Adsorption of IgG on/in a PAH/PSS multilayer film: Layer structure and cell response

The binding of immunogloblulins (IgG) (mouse monoclonal recognizing IFNγ) on precoated polystyrene or silica surfaces by the layer-by-layer technique has been investigated with QCM-D and DPI. The aim of the work was to increase the sensitivity of the conventional enzyme-linked immunosorbent spot (ELISpot) assay. The polyelectrolytes used to build the multilayers were poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) alternately adsorbed from 150 mM NaCl. The multilayer build up is linear and the internal structure of the PAH/PSS multilayer is compact and rigid as observed by low relative water content (20–25%) and high layer refractive index (n ∼ 1.5) after the formation of five bilayers. Incorporation of IgG within the PAH/PSS multilayer did not give rise to overcharging and did not affect the linear build up. ELISpot test on PAH/PSS multilayer modified polystyrene wells showed that the cytokine response was significantly smaller than on the regular PVDF backed polystyrene wells. This may be due to the compact and rigid nature of the PAH/PSS multilayer, which does not allow formation of the kind of three dimensional support needed to achieve bioactive IgG binding to the surface. Immunological tests of the polyelectrolyte multilayers in the absence of IgG showed that PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view.

Schematic drawing of the antigen secreting cells on antigen (IgG) coated polyelectrolyte multilayers and there cytokine response.Figure optionsDownload high-quality image (51 K)Download as PowerPoint slideResearch highlights
► LbL assembly of oppositely charged polyelectrolytes (PAH/PSS) with incorporated/adsorbed IgG.
► Aim is to increase the surface density of IgG and sensitivity of the conventional ELISpot assay.
► PAH/PSS multilayer structure is very compact with a low water content.
► Its rigid structure does not do them appropriate for forming a 3D antibody-binding support.
► The cytotoxicity of PAH terminated layers induced cytokine response whereas PSS terminated ones did not.