Development of a platform for biochemical sensing based on overlayered long period gratings working in transition

In this work, we present preliminary results concerning the development of a platform for label-free biochemical sensing, based on overlayered Long Period Gratings (LPGs) working in transition mode. Nano-scale layers of Polystyrene (PS) with different thicknesses were deposited onto the same LPG to test the performances of the device in different operating points of its sensitivity characteristic, drastically modified by the modal transition phenomenon. The physical adsorption dynamic of Biotinylated Bovine Serum Albumin (BBSA) onto the PS surface and the subsequent binding of Streptavidin (SA) on the BBSA layer were recorded by monitoring the variation of LPG transmission dips spectral position. Experimental results demonstrated overlayered LPGs to be among the most sensitive transducers that can be employed in biosensing. Moreover wide margins of further optimization exist.