Nanoparticles Assembled Inside Tumors Trap Drugs and Imaging Agents

July 17, 2010

( -- Virtually every study that uses nanoparticles to deliver drugs and imaging agents to tumors starts by loading the clinical payload into the nanoparticle and then injecting the resulting delivery agent into the body. While effective at reducing clearance from the body and improving drug or imaging agent retention in a tumor, the nanoparticles do move relatively slowly from the circulation into the heart of the tumor.

Now, a pair of investigators from the University of Toronto have shown that a system that assembles itself into a nanoparticle, complete with drug or imaging agent, once it gets inside a tumor can dramatically increase the rate at which clinically important molecules get into tumors and still trap those molecules inside the tumor. Warren Chan and postdoctoral fellow Steven Perrault conducted the study and published the results of their work in the .

The goal of this project was to develop a nanoparticle system that would combine the fast “in” rate for small molecule drugs or imaging agents with the glacial “out” rate associated with nanoparticles. This would allow as much drug or imaging agent to get into and stay in tumors while allowing the body to excrete rapidly any of the active material that remained in the or that happened to get inside of non-targeted tissue. To create a system that would marry these two seemingly incompatible characteristics, Drs. Chan and Perrault first inject 30 nanometer diameter gold nanoparticles coated with a biotin terminated ; the polmer keeps the particles from sticking to one another and the biotin allows for later conjugation to imaging agents or drugs. Over the course of the next 24 hours, many of the gold nanoparticles accumulate in tumors, while the rest are excreted from the body.

Next, the researchers inject the active substance linked to streptavidin, a molecule that binds tightly and specifically to biotin. This small molecule construct readily enters tumors, as well as other tissues, but once in the tumors it sticks in an almost irreversible manner to the gold nanoparticles, greatly reducing the rate at which the active molecule will exit the tumor.

Using a fluorescent dye as the active molecule linked to streptavidin, Drs. Chan and Perrault were able to track the kinetics of drug accumulation in . The results were remarkable: the active molecule accumulated nearly 200-fold increase in the rate at which drug accumulated in tumors compared to animals that did not receive the biotin-coated gold . In addition, pretreated tumors accumulated five times more of the fluorescent probe than did the control animals.

This work is detailed in a paper titled, “In vivo assembly of nanoparticle components to improve targeted cancer imaging.” An abstract of this paper is available at the journal’s Web site.

Explore further: Nanoparticles Designed for Dual-Mode Imaging

Related Stories

Nanoparticles Designed for Dual-Mode Imaging

December 18, 2006

Nanoscale, inorganic fluorescent imaging agents such as quantum dots have become an important tool for researchers studying key biomolecules involved in cancer. At the same time, magnetic iron oxide nanoparticles are proving ...

New Nanoparticles for Targeting Tumors

March 27, 2008

As a wide variety of nanoparticles continue to demonstrate their ability to improve the delivery of imaging agents and drugs to tumors, nanoparticle researchers have turned their attention to the challenge of systematically ...

Nanoparticles Cooperate to Detect and Treat Tumors

March 26, 2010

( -- If one nanoparticle is good, two may be better, especially when they are designed to cooperate with each other to diagnose and treat cancer. That finding comes from work led by Michael Sailor, Ph.D., a member ...

Potential for New Nanoparticle-Based Cancer Detection

May 25, 2010

( -- Recent studies support the idea that the standard methods of screening men for prostate cancer leave much to be desired, particularly in terms of their inability to have much effect on prostate cancer survival.

Recommended for you

Touchless displays superseding touchscreens?

October 2, 2015

While touchscreens are practical, touchless displays would be even more so. That's because, despite touchscreens having enabled the smartphone's advance into our lives and being essential for us to be able to use cash dispensers ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.