Previous studies have used water-soluble particles to bring organic
molecules into water. What is novel about this system is the use of a
photoswitching mechanism in combination with these particles.
This image shows live cells incubated with the polymer
nanoparticles. The green color is the fluorescence coming from the
molecules trapped within the nanoparticles
The findings published online by Chemistry-A European Journal,
describe the creation of a fluorescent photoswitchable system that is
more efficient than current technologies, says Francisco Raymo,
professor of chemistry at the UM College of Arts and Sciences and
principal investigator of this study.
"Finding a way to switch fluorescence inside cells is one of the main
challenges in the development of fluorescent probes for bioimaging
applications," Raymo says. "Our fluorescent switches can be operated in
water efficiently, offering the opportunity to image biological samples
with resolution at the nanometer level."
Fluorescent molecules are not water soluble; therefore Raymo and his
team created their system by embedding fluorescent molecules in
synthetic water-soluble nanoparticles called polymers that serve as
transport vehicles into living cells. Once inside the cell, the
fluorescence of the molecules trapped within the nanoparticles can be
turned on and off under optical control.
"The polymers can preserve the properties of the fluorescent
molecules and at the same time assist the transfer of the molecules into
water," Raymo says. "It's a bit like having a fish in a bowl, so the
fish can carry on with its activities in the bowl and the whole bowl can
be transferred into a different environment."
The new system is faster and more stable than current methods. The
fluorescent molecules glow when exposed simultaneously to ultraviolet
and visible light and revert back to their original non-luminous state
in less than 10 microseconds after the ultraviolet light is removed.
By using engineered synthetic molecules, the new system is able to
overcome the natural wear down process that organic molecules are
subject to when exposed to ultraviolet light.
"The system can be switched back and forth between the fluorescent
and non-fluorescent states for hundreds of cycles, without sign of
degradation," Raymo says.
The surface of the system can be customize to help it attach to
specific molecules of interests, thus allowing researchers to visualize
structures and activity within cells, in real time, with a resolution
that would otherwise be impossible to achieve.
Raymo and his team will continue improving the properties of the
molecules for future biomedical applications. The study is titled "Fast
Fluorescence Switching within Hydrophilic Supramolecular Assemblies"
Co-authors are Janet Cusido, Mutlu Battal, Erhan Deniz and Ibrahim
Yildiz,Ph.D., students in the Department of Chemistry at UM; and
Salvatore Sortino, associate professor of chemistry in the Department of
Drug Sciences, University of Catania, Italy. The research was supported
by the National Science Foundation.
From sciencedaily
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