title: Probing insulin's secondary structure after entrapment into alginate/chitosan nanoparticles.
abstract: The aim of the present study was to probe the structural integrity of insulin after being entrapped into chitosan/alginate nanoparticles produced by ionotropic polyelectrolyte pre-gelation. By manipulating the alginate:chitosan mass ratio and the pH during nanoparticle production, desired nanoparticles with a mean size of 850 (+/-88)nm and insulin association efficiency of 81 (+/-2)% were obtained. Insulin secondary structure was assessed by Fourier transform infrared (FTIR) and circular dichroism (CD) after entrapment into nanoparticles and after release from the particles under gastrointestinal simulated conditions. FTIR second-derivative spectra and area-overlap compared to an insulin standard confirmed that no significant conformational changes of insulin occurred in terms of alpha-helix and beta-sheet content. Far-UV-CD spectra corroborated the preservation of insulin structure during the nanoparticle production procedure. The presented nanoparticulate system is a promising carrier for insulin oral delivery since it preserves insulin structure and therefore also, potentially, its bioactivity.
authors.affiliation: Department of Pharmaceutical Technology, Faculty of Pharmacy of the University of Porto, Porto, Portugal. bruno.sarmento@ff.up.pt
authors.forename: B
authors.initials: B
authors.lastname: Sarmento
authors.forename: D C
authors.initials: DC
authors.lastname: Ferreira
authors.forename: L
authors.initials: L
authors.lastname: Jorgensen
authors.forename: M
authors.initials: M
authors.lastname: van de Weert
mesh_terms: D000284:Administration, Oral; D000464:Alginates / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D048271:Chitosan / Q000737:chemistry*; D002942:Circular Dichroism; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D004339:Drug Compounding; D004355:Drug Stability; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000737:chemistry*; D007328:Insulin / Q000008:administration & dosage / Q000737:chemistry*; D007700:Kinetics; D053758:Nanoparticles; D010316:Particle Size; D017433:Protein Structure, Secondary; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013678:Technology, Pharmaceutical / Q000379:methods
chemical_list: D000464:Alginates; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D006603:Hexuronic Acids; D007004:Hypoglycemic Agents; D007328:Insulin; D020723:Glucuronic Acid; D048271:Chitosan