Studies On TPGS Emulsified And Nimesulide-loaded Nanostructured Lipid Nanoparticles

Nanostructured lipid nanoparticles(NLC) is developed after solid lipidnanoparticles(SLN) and is the second generation of lipid nanoparticles. In this new drugdelivery system, both liquid and solid lipid were added. NLC was able to overcome manydisadvantages of SLN such as high level of crystallization of solid lipid, low level of drugloading, drug leakage during storage, large amount of water in water dispersion systemand so on. In this study high pressure homogenization method was used to developTPGS-emulsified and nimesulide-loaded NLC, and its transdermal drug delivery was alsostudied.D-α-tocopherol polyethylene glycol1000succinate(TPGS) was widely used assurfactant in nano drug delivery system. However, the di-esters in TPGS impact theemulsifying capacity. In this study, high performance liquid chromatography forsimultaneously analysis of mono-and di-TPGS with gradient elution solvent system ofethanol/water as mobile phase was established. With recoveries of mono-and di-TPGSas targets, the single factor design and orthogonal design were used to study the influenceof loading amount, feeding concentration and flow rate on the column chromatographyseparation process of mono-and di-TPGS. The optimum separation parameters weredetermined and the optimum recoveries of mono-and di-TPGS were95.26±0.52%and94.08±0.61%, respectively.In the preformulation study, a HPLC method with0.1%H3PO4solution (pH7.0,adjusted by NH3H2O)/acetonitrile(60:40) as mobile phase was developed. The solubilityand oil-water partition coefficient of nimesulide were mesured. In the formulation study,high pressure homogenization method was used to prepare TPGS-emulsified andnimesulide-loaded NLC. Firstly, the particle size and drug entrapment efficiency wereused as the targets to study the influence of ratio of solid-liquid lipid, lipid amount, typeand amount of surfactant and the ratio of drug-lipid on nimesulide NLC. Then，influenceof process parameters, including temperature of pre-emulsion preparation,homogenization pressure and homogenization cycles, on particle size and entrapmentefficiency was studied. Finally, orthogonal design was used to determine the optimumformulation and preparation parameters. The optimum formulation was10:3of solid toliquid lipid,3%of lipid amount,3%of TPGS and1:40of drug to lipid. The optimumpreparation method was preparing pre-emulsion under75℃and homogenizing for4 cycles under90Mpa. The particle size and entrapment efficiency of NLC under optimumconditions were132.6±1.4nm and82.35±1.23%respectively.Scanning electron microscope(SEM) was used to study the surface feature ofdrug-loaded NLC, and nanoparticle size analyzer was used to study the particle size andZeta potential. Dialysis and centrifugation methods were compared in measuringentrapment efficiency, and centrifugation method was selected at last. In vitro releasingand stability of the prepared drug-loaded NLC were also studied. The results showed thatthe prepared NLC was in spherical shape, with Zeta potential between-10mv and-20mv.The in vitro releasing curve accorded with Higuchi model. The particle size andentrapment efficiency were stable within one month under25℃and the stability wasbetter than that of4℃.Finally, transdermal property of NLC was studied. Transdermal capacity ofnimesulide-loaded NLC and nimesulide solution were compared. It showed thattransdermal rate constant of nimesulide NLC and nimesulide solution were5.18μg·h-1·cm-2and1.42μg·h-1·cm-2respectively, which indicated that the prepared NLChad a good transdermal capacity.