Presentation on theme: "R. Almog Biosensors ביו-חיישנים – עקרונות ויישומים מרפואה ביתית ועד לניטור סביבתי Dr. Ronen Almog מכון טכנולוגי חולון."— Presentation transcript:
R. Almog Biosensors ביו-חיישנים – עקרונות ויישומים מרפואה ביתית ועד לניטור סביבתי Dr. Ronen Almog מכון טכנולוגי חולון
R. Almog Biosensors Detection principles: Electrochemical Optical Mechanical Lab on a chip/BioMEMS Examples: Diabetes - glucose monitoring Water toxicity detection Outline
R. Almog Elements of a biosensor
R. Almog An integrated device consisting of a biological recognition element and a transducer capable of detecting specific biological/chemical compound and converting it into an electronic signal. Biosensor definition
R. Almog Biosensors applications and importance Medical/health monitors Homeland security Pharmaceutical industry Food industry Simplicity Selectivity Sensitivity Miniaturization Rapid Biosensors Features
R. Almog Enzymes and their substrates Antibodies and their antigens Nucleic acids and their complementary sequences Whole cell Biological recognition elements A - T G - C
R. Almog On Size and Scale
R. Almog Enzymes Large protein molecules. Catalyze chemical reactions. Used as tools to perform various biochemical reactions in the cell. Participates actively in the transformation of chemical A (the substrate) to chemical B (the product) but remains unchanged at the end of the reaction.
R. Almog Immunosensors: Antibody – Antigen recognition Antibody - proteins, produced by the immune system of higher animals in response to the entry of foreign materials into the body, eg. viruses, bacteria Bind tightly to the foreign material (the antigen) that provoked the response and mark it for attack by other elements of the immune system. Antibodies are also very specific- they need to be, in recognizing and binding to the foreign substance only and not to materials native to the organism. This will change some physicochemical parameter (usually mass or an optical parameter) of the environment at the transducer surface of the sensor and that change is subsequently detected. If an antigen is present in that medium, it will be bound by the antibody to form a larger, antigen-antibody complex.
R. Almog Antibody structure
R. Almog 1. Electrochemical-Amperometric : Measures currents generated when electrons are exchanged between a biological system (in solution) and an electrode in a constant potential. 4. Conductometric/Impedimetric : detect changes in conductivity/impedance between two electrodes. The transducer Chemical changePhysical change 2. Optical detection - refractive index change or fluorescence 3. Mechanical detection The most common are: The key part of a biosensor is the transducer which makes use of a physical change accompanying the reaction.
R. Almog Transducers - sensing methods in biosensors
R. Almog MEMS - MicroElectroMechanichal sensors Use: Bioassay of prostate-specific antigen (PSA)
R. Almog Optical sensors - Biacore example
R. Almog Reasons for Miniaturization
R. Almog Biochips Microelectronic-inspired devices that are used for delivery, processing, analysis, or detection of biological molecules and species. These devices are used to detect cells, microorganisms, viruses, proteins, DNA and related nucleic acids, and small molecules of biochemical importance and interest. BioMEMS Biomedical or biological applications of MEMS (micro electro mechanical systems)
Lab-on-a-chip Burns et al. Science 282, 484, 1998
R. Almog BioChip/BioMEMS Materials Silicon Glass, Quartz Polymers – Poly (dimethylsiloxane) (PDMS) – Poly (methyl methacrylate) (PMMA) – Teflon, etc. Considerations Biocompatibility, ideal for biomedical devices Transparent within the visible spectrum Rapid fabrication Photo-definable Chemically modifiable
R. Almog Biochip - microfluidics Key Attributes of Biochips 1. Small length scale 2. Small thermal mass 3. Laminar flow 4. High surface-to-volume ratio
