tumor homing self-amplifying drug-carrying nanomolecules

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Tumor-Homing, Self-Amplifying Nanoparticles Developed



NEW YORK (Reuters Health) Jan 08 - Scientists have created nanoparticles with amplified tumor-homing abilities. Adding an anti-cancer drug to these nanoparticles "is envisioned," they add in a paper in PNAS Early Edition published online January 8.

"The promise of nanomedicine is based on the fact that a particle can perform more functions than a drug," Dr. Erkki Ruoslahti from the Burnham Institute for Medical Research at the University of California, Santa Barbara told Reuters Health.

The nanoparticles in this case are coated with a peptide that recognizes clotted plasma proteins, and they selectively home in on tumors. This triggers local clotting, which creates more particle binding sites. "More particles find the tumor target than would be the case without the self-amplification," Dr. Ruoslahti explained.

"The system mimics platelets, which also circulate freely but accumulate at a diseased site and amplify their own accumulation at that site," the researchers point out.

Studies in mice show that the tumor-targeted nanoparticles selectively accumulate in tumor blood vessels and "partially obstruct blood circulation to the tumor."

"Having shown the principle," Dr. Ruoslahti said, "we are now optimizing the process, hoping to obtain a more complete shut-down of blood flow to the tumor, which would strangle the tumor. We are also in the process of adding a drug delivery function to the nanoparticles."

PNAS Early Edition 2007.

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Hope over tumour fighting therapy

The technique could stop vital nutrients reaching tumours
Scientists believe they have found a way to block the supply of nutrients to cancer tumours.
Researchers mimicked the action of blood cells known as platelets by creating tiny nanoparticles to create clots to stop blood getting to tumours.

The particles may also be able to deliver chemotherapy drugs to the area, the California University team said.

The study, carried out on mice, was published in the Proceedings of the National Academy of Sciences journal.


The use of nanoparticles to deliver drugs to tumours is an exciting prospect for the future of cancer treatment, and is the subject of much research
Dr Anthea Martin, of Cancer Research UK

The researchers used the nanoparticles to zero in on the network of blood vessels that supply the tumours in mice with nutrients and oxygen.

A potentially powerful function of nanoparticles is the ability to home in on particular targets inside the body.

While various nanoparticles have been designed to target tumours, the efficiency is relatively low.

The researchers developed a technique for amplifying this homing ability by designing a multifunctional nanoparticle that binds to a protein structure found only in tumours and associated blood vessels.

To test the particles' homing ability, the researchers injected the nanoparticles into mice and found that the particles bound only to tumour vessels.

Upon binding, the particles induced selective blood clotting that attracted more nanoparticles, reminiscent of platelet and clotting action.

Tests

The tests showed that within hours of the injection, the artificial platelets began blocking the supply without harming normal tissues.

The scientists believe the nanoparticles could also be used to carry drugs to the tumour.

Lead researcher Dr Erkki Ruoslahti said: "Nanoparticle-based diagnostics and therapeutics hold great promise because multiple functions can be built into the particles.

"One such function is an ability to home to specific sites in the body.

"We envisage the design of drug-carrying nanoparticles that accumulate in tumour vessels and slowly release the drug payload while simultaneously occluding the vessels."

Dr Anthea Martin, cancer information officer at Cancer Research UK, said it was an exciting area of research, but there was still some way to go before it would be available to patients.

"The use of nanoparticles to deliver drugs to tumours is an exciting prospect for the future of cancer treatment, and is the subject of much research.

"The unique feature of this system is that once the particles start to bind to the tumour, they increase the rate at which more nanoparticles bind, setting off a chain reaction that leads to more and more nanoparticles binding.

"The system has not been tested in patients yet, but we look forward to hearing the results of further research."