Atomic force microscopy studies of solid lipid nanoparticles.
OBJECTIVE
Solid Lipid Nanoparticles (SLN) are an alternative carrier system for the controlled delivery of drugs. In most cases prednisolone loaded SLN show a biphasic release behaviour. The initial phase is characterised by a fast drug release, which is followed by a sustained drug release over several weeks.


METHODS
The particles are produced by high pressure homogenisation of a lipid (e.g. compritol, cholesterol) dispersed in an aqueous surfactant solution. In this study atomic force microscopy was used to image the original unaltered shape and surface properties of the particles. The crystallinity of the nanoparticles was investigated by differential scanning calorimetry.


RESULTS
The AFM investigations revealed the disc like shape of the particles. From differential scanning calorimetry data it can be concluded that the particle core is in the crystalline state. Additionally it was proven that the particles are surrounded by a soft layer.


CONCLUSIONS
Thus it is conceivable that the fast initial drug release during in vitro dissolution tests takes place by drug release of the outer noncrystalline layers of the particles. The following sustained drug release can be assigned to the predisolone release of the inner crystalline particle layers.
Department of Pharmaceutics, Biopharmaceutics and Biotechnology, Freie Universität Berlin, Germany.
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Niehus
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Mehnert
D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry; D008055:Lipids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force / Q000379:methods*; D010316:Particle Size; D011239:Prednisolone / Q000493:pharmacokinetics; D012825:Silicon / Q000737:chemistry
D004337:Drug Carriers; D005227:Fatty Acids; D008055:Lipids; C086409:glyceryl behenate; D002784:Cholesterol; D011239:Prednisolone; D012825:Silicon