R. Almog The Oxygen electrode Clarks Glucose electrode
R. Almog Biosensors History
R. Almog Technology evolution 6 analyses from a drop of blood in about one minute.
R. Almog Diabetes - Glucose Biosensor The user carries a wallet sized case that contains the testing equipment A lancet pierces the skin on the finger The user places this blood sample on a test strip and inserts it into the reader Electrochemical detection
R. Almog Alcohol Test – Drager Alcotest 7110 הינשוף / The Alcotest 7110 Standard is a highly developed measuring instrument for precise determination of breath alcohol concentration. Two different and independent measuring systems: Infrared spectroscopy – λ=9.5µm Electrochemical measurement
R. Almog Example - insect MEMS hybrid The University of California, Berkeley IEEE MEMS, January 2009 A radio-controlled beetle 1.3 g electronic module Max weight: 3 g 6 electrodes affixed to the brain and muscles
R. Almog Example: Toxichip
R. Almog Water toxicity detection - motivation 1. Homeland security THE THREAT: Intentional poisoning of a drinking water source 2. Enviromental pollution THE NEED: A rapid early toxicity warning device 3. Pharmaceutical screening applications
R. Almog Toxicity detection systems Standard toxicity bioassays, mostly designed for environmental purposes, are unsuitable for our needs: size, response time. Toxicity bioassays The only question need to be asked is Is the sample toxic?
R. Almog The goal To develop a portable system that can detect the presence of unknown acute toxicity chemicals in drinking water within 20 minutes.
R. Almog Whole-cell biosensor: The biological material is an intact, living, functioning cell. Toxichip whole cell biosensors: Bacterial cells Genetically modified Bioluminescent Tailored to respond to different cell stress factors Three elements in the solution 3. Analyzer: a small mobile instrument into which the chip will be inserted, and which will provide the reading. 1. Reporter cells: live cells tailored to detect toxicity. We use Escherichia coli (E. coli) bacteria as a whole cell sensor. 2. Biochips: disposable, credit card size, containing the cells. E. Coli bacteria
R. Almog Biochip array E. Coli bacteria
R. Almog Bioluminescence The emission of light by a living organism as the result of a chemical reaction. Chemical energy is converted to light energy. Marine organisms Insects Fungee Bacteria Emission spectrum: Visible - blue-green ( nm)
R. Almog The one that drives or catalyzes the reaction is called a "luciferase." Each organism has its own luciferin and luciferase compounds. Bioluminescence At least two chemicals are required: The one which produces the light is generically called a "luciferin. Luciferin (substrate) Luciferase (enzyme) + Product: Oxyluciferin + light +O2O2
R. Almog Bacteria engineering for toxins detection Two types of biochemical response to toxins : Type I Type II Normally doesnt emit light. Toxin exposure induces light emission. Sensitive to low concentration of toxins with a dose-dependent signal. Constitutive test Normally emits light. In the presence of a toxin, the signal intensity decreases. Respond to high concentration of toxins
R. Almog Sensing element: A promoter of a gene involved in the response to the desired target. Type I - bacteria engineering for toxins detection The fusion of two genetic elements inside a host E. coli bacteria: Reporting element: A Bioluminescent gene. – generates the Luciferin and Luciferase when experssed
R. Almog Toxins list
R. Almog Bacteria response to mitomycin C - chemotherapeutic agent Example - cell bioluminescence response
R. Almog Effect of toxin concentration:
R. Almog Measurement of the bacterial bioluminescence response to different NA concentrations under static condition (no flow). Here the bacteria were suspended in LB. We use Nalidixic Acid (NA ) as the model toxin
R. Almog PDMS Biochip Elastomer, Simple, fast, modular, cheap, reproducible, disposable Microfluidics interface system for the PDMS biochip Inlet Outlet Glass cover PMMA base 10mm PDMS PMMA Glass Inlet OutletSPADs Stainless steel Bacteria immobilized in Agar Single Photon Avalanche photoDiode
R. Almog The biochip layout: 4 main channels: sample, positive, negative and constitutive. The constitutive channel consists of Normally On bacteria. The sample, positive and negative channels consist of four different bacteria strains immobilized in agar. 4 strains