Liposomes loaded with a dirhenium compound and cisplatin: Preparation, properties and improved in vivo anticancer activity

Liposomes loaded with the rhenium compound (bis-dimethylsulfoxido-cis-tetrachlorodi-μ-pivalatodirhenium(III) (cis-Re₂((CH₃)₃CCOO)₂Cl₄·2DMSO, I) and cisplatin in the molar ratio of 4:1 as well as those loaded only with I were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, dynamic light scattering and electronic absorption spectroscopy. The relative stability of liposomes loaded with I is reflected by a minimal change in the electronic absorption spectra over a period of 8 days whereas the stability of those loaded with both drugs is lower, which we ascribe to the formation of new Re-Pt species inside the liposomes. Furthermore, the investigations of the co-encapsulation effects on the anticancer activity of the Re-Pt system were undertaken. Importantly, the coencapsulated liposomes exhibit synergistic or additive anticancer activities in vivo, e.g. introduction of these liposomes into tumor-bearing rats demonstrated their antianemic, nephro- and hepato-protecting effects. These liposomes, which are active in cancer treatment, protect the dirhenium compounds from hydrolysis and preserve the biological properties of the Re-Pt hybrid . This study reveals the importance of combined therapy in nanotechnology and medicine.