Extensive studies in the last fifty years on the development of multifunctional liposomes have improved their drug delivery potential. Specifically, they fulfill to a significant degree the requirements which an effective drug carrier should exhibit, i.e. biocompatibility, biodegradability, drug encapsulation and protection of the drug, targeting to specific cells, reasonable stability in the biological milieu, transport through cell membranes and controlled drug release. However, despite these properties which have been achieved to a significant degree through molecular engineering of the liposome bilayers, a universal liposomal carrier has not yet been developed since it is rather difficult for the above properties to be simultaneously fulfilled. For this purpose a multicompartmentalization strategy was applied through which liposomes encapsulating smaller ones in their aqueous core were prepared. Multicompartment systems have also been prepared by encapsulation of dendrimers in the aqueous core of liposomes. In this manner drug delivery systems were prepared providing a double protection to drugs encapsulated inside the core of the small liposomes or incorporated in dendrimers. The external liposomal bilayer is also susceptible to multifunctionalization while their drug release can more effectively been tuned compared to single-compartment systems. Modular-type strategies have been employed for the preparation of these multicompartment systems. Thus, unilamellar liposomes and mono-dispersed dendrimers are selected as the drug delivery modules from which universal multifunctional and multicompartment drug delivery systems have been obtained i.e. vesosomes, which are liposomes encapsulating smaller liposomes and dendrosomes, which are liposomes encapsulating dendrimers. Examples of the application of drug and gene delivery employing vesosomes and dendrosomes as carriers are critically discussed.
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