The day when patients can “swallow their doctor” has come a step closer with the development of a submicroscopic nanoparticle that acts as an intelligent pill to deliver drugs when and where they are needed in the body.
Each nanoparticle is built to target a specific part of the body and to release their drugs in a controlled manner over a given period of time. They are so small that millions of them could be injected into the bloodstream without harming healthy tissues.
Scientists at the Massachusetts Institute of Technology (MIT) in Cambridge have designed the first nanoparticles designed to target the walls of the arteries around the heart. They bind specifically to the proteins that only stick out from the inner lining of the these blood vessels when they are damaged.
Once the nanoparticles take up position in the diseased arteries they are programmed to release small quantities of drugs over several weeks or months to help cardiovascular patients to recover without exposing other parts of the body to much higher doses of potentially toxic drugs.
The development comes 50 years after a prophetic lecture by the brilliant American physicist Richard Feynman entitled “there is plenty of room at the bottom” where he described possible developments in nanoscience that could one day lead patients to “swallow the doctor” in the form of tiny robotic pills that could carry out internal surgery under autonomous control.
Professor Robert Langer of MIT, who in 2008 won the prestigious Millennium Technology Prize for his medical innovations, said that initial tests carried out on laboratory rats suggest that nanoparticles could be used to treat atherosclerosis and other inflammatory cardiovascular diseases.
“This is a very exciting example of nanotechnology and cell targeting in action that I hope will have broad ramifications,” said Professor Langer. The study was published yesterday in the journal Proceedings of the National Academy of Sciences.
Each particle is just 60 nanometres across – 60 billionths of a metre – and consists of three layers. The inner core contains the drug in question bound to a long-chained molecule, or polymer. A middle layer made of fatty material separates this core from the outer coating of a polymer that protects the particle as is travels in the blood stream.
The scientists have called the particles “nanoburrs” because of their resemblance to the hook-covered seeds designed to stick to passing animals. Each nanoburr is armed with protein fragments to recognise and stick to the proteins of the target tissues.
Once the nanoburr has stuck to the cells in question, they slowly release the drug within their core. The scientists said they can time the rate and length of drug-release phase to suit a doctor’s treatment regime.
Omid Farokhzad of Harvard Medical School, who was part of the research team, said that the surgical insertion of devices called stents, which keep blood vessels open, has already been used to release drugs slowly.
“Here we take a big leap forward by developing nanotechnologies that can do the same thing without interventional techniques that commonly involve taking a patient to the cardiac catherisation lab where stents are placed,” Professor Farokhzad said.
“These particles can be administered intravenously and they are targeted and will find their way to the damaged vascular tissue, and from our experience with stents, we know once the drug gets there and released over about many days that it will work,” he said.
“We're in early stages of exploring this technology and we expect at least another two years of research and development before starting any clinical trials.
“This can be used for any disease where vascular damage or vascular permeability is a commonly observed part of the pathology. This includes almost all solid tumours and most inflammatory diseases such as Inflammatory bowel disease,” Professor Farokhzad added.
“It's another example of the huge impact that nanotechnology will have on medicine. You can rationally design therapeutics that are targeted and release their drugs in a pre-programmed way and these may go far beyond our current state-of-the-art approaches in safety and efficacy,” he said.