Ricerc@Sapienza

The present proposal deals with the development of a novel optical platform for biosensing, which makes use of the random laser as optically active sensing tool combined with a highly sensitive avalanche photodetector based receiver. In a random laser the optical feedback is assured by diffusion rather than by the coupling with an optical cavity as in a conventional laser. For this reason its emission properties are extremely sensitive to small scale alterations in dimension, distribution and optical response of scatterers, providing a great opportunity to create a new kind of active optical sensors. As for the random laser, two different configurations will be considered, characterized by two different active elements. In one case the active element is constituted by a fluorophore solution properly excited and contained in a small hollow core glass bulge located at the end of an optical fiber. In the second case, the active element is represented by a rare-earth-doped optical fiber with a distal end dipped in the liquid sample. In both cases the photoreceiver continuously tracks both intensity and wavelength variations of the random laser. These two different configurations will be coupled to two different assay formats. Homogeneous bioassay with the interaction of the analyte with the biologic recognition element (BRE) in solution and heterogeneous bioassay with the analyte interacting with the BRE within a sensing layer will be the two different "bioconfiguration" coupled with two different random laser configurations and capable to tune the random laser emission. In this way changes in the lasing properties of random laser can be associated to the concentration of the analyte, which will be detected reaching very low limit of detection. In particular the new optical platform will be applied to the detection of Tau protein, the detection of which is becoming strategic in pathologies and dementias of the nervous system such as Alzheimer's and Parkinson's disease.