Tailoring novel soft nano-vesicles 'Flexosomes' for enhanced transdermal drug delivery: Optimization, characterization and comprehensive ex vivo - in vivo evaluation.

The transdermal route is a convenient non-invasive way for drug delivery, however, the hydrophobic compact nature of stratum corneum (SC) forms an obstacle hindering the diffusion of drugs particularly hydrophilic ones. Hence, the purpose of this study was to develop novel soft nano-vesicles, entitled Flexosomes, amalgamating two penetration enhancers, ethanol and one edge activator (EA) from various types and different hydrophilic-lipophilic balances. The tailored vesicles were loaded with tropisetron hydrochloride (TRO), a potent highly-soluble anti-emetic, and compared with ethosomes. Aiming to preclude the formation of rigid non-deformable mixed micelles, all critical parameters; EA type, phosphatidylcholine-to-EA molar ratio, and cholesterol concentration, were optimized proving their influences on vesicle-to-micelle transitions. The prepared formulations were characterized in terms of visual inspection, particle size, polydispersity, zeta potential, turbidity measurements, entrapment efficiency, and vesicle morphology. The permeation mechanisms were assessed by differential scanning calorimetry on isolated SC. The modified vesicles, based on ethanol and either vitamin E or PEGylated castor oil derivatives exhibited the highest transdermal fluxes confirmed by a deeply tracking to dermis using confocal laser microscopy. Both vesicles demonstrated higher bioavailability relative to ethosomes, topical and oral aqueous solutions. The findings endorsed the effectiveness of tailored nano-vesicles in boosting TRO skin transport suggesting their applicability with various drug entities for enhanced transdermal delivery.

Nanoethosomes for transdermal delivery of tropisetron HCl: multi-factorial predictive modeling, characterization, and ex vivo skin permeation.

OBJECTIVE: The aim of the present work is to exclusively optimize and model the effect of phospholipid type either egg phosphatidylcholine (EPC) or soybean phosphatidylcholine (SPC), together with other formulation variables, on the development of nano-ethosomal systems for transdermal delivery of a water-soluble antiemetic drug. Tropisetron HCl (TRO) is available as hard gelatin capsules and IV injections. The transdermal delivery of TRO is considered as a novel alternative route supposing to improve BAV as well as patient convenience. METHODS: TRO-loaded ethanolic vesicular systems were prepared by hot technique. The effect of formulation variables were optimized through a response surface methodology using 3 × 22-level full factorial design. The concentrations of both PC (A) and ethanol (B) and PC type (C) were the factors, while entrapment efficiency (Y1), vesicle size (Y2), polydispersity index (Y3), and zeta potential (Y4) were the responses. The drug permeation across rat skin from selected formulae was studied. Particle morphology, drug-excipient interactions, and vesicle stability were also investigated. RESULTS: The results proved the critical role of all formulation variables on ethosomal characteristics. The suggested models for all responses showed good predictability. Only the concentration of phospholipid, irrespective to PC type, had a significant effect on the transdermal flux (p < 0.01). The ethosomal vesicles were unilamellar with a nearly spherical shape. EPC-based ethosomes proved good stability. CONCLUSION: The study suggests the applicability of statistical modeling as a promising tool for prediction of ethosomal characteristics. The ethanolic vesicles were considered as novel potential nanocarriers for accentuated transdermal TRO delivery.