Novel formulations for nanoparticulate X-ray blood pool contrast agents using high molecular weight nonionic surfactants

A composition comprising nanoparticles containing an x-ray diagnostic compound, having a high molecular weight surfactant as a surface modifier adsorbed on the surface thereof and a cloud point modifier associated therewith and methods of making nanoparticles is described. A preferred surfactant is poloxamine and preferred cloud point modifiers include dimyristoylphosphatidylglycerol and dioctylsulfosuccinate. A method for diagnostic imaging for use in medical procedures comprising administering to the body of a test subject in need of an x-ray an effective contrast producing amount of the above composition is also described.