LSPR NANOSENSOR FOR THE QUANTIFICATION OF MULTIPLE ANTIGENS

J.C.FRAIRE ; R. D. MOTRICH ; E. A. CORONADO

El Chalten

Congreso; Discussions on Nano & Mesoscopic Optics; 2015

CIBION (CONICET)

In this work we report the design and develop of an ultrasensitive optical bionanosensor with a widespread capability for antigens detection, based on the strong interactions of the streptavidin (STV)-biotin system combined with the high specific biomolecular recognition of immunoglobulin (IgG). Ag nanospheres (NSs) were functionalized with the STV-biotin system using a NSs/STV/biotin 1:1:1 ratio. The biosensor consists of a controlled agglomeration (formation of Ag NSs dimers) in the presence of a biotinylated immunoglobulin G (Biot-IgG) acting as a linker between the functionalized NSs. The formation of these dimeric nanostructures (NSTs) is experimentally evidenced by a decrease in the intensity of the extinction spectra, as the extinction cross-section of dimers is lower than for monomers. The temporal variation of the extinction spectrum allows obtaining the agglomeration rate constant (kAglo) for the dimers formation. A concentration of Biot-IgG is chosen to guarantee to be in the regime where dimer formation is favored. In these conditions, when an antigen is added (analyte to be determined) increasing it concentration, an inhibition of the formation of dimeric NSTs is observed (decrease in the absolute value of kAglo). A spectral dependence of the kAglo with the antigen concentration was observed, which allows performing calibration curves and quantifying the specific antigen. This system can be applied to the detection of any antigen just by using the corresponding IgG-Biot. In this case two different antibodies where used to detect two different antigens (Interleukin 10 and Interferon g), reaching detection limits of 0.014 10-12 g/mL and 0.016 10-12 g/mL, respectively. In addition, studies in the presence of interfering molecules with very similar molecular structures and in biological fluids were carried out with excellent results, probing that these NSTs represent an ultrasensitive optical bionanosensor with high reproducibility, stability, sensibility and sensitivity.