News Release

Light turns on anticancer agents

Peer-Reviewed Publication

Virginia Tech

Blacksburg, Va., Aug. 24, 2004 – In order to not harm innocent tissue while aggressively treating diseases such as cancer with powerful medicine, scientists have been creating therapy agents that they can activate with light only at the site of a tumor.

Until now, almost all photodynamic therapy agents have required oxygen. Yet, tumors are often oxygen depleted. Now, Virginia Tech researchers have developed light-activated therapy agents that are oxygen independent.

The research will be presented at the 228th American Chemical Society National Meeting in Philadelphia August 22-26, 2004

Karen Brewer's chemistry-biology group is working with cell cultures to compare the effectiveness of the agents in the dark and in visible light. "Another improvement for our systems is that the agents are activated by visible light, as opposed to UV light," said Brewer, associate professor of chemistry. "Using only visible light is a safeguard against inadvertent damage of tissue."

Brewer will present the talk, " Light induced DNA cleavage and photodynamic therapy properties of MMCT states of rhodium centered supramolecular complexes," at 4:30 p.m., Tuesday, Aug. 24, at Pennsylvania Convention Center room 111B as part of the at the Bioinorganic Chemistry symposium. Co-authors are Brewer, former post-doctoral associate Alvin A. Holder, graduate students Mark Elvington of Blacksburg and R. Lee Williams of Virginia Beach, and undergraduate Jerita Dubash of Ashburn, Va., all with Virginia Tech's chemistry department, and Virginia Tech biology professor Brenda S.J. Winkel.

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The research has been funded by the Virginia Tech Applied Biosciences Center and the National Science Foundation. The researchers have applied for a patent for the new photodynamic therapy agents.

Abstract

INOR 427 Light induced DNA cleavage and photodynamic therapy properties of MMCT states of rhodium centered supramolecular complexes

Triads of the form LA-BL-Rh(III)-BL-LA can be designed to possess low lying metal to metal charge transfer (MMCT) states (LA = Ru(II) or Os(II) polypyridine light absorber, BL = polyazine bridging ligand). In these systems with low lying MMCT states, visible light excitation leads to reduction of the rhodium center. This MMCT excited state displays interesting reactivity with DNA and these complexes function as photodynamic therapy agents. The DNA reaction is oxygen independent. The photodynamic properties of these complexes have been studied using cell cultures. Aspects of the photochemical reactivity of these complexes with DNA and cell cultures will be presented.


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