title: Efficacy and mechanism of action of chitosan nanocapsules for oral peptide delivery.
abstract: OBJECTIVE
  We have previously shown that high molecular weight (MW > 100 kDa) chitosan nanocapsules are efficient vehicles for improving the oral absorption of salmon calcitonin (sCT). In the present work, our objectives were, first, to investigate the influence of some formulation parameters on the efficacy of chitosan nanocapsules as carriers for the oral administration of sCT and, second, to elucidate the mechanism of interaction of chitosan nanocapsules with intestinal model cell lines.
  
  
  METHODS
  sCT-loaded chitosan nanocapsules were prepared by the solvent displacement technique. They were characterized for their size, zeta potential, and sCT loading. The ability of chitosan nanocapsules to enhance the oral absorption of sCT was investigated in rats by monitoring the serum calcium levels. Finally, the mechanism of interaction of chitosan nanocapsules with the Caco-2 cell model or in the coculture of Caco-2 with HT29-M6 cells was investigated by confocal fluorescence microscopy.
  
  
  RESULTS
  Chitosan nanocapsules presented a particle size in nanometer range, a positive surface charge, and an efficient encapsulation of sCT. Following oral administration to rats, all formulations of nanocapsules exhibited the ability to reduce calcemia levels; however, the intensity of the response varied depending on the formulation conditions. With regard to the mechanism of interaction of chitosan nanocapsules with cell culture, the xz images evidenced that chitosan nanocapsules interact and remain associated to the apical side of both model cell cultures. In addition, chitosan nanocapsules showed a preferable association to the mucus-secreting cells (HT29-M6).
  
  
  CONCLUSIONS
  Chitosan nanocapsules are able to enhance and prolong the intestinal absorption of sCT and this effect could be mainly ascribed to their mucoadhesive character and intimate interaction with the intestinal barrier.
authors.affiliation: Department of Pharmaceutical Technology, School of Pharmacy, University of Santiago de Compostela (USC), Campus Sur, 15782, Santiago de Compostela, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Prego
authors.forename: M
authors.initials: M
authors.lastname: Fabre
authors.forename: D
authors.initials: D
authors.lastname: Torres
authors.forename: M J
authors.initials: MJ
authors.lastname: Alonso
mesh_terms: D000284:Administration, Oral; D000818:Animals; D018938:Caco-2 Cells; D002116:Calcitonin / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism; D002118:Calcium / Q000097:blood; D002626:Chemistry, Pharmaceutical; D048271:Chitosan / Q000737:chemistry / Q000378:metabolism*; D004337:Drug Carriers; D019073:HT29 Cells; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D009093:Mucus / Q000378:metabolism; D049329:Nanostructures; D010455:Peptides / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
chemical_list: D004337:Drug Carriers; D010455:Peptides; C028815:salmon calcitonin; D002116:Calcitonin; D048271:Chitosan; D002118:Calcium