title: Formulation and process considerations for the design of sildenafil-loaded polymeric microparticles by vibrational spray-drying.
abstract: OBJECTIVE
  The current study reports the preparation and characterization of sildenafil-loaded poly(lactide-co-glycolide) (PLGA)-based microparticles (MPs) by means of vibrational spray-drying. Emphasis was placed on relevant formulation and process parameters with influence on the properties of obtained powders. Materials and methods, results and discussion: The solid state solubility of sildenafil in spray-dried PLGA-MPs amounted to 17 wt.%. Thus, a drug loading below and above the determined solubility limit resulted in solid solutions and phase separation (i.e. solid dispersions), respectively. Furthermore, interactions between sildenafil and the PLGA matrix were observed for the spray-dried MPs. Optimization of spray-drying conditions allowed for a fabrication of defined MPs (size range of ∼4-8 μm) displaying a high sildenafil encapsulation efficiency (>90%) and sustained sildenafil release (from ∼4 to >12 h). The individual drug release rates from the spray-dried formulations were mainly a function of the drug loading, applied polymer and MP size. Finally, a scale-up of the preparation process did not result in a relevant change of the physicochemical and in vitro drug release properties of the prepared powders.
  
  
  CONCLUSIONS
  Identification of relevant formulation and spray-drying parameters enabled the fabrication of tailored sildenafil-loaded PLGA-based MPs, which meet the needs of the individual application (e.g. controlled drug delivery to the lungs).
authors.affiliation: a Medical Clinic II, Department of Internal Medicine, Justus-Liebig-Universität , Giessen , Germany.|b Department of Pharmaceutics and Biopharmacy , Philipps-Universität , Marburg , Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Beck-Broichsitter
authors.affiliation: c Department of Pharmacy , Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark.
authors.forename: Adam
authors.initials: A
authors.lastname: Bohr
authors.affiliation: d Unit of Functional and Adaptive Biology CNRS UMR 8251, Université Paris Diderot , Paris , France , and.
authors.forename: Leticia
authors.initials: L
authors.lastname: Aragão-Santiago
authors.affiliation: e Department of Cell Biology , Philipps-Universität , Marburg , Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Klingl
authors.affiliation: b Department of Pharmaceutics and Biopharmacy , Philipps-Universität , Marburg , Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kissel
mesh_terms: D002626:Chemistry, Pharmaceutical; D004339:Drug Compounding; D008863:Microspheres; D010316:Particle Size; D000068677:Sildenafil Citrate
chemical_list: D000068677:Sildenafil Citrate
keywords: Controlled drug delivery; lungs; poly(lactide-co-glycolide)