Incorporation of the model drug ubidecarenone into solid lipid nanoparticles

Purpose. The impact of drug incorporation on melt-homogenized tripalmitin n anoparticles is investigated with ubidecarenone as a model drug. The disper sions are studied with respect to their drug loading capacity, localization and physical state of the drug as well as to potential changes of the nano particle properties due to interactions between drug and triglyceride matri x. Methods. The investigations were carried out using photon correlation spect roscopy, differential scanning calorimetry, synchrotron radiation X-ray dif fraction, ultracentrifugation, and cryo- and freeze-fracture transmission e lectron microscopy. Results. Ubidecarenone can be incorporated into the dispersions in concentr ations higher than 50% of the dispersed phase. The drug is associated with the nanoparticles such that small drug amounts are bound tightly to the car rier matrix while excess drug adheres as a liquid phase to the crystalline particles. Drug incorporation lowers the crystallization and melting temper ature of the particle matrix and accelerates the transition of the triglyce ride into the stable beta -polymorph after crystallization. Conclusions. Drug incorporation may significantly alter important physicoch emical parameters of solid lipid nanoparticles. Slow release of ubidecareno ne may only be possible for the fraction of drug which is tightly bound to the matrix while the liquid fraction should be rapidly released.