title: Preparation, characterization and optimization of sildenafil citrate loaded PLGA nanoparticles by statistical factorial design.
abstract: The objective of the present study was to formulate and optimize nanoparticles (NPs) of sildenafil-loaded poly (lactic-co-glycolic acid) (PLGA) by double emulsion solvent evaporation (DESE) method. The relationship between design factors and experimental data was evaluated using response surface methodology.
  
  
  METHODS
  A Box-Behnken design was made considering the mass ratio of drug to polymer (D/P), the volumetric proportion of the water to oil phase (W/O) and the concentration of polyvinyl alcohol (PVA) as the independent agents. PLGA-NPs were successfully prepared and the size (nm), entrapment efficiency (EE), drug loading (DL) and cumulative release of drug from NPs post 1 and 8 hrs were assessed as the responses.
  
  
  RESULTS
  The NPs were prepared in a spherical shape and the sizes range of 240 to 316 nm. The polydispersity index of size was lower than 0.5 and the EE (%) and DL (%) varied between 14-62% and 2-6%, respectively. The optimized formulation with a desirability factor of 0.9 was selected and characterized. This formulation demonstrated the particle size of 270 nm, EE of 55%, DL of 3.9% and cumulative drug release of 79% after 12 hrs. In vitro release studies showed a burst release at the initial stage followed by a sustained release of sildenafil from NPs up to 12 hrs. The release kinetic of the optimized formulation was fitted to Higuchi model.
  
  
  CONCLUSIONS
  Sildenafil citrate NPs with small particle size, lipophilic feature, high entrapment efficiency and good loading capacity is produced by this method. Characterization of optimum formulation, provided by an evaluation of experimental data, showed no significant difference between calculated and measured data.
authors.forename: Elham
authors.initials: E
authors.lastname: Ghasemian
authors.affiliation: Pharmaceutics Department, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran. vatanara@tums.ac.ir.
authors.forename: Alireza
authors.initials: A
authors.lastname: Vatanara
authors.forename: Abdolhossein
authors.initials: A
authors.lastname: Rouholamini Najafabadi
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Rouini
authors.forename: Kambiz
authors.initials: K
authors.lastname: Gilani
authors.forename: Majid
authors.initials: M
authors.lastname: Darabi