that hepatocytes
play a key role in triggering these responses by producing inflammatory
signals such as cytokines and reactive oxygen species (ROS). In the
present study, we employed a cell culture/biosensor platform consisting
of electrode arrays integrated with microfluidics to monitor extracellular
H<sub>2</sub>O<sub>2</sub>, one of the major ROS types, produced by
primary rat hepatocytes during alcohol injury. The biosensor consisted
of hydrogel microstructures with entrapped horseradish peroxidase
(HRP) immobilized on an array of miniature gold electrodes. These
arrays of sensing electrodes were integrated into microfluidic devices
and modified with collagen (I) to promote hepatocyte adhesion. Once
seeded into the microfluidic devices, hepatocytes were exposed to
100 mM ethanol and the signal at the working electrode was monitored
by cyclic voltammetry (CV) over the course of 4 h. The CV experiments
revealed that hepatocytes secreted up to 1.16 μM H<sub>2</sub>O<sub>2</sub> after 3 h of stimulation. Importantly, when hepatocytes
were incubated with antioxidants or alcohol dehydrogenase inhibitor
prior to alcohol exposure, the H<sub>2</sub>O<sub>2</sub> signal was
decreased by ∼5-fold. These experiments further confirmed that
the biosensor was indeed monitoring oxidative stress generated by
the hepatocytes and also pointed to one future use of this technology
for screening hepatoprotective effects of antioxidants