BME 210 Lecture 20 Biosensors - 20. Biosensors Biosensors...

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Unformatted text preview: 20. Biosensors Biosensors overview Biosensor a device incorporating a biological sensing element connected to a transducer which generates electrical signal The name comes from the nature of the sensing element, not from the nature of the analyte Biological sensing elements Proteins Antibodies Enzymes DNA probes Cells A biosensor typically has a high specificity for a certain compound in an analyte mixture Biosensor transducers Transducer transforms the signal resulting from the interaction of the analyte with the biological element into electrical signal that can be easily measured and quantified Transducer types: Electrical Electrochemical Mass-sensitive Optical: Light absorption Fluorescence Surface plasmon resonance this is emerging as one of the most versatile approaches for detection of biomolecules, toxins and microorganisms Surface Plasmon Resonance Surface plasmon resonance (SPR)- a universal method to detect and study protein-ligand interaction The method is based on measurements of changes of the refractive index caused by protein-ligand binding Changes of refractive index are detected via measurements of total internal reflection at a boundary between two materials Total Internal Reflection When light crosses a boundary between materials with different refractive indices , the light beam is partially refracted at the boundary, and partially reflected If the angle of incidence is greater than the critical angle c (the angle of incidence at which light is refracted such that it travels along the boundary) - then the light will stop crossing the boundary and instead be totally reflected back - this is total internal reflection (TIR) TIR can only occur where light travels from a medium with a higher refractive index to one with a lower refractive index (e.g., from glass to air, water to air) 1 2 Intensity of reflected light at the Glass-Air interface For light incident at any angle 1 > c , all light is reflected (100% of TIR) I refl /I inc 1 c 100% TIR 1 I refl I inc If the reflecting surface is coated with a layer of a metal (e.g., If the reflecting surface is coated with a layer of a metal (e....
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BME 210 Lecture 20 Biosensors - 20. Biosensors Biosensors...

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