Written by: Ulf Nobbmann
Lipid emulsions are administered intravenously for a variety of purposes:
- To help feed patients with temporary difficulty in ingesting food orally
- For better transport of lipophilic drugs (fat-friendly active ingredient (API) which is not soluble in water)
- For controlled release of drugs (size related to uptake and retention)
- To decreasing adverse reactions to drugs
- To improve targeting of drugs
- In emerging gene therapies for cellular and gene delivery, and personalized medicine
Control and understanding of colloidal properties – such as droplet size and zeta potential – enable the design and optimization of appropriately stable emulsions. The figure to the right shows both size
and zeta potential data for a series of lipid emulsions produced using differing recipes and methods.
The sample labeled A2 showed the largest hydrodynamic size and the lowest zeta potential. These measurements correlate well with the fact that creaming was observed in this sample after 6 months storage at room temperature. Samples B1 and B2 both exhibited a smaller particle size and a stronger zeta potential, which was consistent with their 2-year shelf life stability. A strong effective charge of the emulsion droplets as seen by their zeta potential prevents the bridging, merging and flocculation of the suspended lipid particles.
Aditional information on these types of experiments can be found in the below application notes, which you might find useful:
- When adding specific salts, for example, calcium salts (Ca2+), in sufficient amounts, an emulsion can be ‘broken’: Calcium-induced flocculation of intralipid
- Triglyceride oil-in-water emulsion for parenteral nutrition is influenced by addition of amino acids, minerals, vitamins and this must be taken into account when trying to improve product formulations: Zeta potential characterization of concentrated lipid emulsions
- Top five ways to help improve the stability of your formulation explains what stability means and how to check for effects of pH, temperature, additives, kD
I hope that the next time you encounter lipid emulsions, intralipids or colloids in general, the above tips will help!