Stable dispersion of nano-hydroxyapatite in water or PBS

[yesbeckng]

I have synthesized nano-hydroxyapatite particles via wet chemistry precipitation of a Ca-PO4 solution. In water and PBS, these crystals tend to clump together in aggrigates up to 20-30 microns. The only way that I can get them to disperse is to sonicate them in either Hexafluoro-2-propanol or Dimethylformamide. I have also tried adding acid groups to the surfaces of the particles, such as 12 aminododecanoic acid and dodecanedioic acid, but so far all of my attempts have been unsuccessful. Are there any simple methods to get a well dispersed solution of nano-hydroxyapatite in water or PBS? I was thinking I would continue to try adding other molecules to the surface of the crystals, but I am unsure which direction to go in. Any insight would be appreciated.

 

[yesbeckng]

Thank you for the reply. Since creating this thread I've tried various other methods and finally created a stable suspension using low MW polyacrylic acid. I have not had time to fully characterize the crystal suspension, but if my work is published I will post a link so that others can know the exact methods.

To answer your questions...

Is it necessary to have it in water or PBS?

The application requires that the solvent not denature proteins or be cytotoxic, so most likely yes.

What method did you follow to cover the surface by long-chain acids?

I made a solution of CaNO3 and NaH2PO4, heated it to 85C and then added NH3-H20 which caused crystal formation. After a minute, the acid was added to the solution. This method has been previously published.