1. Department of Biomedical Sciences, Section of Microbiology and Virology, University of Cagliari, 09042 Cagliari, Italy
2. Department of Chemical and Geological Sciences, University of Cagliari, 09042 Cagliari, Italy
3. Research Unit of the National Consortium of Materials Science and Technology (INSTM), University of Cagliari, 09042 Cagliari, Italy