The principle of Surface Plasmon Resonance imaging (SPRi)

Surface Plasmon Resonance (SPR) is an optical detection process that occurs when a polarized light hits a prism covered by a thin (gold) metal layer. Under certain conditions (wavelength, polarization and incidence angle) free electrons at the surface of the biochip absorb incident light photons and convert them into surface plasmon waves. A dip in reflectivity of the light is seen under these SPR conditions.

Perturbations at the gold surface of the biochip, such as an interaction between probe molecules immobilized on the chip and captured target molecules, induce a modification of resonance conditions which are in turn seen as a change in reflectivity and which can be measured. This is the basis for Surface Plasmon Resonance measurements.

The SPR imaging technology takes SPR analysis a step further. It is a sensitive label-free method of visualizing the whole of the biochip via a video CCD camera. This design enables the biochips to be prepared in an array format with each active site (spot) providing SPR information simultaneously.

With the SPRi range of equipment, SPR imaging is provided in a robust and sensitive manner. A broad-beam monochromatic polarized light from a laser diode (at a specific wavelength) illuminates the whole functionalized area of the SPRi-Biochip™ surface (which is mounted within the instrument detection chamber). The high resolution CCD video camera provides real-time difference images across the array format with up to 400 active spots. It captures all of the local changes at the surface of the biochip providing detailed information on molecular binding, biomolecular interactions and kinetic processes.

Click here to view the SPRi storyboard