1.Overview Our group is focused on development of electronic sensors for sensitive, rapid, low cost...
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1.Overview Our group is focused on development of electronic sensors for sensitive, rapid, low cost and on-site applicable detection of diseases/illness
1.Overview Our group is focused on development of electronic
sensors for sensitive, rapid, low cost and on-site applicable
detection of diseases/illness. These devices that are based on
electrochemical and electromagnetic signal detection are currently
under investigation using bio-affinity reagents such as Antibodies,
Aptamers and recombinant proteins. Electrochemical devices have
shown a dynamic detection range spanning 6-7 orders of target
analyte concentrations, in general ranging from 0.01ng/mL to
10ug/mL based on the target molecules. On the other hand the
electromagnetic sensor has shown a dynamic detection range spanning
8-9 orders of applied magnetic field, thus these sensors are
expected to be much more sensitive as compared to electrochemical
devices, where non-specific signal limits the sensitivity to around
low ng/mL range 1-2. 5.Electromagnetic Biosensor platform
2.Electrochemical Biosensor platform Electrochemical biosensing is
based on the perturbation of charge transfer dynamics at the
surface of the metal electrode by the bioactive layer and the
observed impedance change can be correlated with biomolecular
activity. Electrochemical Impedance Spectroscopy can be used to
monitor both fast events (electron transfer) at high frequencies
and slow events (biomolecular diffusion) at low frequencies 1. PrA
Immobilized Binding with IgG Regeneration Native e-e- e-e- + - L G
W W G H -ve +ve X Y Distance from electrode C dl R ct ZwZw
Electrode R sol Z (imaginary) Z (Real) Diffusion Layer Double Layer
Bulk Solution R sol R sol + R ct Mass transfer control Electron
transfer control Decreasing Frequency Fig. 1 shows the typical
layout and geometrical parameters for IDEs Randles equivalent
electrical circuit (REEC) can be related to the interfacial EIS
parameters and the experimental data using Nyquists plots. The
electrodes are sensitive to the electrochemical environment (redox
probe). The biomolecular layer impedes the electron flow between
the electrode and ions in solution and is observable by change in
diameter of semicircular portion of the Nyquists Plot and
quantifiable by fitting data in a Randles circuit Electromagnetic
biosensing is based on magnetoresistance i.e., change in resistance
of a material in response to a small externally applied
electromagnetic field. This effect is significant in some
multilayer systems where a large change in resistance of up to 80%
have been reported 3-4. This phenomenon, which is based upon the
quantum mechanical exchange coupling between nm thin layers of
magnetic materials (Fe/Co/Ni) that are separated by comparably thin
layers of nonmagnetic materials (Cu), is known as giant
magnetoresistance (GMR) 3-4. TargetApplication areaDetection
RangeSensitivity (IC50) C-Reactive Protein 1 Cardiovascular 1
100pg-1ug/mL4.82ng/mL AntiTG-Abs 2 Gluten Allergy 2
10pg-10ug/mL35.6ng/mL Ryaonidine Receptor - Fk506 Muscular
(drug-protein) (Ca++ channel) 0.01-100nM15.86nM HE4Ovarian
Cancer1-100ng/mL5.03ng/mL Atrazine /
2,4-DPesticides/Environment0.05ppb-500ppbTo be determined
3.Electrochemical Device status 6.Electromagnetic Device status
G/W/H=480/1522/200nm Fig. 2 IDEs were designed for different
combinations of gap (G), width (W) and height (H) of the electrode
digits the length (L) was considered constant and >> G/W/H.
It was observed that device sensitivity increased significantly
with G < 800nm (Singh et al. 2010). Optimized IDE design with
G=500nm, H=200nm, W=1500nm and L=180um arranged in an 8 electrodes
linear array in a SD card format with a microfluidic chamber
determined on top of the electrodes. The graph shows results of
gluten allergy biomarker using IDEA chip and EIS as detection
technique. Fig_4 A 15 electrode (3X5) GMR sensor chip designed in
XD card format. Initial Measurement setup showing external magnetic
coils for horizontal biasing and magnetization of bound NPs. AFM of
surface bound PrA-NPs on IgG functionalized chip. A graph showing
relative change in impedance of GMR chip functionalized with IgG
Abs upon binding of PrA-MNPs at different dilutions 0, 10 and 100x
4.Target applications 7.Biosensor systems Table 1: Performance of
some of the biosensors that we have developed. Substrate +ve-ve
Substrate +ve -ve NS NSNS Fig 3a. The magnetic microdomains are
pinned unidirectionally during fabrication Fig 3b. MNPs cause
microdomain reorientation and change the electrical signal Fig 3c.
The GMR sensor is affected by horizontal component of externally
applied electromagnetic field Fig 3d. The GMR sensor signal is
proportional to the externally applied Horizontal magnetic field
Blood Separation Matrix(removes large cells/RBCs) Plasma filtration
Matrix NP-label Conjugate Release Matrix Waste/ Overflow GMR sensor
Blood (5-50ul) Buffer/reagents (20- 100ul) + Control Ab Test Ab Fig
5. Schematic showing the components of a GMR biochip IDEA
electrochemical biosensor platform capable of detection in the
1ng-10ug/mL. High non-specific signal at low concentrations (