A step-by-step guide on how to produce a nanoemulsion using a surfactant system.
In this example, we will describe exactly how to produce a nanoemulsion with small particle size using Qsonica’s Q700 sonicator model. In addition to a sonicator, you will need some basic ancillary equipment such as a hot plate, scale, measuring tools and filters.
Surfactants are necessary to create nanoemulsions with a wide range of active pharmaceutical ingredient (API) concentrations. The particle size, stability and resulting performance of a nanoemulsion will vary based on the surfactant used, the quantity of surfactant and the presence of other functional ingredients needed to maintain the stability of a nanoemulsion. You will also have to experiment with the ratio of surfactant to active ingredient input used when validating a nanoemulsion formulation.
To begin, scale the water weight, surfactant and input oil as needed for other batch sizes and/or loading according to:
Wo = Co x We/1000
Wsurfactant = (3 to 8) x Wo (the “3 to 8” refers to choosing a number in that range depending on the ratio of surfactant used)
WW = We – Wsurfactant – Wo
- Wo = Weight of input oil required (g)
- Co = Desired oil concentration (mg/g)
- We = Total final emulsion weight desired (g)
- Wsurfactant = Weight of surfactant required (g)
- WW = Weight of distilled water required (g)
1. Place a magnetic stir bar in a 100mL beaker and place the beaker on a scale. Tare the scale and add your surfactant.
2. Heat the beaker on a hotplate until the surfactant covers the beaker bottom, keeping the temperature between 40˚C and 60˚C as measured with an infrared thermometer.
3. When the surfactant is fluid, place the beaker back on the scale, tare the scale and add the oil to encapsulate into the surfactant.
4. Place the beaker back on the hotplate and stir thoroughly until the oil is dispersed into the surfactant.
5. While still stirring, add the distilled water. Turn off the heat and stir until the emulsion is milky white and minimal solids are visible on the beaker wall.
6. Turn off the stirrer, insert the beaker into a larger container on the hotplate that will serve as an ice bath and restart the stirrer.
7. Add ice while the stir bar continues to stir the emulsion.
8. Turn off the stirrer and submerse the sonotrode into the emulsion.
9. Set the generator amplitude and start the sonicator, pausing periodically.
10. Run subsequent sonication cycles and sample the particle size. Repeat this process until the particle size is < 40nm (using a dynamic light scattering analyzer as measured by intensity method), refreshing the ice as needed while the generator is paused. If a particle size analyzer is not available, the translucence of the emulsion is an effective indicator of particle size. The sonotrode should be visible under the surface of the emulsion when the particle size is sufficiently small as shown below.
11. Once the emulsion has reached a sufficiently low particle size or level of translucence the processing may stop. The final emulsion should be clear, translucent with no surface oil observed. The nanoemulsion below is one that is produced using our µGOO.
12. The emulsion must then be filtered. Discharge the filtered emulsion into an autoclaved container. Refrigerate the final emulsion.