Abstract: Analytical immunosensor device and method for obtaining thereof based on sequential deposition of self-assembled monolayers of polymers and affinity elements and their uses for the detection and quantitation of any analyte or target antigen in a liquid sample, allowing to perform the analysis by quasi-reagentless or reagentless displacement assay, and minimizing nonspecific adsorption and thus decreasing the detection limit. The device is arranged from a sensor surface covered with polymer monolayers (redox or non-redox) on top of which submonolayers of affinity elements are deposited and then, to let the affinity reaction to take place with the antigen, pseudo-antigen or the hapten labelled with a protein, preferably an enzyme (redox or non-redox), or with a nanoparticle enabling the method of the invention to develop “ad hoc” immunosensors, with a signal transduction by electrochemical, optical and/or piezoelectric means.