Effect of pH and electrolytes on the colloidal stability of stearic acid–based lipid nanoparticles

  • Alexander F. IfeEmail author
  • Ian H. Harding
  • Rohan M. Shah
  • Enzo A. Palombo
  • Daniel S. Eldridge
Research Paper


Stearic acid–based solid lipid nanoparticles, stabilised with Tween® 20, were synthesised using a microwave-assisted microemulsion technique and their stability was tested in simulated blood plasma, several liquids mimicking gastrointestinal fluids and solutions containing different electrolyte compositions and pH levels. It was discovered that simulated blood plasma had a stabilising effect on the particles, as did simulated saliva and intestinal fluid, which was due to hydration forces, facilitated by the presence of hydrated cations. It was determined that the hydration stabilisation was pH dependent, with highly acidic conditions depriving the solid lipid nanoparticles of the negative charge required for the cations to hydrate the surface. In environments lacking hydrated cations, the particles were predominately reliant on steric stabilisation and were particularly susceptible to pH extremes due to hydrolysis/oxidation of the Tween® 20 layer. The results suggest that the SLNs have potential as a systemic drug carrier, as the physicochemical conditions of blood provide a stabilising environment that inhibits particle growth.


Solid lipid nanoparticles Hydration forces Steric stabilisation Tween® 20 Simulated body fluids Colloidal drug carriers 



Brookhaven Instruments Corporation


Electrophoretic light scattering


Photon correlation spectroscopy


Research Training Program


Simulated body fluid(s)


Simulated gastric juice


Simulated intestinal fluid


Solid lipid nanoparticle(s)


Simulated saliva



We are thankful to Savithri Galappathie who prepared several solutions that were used throughout the course of this research.

Funding information

This study received financial support from the Australian Government’s Research Training Program (RTP).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Department of Chemistry and BiotechnologySwinburne University of TechnologyHawthornAustralia

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