Preparation and characterisation of liposomes encapsulating ketoprofen–cyclodextrin complexes for transdermal drug delivery

Multilamellar vesicle (MLV) liposomes containing ketoprofen–cyclodextrin complexes intended for drug topical delivery were prepared,with the aim of simultaneously exploiting the favourable properties of both carriers. Drug complexes with _-cyclodextrin (_Cyd) and hydroxypropyl-_Cyd (HP_Cyd),prepared by coevaporation and sealed-heating methods,were characterised by differential scanning calorimetry,hot stage microscopy,scanning electron microscopy and tested for dissolution properties. The coevaporated system with HP_Cydwas the most effective,enabling an about 11-fold increase in drug dissolution. Drug and drug-Cyd systems were incorporated inMLVliposomes prepared by the thin layer evaporation technique. All liposomal formulations were characterised for encapsulation efficiency,particle size and morphology,using dialysis,light scattering and transmission electron microscopy techniques,respectively. MLV formation was negatively influenced by the presence of Cyd; nevertheless,it was possible to prepare stable MLVs containing ketoprofen-Cyd complexes. The presence of the Cyd complex affected MLV dimensions but not their lamellar structure. The complex with HP_Cyd,in virtue of its greater stability than the _Cyd one,allowed higher percentages of encapsulation and gave rise to more stable MLV systems. Permeability studies of drug and drug-Cyd complexes,as such or incorporated in liposomes,performed both across artificial membranes and rat skin,highlighted a favourable effect of Cyd on drug permeation rate,due to its solubilizing action; by contrast,unexpectedly,no skin-permeation enhancer property of liposomes has been evidenced. Confocal laser scanning microscopy studies carried out with the rhodamine-Cyd complex as fluorescent marker,confirmed such results,showing that the label permeated deeper across rat skin layers when it was in solution than when entrapped in liposomes.