title: Surface analysis of PEGylated nano-shields on nanoparticles installed by hydrophobic anchors.
abstract: OBJECTIVE
  This work describes a method for functionalisation of nanoparticle surfaces with hydrophilic "nano-shields" and the application of advanced surface characterisation to determine PEG amount and accumulation at the outmost 10 nm surface that is the predominant factor in determining protein and cellular interactions.
  
  
  METHODS
  Poly(lactic-co-glycolic acid) (PLGA) nanoparticles were prepared with a hydrophilic PEGylated "nano-shield" inserted at different levels by hydrophobic anchoring using either a phospholipid-PEG conjugate or the copolymer PLGA-block-PEG by an emulsification/diffusion method. Surface and bulk analysis was performed including X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR) and zeta potential. Cellular uptake was investigated in RAW 264.7 macrophages by flow cytometry.
  
  
  RESULTS
  Sub-micron nanoparticles were formed and the combination of (NMR) and XPS revealed increasing PEG levels at the particle surface at higher PLGA-b-PEG copolymer levels. Reduced cellular interaction with RAW 264.7 cells was demonstrated that correlated with greater surface presentation of PEG.
  
  
  CONCLUSIONS
  This work demonstrates a versatile procedure for decorating nanoparticle surfaces with hydrophilic "nano-shields". XPS in combination with NMR enabled precise determination of PEG at the outmost surface to predict and optimize the biological performance of nanoparticle-based drug delivery.
authors.affiliation: Interdisciplinary Nanoscience Center-iNANO, Department of Molecular Biology and Genetics, University of Aarhus, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark.
authors.forename: M F
authors.initials: MF
authors.lastname: Ebbesen
authors.forename: B
authors.initials: B
authors.lastname: Whitehead
authors.forename: B
authors.initials: B
authors.lastname: Ballarin-Gonzalez
authors.forename: P
authors.initials: P
authors.lastname: Kingshott
authors.forename: K A
authors.initials: KA
authors.lastname: Howard
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D057927:Hydrophobic and Hydrophilic Interactions; D019344:Lactic Acid / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000378:metabolism; D011098:Polyglactin 910 / Q000737:chemistry* / Q000378:metabolism; D011100:Polyglycolic Acid / Q000737:chemistry / Q000378:metabolism; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D013499:Surface Properties
chemical_list: C102418:poly(lactic-glycolic acid)-poly(ethyleneglycol) copolymer; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D011098:Polyglactin 910; D011092:Polyethylene Glycols