Surface Plasmon Resonance Technology 

SPR Technology is a surface-sensitive analytical method for chemical and biochemical sensing that detects changes in the refractive index in the immediate vicinity of the surface layer of a sensor chip. SPR is observed as a sharp decrease in the reflected light from the surface at a resonance angle that is dependent on the mass and thickness of material at the surface. The SPR angle or wavelength shifts (I and II) when biomolecules bind to the surface and change the thickness of the surface layer. This change in resonant position can be monitored in real time as a plot of resonance signal (proportional to mass change) versus time.
SPR surface plasmon resonance spectral interrogation
II. SPR sensing. Spectral interrogation method.​
This method employs collimated white light beam and optimal for biodetection with larger sensing spot. It is used with open cuvette or petri dish for live cells or bacteria analysis. SPR device using spectral interrogation method can also be used for combined impedance and SPR detection of cell behavior.
I. SPR sensing. Angular interrogation method.
The most sensitive method of SPR detection. The sensing spot is less than 1mm2 and optimal for work in flow-injection setup and microfluidics.
SPR surface plasmon resonance angular interrogation

Applications

DNA hybridization sensor

SPR DNA hybridization sensor
The scheme of hybridization between the probe P2 immobilized on the sensor surface and the targets T2 (perfect match) and TN (single base mismatch).
Surface plasmon resonance DNA oligonucleotide biosensing response
 SPR response for hybridization between the surface-bound DNA capture probe P2 and the complementary DNA target T2 at various concentrations.

Electrochemical surface plasmon resonance sensing with absorptive redox mediator film

Electro chemical surface plasmon resonance sensor switch
Conformational change from the “ON” state to the “OFF” state: concentration of reduced and oxidized states of Methylene Blue label induce refractive index variation.
Surface Plasmon Switch biosensor
Spectral SPR curves at Methylene Blue (MB) resonance wavelength (SPR= max) for different MB concentrations (black = 0.1 mM, red = 1 mM, blue = 2 mM) and gold layer thickness(40, 50, 65 nm). The influence of gold film thickness on the SPR intensity response to variations in MB concentration is shown.
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