Scientists now offer a promising new weapon that could help fight high cholesterol levels and the deadly heart disease that often results: synthetic high-density lipoprotein, or HDL -- the "good" cholesterol. The researchers successfully designed synthetic HDL and show that their nanoparticle version is capable of irreversibly binding cholesterol. The synthetic HDL, based on gold nanoparticles, is similar in size to HDL and mimics HDL's general surface composition.