Polyaniline is an electroactive polymer, which presents attractive properties for its use as a transducer in electro-biosensors. Covalent binding of bioreceptors on the polymeric surface is necessary to perform selective and efficient bioanalyte detection. To achieve this goal, acrylic acid (AAc) is grafted on polyaniline films. Acrylic grafting on polyaniline introduces a new access to its biochemical functionalization. Carboxylic groups can be used for covalent immobilization of proteins, like ICHA antigen, by means of standard coupling agents (carbodiimide and succinimide). Surface analysis shows that there is a higher amount of antigen immobilized on the surface as compared with simple physical adsorption. The composition and structure of the modified surfaces are characterized by X-ray photoelectron spectroscopy (XPS) at each step of the process. Time-of-flight-secondary ion mass spectrometry (Tof-SIMS) is also used to analyze acrylic grafted polyaniline surfaces.