I am working on nanoemulsions for topical drug delivery. However, due to limitations with the equipment available, I am wondering is it possible to prepare my nanoemulsion in small volume, and proceed to dilute it with water? Will this process causes breakdown of the micellar structure of NE?
Swee Liang Kho
O / W nanoemulsions have a certain composition according to the amount of water, surfactant, water-insoluble drug. These ratios can be changed within certain limits. If you go beyond these limits, you can destroy the nanoemulsion or transform it upon dilution into a W / O microemulsion. Therefore, dilute by adding water drop by drop and observing its condition.
Cant say Ive ever seen an o/w emilsion invert with added water. You should be able to dilute most o/w emulsions with water. If we were talking about microemulsions it would be a more interesting discussion.
With that said there is a limit to the volume fraction of oil in an o/w emilsion before you are at risk of flipping the continuous phase particularly if you have a surfactant tgat is near balanced from a curvature perspective.
Your rmulsions will also become viscous as the volume fraction is around 50% or more.
There should not be any problem with the stability of the emulsion if the ratio of O/W is kept the same as that of the small volume you are preparing. External phase is not the main issue, however, changing an oil phase can lead to invert emulsion.
The W/O microemulsions were simply diluted by a substantial volume of water at 70 or 80 °C in our studies. The hydration of surfactants rises fast with the addition of water, and the surfactants begin to invert and migrate to produce additional oil/water interfaces. Nanosized spherical droplets spontaneously produced.
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