title: N,O6-partially acetylated chitosan nanoparticles hydrophobically-modified for controlled release of steroids and vitamin E.
abstract: Diosgenin, two synthetic analogs of brassinosteroids, testosterone and dl-α-tocopherol were covalently linked to synthetic water-soluble N,O6-partially acetylated chitosan, for their controlled release. Drug linking was confirmed by FTIR spectroscopy and proton NMR. Conjugates were also characterized by differential scanning calorimetry and wide-angle X-ray diffraction. These conjugates formed self-assembled nanoparticles in aqueous solution with particle sizes ranging from 197 to 358 nm and drug contents between 11.8 and 56.4% (w/w). Spherical 30-60 nm nanoparticles were observed by scanning electron microscopy and transmission electron microscopy upon drying. In vitro release studies performed at acid pH indicated a drug release dependence on substitution degree and particle sizes. Almost constant release rates were observed during the first 6-8h. Brassinosteroids-modified nanoparticles showed good agrochemical activity in radish seeds bioassay at 10(-1) to 10(-4) mg mL(-1). Tocopheryl-modified nanoparticles exhibited radical scavenging activity in DPPH test.
authors.affiliation: Center of Natural Products, Faculty of Chemistry, University of Havana, Havana, Cuba. javierp@fq.uh.cu
authors.forename: Javier Pérez
authors.initials: JP
authors.lastname: Quiñones
authors.forename: Kurt Vesterager
authors.initials: KV
authors.lastname: Gothelf
authors.forename: Jørgen
authors.initials: J
authors.lastname: Kjems
authors.forename: Ángeles María Heras
authors.initials: ÁM
authors.lastname: Caballero
authors.forename: Claudia
authors.initials: C
authors.lastname: Schmidt
authors.forename: Carlos Peniche
authors.initials: CP
authors.lastname: Covas
mesh_terms: D000107:Acetylation; D001713:Biphenyl Compounds / Q000737:chemistry; D060406:Brassinosteroids / Q000737:chemistry* / Q000494:pharmacology; D048271:Chitosan / Q000737:chemistry*; D003692:Delayed-Action Preparations; D004337:Drug Carriers / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology; D057927:Hydrophobic and Hydrophilic Interactions; D053758:Nanoparticles / Q000737:chemistry*; D010851:Picrates / Q000737:chemistry; D010937:Plant Growth Regulators / Q000737:chemistry / Q000494:pharmacology; D031224:Raphanus / Q000187:drug effects / Q000254:growth & development; D024505:Tocopherols / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D001713:Biphenyl Compounds; D060406:Brassinosteroids; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D016166:Free Radical Scavengers; D010851:Picrates; D010937:Plant Growth Regulators; D048271:Chitosan; C004931:1,1-diphenyl-2-picrylhydrazyl; D024505:Tocopherols