title: Probing insulin bioactivity in oral nanoparticles produced by ultrasonication-assisted emulsification/internal gelation.
abstract: Alginate-dextran sulfate-based particles obtained by emulsification/internal gelation technology can be considered suitable carriers for oral insulin delivery. A rational study focused on the emulsification and particle recovery steps was developed in order to reduce particles to the nanosize range while keeping insulin bioactivity. There was a decrease in size when ultrasonication was used during emulsification, which was more pronounced when a cosurfactant was added. Ultrasonication add-on after particle recovery decreased aggregation and led to a narrower nanoscale particle-size distribution. Insulin encapsulation efficiency was 99.3%±0.5%, attributed to the strong pH-stabilizing electrostatic effect between insulin and nanoparticle matrix polymers. Interactions between these polymers and insulin were predicted using molecular modeling studies through quantum mechanics calculations that allowed for prediction of the interaction model. In vitro release studies indicated well-preserved integrity of nanoparticles in simulated gastric fluid. Circular dichroism spectroscopy proved conformational stability of insulin and Fourier transform infrared spectroscopy technique showed rearrangements of insulin structure during processing. Moreover, in vivo biological activity in diabetic rats revealed no statistical difference when compared to nonencapsulated insulin, demonstrating retention of insulin activity. Our results demonstrate that alginate-dextran sulfate-based nanoparticles efficiently stabilize the loaded protein structure, presenting good physical properties for oral delivery of insulin.
authors.affiliation: Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal ; CNC - Center for Neuroscience and Cell Biology, Coimbra, Portugal.
authors.forename: Marlene A
authors.initials: MA
authors.lastname: Lopes
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Abrahim-Vieira
authors.affiliation: I3S, Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal ; Group Genetics of Cognitive Dysfunction, IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal.
authors.forename: Claudia
authors.initials: C
authors.lastname: Oliveira
authors.affiliation: REQUIMTE, Department of Chemical Sciences - Applied Chemistry Lab, Faculty of Pharmacy, University of Porto, Porto, Portugal ; CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde, Gandra, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Fonte
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Alessandra M T
authors.initials: AM
authors.lastname: Souza
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Tammy
authors.initials: T
authors.lastname: Lira
authors.affiliation: Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal ; CNC - Center for Neuroscience and Cell Biology, Coimbra, Portugal.
authors.forename: Joana A D
authors.initials: JA
authors.lastname: Sequeira
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Rodrigues
authors.affiliation: Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Lúcio M
authors.initials: LM
authors.lastname: Cabral
authors.affiliation: REQUIMTE, Department of Chemical Sciences - Applied Chemistry Lab, Faculty of Pharmacy, University of Porto, Porto, Portugal ; CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde, Gandra, Portugal ; INEB - Instituto de Engenharia Biomédica, University of Porto, Porto, Portugal.
authors.forename: Bruno
authors.initials: B
authors.lastname: Sarmento
authors.affiliation: IBILI - Institute of Biomedical Research in Light and Image, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Seiça
authors.affiliation: Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal ; CNC - Center for Neuroscience and Cell Biology, Coimbra, Portugal.
authors.forename: Francisco
authors.initials: F
authors.lastname: Veiga
authors.affiliation: Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal ; I3S, Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal ; Group Genetics of Cognitive Dysfunction, IBMC - Instituto de Biologia Molecular e Celular, Porto, Portugal.
authors.forename: António J
authors.initials: AJ
authors.lastname: Ribeiro
mesh_terms: D000464:Alginates / Q000737:chemistry; D000818:Animals; D016264:Dextran Sulfate / Q000737:chemistry; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy*; D004655:Emulsions; D005782:Gels / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007328:Insulin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D053758:Nanoparticles / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D014465:Ultrasonics / Q000379:methods*
chemical_list: D000464:Alginates; D004655:Emulsions; D005782:Gels; D006603:Hexuronic Acids; D007004:Hypoglycemic Agents; D007328:Insulin; D020723:Glucuronic Acid; D016264:Dextran Sulfate
keywords: biopolymers; insulin secondary structure; microparticle; molecular modeling; nanoencapsulation processing; oral delivery