Registration of immunoglobuline AB/AG reaction with planar polarisation interferometer

Immobilisation of human immunoglobuline (IgG) (AG) and goat on human IgG antibodies (AB) as well as AB/AG specific reaction were studied with planar polarisation interferometery (PPI). In this novel method, polarised laser beam was coupled into the planar waveguide made on silicon wafer and consisted of 20nm Si3N4 layer sandwiched between two 1.5 mum SiO2 layers with the sensing window etched in the toy SiO2 layer. One of the immune components (AG or AB) was deposited by means of polyelectrolyte self-assembly on top of the Si3N3 layer within the sensing window. P-component of the polarised light is sensitive to adsorption, while s- component serves as a reference. Thus the outcoming light intensity depends on the phase shift between s- and p- components. Different sequences of immobilisation of the immune components were studied with both surface plasmon resonance (SPR) and PPI methods. It was shown that predeposition of a monolayer of protein A (from Staphylococcus Aureus), which is believed to affect the orientation of the immune components, causes an additional increase in the sensitivity. PPI method allowed us to improve substantially the sensitivity towards AB/AG reaction as compared to traditional SPR method. Particularly, of specific binding of 3ng/ml AG was registered.