biosensors lecture 14

Surface Plasmon Resonance

what is SPR

a real-time, label-free measurement of binding kinetics and affinity

what is the operating principle of SPR

collimated light beam undergoes total internal reflection at a glass/thin metal/ dielectric interface

two important regions of the SPR binding graph

increasing signal: absorption (association) kinetic

decreasing signal: desorption (disassociation) kinetic

4 types of signal modulation for SPR

1. angular

2. wavelength

3. amplitude

4. phase

angular modulation

• the metallic film surface is irradiated with monochromatic light and scanned for a certain range angle

two modes of angular modulation

1. rotating light source

2. rotating prism with a light source with a fixed angle

wavelength modulation

fixed angle of the incident light at a certain value and modulating the wavelength of the light source

amplitude modulation

• at a fixed incidence angle and wavelength, RI variation is measured by the intensity change

• the drawback of this approach is given by the low sensitivity and resolution because the output noise and resolution increase with the noise generated by the light source

phase modulation

• RI change of the medium causes the phase change of the light source

• the sensitivity of the phase to RI variations is at least at 10 times larger than the sensitivity of amplitude

• phase noises are orders of magnitude lower compared to amplitude ones, providing a better signal-to-noise ratio

Advantages of SPR

• label free detection

• ability to perform real-time measurement

• exceptional sensitivity

• small quantities of purified reagents are required

SPRi

• imaging technique for surface plasmon resonance sensor for array detection (multiplexability)

• high throughput

• amplitude modulation is used (less sensitive)