title: Microencapsulation of bioactive principles with an airless spray-gun suitable for processing high viscous solutions.
abstract: OBJECTIVE
  to design, assemble and test a prototype of a novel production plant, suitable for producing microparticles (MPs) by processing highly viscous feed solutions (FSs).
  
  
  METHODS
  the prototype has been built using a commercial air compressor, a piston pump, an airless spray-gun, a customized air-treatment section, a timer, a rotating base, and a filtration section. Preliminary prototype parameter setting was carried out to individuate the best performing nozzle's dimension, the nebulization timing, and the CaCl2 concentration in the gelation fluid. In addition, prototype throughput (1 L to 5 L) and the range of practicable feed solution (FS) viscosities were assayed. A set of four batches was prepared in order to characterize the MPs, in terms of mean particle size and distribution, flow properties, swelling, encapsulation efficiency and release.
  
  
  RESULTS
  according to a qualitative scoring, the large nozzle was suitable to nebulize FSs at a higher alginate concentration. Conversely, the small nozzle performed better in the processing of FSs with an alginate concentration up to 2% w/v. Only at the highest degree of viscosity, corresponding to 5% w/v of alginate, the FS processing was not technically possible. Among the CaCl2 concentrations considered, 15% w/v was recognized as the most versatile. The prototype appears to be convenient and suitable to grant a high yield starting from 2 L of FS. The flow behavior of the FSs assayed can be satisfactorily described with the Carreau-Yasuda equation and the throughput begins to slightly decrease for FSs at alginate concentrations exceeding 3% w/v. MP morphology was irregular with crumpled shape. The angle of repose indicates a good flowability and the release studies showed gastro-resistance and potential prolonged release applications.
  
  
  CONCLUSIONS
  the novel prototype of production plant is suitable to process large amounts (2 L or more) of FSs, characterized by a high viscosity, to produce MPs suitable for bioactive principle delivery.
authors: Callerio Foundation Onlus, Institutes of Biological Researches, Trieste 34127, Italy. m.cocchietto@callerio.org.
authors: Moreno
authors: M
authors: Cocchietto
authors: Department of Pharmaceutical Sciences, University of Perugia, Perugia 06123, Italy. paolo.blasi@unipg.it.
authors: Paolo
authors: P
authors: Blasi
authors: Department of Materials and Natural Resources, University of Trieste, Trieste 34127, Italy. romano.lapasin@di3.units.it.
authors: Romano
authors: R
authors: Lapasin
authors: Callerio Foundation Onlus, Institutes of Biological Researches, Trieste 34127, Italy. chiaramoro87@gmail.com.
authors: Chiara
authors: C
authors: Moro
authors: Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua 35131, Italy. davide.gallo.3@studenti.unipd.it.
authors: Davide
authors: D
authors: Gallo
authors: Callerio Foundation Onlus, Institutes of Biological Researches, Trieste 34127, Italy. g.sava@callerio.org.
authors: Gianni
authors: G
authors: Sava