Investigations on the transfer of lipophilic drug models from lipid nanoparticles to lipophilic acceptor compartments using different techniques
To better mimic the environment encountered by the drug after administration, many lipophilic compartments were used to which the transfer of different drug models was measured. The detection of the substances transferred from lipid nanoparticles into the different lipophilic compartments was performed using three techniques: centrifugation, ion exchange and flow cytometry. Different lipid donor nanoparticles were prepared using trimyristin as matrix lipids. Ultracentrifugation was carried out to separate the nanoparticles from the excess phospholipid used as emulsifier. The nanoparticles were loaded with porphyrin, Nile red and DiI. Different lipophilic acceptors were used such as vesicles and o/w emulsion. Monoolein dispersions were introduced as new lipophilic acceptors. The transfer of porphyrin was moderate to the acceptor MLV and rapid to the acceptor unilamellar vesicles. With monoolein dispersions and emulsions, the transfer was very rapid. The transfer of Nile red, which is less lipophilic than porphyrin, was very rapid to all different acceptors. The transfer of DiI to the acceptor monoolein cubic particles was slower than that of porphyrin. The transfer rate constant derived from the centrifugation and ion exchange column technique was higher than that obtained from the flow cytometric technique. In conclusion, this study shows that the transfer depends on several factors such as the physical state of the nanoparticles, particle size of the acceptors, molar ratio between the donor and acceptor, the type of the lipid that is used in the preparation of the acceptors, the total lipid concentration in the transfer mixture and the lipophilicity of the drug model. All three techniques studied are suitable to investigate the transfer of DiI while the flow cytometric technique is the best one to measure the very rapid transfer. Finally, monoolein dispersions are very useful as acceptor particles for transfer studies with lipophilic drugs.