[Carina]

Hi all,

I'm synthesizing polymeric nanoparticles using the simple oil-in-water (o/w) emulsion. First I dissolved the polymer in an organic solvent (I tried with dichloromethane and ethyl acetate). The resulting organic solution is dispersed into nanodroplets in an aqueous solution using a dispersing agent (I tried with 3% PVA and 0,3% PVA) and high-speed homogenization. After the formation of a stable emulsion, a nanoparticle suspension is formed by the evaporation of the solvent. However, when I tried to centrifuge, it did not form any pellet. The water phase looks cloudy and I also think that the particles are less dense than water. So what should I do? Should I lyophilize the water phase and try to wash the surfactant later?

Thank you.

*MOD Edit -- more descriptive title*

[vex]

If the particles are actually less dense than water, then you might try filtering through some very fine paper or a membrane, or lyophilization if you're more familiar with that (I'm not).

But, if the particles are more dense, it should be possible to spin them out. If you have a stable suspension, it's because you've hit a sweet spot in surface charge depth and it's electrostatics that are keeping your particles in solution (google "zeta potential"). In that case, you can disrupt the interactions by increasing the ionic strength of the solution. I usually use ammonium nitrate since it decomposes readily upon heating. So, if you toss in some ammonium nitrate, I would expect your particles to condense at the bottom and form a pellet on centrifugation.

[Stepan]

If what you prepare is true nano-particles, I do not think you can filtrate them. Most commercial filters have pore size from 220 nm and up. Analytical ultra high speed centrifuges can separate from 5 nm. I think (but I am not an expert) most laboratories use osmosis for sample concentration.

[dimidola12]

dialyze them with dialysis membrane bags in water. Otherwise you can go for ultrafiltration.