1. Department of Mechanics, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy, Department of Clinical and Experimental Medicine, University of Eastern Piedmont, Via Solaroli 17, 28100 Novara, Italy, and Laboratory of Water-Soluble Polymers, Polyelectrolytes and Biopolymers, Faculty of Chemistry, University of Sofia, James Bourchier Blvd 1, 1164 Sofia, Bulgaria