title: Physical characterization and in vitro skin permeation of solid lipid nanoparticles for transdermal delivery of quercetin.
abstract: OBJECTIVE
  Quercetin, a phenolic compound isolated from plants, can act as an antioxidant to protect the skin from oxidative stress induced by ultraviolet rays. The aims of this work were (i) to compare the physical characterization of quercetin-loaded solid lipid nanoparticles (QSLNs) and (ii) to investigate the enhanced skin permeation of quercetin using QSLNs.
  
  
  METHODS
  QSLNs were prepared with a certain amount lipid (palmitic acid) and the different ratio of surfactant (Tween(®) 80) by homogenization and ultrasonification method.
  
  
  RESULTS
  QSLNs showed mono-dispersed particle size distribution in the ranges of 274.0-986.6 nm and zeta potential from -50.4 to -29.4 mV. Entrapment efficiency of QSLN was 15.2-46.2%, and their crystallinity index was low (0-18.2%). In vitro occlusion test showed QSLN-2 has the highest occlusive effect due to its smallest particle size (274.0 nm), and through these result, QSLN-2 was selected as the optimum formulation. Transmission electron microscopy (TEM) analysis further confirmed the uniform spherical shape of QSLN-2 particles. Field emission-scanning electron microscope (FE-SEM) analysis and histological observation of hairless rat skin showed that the lipid particles of QSLN-2 formed a fused lipid film and, subsequently, it hydrated the surface of the rat skin. Franz diffusion cell was used to measure in vitro skin permeation of quercetin dissolved in propylene glycol (QPG), QSLN-2 and QSLN-3. The results showed that QSLN-2 (33.5 μg cm(-2) , 21.9%) exhibited higher skin permeability than QPG (6.6 μg cm(-2) , 4.2%) and QSLN-3 (14.2 μg cm(-2) , 9.1%), which was visually confirmed by confocal laser scanning microscope (CLSM) image analysis as well.
  
  
  CONCLUSIONS
  The results suggest that QSLN-2, prepared with a surfactant content of 2%, could be used as useful skin delivery system for transdermal delivery of hydrophobic antioxidants such as quercetin.
authors.affiliation: Department of Fine Chemistry, Nanobiocosmetic Laboratory, and Cosmetic R&D Center, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul, 139-743, Korea.
authors.forename: S B
authors.initials: SB
authors.lastname: Han
authors.forename: S S
authors.initials: SS
authors.lastname: Kwon
authors.forename: Y M
authors.initials: YM
authors.lastname: Jeong
authors.forename: E R
authors.initials: ER
authors.lastname: Yu
authors.forename: S N
authors.initials: SN
authors.lastname: Park
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D016503:Drug Delivery Systems / Q000379:methods* / Q000592:standards; D004817:Epidermis / Q000502:physiology*; D006651:Histocytochemistry; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000378:metabolism* / Q000648:ultrastructure; D019308:Palmitic Acid / Q000737:chemistry; D010316:Particle Size; D011136:Polysorbates / Q000737:chemistry; D011794:Quercetin / Q000494:pharmacology*; D051381:Rats; D012869:Skin Absorption / Q000502:physiology*
chemical_list: D000975:Antioxidants; D011136:Polysorbates; D019308:Palmitic Acid; D011794:Quercetin
keywords: physical characterization; quercetin; skin hydration; skin permeation; solid lipid nanoparticles (SLNs)