Hypothesis: The use of polymer-based surfactants in the double-emulsion (water/oil/water, W/O/W) solventevaporation
technique is becoming a widespread strategy for preparing biocompatible and biodegradable
polymeric nanoparticles (NPs) loaded with biomolecules of interest in biomedicine, or biotechnology. This
approach enhances the stability of the NPs, reduces their size and recognition by the mononuclear phagocytic
system, and protects the encapsulated biomolecule against losing biological activity. Different protocols to add
the surfactant during the synthesis lead to different NP colloidal properties and biological activity.
Experiments: We develop an in vitro model to mimic the first step of the W/O/W NP synthesis method, which
enables us to analyze the surfactant-biomolecule interaction at the O/W interface. We compare the interfacial
properties when the surfactant is added from the aqueous or the organic phase, and the effect of pH of the
biomolecule solution. We work with a widely used biocompatible surfactant (Pluronic F68), and lysozyme,
reported as a protein model.
Findings: The surfactant, when added from the water phase, displaces the protein from the interface, hence
protecting the biomolecule. This could explain the improved colloidal stability of NPs, and the higher biological
activity of the lysozyme released from nanoparticles found with the counterpart preparation.
