The present invention relates to an optical biosensor comprising a porous matrix. In the specific case, reference is made to anodized porous alumina, on the surface of which the biological component specific for the analyte in question is immobilized, and to an optical-signal detector connected to said matrix. The present patent further relates to a biosensor having the porous matrix and the optical detector integrated in a single structure, in particular to biosensors with porous matrix other than porous alumina, for example porous silicon.