title: Chitosan rate of uptake in HEK293 cells is influenced by soluble versus microparticle state and enhanced by serum-induced cell metabolism and lactate-based media acidification.
abstract: Chitosan is a biocompatible polysaccharide composed of glucosamine and N-acetylglucosamine. The polymer has a unique behavior of fluctuating between soluble chains at pH 6 and insoluble microparticles at pH 7. The purpose of this study was to test the hypothesis that chitosan structure, solubility state, and serum influence the rate of cell uptake. Chitosans with 80% and 95% degree of deacetylation (medium and low viscosity) were tagged with rhodamine and analyzed for particle size, media solubility, and uptake by HEK293 epithelial cells using live confocal microscopy and flow cytometry. In media pH 7.4 with or without 10% serum, chitosans fully precipitated into 0.5 to 1.4 µm diameter microparticles with a slight negative charge. During 24 h of culture in serum-free medium, chitosan particles remained extracellular. In cultures with serum, particles were taken up into intracellular vesicles in a serum dose-dependent manner. Opsonization of chitosan with serum, or replacement of serum by epidermal growth factor (EGF) failed to mediate serum-free chitosan particle uptake. Serum stimulated cells to acidify the media, partly by lactate generation. Media acidified to pH 6.5 by 7 mM lactate maintained 50% of chitosan in the soluble fraction, and led to minor uniform serum-free uptake in small vesicles.
  
  
  CONCLUSIONS
  Media acidification mediates minor in vitro uptake of non-biofouled soluble chitosan chains, while serum-biofouled insoluble chitosan microparticles require sustained serum exposure to generate energy required for macropinocytosis.
authors: Department of Chemical Engineering, Institute of Biomedical Engineering, FRQS Groupe de Recherche en Sciences et Technologies Biomédicales (GRSTB), Ecole Polytechnique, 2900 Blvd. Edouard Montpetit, Montreal, Quebec, H3T 1J4, Canada. caroline.hoemann@polymtl.ca
authors: Caroline D
authors: CD
authors: Hoemann
authors: Jessica
authors: J
authors: Guzmán-Morales
authors: Nicolas
authors: N
authors: Tran-Khanh
authors: Geneviève
authors: G
authors: Lavallée
authors: Mario
authors: M
authors: Jolicoeur
authors: Marc
authors: M
authors: Lavertu
mesh_terms: D002236:Carbohydrate Conformation; D048271:Chitosan / Q000737:chemistry / Q000378:metabolism*; D003470:Culture Media; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D008027:Light; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010316:Particle Size; D012235:Rhodamines / Q000737:chemistry / Q000378:metabolism; D012542:Scattering, Radiation; D044967:Serum / Q000502:physiology*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003470:Culture Media; D005456:Fluorescent Dyes; D012235:Rhodamines; D019344:Lactic Acid; D048271:Chitosan; C027755:rhodamine isothiocyanate