All About Chemistry... 2011 and beyond

Related Stories

Shaken, not stirred, is best for cancer imaging

James Bond liked his martini to be 'shaken not stirred', and now A*STAR researchers have found that shaking, rather than stirring, also produces better nanoparticles for bioimaging -- with important implications for spying on cancer.

Fluorescent probes currently used for bioimaging (for example, cadmium selenide quantum dots) fluoresce brightly enough to show up on detectors but may be toxic and thus unsuitable for use in the body. Now, Bin Liu and her colleagues from the A*STAR Institute of Materials Research and Engineering have successfully fabricated nanoparticle probes that are biocompatible and also have a high specificity and photostability. Furthermore, these new probes have excellent performance in the far-red to near-infrared region of the electromagnetic spectrum, which is of particular interest for cancer imaging.

The team's method is elegant in its simplicity -- it improves the optical properties of the probes by just varying the size and shape of the nanoparticles (1). "This allows us to circumvent complicated molecular design and synthesis processes," explains Liu. "It provides a facile but efficient method for developing highly far-red-near-infrared fluorescent probes."

The researchers produced the nanoparticles in water by two methods -- stirring and ultrasonication (that is, 'shaking' at very high frequencies). Ultrasonication yielded nanoparticles with average sizes of 4 nanometers, which is considerably smaller than their stirred counterparts. These nanoparticles were also much brighter, having a quantum yield of 26 per cent in water -- more than five times brighter than the nanoparticles produced by stirring.

Liu explains that ultrasonication produces polymer chains that are closer together, resulting in "compact structures that can effectively prevent water invasion and thus suppress quenching, yielding enhanced fluorescence."

The researchers then tested the behavior of the nanoparticles produced by sonication in a biological setting to determine whether they would be effective probes for a specific biological target. They chose streptavidin, a protein that has a high affinity for epithelial cell adhesion molecule (EpCAM) ― a common biomarker for various cancers. After conjugating streptavidin to the surfaces of the nanoparticles, the researchers investigated the nanoparticles' effectiveness as an extracellular probe for EpCAM by employing MCF-7 breast cancer cells as a model cell line (see image). The nanoparticles exhibited an excellent photostability and a much higher fluorescence than a commercially available probe (Cy3-SA).

Liu notes that by switching streptavidin with another protein the same nanoparticles could be used to target other biomarkers. "This will lead to a new generation of fluorescent probes for image-guided therapy," she says.

Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.

Share this story with your friends!

Social Networking

Please recommend us on Facebook, Twitter and more:

Other social media tools

Global Partners

Tell us what you think of Chemistry 2011 -- we welcome both positive and negative comments. Have any problems using the site? Questions?

About us

Chemistry2011 is an informational resource for students, educators and the self-taught in the field of chemistry. We offer resources such as course materials, chemistry department listings, activities, events, projects and more along with current news releases.

Events & Activities

Are you interested in listing an event or sharing an activity or idea? Perhaps you are coordinating an event and are in need of additional resources? Within our site you will find a variety of activities and projects your peers have previously submitted or which have been freely shared through creative commons licenses. Here are some highlights: Featured Idea 1, Featured Idea 2.

About you

Ready to get involved? The first step is to sign up by following the link: Join Here. Also don’t forget to fill out your profile including any professional designations.

Global Partners