title: Chitosan-coated boron nitride nanospheres enhance delivery of CpG oligodeoxynucleotides and induction of cytokines.
abstract: BACKGROUND
  Cytosine-phosphate-guanine (CpG) oligodeoxynucleotides activate Toll-like receptor 9, leading to induction of proinflammatory cytokines, which play an important role in induction and maintenance of innate and adaptive immune responses. Previously, we have used boron nitride nanospheres (BNNS) as a carrier for delivery of unmodified CpG oligodeoxynucleotides to activate Toll-like receptor 9. However, because CpG oligodeoxynucleotides and BNNS are both negatively charged, electrostatic repulsion between them is likely to reduce the loading of CpG oligodeoxynucleotides onto BNNS. Therefore, the efficiency of uptake of CpG oligodeoxynucleotides is also limited and does not result in induction of a robust cytokine response. To ameliorate these problems, we developed a CpG oligodeoxynucleotide delivery system using chitosan-coated BNNS as a carrier.
  
  
  METHODS
  To facilitate attachment of CpG oligodeoxynucleotides onto the BNNS and improve their loading capacity, we prepared positively charged BNNS by coating them with chitosan preparations of three different molecular weights and used them as carriers for delivery of CpG oligodeoxynucleotides.
  
  
  RESULTS
  The zeta potentials of the BNNS-CS complexes were positive, and chitosan coating improved their dispersity and stability in aqueous solution compared with BNNS. The positive charge of the BNNS-CS complexes greatly improved the loading capacity and cellular uptake efficiency of CpG oligodeoxynucleotides. The loading capacity of the CpG oligodeoxynucleotides depended on the molecular weight of chitosan, which affected the positive charge density on the surface of the BNNS. CpG oligodeoxynucleotides loaded onto BNNS-CS complexes significantly enhanced production of interleukin-6 and tumor necrosis factor-α by peripheral blood mononuclear cells compared with CpG oligodeoxynucleotides directly loaded onto BNNS, or when Lipofectamine™ 2000 was used as the carrier. The molecular weight of the chitosan used to coat the BNNS affected the magnitude of cytokine induction by varying the strength of condensation of the CpG oligodeoxynucleotides.
  
  
  CONCLUSIONS
  Although the loading capacity of BNNS coated with low molecular weight chitosan preparations was the lowest of all the preparations, they induced the highest levels of cytokines.
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo, Japan.
authors.forename: Huijie
authors.initials: H
authors.lastname: Zhang
authors.forename: Song
authors.initials: S
authors.lastname: Chen
authors.forename: Chunyi
authors.initials: C
authors.lastname: Zhi
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hanagata
mesh_terms: D001896:Boron Compounds / Q000737:chemistry* / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D048271:Chitosan / Q000737:chemistry* / Q000633:toxicity; D016207:Cytokines / Q000378:metabolism*; D004337:Drug Carriers / Q000737:chemistry* / Q000493:pharmacokinetics / Q000633:toxicity; D006801:Humans; D054118:Nanospheres / Q000737:chemistry* / Q000633:toxicity; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D001896:Boron Compounds; D016207:Cytokines; D004337:Drug Carriers; D009838:Oligodeoxyribonucleotides; C017282:boron nitride; D048271:Chitosan
keywords: CpG oligodeoxynucleotides; boron nitride nanospheres; chitosan; cytokines; drug delivery