Plasmonics Biosensors

Surface Plasmon Resonance Biosensors

Surface Plasmon Resonance (SPR) is a one of the most powerful biosensing techniques to evaluate biomolecular interactions in real-time and in a label-free scheme. We have developed several custom-designed SPR platforms, including standard SPR sensors based on Krestchman configuration, a magneto-optical SPR, a cantiplasmon (combining SPR & cantilever technology), a lambda-modulated SPR and a multiplex-SPR.

All our platforms are potable and of low weight, allowing the use of the SPR sensor outside the laboratory. Currently, seven platforms are fully operative. Our technology was spin-out in 2004 to the company SENSIA, SL.

Improving sensitivity in SPR by novel plasmonic techniques

For diverse applications, the development of new plasmonic biosensor devices able to surpass the limit-of-detection of the conventional Surface Plasmon Resonance (SPR) biosensor is an essential concern. There are, mainly, two different strategies to increase the sensitivity of the SPR biosensor: (i) the enhancement of the extraordinary properties of the surface plasmon, such as the intensity of the electromagnetic field or its propagation and penetration lengths (as in nanoplasmonics); and (ii) the development of novel plasmonic techniques, as modulated-SPR biosensors.

 

We have been working in the improvement of the sensitivity by modulating the surface Plasmon working principle through two novel ideas:

 

  • MOSPR: Magneto-Optical Surface Plasmon Resonance sensor, which arises from the combination of the Surface Plasmon Resonance in thin metallic layers and the magneto-optic (MO) activity of ferromagnetic metallic materials. Such combination generates a large enhancement of the MO effects closely localized at the surface plasmon resonance.

Figure. (a) Basic principle of the MP effect. (b) SPR and MP angular resonance response of a MP multilayer structure in prism-coupling configuration. (c) Operating principle of the MOSPR biosensor: sensing response ΔS generated in a MOSPR sensor by a refractive index change (Δnd) of the dielectric medium, nd.

 

  • LMSPR: Wavelength Modulated Surface Plasmon Resonance biosensor (lMSPR), based on the strong dependence of the dielectric constant of the metals (gold in the case of plasmonic transducers) with the incident wavelength. Thanks to this dependence, it is possible to modulate the SP wavevector (kspp) and to use this modulation as a sensing variable. A main advantage is that lMSPR can use the same gold chip than SPR allowing the employment of the standard SPR biofunctionalization protocols.

Figure. (left) Schematic view of the lMSPR biosensor set-up. (right) Comparative between the angular detection curve for the same plasmonic transducer (50nmAu/2nmTi/glass) in the SPR and the lMSPR biosensor