Preparation And Evaluation In Vitro And In Vivo Of Nano-mixed Micelles Loaded With Dexamethasone Palmitate

Rheumatoid arthritis(RA)is a common chronic inflammatory disorder.Autoantigens trigger the release of cytokines from the immune system that erode articular cartilage and bone,leading to joint swelling,bone deformation,and even disability,seriously affecting the work and life of patients.Glucocorticoids(GCs)play an irreplaceable role in the treatment of rheumatoid arthritis.At the same time,its application also has limitations,such as multi-targeting of systemic administration,low bioavailability.To solve the above problems,we encapsulated dexamethasone palmitate(DMP)in egg yolk lecithin/sodium glycocholate mixed micelles(EYL/SGC-MMs)to improving the solubility of insoluble drugs and increasing the distribution in the inflammatory sites.DMP-MMs were prepared by thin film hydration method.The effects of formulation and process conditions on particle size and encapsulation efficiency(EE%)of mixed micelles were investigated.Malvern laser particle size analyzer was used to determine particle size distribution and Zeta potential.Micellar size and surface morphology was identified by transmission electron microscopy(TEM)and atomic force microscopy(AFM).Liquid chromatography method was established to determine the EE% and drug loading(DL%)of DMP-MMs.And Pyrene fluorescent probe method combined with Origin curve fitting determined critical micelle solubility(CMC)of mixed micelles.Then we established acute paw swelling model of rat induced by carrageenan.After 30 minutes of drug administration,0.1 ml of 1% carrageenan solution was subcutaneously injected into the paw.The anti-inflammatory effects of micelles and the commercial formulation(Limetason?)were evaluated by measuring the paw volume at different time points and histopathological analysis.Subsequently,we established an adjuvant induced arthritis(AIA)model.The therapeutic effects of different doses of DMP-MMs and Limetason? were evaluated by measuring body weight,paw volume,spleen index,level of pro-inflammatory cytokines in serum,ankle joint pathology analysis and CT scan.In addition,we performed pharmacokinetic experiments to analyze the pharmacokinetic parameters of DMP-MMs and Limetason?.Finally,we prepared the Dir loaded mixed micelles(Dir-MMs)and Dir emulsion(Dir-EL).In vivo imaging system of small animals was used to observe the distribution of the Dir preparation in AIA rats.The particle size of DMP-MMs was 49.14±0.44 nm with a narrow size distribution.The zeta potential was-33.07±1.35 m V.TEM and AFM images illustrated that DMP-MMs had a spherical structure with uniform distribution.EE% and DL% of DMP were 94.5±1.4% and 12.7±0.2%.CMC value of EYL/SGC-MMs was 0.096 mg/m L.The results of paw swelling induced by carrageenan showed that the swelling degree increased from 1h to 3h after inflammation,peaked at 3h,and decreased at 4h.Compared with the saline group,the swelling degree of the low,medium and high concentration groups of the DMP-MMs was improved to some extent.The number of inflammatory cells in the tissue was significantly reduced.Results of adjuvant arthritis showed that the degree of paw swelling obviously decreased in all drug treated groups from day 12 to 28 with a dose-dependent manner compared to the saline group.And there was a significant difference between the micelles and the Limetason? same dose group.CT images of the ankle joint of the saline group showed that soft tissue got swelling,joint space became smaller,the end of the bone showed osteoporosis,and distal interphalangeal joint deformed.The results of hematoxylin and eosin(H&E)staining of the ankle joint showed that the joint space of the saline group was narrowed,the bone and cartilage were severely eroded,and the joint spasm was formed,and the administration groups were significantly improved.The results of biodistribution showed that the Dir-MMs had accumulated in the inflammatory joints at 5 min.The distribution of Dir-EL in the inflammation site was less than that of the micelles.The distribution of free Dir in the inflamed joints is extremely small,indicating that the DMP-MMs with a smaller diameter have a stronger targeting effect at the inflammation site.After the insoluble drug DMP was prepared into DMP-MMs,the solubility was greatly improved,and it also showed good therapeutic effect in the acute and chronic inflammatory models of rats.DMP-MMs could inhibit the inflammatory response and reduce the joint injury.In addition,micelles exhibited higher bioavailability and passive targeting for inflammatory sites in this research.Therefore,it has guiding significance for the clinical treatment of inflammatory diseases,and is promising for industrial production.