Preparation,Characterization And Transdermal Mechanism Of Donepezil HCL

Objective:This study intends to design a topical drug delivery system of Donepezil HCL,which is optimized by the prescription process to increase the cumulative transdermal amount of Donepezil HCL to achieve an effective therapeutic concentration,and to explore the transdermal mechanism of Donepezil HCL ethosomes.Methods:1.Determine the factors affecting the particle size,potential,encapsulation efficiency and cumulative transdermal volume of Donepezil HCL,and determine the optimal prescription through the single factor analysis;2.The configuration of phospholipids in the stratum corneum of the skin was studied by attenuated total reflection fourier transform infrared spectroscopy and laser confocal Raman;The thermodynamic changes of the stratum corneum were studied by differential scanning calorimetry;The surface morphology of the stratum corneum and the ultrastructural morphology of the horny longitudinal were studied by scanning electron microscopy and transmission electron microscopy;The distribution of fluorescently labeled ethosomes in the skin and in keratinocytes was studied by confocal laser microscopy;3.Study whether the skin treated by blank ethosomes in advance can be used as a universal technique to increase drugs penetration through skin recovery performance test.Results:The Donepezil HCL ethosomes were prepared by ethanol injection.The three influencing factors that lipid content,drug content and ethanol content were determined.According to the prescription process,the optimized prescription was determined as follows:soy lecithin content was 20 mg/mL,Donepezil HCL content was 20 mg/mL,and ethanol content was 30%.The Donepezil HCL ehosomes prepared by the optimized prescription had a milky white color with light blue opalescence and a uniform particle size.The shape was relatively round at about 120 nm,showing vesicular structure and encapsulation efficiency for 78.211±0.37%.The cumulative transdermal volume in vitro at 24h was 183.73±38.65μg/cm2,which was 13.13 times of the control group.This paper focused on the transdermal mechanism of ethosomes.The attenuated total reflection fourier transform infrared spectroscopy revealed that the C-H bond conformation of stratum corneum phospholipid was transformed from the trans conformation with the lowest energy state to the relatively unstable gauche conformation,and the orthogonal lattice structure of phospholipids reduced.Laser confocal Raman demonstrated that the phospholipid C-C bond of stratum corneum was transformed from all-trans conformation to gauche conformation,and the C-H bond changes were consistent with attenuated total reflection fourier transform infrared spectroscopy results.Differential scanning calorimetry showed that the average transformation temperature(Tm)and enthalpy(△H)of stratum corneum treated by Donepezil HCL ethosomes showed a significant decrease.Scanning electron microscopy showed that the stratum corneum of the skin treated by Donepezil HCL ethosomes had separation and desquamation.Transmission electron microscope observation showed that the skin treated with Donepezil HCL ethosomes showed a tightly packed stratum corneum cell layer without an increase in keratinocyte space and swelling of the stratum corneum cell layer.It was found that the fluorescence of the ethosomes was mainly distributed in the stratum corneum,and the fluorescence intensity of phospholipids decreased in confocal laser scanning microscope.In the deeper layer of stratum corneum,the phospholipids in ethosomes were separated from the Rhodamine B which took place of the drug.And Rhodamine B entered the dermis layer.Furthermore,in this process,the ehosomes were mainly delivered through inter-keratinocyte pathway.Moreover,it was found that the ethosomes did not enter the cell through cell level studies.Skin recovery performance test indicated that the drug encapsulated into ethosomes was essential for promoting drug penetration through the stratum corneum.Conclusion:The optimized Donepezil HCL ethosomes had a good transdermal effect in vitro.The results of the mechanism study showed that the phospholipid molecules in the stratum corneum treated by Donepezil HCL ethosomes had higher conformational energy which was relatively unstable.At the same time,the fluidity of lipids in the stratum corneum increased,which made the drug and carrier easier to penetrate.In addition,Donepezil HCL ethosomes could dissolve and extract lipids in stratum corneum,which also made the skin permeability increase.This study also demonstrated that ethosomes were primarily delivered through the intercellular pathway of the skin.