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Bone morphogenetic protein 2 (BMP-2) has a high tendency to aggregate at physiological pH and physiological ionic strength, which can complicate the development of growth factor delivery systems. The aggregation behavior in differently concentrated BMP-2 solutions was investigated using dynamic and static light scattering. It was found that at higher concentrations larger aggregates are formed, whose size decreases again with increasing dilution. A solubilizing effect and therefore less aggregation was observed upon the addition of albumin. Imaged capillary isoelectric focusing and the simulation of the surface charges of BMP-2 were used to find a possible explanation for the unusually low solubility of BMP-2 at physiological pH. In addition to hydrophobic interactions, attractive electrostatic interactions might be decisive in the aggregation of BMP-2 due to the particular distribution of surface charges. These results help to better understand the solubility behavior of BMP-2 and thus support future pharmaceutical research and the development of new strategies for the augmentation of bone healing.

Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted completely (lipid recoveries were close to 100%) but there was a loss of incorporated drugs during separation with a strong dependence on the octanol-water partition coefficient of the drug. Whereas corticosterone (partition coefficient ~2) was washed out more or less completely (recovery about 2%), loss of temoporfin (partition coefficient ~9) was only minor (recovery about 80%). All fractionations were well repeatable under the experimental conditions applied in the present study.

Viele neue pharmazeutische Wirkstoffe sind schlecht wasserlöslich. Lipidnanopartikel (LNP) stellen ein vielversprechendes Trägersystem für diese Wirkstoffe dar und können aufgrund ihrer geringen Teilchengröße direkt in die Blutbahn appliziert werden. Um die Einsatzmöglichkeiten dieser Trägersysteme bewerten zu können, sind Kenntnisse über ihr Wirkstofffreisetzungsverhalten wichtig. Die verwendeten Akzeptormedien sollten lipophile Kompartimente enthalten, um die physiologischen Bedingungen möglichst genau darzustellen. Allerdings erschwert die geringe Größe der Trägerpartikel die Trennung von Donor- und Akzeptorsystem in Freisetzungsuntersuchungen unter realitätsnahen Bedingungen erheblich, da sie im selben Größenbereich wie die lipophilen Akzeptorpartikel liegt. Diese Arbeit beschreibt die Entwicklung einer neuen Methode zur Bestimmung der Freisetzungs-eigenschaften von echten Wirkstoffen aus LNP unter realitätsnahen Bedingungen, ohne vorherige Trennung von Donor- und Akzeptorpartikel. Die Methode basiert auf der Messung der Kristallisationstemperatur (TKrist) von Trimyristin(TM)-Nanopartikeln mittels DSC. Die TKrist der LNP sinkt proportional mit der Menge an eingeschlossenem Arzneistoff und erhöht sich mit Wirkstofffreisetzung. TM-Nanoemulsionen, die mit den schwer wasserlöslichen Wirkstoffen Fenofibrat, Orlistat, Tocopherolacetat und Ubidecarenon beladen waren, wurden in drei Akzeptormedien mit steigender Annäherung an physiologische Bedingungen untersucht: in einer Rapsöl-Nanoemulsion, in Schweineserum und Schweineblut. Die Ergebnisse zeigten eine Korrelation der Freisetzungseigenschaften mit der Lipophilie der Wirkstoffe: je höher der logP-Wert, desto langsamer war die Freisetzung. Eine erhöhte Freisetzung in einer Rapsöl-Nanoemulsion im Vergleich zu Serum und Blut deutete darauf hin, dass das Ausmaß der Freisetzung von einem Verteilungsgleichgewicht bestimmt wurde. Bei der Methodenentwicklung wurde beobachtet, dass die Verdünnung von Poloxamer 188-stabilisierten TM-Nanoemulsionen mit Wasser zu einem Anstieg der TKrist führte, während sie bei anderen Emulgatoren wie Tyloxapol, Poloxamer 407, Saccharoselaurat und einer Lecithin/Glycocholat-Kombination unverändert blieb. Es wurde eine Veränderung der Partikelzusammensetzung und der Grenzflächenbelegung mit dem Emulgator vermutet und weitergehende Untersuchungen wiesen auf eine Abhängigkeit der TKrist von der Poloxamer 188-Konzentration an der Partikelgrenzfläche hin., Lipid nanoparticles are an interesting parenteral delivery system for poorly water-soluble drugs. In order to approach physiological conditions when conducting release studies from such systems, the release media should contain lipophilic acceptor compartments. In practice, drug release studies under such close to physiological conditions may be complicated by the small size of lipid nanoparticles, which is in the same range as that of the acceptor particles. This work describes a novel method for drug release measurements which works without separation of donor and acceptor particles. The technique is based on measuring the crystallization temperature (Tcryst) of poloxamer (pol) 188 -stabilized trimyristin (tm) nanoparticles by DSC. The Tcryst of the nanoparticles decreases proportionally with the amount of drug incorporated and thus increases as a result of drug release. Liquid tm-nanoparticles loaded with fenofibrate, orlistat, tocopherol acetate and ubidecarenone were studied in three release media with increasing comparability to physiological conditions: a rapeseed oil nanoemulsion, porcine serum and porcine blood. Using the new method, a correlation between release behavior and drug lipophilicity was observed: the higher the logP value of the drug, the slower the release. The extent of drug release was influenced by partition equilibrium as indicated by increased drug release in the rapeseed oil nanoemulsion compared to porcine serum and blood. Based on the method developed in this thesis, it is possible to investigate slow transfer processes from lipid emulsion systems. However, the applicability of this method is limited to supercooled tm donor nanoparticles and similar systems. During method development, it was observed that dilution of pol 188-stabilized tm nanoemulsions with water caused an increase in Tcryst while it remained the same with other emulsifiers like tyloxapol, pol 407, sucrose laurate and a lecithin/sodium glycocholate combination. Pol 188 was the only emulsifier used in a concentration below the critical micelle concentration (cmc). Presumably, the monomers were driven out of the nanoparticle interface to reach a new equilibrium after dilution with water. In contrast, when diluted with a solution of the same pol 188 concentration, monomers from the interface were no longer needed and no change in Tcryst was observed. Furthermore, it was shown that the pol 188 content of the system correlated with the Tcryst of tm nanoparticles.