1. Contribution from the Bioindustry Park del Canavese, Via Ribes 5, I-10010 Colleretto Giacosa (TO), Italy, Istituto di Ricerca Cesare SeronoDrug Delivery Systems; Via Ribes 5, I-10010, Colleretto Giacosa (TO), Italy, and Department of Chemistry I.F.M., University of Turin, Via P. Giuria 7, I-10125 Turin, Italy