Process for the preparation of crystalline nano-particle dispersions
A process for the preparation of a dispersion of crystalline nanoparticles in an aqueous medium is disclosed. Specifically, a first solution comprising a substantially water-insoluble substance in a water-miscible organic solvent is rapid mixed with an aqueous phase comprising water, and optionally a stabilizer, to form a dispersion of amorphous particles. The dispersion of amorphous particles is then sonicated for a sufficient period to form crystalline nanoparticles of the substantially water-insoluble substance. The process provides nanocrystals with a mean hydrodynamic diameter of less than 1 micron, particularly less than 300 nm, and is particularly useful for the preparation of nanocrystalline dispersions of pharmaceutical substances.
1. A process for the preparation of a dispersion of nano-crystalline particles in an aqueous medium, the process comprising the steps:
(a) combining in less than 30 seconds a first solution and an aqueous phase under rapid mixing to form a dispersion of amorphous particles, wherein:
(i) the first solution comprises a substantially water-insoluble substance in a water-miscible organic solvent, and
(ii) the aqueous phase comprises water and optionally a stabilizer,
(b) sonicating the dispersion of amorphous particles for at least 10 minutes to form nanocrystalline particles having a mean particle size of from 10 to 200 nm of the substantially water-insoluble substance; and
(c) optionally removing the water-miscible organic solvent.
2. The process according to claim 1 , wherein the substantially water-insoluble substance is a pharmacologically active compound.
3. The process according to claim 1 , wherein the concentration of the substantially water-insoluble substance in the aqueous medium following step (a) is 10 mM or less.
4. The process according to claim 3 , wherein the concentration of the substantially water-insoluble substance in the combined solution and aqueous phase following step (a) is from 0.5 to 3 mM.
5. The process according to claim 1 , wherein the aqueous phase contains a stabiliser.
6. The process according to claim 5 , wherein the stabiliser comprises a polymeric dispersant and an amphiphilic surfactant.
7. The process according to claim 6 , wherein the amphiphilic surfactant is an anionic, cationic, or non-ionic surfactant.
8. The process according to claim 7 , wherein the polymeric dispersant is polyvinylpyrrolidone and the anionic surfactant is sodium dodecyl sulfate.
9. The process according to claim 6 , wherein the amphiphilic surfactant is at a concentration below the critical association concentration for the amphiphilic surfactant and polymeric dispersant.
10. The process according to claim 1 , wherein rapid mixing comprises using sonication during the combination.
11. The process according to claim 1 , wherein the first solution is added to the aqueous phase.
12. The process according to claim 1 , wherein the dispersion of amorphous particles is sonicated at a temperature below 50° C.
13. The process according to claim 1 , further comprising isolating the nano-crystalline particles after formation of the nanocrystalline particles or after removal of the water-miscible organic solvent.
14. The process according to claim 1 , wherein the dispersion of amorphous particles is sonicated for 20 to 100 minutes.
15. The process according to claim 1 . wherein the first solution is added to the aqueous phase, wherein the aqueous phase comprises water. a polymeric dispersant, and an amphiphilic surfactant, and the concentration of the substantially water-insoluble substance in the combined first solution and aqueous phase following step (a) is 10mM or less.
16. The process according to claim 15 , wherein the first solution and aqueous phase are combined by rapid mixing using sonication during the combination.