Presentation on theme: "Department of Electrical and computer Eng."— Presentation transcript:
1Department of Electrical and computer Eng. BiosensorsPresented by:Dr. Manouchehr BahramiPrepared by MEMS groupUniversity of TabrizDepartment of Electrical and computer Eng.
2Outline Introduction to Biosensors 2) Bioreceptors 3) Immobilization of Bioreceptors4) Transduction methods and example devices
3Introduction to Biosensors A biosensor is an analytical device which is used to determine the presence and concentration of a specific substance in a biological analyteDesired moleculeSignal ProcessingBioreceptorTransducerDisplayBiosampleBiosensorTransductionSignal ProcessingRecognition
4Introduction to Biosensors BioreceptorTransducerAbsorptionFluorescenceAntibodyOpticalInterferencepotentiometricEnzymeElectrochemicalamperometricconductimetricNucleic Acid (DNA)Mass basedCellTemperature basedDielectric propertiesElectric & MagneticPermeability propertiesMIPVoltage or Current
5Antigen Antibody Bioreceptors Antibodies are biological molecules that exhibit very specific binding capabilities for specific structure (antigens).AntigenmembraneIt can be recognized by antibody.
7BioreceptorsEnzymeEnzyme 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
9DNA structure Four chemical bases: Bioreceptors 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)
10Principles of DNA biosensors BioreceptorsPrinciples of DNA biosensorsNucleic acid hybridization(Target Sequence)ssDNA (Probe)(Hybridization)(Stable dsDNA)
17Immobilizatiom Physical Entrapment Adsorption The immobilization is done either by physical entrapment or chemical attachment.Physical EntrapmentBioreceptor (Antibody, Enzyme, Cell, …) + polymer solution → polymerizationAdsorptionadsorptive interactions such as ionic, polar or hydrogen bonding and hydrophobic interaction.
18Immobilizatiom Covalent bounding Cross-linking formation of a stable covalent bond between functional groups of the bioreceptor components and the transducerCross-linkingbridging 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
20Transducers- Optical methods Concept: Capture analyte and detect binding by optical tag or binding-sensitive optical phenomenonAbsorptionI1/I0 = e−αlcl is the pass lengthC is the concentration of absorbing materialα is the absorption coefficient
21Transducers- Optical methods- Absorption A device to determine a patient’s blood oxygen content: “the oximeter”The absorption spectra (α) 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.
22Transducers-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 dyesAn optical system forFlorescence measurement
23Transducers-Optical methods- Florescence GratingAntigens modified by florophor dyeEvanescent-field.Planer waveguideExcitation lightFlorescencedetectorA device for florescence measurement
24Transducers-Optical methods- Florescence Taq-Man probe in its preliminary condition for real time PCR deviveReleasing fluorophore dyeduring extensionHybridisation of primer and Taq-Manprobe at annealing temperature
25Transducers-Optical methods- Florescence Real time Chamber PCR device with integrated fluorescence detectionPhotodiode implanted at the bottom of the chamber and CdS film covers the photodiodeOptical fibre used to introduce excitation energyTemperature sensor and heatersSiPyrexPhotodiode pattern to reduce direct illumination
27Transducers-Optical methods-refractive index The reflected wavelength (λB), called the Bragg wavelength, is defined by
28Optical waveguide based biosensor Transducers-Optical methods-refractive indexOptical waveguide based biosensor
29Transducers-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 electricalproperties of the solution which can be sensed out and used as measuring parameter
34Transducers-Electric methods Concept: Capture analyte and detect changes in electrical parameters of sampleImmunosensing at micro-sized Au electrodes based on the change of conductivity between the Au strips upon binding of Au nanoparticles
35Transducers-Electric methods Capacitive sensor byMIP dielectricVariation of
36Transducers-Electric methods F= 20KHz, AC amplitude of 40 mV peak to peak
37Transducers-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.
38Detection by cantilevers Transducers-Mass based methodsDetection by cantilevers
39Detection by cantilevers Transducers-Mass based methodsDetection by cantileversChange in the resonance frequency: AcV1 antibody (green) and baculovirus particles (red).
40Detection by cantilevers Transducers-Mass based methodsDetection 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
41Detection by cantilevers Transducers-Mass based methodsDetection by cantileversMicrocantilever technology: a) with immobilised protein for a specific bacterium b) bending after adsorption of bacteria to the protein
43Transducers-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
44Transducers-Temperature methods A three-dimensional schematic representation of the proposed microcalorimeter with integrated microfluidic channels.