**Acknowledgements**

This work was supported by funds from Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale (2012CK5RPF\_004) and POR Campania FSE 2007–2013, Project CRÈME. The authors thank Dr. P. Dardano from IMM-CNR for AFM analysis and Prof. G. Scala and C. Palmieri from University "Magna Graecia" for providing Id-peptides.
