Is it necessary to add a cryoprotectant to PLGA nanoparticles before lyophilization? If so, how much?

I made PLGA drug loaded nanoparticles (without any surfactants). Before lyophilization, I put them in -70C for a day or more. When I take them out from the deep freezer and let them thaw, they are...

10 February 2014 5,476 16 View