Abstract
PURPOSE: Lipid suspensions as drug carriers, including conventional liposomes, ethosomes, transferosomes, proniosomes, niosomes, PEG-PPG-PEG niosomes and stratum corneum liposomes (cerosomes), were formulated and compared. METHODS: Lipid vesicles were formulated and assessed with regards to enhancement of skin permeation of diclofenac and stability profiles of the formulations. Formulation-induced changes of the biophysical structure of excised human skin were monitored using the Fourier transform infrared spectroscopy. RESULTS: The stability profiles of these suspensions over 12 weeks did not show any significant drug leakage from the vesicles of interest (p > 0.05). FTIR observations indicated that the vesicles increased stratum corneum (SC) lipid fluidization and altered protein conformation. Skin permeability experiments showed that the free unencapsulated drug in the cerosomal formulations caused significant increase in drug permeation across the skin (p < 0.01). Low skin permeability of drug from the other lipid suspensions could be due to the entrapment of diclofenac within these vesicles which decreased the solubility of the hydrophilic drug in the skin lipids and the partition coefficient of the drug from these vesicles into the SC. CONCLUSION: Optimal drug entrapment in vesicles or alteration of the skin structure may not necessarily enhance the permeation of hydrophilic drugs across the human skin. These lipid vesicles may be further developed into carriers of both hydrophilic and hydrophobic drugs for topical and transdermal delivery, respectively.