Thermodynamic and structural characterization of Liposomal-Locked in-Dendrimers as drug carriers

A new Liposomal-Locked in-Dendrimer (LLD) formed by DPPC–DPPG and PAMAM 3.5 incorporating the anticancer drug DOX was studied by means of spectroscopic and DSC investigations. Multilamellar Lipid Bilayers were also considered for the sake of comparison. The results were in line with a picture of phase separation between DPPC–DPPG lipids and dendrimer that promotes the stability of the liposome membrane and the cooperativity of the relevant gel-to-liquid-crystal transition, which is enhanced in the presence of the dendrimer and the drug. As a result, the inner core of the liposome contained large amounts of dendrimer–DOX complex and was protected by a very stable membrane. This view was given a more general validation through investigations performed with other types of dendrimers, namely PG1 and PG2. The thermodynamic interpretation of the DSC data allowed a better understanding of the physico-chemical factors that justify this behaviour that makes these LLDs very promising as a new class of Modulatory Liposomal Controlled Release System (MLCRS) that could lead to drug formulations with higher safety and efficacy profiles.