Surface Plasmon Resonance

Surface Plasmon Resonance (SPR) studies

BioNano gold thin films are widely used in surface plasmon (SPR) resonance studies. SPR technology has become a leading technology in the field of real-time observation of biomolecular interactions.

Typical SPR measurement:
In a standard configuration, the BioNano gold glass slide is placed in contact with a prism using an index matching fluid. Polarized light is shined from the backside of the substrate. The reflected intensity is measured as a function of the angle, or at a fixed angle and as a function of time. The following picture is a drawing of the reflected intensity as a function of the angle.

Surface plasmon resonance is observed as a sharp dip in the reflected intensity. The angle at which the resonance is observed is dependent on the mass of material at the surface for a given optical setup. The SPR angle shifts when molecules bind to the surface and change the mass of the layer. Surface plasmons are surface electromagnetic waves that propagate along a metal - dielectric interface. These waves are sensitive to changes at this interface induced by the adsorption of molecules to the metal surface.
For the monitoring of a molecular interactions in real-time, the SPR signal is measured at a fixed angle close to the minimum of the dip and changes in the reflected intensity are observed as a function of time.

Examples of SPR applications:

• Surface plasmon resonance (SPR) technology is used in the drug discovery process by the pharmaceutical industry. In the case of a monitoring of a molecular interaction, a ligand, one binding partner is immobilized on the gold surface and an analyte, the other binding partner is injected over the surface to measure the binding interaction. To learn more, see R. L. Rich, and D. G. Myszka, Today Technologies, vol 1 n°3 (2004). For a review on optical biosensors in drug discovery see: M. A. Cooper, Nature Reviews 1 (2002), 515.
• Surface plasmon resonance (SPR) biosensors are becoming increasingly important in the food industry for application in safety and quality control. This technology is for instance used to test veterinary drug residues in foodstuffs and has been used to detect genetically modified organisms (GMOs). To learn more, see Journal of AOAC International, vol 89, issue 3 (2006). Atypon-link.com.
• SPR technology can also be used to monitor the thickness of adsorbed self-assembled films on the metal surface. For a review on surface plasmon resonance sensors, see J. Homola et al, Sensors and Actuators B 54 (1999) 3-15.

Digital Holographic Microscope (DHM) studies

BioNano gold thin films are used as substrates for various organic or inorganic species studied with a digital holographic microscope. For more information about the DHM

Teaching and Presentations

BioNano gold thin films are used for scanning probe microscopy (SPM) studies for educational purposes. The substrates can be advantageously used to study the growth of metals on glass, and to let students learn about atomic force microscopy.