Abstract: A novel method of delivering drugs and diagnostics across the blood-brain barrier or blood-nerve barrier is disclosed. Drugs or diagnostic agents are incorporated into nanoparticles which have been fabricated in conventional ways. These nanoparticles are then coated with additional surfactant and given to the body of animals or humans. This allows drugs or diagnostic agents to cross the blood-brain barrier (bbb) to achieve one or more of the following benefits: (1) reducing the dose of a therapeutic drug or diagnostic agent which, when given peripherally, maintains the biological or diagnostic potency in the nervous system, (2) allowing drugs that normally do not cross the bbb to penetrate into the nervous system, and (3) reducing the peripheral side effects by increasing the relative amount of the drug reaching the brain.