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Biosensors

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... device which is used to determine the presence and concentration of a specific substance in a biological analyte Biosensor ... Fluorescence Interference ... – PowerPoint PPT presentation

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Title: Biosensors


1
Biosensors
  • Presented by
  • Dr. Manouchehr Bahrami
  • Prepared by MEMS group
  • University of Tabriz
  • Department of Electrical and computer Eng.

2
Outline
  • Introduction to Biosensors
  • 2) Bioreceptors
  • 3) Immobilization of Bioreceptors
  • 4) Transduction methods and example devices

3

Introduction to Biosensors
A biosensor is an analytical device which is used
to determine the presence and concentration of a
specific substance in a biological analyte
Desired molecule
Signal Processing
Bioreceptor
Transducer
Display
Biosample
Biosensor
Recognition
Transduction
Signal Processing
4
Introduction to Biosensors
Bioreceptor
Transducer
Absorption
Fluorescence
Antibody
Optical
Interference
potentiometric
Enzyme
Electrochemical
amperometric
conductimetric
Nucleic Acid (DNA)
Mass based
Cell
Temperature based
Dielectric properties
Electric Magnetic
Permeability properties
MIP
Voltage or Current
5
Bioreceptors
  • Antibody

Antibodies are biological molecules that exhibit
very specific binding capabilities for specific
structure (antigens).
  • Antigen

membrane
It can be recognized by antibody.
6
Bioreceptors
Bioreceptor
Display
7
Bioreceptors
  • Enzyme

Enzyme is a large protein molecule that acts as a
catalyst in chemical reactions. Enzymes are often
chosen as bioreceptors based on their specific
binding capabilities as well as their catalytic
activity
8
Bioreceptors
Bioreceptor
Display
9
Bioreceptors
  • DNA structure

Another biorecognition mechanism involves
hybridization of deoxyribonucleic acid (DNA) or
ribonucleic acid (RNA), which are the building
blocks of genetics.
  • Four chemical bases
  • adenine(A), guanine (G),
  • cytosine (C), and thymine (T)

10

Bioreceptors
Principles of DNA biosensors
  • Nucleic acid hybridization

(Target Sequence)
ssDNA (Probe)
(Hybridization)
(Stable dsDNA)
11
Bioreceptors
Bioreceptor
Display
12
Bioreceptors
  • Living Cell

Nourishment
Product
13
Bioreceptors
Bioreceptor
Display
14
Bioreceptors
  • MIP (Molecular Imprinted Polymer)

15
Bioreceptors
MIP as a bioreceptor
16
Bioreceptors
Bioreceptor
Display
17
Immobilizatiom
  • The immobilization is done either by physical
    entrapment or chemical attachment.

Physical Entrapment
Bioreceptor (Antibody, Enzyme, Cell, )
polymer solution ? polymerization
Adsorption
adsorptive interactions such as ionic, polar or
hydrogen bonding and hydrophobic interaction.
18
Immobilizatiom
Covalent bounding
formation of a stable covalent bond between
functional groups of the bioreceptor components
and the transducer
Cross-linking
bridging between functional groups on the outer
membrane of the receptor by multifunctional
reagents to transducer. The cells can be bounded
directly onto the electrode surface or on a
removable support membrane, which can be placed
on the transducer surface
19
conductimetric
20
Transducers- Optical methods
Concept Capture analyte and detect binding by
optical tag or binding-sensitive optical
phenomenon
Absorption
I1/I0 e-alc
l is the pass length C is the concentration
of absorbing material a is the absorption
coefficient
21
Transducers- Optical methods- Absorption
A device to determine a patients blood
oxygen content the oximeter The absorption
spectra (a) of haemoglobin (Hb) and
oxyhaemoglobin (HbO2) differ, which makes it
possible to measure the ratio of both
concentrations in blood by measuring the
absorption of light of two different wavelengths,
e.g. 660 nm and 805 nm.
22
Transducers-Optical methods- Florescence
Fluorescence is a molecular absorption of light
at one wavelength and its instantaneous emission
of at longer wavelengths. Some molecules
fluoresce naturally and others such as DNA can be
modified for fluorescence detection by attachment
of special fluorescent dyes
An optical system for Florescence measurement
23
Transducers-Optical methods- Florescence
Grating
Antigens modified by florophor dye
Evanescent-field.
Planer waveguide
Excitation light
Florescence detector
A device for florescence measurement
24
Transducers-Optical methods- Florescence
Taq-Man probe in its preliminary condition for
real time PCR devive
Releasing fluorophore dye during extension
Hybridisation of primer and Taq-Man probe at
annealing temperature
25
Transducers-Optical methods- Florescence
Real time Chamber PCR device with integrated
fluorescence detection
26
Mach-Zehnder interferometer
Transducers-Optical methods-refractive index
27
Transducers-Optical methods-refractive index
The reflected wavelength (?B), called the Bragg
wavelength, is defined by
28
Optical waveguide based biosensor
Transducers-Optical methods-refractive index
29
Transducers-Electrochemical methods
The underlying principle for this class of
biosensors is that many chemical reactions
produce or consume ions or electrons which in
turn cause some change in the electrical propertie
s of the solution which can be sensed out and
used as measuring parameter
30
Transducers-Electrochemical
methods-amperometric
amperometric glucose biosensors
31
Transducers-Electrochemical
methods-amperometric
amperometric glucose biosensors
32
Transducers-Electrochemical
methods-potentiometric
Schematic diagram of an integrated enzyme-based
flow-through glucose sensor.
33
Transducers-Electrochemical
methods-potentiometric

34
Transducers-Electric methods
Concept Capture analyte and detect changes in
electrical parameters of sample

Immunosensing at micro-sized Au electrodes based
on the change of conductivity between the Au
strips upon binding of Au nanoparticles
35
Transducers-Electric methods
Capacitive sensor by MIP dielectric
Variation of
36
Transducers-Electric methods
F 20KHz, AC amplitude of 40 mV peak to peak
37
Transducers-Mass based methods
The principle is to change in the frequency of
vibrating element. when the mass increases due to
binding of chemicals, the oscillation frequency
of the device changes and the resulting change
can be measured electrically and be used to
determine the additional mass.
38
Transducers-Mass based methods
Detection by cantilevers

39
Transducers-Mass based methods
Detection by cantilevers
Change in the resonance frequency AcV1 antibody
(green) and baculovirus particles (red).
40
Transducers-Mass based methods
Detection by cantilevers
(a) A mechanical cantilever resonator
containing an embedded microfluidic channel.
(b) Decrease in resonant frequency as the density
inside the embedded channel increases. (c)
Frequency modulation by single particle movment
41
Transducers-Mass based methods
Detection by cantilevers
Microcantilever technology a) with immobilised
protein for a specific bacterium b) bending after
adsorption of bacteria to the protein
42
Transducers-Mass based methods
43
Transducers-Temperature methods
This type of biosensor is exploiting one of the
fundamental properties of biological reactions,
namely absorption or production of heat, which in
turn changes the temperature of the medium in
which the reaction takes place. They are
constructed by combining immobilized enzyme
molecules with temperature sensors. When the
analyte comes in contact with the enzyme, the
heat reaction of the enzyme is measured and is
calibrated against the analyte concentration. The
total heat produced or absorbed is proportional
to the molar enthalpy and the total number of
molecules in the reaction
44
Transducers-Temperature methods
A three-dimensional schematic representation of
the proposed microcalorimeter with integrated
microfluidic channels.
45
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