Optical Immunosensor Based on Nanostructured ZnO Thin Films for Agricultural Purposes

― Optical, structural and adsorptional properties of ZnO nanostructured thin films have been studied for the development of highly sensitive optical immunosensor. Photoluminescent properties of ZnO thin films, deposited by atomic layer deposition (ALD) on the silicon substrates were applied for determination of Grapevine virus A-type proteins (GVA-antigens). The immobilization of anti-GVA antibodies on the surface of ZnO films resulted in the increase of photoluminescence intensity of NBE peak of ZnO and appearance of new photoluminescence band in the region of 400–550 nm. The GVA-antigen detection was performed by the evaluation of changes and behavior of a photoluminescence band around 425 nm appeared after immobilization of GVA antibodies on the surface of ZnO thin films. The sensitivity of the obtained label-free biosensor towards GVA-antigens was in the range from 1 pg/ml to 10 ng/ml. The possibility to detect GVA-antigens without additional labels (e.g enzymes or fluorescent dyes) has been demonstrated. Some aspects of the mechanism of interaction between ZnO and $\mathrm{TiO}_{2}$ nanostructures and proteins are discussed.