Present study reports optimal conditions for the preparation of cyclosporin A loaded PLGA nanoparticles with a diameter < 200nm. In a systematic approach, various process variables such as homogenization/sonication, choice of suitable stabilizer and its concentration, drug loading etc. were optimized to achieve maximum drug loading and desired particle size ( < 200nm) and the optimized formulation was further characterized for shape and morphology by atomic forced microscopy (AFM), nature of drug inside the nanoparticles by X-ray diffraction pattern (XRD) analysis and in-vitro drug release. A step wise freeze drying cycle was developed and suitable lyoprotectants were screened for long term shelf storage of the formulation in dried form. Accelerated stability testing was also carried out to determine the change in physicochemical characteristics of the nanoparticles during storage. Nanoparticles were successfully prepared with high encapsulation efficiency ( > 85%w/w) and low particle size (163 nm) using 2% w/v PVA as surfactant with probe sonication technique. AFM images confirmed the spherical shape and smooth surface of the particles and drug was found to be molecularly dispersed in the polymer matrix of nanoparticles as revealed by XRD analysis. Developed formulation showed a zero order in vitro release pattern up to 20 days with no initial burst release when carried out using a cellulose dialysis bags with a molecular mass cut-off of 12000 Da. Step wise freeze drying was successfully carried out using relatively low concentration (2.5%w/v) of dextrose and mannitol as lyoprotectants with insignificant changes in particle size and entrapment efficiency. No significant changes in characteristics of nanoparticles were observed after 3 months of storage in accelerated stability conditions. The developed formulation can be successfully used as potential delivery vehicle for delivery of cyclosporin A through oral/topical routes for possible systemic or dermatological applications. The nanoparticles would be loaded into a gel for possible topical application and such studies are underway in our laboratory.
Keywords: Cyclosporin A, PLGA, nanoparticles, Freeze drying, AFM, XRD