Recent studies on the delivery of hydrophilic drugs in nanoparticulate systems

Some approaches to enhance the entrapment efficiency within nanoparticulate systems, chiefly of hydrophilic molecules, developed mainly by the Turin University Pharmaceutical Technology group, are discussed. Several approaches have been developed: the first entails associating anticancer hydrophilic molecules to liposomes, developing lipophilic prodrugs of these molecules, and encapsulating them in liposomes. The transformation of hydrophilic drugs into lipophilic prodrugs can also overcome problems of poor entrapment efficiency and rapid release from polymer nanocarriers. Examples are nanospheres and nanocapsules produced from various PEGylated poly(alkylcyanoacrylate) copolymers. Strategies have also been developed to enhance hydrophilic drug entrapment in solid lipid nanoparticles (SLN). Hydrophobic ion pairing was designed to enable various antitumor drugs to be entrapped in SLN, produced by the coacervation method. Another technique comprises the covalent linkage of antitumoral or antiviral drugs to a squalenoyl-derived chain, affording bioconjugates that self-assemble as stable nanoparticles. A further development comprises mesoporous silica nanoparticles with immobilized hydrophilic antioxidants, for topical applications: they were complexed with hydrophilic antioxidants (Trolox® or rutin). Polymer-shelled and perfluoropentane-cored nanobubbles have also been designed, as versatile multifunctional carriers for the delivery of gases, drugs, and genes; the size range is below 500 nm, with shell thickness in the 30–50 nm range.

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