Faculty Spotlight – Dr. Claudia Turro

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Claudia Turro has been an Ohio State faculty member in the Department of Chemistry since 1996. She worked with Daniel G. Nocera and George E. Leroi at Michigan State University and received her Ph.D. in 1992. She was awarded a Jane Coffin Childs Memorial Fund for Medical Research Postdoctoral Fellowship to continue postdoctoral work at Columbia University with Nicholas J. Turro (no relation) from 1992 to 1995. She received the Early CAREER Award by the National Science Foundation in 1998 and the Arnold and Mabel Beckman Foundation Young Investigator Award in 1999.

In general, the research in the Turro group focuses on the design of advanced molecular materials that absorb light in a desired energy range, thus generating excited states. These materials are built such that their excited states emit photons of light or engage in charge transfer or unique chemical reactivity upon irradiation. The applications of the materials currently being explored in the group are diverse, with some examples listed below:

  • Biomedical imaging and detection of cancer tissue
  • