Non-surfactant nanospheres of progesterone inclusion complexes with amphiphilic beta-cyclodextrins

Amphiphilic beta-cyclodextrins were formulated as nanospheres and characterised by particle size, zeta potential and TEM following freeze-fracture. The nanospheres were loaded with progesterone with different loading techniques involving the spontaneous formation of nanospheres from pre-formed inclusion complexes of amphiphilic beta-cyclodextrins modified on the primary or secondary face with progesterone. Inclusion complexes were characterised with various techniques including Differential Scanning Calorimetry (DSC), Fast Atom Bombardment Mass Spectrometry (FAB MS) and 1H NMR spectroscopy; and progesterone was believed to be partially included in the CD cavity. Loading properties of conventionally-loaded nanospheres were compared with those prepared directly from pre-formed inclusion complexes and loading technique was found to enhance associated drug percentage significantly (P<0.05). Although both amphiphilic beta-cyclodextrins (6-N-CAPRO-beta-CD and beta-CDC6) were capable of high progesterone loading, beta-CDC6 displayed slightly higher entrapment efficiency due to the possible higher affinity of progesterone to the 14 alkyl chains surrounding this molecule resulting in higher drug adsorption to particle surface. Progesterone was released within a period of 1 h from all formulations. Progesterone-loaded amphiphilic beta-CD nanospheres were proved to be a promising non-surfactant injectable delivery system providing high-quantity of water-insoluble progesterone rapidly within 1 h.