Amine-passivated gold nanoparticles and methods of making and using such nanoparticles are described. The nanoparticles can be prepared in a manner in which amine-containing drugs or imaging agents associate with the surface of the nanoparticles to allow delivery of the drugs or agents in vivo, but the association is weak enough to allow the amine-containing drug or imaging agents to be released from the nanoparticle upon reaching its target. Amine passivated gold nanoparticles including targeting molecules which are attached through a thiol linkage can also be prepared and used.
