In the emulsion technique, a small volume of cell-polymer suspension (discontinuous phase) is added to a large volume of a vegetable oil (continuous phase) such as soybean oil, sunflower oil, canola oil or corn oil. In some studies, white light paraffin oil (Rao et al. 1989) and mineral oil (Groboillot et al. 1993) have been used. The mixture is homogenized to form a water-in-oil (w/o) emulsion. In some cases emulsifiers are added to form more stable emulsions, since these agents lower the surface tension of droplets leading to smaller spheres. The most common emulsifier used is Tween 80 at low concentrations. Once the emulsion is formed, solidification occurs after the addition of an adequate solidifying agent to the emulsion. In the emulsion procedure, adjustment of agitation speed and phase ratio enables production of the targeted bead size. The size of the beads can vary between 25 mm and 2 mm.
Dialysis is the only way to sterlize the alkalies, still they remain streile, no action is needed.
Terminal heat sterilization or sterile filtration techniques are generally used. Heat sterilization provides better sterilization. In case your emulsion is stable under heat, sterile filtration technique is suitable.
Once I understand the reason for sterilization, I may be able to recomend the best way (Is it for adding to food? is it to be injected to animal body? or...)
If there would only be water, oil and surfactant (Tween80), I would try to sterilize with UV-light of high intensity. (Gamma-rays would be an alternative, or heat under pressure, in order to avoid bubbling and boiling.) But, if I see it right, you mention a cell fraction in your formulation. Is it right that you work with living cells in this context ? If yes, it depends on your cells, of course, what you can use for sterilization.
No problems, on the same way that you stelized any solution, yo must care with thermal stalility of the sample.
Heat is always the first choice for sterilization; cf. pasteurization for milk. However, that may be a problem with your cellular content, which is not described further. In addition, initial sterilization is not maintained during downstream processing or use, unless additional biocide is added to the mixture. [see below for more on biocides]
But an additional issue may arise from your use of heat: cloud point of your surfactant. That is the temperature above which your surfactant falls out of solution, and therefore looses its effectiveness as a surfactant. Cloud points are common in nonionic surfactants, and frequently occur well below the boiling point of water. Your supplier of Tween80 can provide you with the cloud temperature of that surfactant, from which you can determine if pasteurization is feasible for your end use.
Anionic surfactants are more efficient than nonionics, are not prone to cloudpoint problems, and are frequently lower in cost at use levels. I would consider particularly the sulfonate (not sulfate), phosphate, and imadazoline classes for further consideration.
In the coatings industry, we use vast amounts of emulsion-polymerized polymers to make water-based paints. It is crucial to sterilize both the latex and the final paint before shipping, and maintain that sterility during downstream processing and use. We routinely use biocides to accomplish the desired sterilization/preservation of water-based coatings. Dow is a well-known supplier of biocides for such end-use. But there is still the issue of the cellular component in your formulation, and whether that would be damaged by biocides. If you could explain that, we could better advise you.
I am intrigued about your comment of retrieving beads at the end of the emulsification step, which suggests some form of suspension polymerization in the interim, which is not obvious from your other comments. So please clarify this as well.
Thank for your valuable and constructive comments.
It is important to note that, the aim of sterilization of tween 80 and vegetable oil (corn oil) is to microencapsulation of probiotic bacteria via emulsion technique in order to work in sterile condition.
- Badges
- Science topic
- Similar topics
- Social Psychology
- Attitude