title: Effect of Aerosil on the properties of lipid controlled release microparticles.
abstract: Theophylline-loaded microparticles of a lipid carrier, Precirol ATO 5, were prepared by the ultrasonic spray-congealing method. The goal of the work was to investigate the effect of different concentrations and kind of colloidal silicon dioxide (Aerosil 90, 200 and 300) on the microparticle characteristics (particle size, drug loading, morphology and kinetics of release). The results showed that the introduction of Aerosil improved the drug distribution in the different particle sizes and that the mean diameter of the microparticles decreased with the viscosity of the suspension to be nebulized, especially that with Aerosil 300. Whatever the microparticles formulation is, SEM and image analysis did not reveal any remarkable difference of the microparticle shape and surface area, suggesting that other parameters could influence the dissolution behaviour. Actually, the dissolution profiles of all the formulations appeared to be closely related to the physico-chemical properties of Aerosil, especially to its gelation properties, which are a function of its specific surface area. In particular, microparticles having high concentration of Aerosil 200 and 300 approached a zero order release kinetics, while Aerosil 90 microparticles followed a first order release kinetics. Therefore, the drug release rate is controlled by the extent and rate of water absorption/swelling of the Aerosil employed. Finally, DSC, HSM, XRD and FT-IR evidenced the permanence of the drug in its original state.
authors.affiliation: Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via S. Donato 19/2, 40127 Bologna, Italy. beatrice@biocfarm.unibo.it
authors.forename: Beatrice
authors.initials: B
authors.lastname: Albertini
authors.forename: Nadia
authors.initials: N
authors.lastname: Passerini
authors.forename: Marisa L
authors.initials: ML
authors.lastname: González-Rodríguez
authors.forename: Beatrice
authors.initials: B
authors.lastname: Perissutti
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Rodriguez
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003692:Delayed-Action Preparations; D004075:Diglycerides; D004337:Drug Carriers; D004355:Drug Stability; D004356:Drug Storage; D005079:Excipients; D007700:Kinetics; D008081:Liposomes; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D012822:Silicon Dioxide / Q000494:pharmacology*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013806:Theophylline / Q000008:administration & dosage / Q000032:analysis; D014465:Ultrasonics; D014961:X-Ray Diffraction
chemical_list: D003692:Delayed-Action Preparations; D004075:Diglycerides; D004337:Drug Carriers; D005079:Excipients; D008081:Liposomes; D012822:Silicon Dioxide; D013806:Theophylline; C009032:precirol