Preparation of PEG-Coated Nanospheres

PEG-coated nanospheres were also prepared by the solvent diffusion method by using water-miscible organic solvents, such as acetone (Bazile et 

One of the advantages of this type of nanospheres is that, owing to the amphiphilic nature of the block copolymers PEG-R and PEG -R, the use of other surfactants (not always biocompatible) can be avoided. This is not the case with PLA (Bazile et al, 1995) or PLGA (Gref et al, 1994) polymers, whatever the nanosphere preparation method. The use of surfactants such as poly(vinyl alcohol) (PVA) or Pluronic is necessary for the formation of PLA and PLGA nanoparticles, and thus additional washing steps are required to remove adsorbed surfactant. 

Water-soluble PLA-PEG copolymers with PLAiPEG ratios of 2 5 and 3 4 (PEG chains of 5 and 2kDa, respectively) were used to coat PLGA nanospheres and thus prepare sterically stabilized particles (Stolnik et al, 

For this, the PLGA nanospheres were either prepared in the presence of PEG-PLA copolymers by the precipitation-solvent evaporation method or were prepared without any stabilizing agent and subsequently coated by incubation in aqueous solutions of PEG-PLA. 

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