The development of nanotechnology pushes the limits of biomedicine in regions where the size of solid state based devices and biomolecules are in the same range of magnitude. The integration of bionanodevices in the molecular diagnostic field leads towards improvements in our life quality by assuring fast and cheap diagnosis devices. Low cost production hand-held biochips are foreseen to be incorporated in the next generation of bionanodevices. Among them, tunneling magnetoresistive (TMR) biosensors are of great interest and their improvements constitute the subject of the present thesis.