Concentration

How to determine biologically relevant concentrations with non-invasive and real-time MP-SPR measurement

Concentration analysis is an interaction measurement between immobilized ligand and analyte. Level of MP-SPR response (Refractive Index Units, RIU) depends on concentration of the analyte. It can be utilized to determine concentration of unknown sample. Known standard samples response is used as a reference.

Why to choose MP-SPR for concentration analysis?

There are multiple well-established methods, like ELISA, to determine concentration. However MP-SPR provides advantageous method for concentration analysis enabling not only end-point but also rate-based measurements. Label-free MP-SPR is beneficial especially for light absorbing samples. Since the light is not going through the sample, MP-SPR provides easy detection, high sensitivity and decreases the demand on molecule size compared to ELISA.

MP-SPR is able to distinguish bulk effect from real binding with unique PureKinetics feature. This enables high-quality results without the hinderance caused by variations in liquid composition. 

Example of concentration analysis: Cocaine detection from saliva samples

Cocaine_concentration.png

In this example, MP-SPR was used to detect cocaine concentration from saliva samples. 

Above: The sensor surface is modified to decrease non-specific binding from saliva using blocking molecules. A protein conjugate is immobilized on the surface to provide specific binding site for the analyte.

Right: Calibration curve and concentration response curves of three different samples are shown. The concentrations are 0.1 ng/ml, 1 ng/ml and 5 ng/ml of cocain in saliva.

 

Ref. Susanna Sonny, Adama M. Sesay, Vesa Virtanen Proc. SPIE 7376, 737605 (2010)