Public Release: 

Medical molecules designed to respond to visible light that can penetrate tissue

Virginia Tech

Blacksburg, Va. -- If you have ever covered a flashlight with your hand and seen the red light that still comes through, then you have seen light in the therapeutic window - that magic wavelength that is not absorbed or reflected away by tissue. Scientists believe that they can use light at that wavelength to signal manmade molecules to release drugs at disease sites in the body.

Such possibilities will be discussed in a poster and a talk by Virginia Tech researchers presenting at the 229th American Chemical Society national meeting in San Diego on March 13-17.

Researchers in Karen Brewer's group at Virginia Tech have designed supramolecular complexes that can hold and, when signaled by light (photoinitiatied), will generate pharmaceutical compounds that can cleave DNA, such as in a tumor cell. "The challenge has been that tissue blocks light so we can't signal molecules deep within the body to deliver drug therapy," says Brewer, associate professor of chemistry.

Matthew Mongelli of Maywood N.J., a postdoctoral associate in chemistry, and his colleagues in chemistry and biology at Virginia Tech, have been working with Theralase Technologies Inc. to design molecular systems that use light that is in the therapeutic window. Starting with a complex with known DNA cleaving qualities, they changed the light absorber unit to one that responds to the red wavelength.

"Investigations into polyazine supermolecular complexes containing Ru and Os with Rh centers that possess photoactive MMCT states: Visible light induced, oxygen independent DNA photocleavage (INOR 329)," will be presented by Mongelli during the general poster session, 7 to 9 p.m., Sunday, March 13, in Convention Center Hall D. The poster has also been selected for the Sci_Mix session 7 to 9 p.m. Monday, March 14, in the Convention Center's Sails Pavilion.

Co-authors are Brewer; undergraduate chemistry students Matthew Jeletic of Centreville, Va. and Jerita Dubash of Ashburn, Va.; and Biology Professor Brenda S. J. Winkel, all of Virginia Tech.

Brewer will also give an oral presentation on designing photochemical molecular devices and applications in photodynamic therapy and in solar energy conversion. Because of the detail offered by Mongelli's poster, Brewer says she will focus on the exciting potential of creating molecules to reduce water to hydrogen. The talk, "Designing photochemical molecular devices utilizing Os and Ru polyazine light absorbers and Rh and Pt reactive sites: Applications in solar energy conversion and photodynamic therapy (INOR 410)," will be presented at 4:50 p.m. Monday, March 14, in Convention Center Room 4. Co-authors are chemistry Ph.D. students Mark Elvington of Blacksburg, Va. and Ran Miao of Zhangzhou City, China, Mongelli, Dubash, Jeletic, and chemistry undergraduate Julie Heinecke of Powhatan, Va.

###

Contact for more information:
Karen Brewer, (540) 231-6579 or kbrewer@vt.edu
Learn more at www.chem.vt.edu/chem-dept/brewer/brewer.html

Poster Abstract: Supermolecular complexes of the form LA-BL-RhIIICl2-BL-LA (LA = RuII or OsII polypyridine light absorber; BL = polyazine bridging ligand) can be designed to have Rh (d_*) LUMOs low lying and MMCT (metal to metal charge transfer) states. Photoinitiated DNA cleavage occurs via an oxygen independent pathway by way of a visible light induced population of the MMCT triplet state. An analysis of factors impacting this reaction with DNA will be presented. Work towards designing systems that utilize light in the therapeutic window will be presented. This work is supported by the NSF (CHE-0408445).

Oral Abstract: Mixed-metal supramolecular complexes are a promising structural motif for the construction of a wide assortment of photochemical molecular devices. Coupling of Ru or Os light absorbers to Rh or Pt reactive centers yields complexes that display an array of interesting photochemical properties. Through modification of the components used in these devices we have produced systems that function as photoinitiated electron collection devices, photocatalysts for the production of hydrogen from water, new types of photodynamic therapy agents and chromophoric DNA binding agents. Factors impacting the selection of device components and aspects of the photochemical reactivity of these complexes will be presented. This work is supported by the NSF (CHE-0408445) and the ACS-PRF.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.