Study On Ascorbyl Palmitate Vesicles And Solid Lipid Nanoparticles As Transdermal Administration Carrier For Tretinoin

Objective: Use ascorbyl palmitate vesicles and solid lipid nanoparticles as transdermal administration carrier for tretinoin, carry out studies on their formulation, preparation technology, entrapment efficiency, stability, release, in vitro skin penetration and retention .Expecting to improve the stability of tretinoin and increase the local concentration of drug when transdermal administration.Methods: (1)Study on the preparation of tretinoin ascorbyl palmitate vesicles and solid lipid nanoparticles. Prepare tretinoin ascorbyl palmitate vesicles by solvent-injection method, and optimize the formulation of vesicles, entrapment efficiency was determinated by dialysis method. Prepare tretinoin solid lipid nanoparticles by nanoemulsion method, formulation determined through study on phase diagram and entrapment efficiency was determinated by Sephadex G50 mini-column.(2) Study on the stability of tretinoin ascorbyl palmitate vesicles and solid lipid nanoparticles. In the study of stability, we examen degradation of drug loaded in ascorbyl palmitate vesicles or solid lipid nanoparticles when exposure to illumination(4500±500 lx). The tretinoin ascorbyl palmitate vesicles were stored two different temperatures(4℃, 25℃) and relative humidity 75% for 6 mouths to carry through testing of stability, drug content and entrapment efficiency were measured. The solid lipid nanoparticles were stored three different temperatures(4℃, 25℃, 40℃) and relative humidity 75% for 3 mouths to carry through testing of stability, drug content, particle size , potential and entrapment efficiency were measured.(3) Study on the release rate, in vitro skin penetration and retention of tretinoin ascorbyl palmitate vesicles and solid lipid nanoparticles. The in vitro release rate of tretinoin from carrier was determined by Franz diffusion cell. Between donor compartment and receptor compartment was cellulose membrane(cut-off molecules 8000～14000 ), the avaiable diffusion area of cell was 2.92 cm2. At appropriate intervals, namely, 2,4,6,8,12,24h, 0.5ml of the receptor medium were withdrawn and replaced by an equal volume of fresh receptor solution immediately. The sample was analyzed by HPLC after treatment .The in vitro skin penetration experiment was carry through by the same method as the in vitro release rate experiments except using the back skin of mouse, rats or rabbits instead of cellulose membrane. When in vitro skin penetration experiment completed, the skin were taken down from cells, cut and homogenated. After these treatment, extracted by 50% isopropanol-normal saline. The extracting solution was analyzed by HPLC after treatment .Results: (1)Optimized formulation and preparation technology of tretinoin ascorbyl palmitate vesicles. 0.1g 1-cysteine hydrochloride and 0.05g EDTANa2 dissolved in 100ml PBS (pH 5.5), as phaseⅠ;0.1g tretinoin, 2.1g ascorbyl palmitate, 1.9g cholesterol and 0.02g BHT dissolved in ethanol-ether(3∶2), as phaseⅡ. PhaseⅡdrop into phaseⅠwhich heated to 60℃slowly at 1000r·min-1 stirring, after dropped, keep stirring 30min at 60℃in order to remove organic solvents, then stop heating and contuniue stirring 30min. The final volume was controlled to 100ml and the vesicles were obtained. The entrapment efficiency was over 90% and determinated by dialysis method . The products have no significant decrease on content and entrapment efficiency when stored at 4℃environment for 6 months but have some decrease when stored at 25℃environment.(2)Optimized formulation and preparation technology of tretinoin solid lipid nanoparticles. 0.5g glycerin monostearate, 0.2g span60, 4g tween80, 5g PEG400, 0.04g ascorbyl palmitate,1g poloxamer F-127, 0.04g butylated hydroxytoluene, mixed and melted in 70℃water bath heating to form a clear solution. Then 0.025g tretinoin was added to this solution at 70℃and 200r·min-1 stirring until it was complete dissolved and another yellow clear solution was obtained. After that 15ml, 70℃water was added to this solution and stirred at 200r·min-1 for 20min to form a stable nanoemulsion. Then pour the nanoemulsion into 78ml, 2℃water(contains 0.01g EDTA) with 1000r·min-1 stirring. The stirring speed reduced to 200r·min-1 after 5min and keep this speed for 2h, and the nanoparticles were obtained. The entrapment efficiency was over 92% and determinated by Sephades G50 mini-column. The products have no significant decrease on content and entrapment efficiency when stored at 4℃, 25℃and 40℃environment for 3 months.(3) Release rate, in vitro skin penetration and retention. The in vitro release rate of tretinoin ascorbyl palmitate vesicles was higher than cream and tretinoin solid lipid nanoparticles. The in vitro tretinoin cumulative penetration quantity indicated higher levels in ascorbyl palmitate vesicles than cream and solid lipid nanoparticles in mouse back skin, but solid lipid nanoparticles had more drug retention in mouse back skin than cream and ascorbyl palmitate vesicles . The result of diffierent animal back skin cumulative penetration quantity of vesicles and solid lipid nanoparticles was mouse>rats>rabbits. The result of diffierent animal back skin retention quantity of vesicles and solid lipid nanoparticles was rabbits >rats> mouse.Conclusions: Prepare tretinoin ascorbyl palmitate vesicles by solvent-injection method and tretinoin solid lipid nanoparticles by nanoemulsion method were simple and reliable. The entrapment efficiency of optimized formulation were over 90%. Solid lipid nanoparticles had better stability than vesicles. Vesicles had higher in vitro release rate and in vitro cumulative penetration quantity than cream and solid lipid nanoparticles, this indicated vesicles can increase the skin penetration quantity of drugs. Solid lipid nanoparticles had lower in vitro release rate than cream and vesicles but had the highest skin retention quantity, this indicated solid lipid nanoparticles can increase local concentration of drugs. Back skin cumulative penetration quantity in vitro of vesicles and solid lipid nanoparticles in mouse was higher than that from rats and rabbits. on the contrary, back skin retention quantity in vitro of vesicles and solid lipid nanoparticles in mouse was lower than rats and rabbits.