Oriented immobilization of antibodies and their fragments on modified silicon for the production of nanosensors

Different methods for the covalent immobilization of specific antibodies and their fragments on a silicon surface with the subsequent formation of immune complexes that consist of an immobilized monoclonal antibody, an antigen molecule, and a molecule of a second monoclonal antibody labeled with gold nanoparticles have been studied. Prostate-specific antigen (PSA), which is a molecular biomarker for prostate cancer, was used as an antigen. A covalent conjugate of the fragments of PSA-specific antibodies with gold nanoparticles has been obtained using the thiol groups of the antibodies. Scanning electron microscopy (SEM) was used for the registration of immune complexes on the surface. The high resolution of the method made it possible to detect individual immune complexes by the presence of gold nanoparticles and to calculate their number. A new method for the chemical modification of silicon by 3-aminopropyltrimetoxysilane (APTMS) and a bifunctional reagent 1,4-phenylene diisothiocyanate (PDITC) has been developed. This method provides a uniform distribution of antigen-binding centers and their availability for the formation of immune complexes. The developed immobilization method is promising for the formation of a biospecific biosensor layer based on silicon nanowires.