May 3, 2011

C Dots Give Doctors Eyes for Cancer

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Cornell Dots or C Dots are tiny glass-encased beacons  that some hope will greatly improve the diagnosis and treatment of cancer. They are about a million times smaller than either one of your eyeballs.  This comparison is by no means trivial; already, C Dots are revolutionizing human optical capability.In 2005, Prof. Uli Wiesner, materials science and engineering, and Hooisweng Ow Ph.D. ’05 first developed C Dots. Ow described them as “a little bit of organic dyes covalently linked to sand molecules.”  C Dots were recently approved for clinical trials at Memorial Sloan-Kettering Cancer Center in New York City and by the Food and Drug Administration.  In fact, the C Dot is the first ever inorganic particle approved by the FDA as a drug. In late 2006, Sloan-Kettering physician Prof. Michelle Bradbury, radiology, began collaborating with Wiesner and his team. Currently, Bradbury is preparing to conduct the first in-human trials, which will involve five metastatic cancer patients.  The C Dots will target surface receptors expressed on certain tumor-surfaces in addition to being radio-labeled. The radio-label will then allow a PET scan to quantitatively determine the tumor’s growth and spread, as well as the C Dots’ uptake and distribution throughout the body. “To get particles to that size and have them behave the way they should is an engineering feat,” remarked Bradbury. She believes this diagnostic tracer study to be the first step on the road to developing a future therapeutic.“To be involved in this process has been very rewarding,” commented Ow. “You work for years and years and years, and actually translating that work into something that is helpful … it is a good feeling.”Wiesner noted how important initial surgery can be for a cancer patient’s prognosis and how “there is no engineering parameter which helps surgeons decide what to take out and what not.  Your best chance is to get a surgeon with a lot of experience.”Like their predecessor quantum dots, C Dots greatly enhance the fluorescence (or brightness) of the dyes they encapsulate.  This can be used to light up cells of interest.Ow explained the physics behind the effect: “These are large and floppy [dye] molecules. There are many ways a molecule can release energy by twisting or releasing it as light or a combination … When we freeze these molecules in glass, the molecules cannot flop around anymore and they release their energy just as light.”However, unlike their predecessors, which are currently composed of such poisonous and mutagenic metals as cadmium, C Dots are made with materials that are inherently safe. They are chemically inert and water-soluble, which are major contributors to their status as both environmentally sound and biocompatible.  “In 20 years, it will be commonplace that you go into a doctor’s office and [snapped] your entire genome will be sequenced,” Wiesner said.  He proceeded to explain how this could allow doctors to screen individuals and then decide what therapy makes the most sense for them personally.  A doctor will then be able to grab a vial of C Dots (or something comparable) off the shelf, attach the appropriate drugs to their surface, and inject them.“You can attach so many drug molecules to these particles,” said Bradbury. “It makes it kind of exciting to contemplate.” Other applications for C Dots are anticipated in sensors, flexible displays, optical computing, and such microarrays as DNA chips.As a Wiesner-team poster at the entrance of Bard Hall puts it, the next step for Cornell scientists is  “‘connecting the dots.”

Original Author: Bob Hackett