title: The characteristics and mechanisms of uptake of PLGA nanoparticles in rabbit conjunctival epithelial cell layers.
abstract: OBJECTIVE
  To delineate the characteristics and mechanisms of uptake of biodegradable poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles in primary cultured rabbit conjunctival epithelial cells (RCECs).
  
  
  METHODS
  Poly(D,L-lactide-co-glycolide) nanoparticles (PLGA 50:50. 101 nm in diameter) containing 6-coumarin (as a fluorescent marker) were used. The effect of size was studied using various particle sizes (100 nm, 800 nm, and 10 microm). The effect of cytochalasin D, nocodazole, and metabolic inhibitors on nanoparticle uptake was investigated. The capability of nanoparticles to enhance the uptake of an encapsulated protein. BSA bound to Texas red (TR-BSA), was evaluated.
  
  
  RESULTS
  Maximal uptake of nanoparticles at 37 degrees C occurred at 2 h, and 100-nm particles had the highest uptake in RCECs in comparison with 800-nm and 10-microm particles. Nanoparticle uptake was saturable over the 0.1-4 mg/ml concentration range. Nanoparticle uptake was confirmed by confocal microscopy and was inhibited significantly by coumarin-free nanoparticles (of similar size), by lower incubation temperature, and by the presence of metabolic inhibitors and cytochalasin D. The uptake of encapsulated TR-BSA in RCECs at 4 h was 28% higher than free BSA application.
  
  
  CONCLUSIONS
  Our findings suggest that PLGA nanoparticle uptake in primary cultured rabbit conjunctival epithelial cells occurs most likely by adsorptive-type endocytosis.
authors.affiliation: Department of Pharmaceutical Sciences, University of Southern California, Los Angeles, California 90089-9121, USA.
authors.forename: Mohamed G
authors.initials: MG
authors.lastname: Qaddoumi
authors.forename: Hideo
authors.initials: H
authors.lastname: Ueda
authors.forename: Johnny
authors.initials: J
authors.lastname: Yang
authors.forename: Jasmine
authors.initials: J
authors.lastname: Davda
authors.forename: Vinod
authors.initials: V
authors.lastname: Labhasetwar
authors.forename: Vincent H L
authors.initials: VH
authors.lastname: Lee
mesh_terms: D000818:Animals; D003228:Conjunctiva / Q000378:metabolism*; D003374:Coumarins / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000378:metabolism*; D019344:Lactic Acid / Q000493:pharmacokinetics*; D008297:Male; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011100:Polyglycolic Acid / Q000493:pharmacokinetics*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000493:pharmacokinetics*; D011817:Rabbits
chemical_list: D003374:Coumarins; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C030123:coumarin