The present invention pertains to therapeutic compositions and delivery systems comprising at least one microparticle or nanoparticle. In various embodiments, the surface of the microparticle or nanoparticle is modified or functionalized with at least a portion of an isolated cellular membrane, such as an isolated plasma membrane. In addition, the microparticle or nanoparticle contains at least one active agent, such as a therapeutic and/or imaging agent. In additional embodiments, the compositions and delivery systems of the present invention may be used for targeted delivery of an active agent. Also provided are methods of making the therapeutic compositions and delivery systems of the present invention.
