Bioactive surfaces for antibody-antigen complex detection by atomic force microscopy

Recently there has been a great develop of new antibodies immobilization procedures, that keep antibodies to retain their orientation and functionality after the binding to a solid support. This allows the formation of immune-complexes useful for the detection of biomarkers from biological samples. We have developed a new method of functionalization for solid substrates that involves an initial surface activation, then a functionalization by means of 3-aminopropyltriethoxysilane-followed by another functionalization step with a layer of very small peptides, which have a high affinity to the Antibody Fc portion, acting as antibody linkers. These antibody binding peptides can immobilize the antibodies with a proper configuration that allows an unambiguous detection of antibody-antigen complexes by means of atomic force microscopy (AFM). The AFM can act as a powerful label free detection technique, which allows to detect, in principle, single molecule interactions, with the only limitation to use substrate with low-roughness surfaces; in this case, the roughness can be interpreted as background noise in the AFM analysis. Moreover, our functionalization method can be used to obtain bioactive surfaces on a wide range of solid supports, making them capable to suitably immobilize the antibodies for the antigenic binding.