4 research outputs found
Electrochemical Signal Amplification for Immunosensor Based on 3D Interdigitated Array Electrodes
We
devised an electrochemical redox cycling based on three-dimensional
interdigitated array (3D IDA) electrodes for signal amplification
to enhance the sensitivity of chip-based immunosensors. The 3D IDA
consists of two closely spaced parallel indium tin oxide (ITO) electrodes
that are positioned not only on the bottom but also the ceiling, facing
each other along a microfluidic channel. We investigated the signal
intensities from various geometric configurations: Open-2D IDA, Closed-2D
IDA, and 3D IDA through electrochemical experiments and finite-element
simulations. The 3D IDA among the four different systems exhibited
the greatest signal amplification resulting from efficient redox cycling
of electroactive species confined in the microchannel so that the
faradaic current was augmented by a factor of ∼100. We exploited
the enhanced sensitivity of the 3D IDA to build up a chronocoulometric
immunosensing platform based on the sandwich enzyme-linked immunosorbent
assay (ELISA) protocol. The mouse IgGs on the 3D IDA showed much lower
detection limits than on the Closed-2D IDA. The detection limit for
mouse IgG measured using the 3D IDA was ∼10 fg/mL, while it
was ∼100 fg/mL for the Closed-2D IDA. Moreover, the proposed
immunosensor system with the 3D IDA successfully worked for clinical
analysis as shown by the sensitive detection of cardiac troponin I
in human serum down to 100 fg/mL
Nonfaradaic Nanoporous Electrochemistry for Conductometry at High Electrolyte Concentration
Nanoporous electrified surfaces create
a unique nonfaradaic electrochemical
behavior that is sensitively influenced by pore size, morphology,
ionic strength, and electric field modulation. Here, we report the
contributions of ion concentration and applied ac frequency to the
electrode impedance through an electrical double layer overlap and
ion transport along the nanopores. Nanoporous Pt with uniform pore
size and geometry (L<sub>2</sub>-ePt) responded more sensitively to
conductivity changes in aqueous solutions than Pt black with poor
uniformity despite similar real surface areas and enabled the previously
difficult quantitative conductometry measurements at high electrolyte
concentrations. The nanopores of L<sub>2</sub>-ePt were more effective
in reducing the electrode impedance and exhibited superior linear
responses to not only flat Pt but also Pt black, leading to successful
conductometric detection in ion chromatography without ion suppressors
and at high ionic strengths
Miniaturized Reverse Electrodialysis-Powered Biosensor Using Electrochemiluminescence on Bipolar Electrode
We
suggest an electrochemiluminescence (ECL)-sensing platform driven
by ecofriendly, disposable, and miniaturized reverse electrodialysis
(RED) patches as an electric power source. The flexible RED patches
composed of ion-exchange membranes (IEMs) can produce voltage required
for ECL sensing by simply choosing the appropriate number of IEMs
and the ratio of salt concentrations. We integrate the RED patch with
a bipolar electrode on the microfluidic chip to demonstrate the proof-of-concept,
i.e., glucose detection in the range of 0.5–10 mM by observing
ECL emissions with naked eyes. The miniaturized RED-powered biosensing
system is widely applicable for electrochemical-sensing platforms.
This is expected to be a solution for practical availability of battery-free
electrochemical sensors for disease diagnosis in developing countries
On-Site Formation of Functional Dopaminergic Presynaptic Terminals on Neuroligin-2-Modified Gold-Coated Microspheres
Advancements in neural interface
technologies have enabled the
direct connection of neurons and electronics, facilitating chemical
communication between neural systems and external devices. One promising
approach is a synaptogenesis-involving method, which offers an opportunity
for synaptic signaling between these systems. Janus synapses, one
type of synaptic interface utilizing synaptic cell adhesion molecules
for interface construction, possess unique features that enable the
determination of location, direction of signal flow, and types of
neurotransmitters involved, promoting directional and multifaceted
communication. This study presents the first successful establishment
of a Janus synapse between dopaminergic (DA) neurons and abiotic substrates
by using a neuroligin-2 (NLG2)-mediated synapse-inducing method. NLG2
immobilized on gold-coated microspheres can induce synaptogenesis
upon contact with spatially isolated DA axons. The induced DA Janus
synapses exhibit stable synaptic activities comparable to that of
native synapses over time, suggesting their suitability for application
in neural interfaces. By calling for DA presynaptic organizations,
the NLG2-immobilized abiotic substrate is a promising tool for the
on-site detection of synaptic dopamine release