The rapid development of biomedical technologies, particularly in the development of new diagnostic devices, has sparked the collaboration of experts from different fields such as biology, materials engineering, and physics. The most important challenge is to create innovative materials and improve biomedical sensors capable of detecting the presence or concentration of specific biological substances.

The possibility of applying poly(4-vinyl pyridine) layers cross-linked with transition metal complexes as active layers in biomedical sensors was tested. The successful modification of the P4VP coating with CuBr2 or ZnBr2 was verified using time of flight--secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The topography of the coatings was examined by using atomic force microscopy. Tests of the biological activity of coatings indicated strong protein adsorption, good biocompatibility, and no antimicrobial activity. The potential of the coatings to be used as active layers of biosensors was verified by systematic impedance-based measurements, which showed the sensitivity of the P4VP:CuBr2 coatings to the presence of proteins and cells in different concentrations and indicated different detection limits for the P4VP:ZnBr2 layers. The high selectivity of the coatings toward the defined analyte was confirmed by the specific antigen--antibody immunoreaction and the possibility of in situ monitoring of protein adsorption and cell adhesion for individual cells. Finally, the conductive response of a bilayer system that mimics an Organic Field Effect Transistor was shown. These results point to a great potential for both coatings to serve as active layers of sensitive and highly selective biosensors.