Atomic force microscopy as a quantitative technique: correlation between network model approach and experimental study

Atomic force microscopy (AFM) has been used for imaging and the quantification of immunological reactions. Mouse monoclonal anti-ferritin immunoglobulins (IgG) were adsorbed onto silane-modified and well-characterized silicon wafers. The IgG adsorbed amount was quantified by radio immunoassay (RIA) using I-125-labeled anti-ferritin antibodies, and the adsorption isotherm was found to follow a Langmuir model. The immunological reaction was then detected by AFM, either using gold labeled polyclonal anti-mouse, or by direct detection of the antigen. A mathematical model based on the network model approach was proposed in order to quantify the immunological reaction. This model was based on the relationship between the roughness induced by the immunological reaction and the number of gold particles or ferritin molecules. The proposed model was found to be well correlated with experimental data for the investigated size of gold particles. The homogeneity of the immunological reaction on the sensitized surface was demonstrated by the investigation of the specifically immobilized distribution of particles on the surface. (C) 1998 Elsevier Science B.V. All rights reserved.