Preparation of nanoparticles by solvent displacement for drug delivery: A shift in the " ouzo region" upon drug loading

Moritz Beck-Broichsitter, Erik Rytting, Tobias Lebhardt, Xiaoying Wang, Thomas Kissel

Research output: Contribution to journalArticlepeer-review

126 Scopus citations


As biodegradable nanoparticles meet with increasing interest for drug delivery applications, a series of investigations were carried out to understand the mechanism of the formation of drug-loaded nanoparticles using the solvent displacement method. Although previous explanations referred to Marangoni convection as the driving force for nanoprecipitation, recent publications describing the so-called " ouzo effect" sparked these current studies using a novel negatively charged polymer, poly(vinyl sulfonate-co-vinyl alcohol)-graft-poly(d,. l-lactide-co-glycolide) (P(VS-VA)-g-PLGA), and a positively charged model drug, salbutamol. Interfacial tension did not influence the nanoparticle formation as would be expected if governed by Marangoni convection, but ternary phase diagrams outlined the so-called " ouzo regions" defining the polymer and solvent concentrations leading to stable nanoparticle suspensions for both this novel polymer and unmodified poly(d,. l-lactide-co-glycolide) (PLGA). Physicochemical properties, morphology and drug loading of the nanoparticles were analyzed, and stable P(VS-VA)-g-PLGA nanoparticles with and without salbutamol ranged in size from 59-191. nm. The " ouzo region" phase diagram boundaries shifted considerably upon drug loading, which can be explained by the increased solubility of the polymer-drug complex. This behavior necessitated a substantial adjustment of polymer concentrations required to produce drug-loaded nanoparticles with characteristics comparable to blank nanoparticles. In conclusion, the use of " ouzo diagrams" is a beneficial tool to manufacture nanoparticles with specified physicochemical properties by the solvent displacement method.

Original languageEnglish (US)
Pages (from-to)244-253
Number of pages10
JournalEuropean Journal of Pharmaceutical Sciences
Issue number2
StatePublished - Oct 2010
Externally publishedYes


  • " ouzo effect"
  • Biodegradable polyesters
  • Nanoparticles
  • Pulmonary drug delivery
  • Salbutamol
  • Solvent displacement

ASJC Scopus subject areas

  • Pharmaceutical Science


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