I am attempting to run a few SPR assays to detect the direct binding of neurosteroids such as Pregenolone directly to a few proteins of interest.

I have found that the steroids tend to crash out of solution almost immediately. I have tried several micromolar concentrations (100uM-1uM) and even 1-3% DMSO in the running buffer. I've attempted to use typical SPR buffers such as 25mM Hepes pH 7.4, 150mM NaCl, Tween-20, and 1X PBS pH 7.4, etc.

Any insight would be greatly appreciated.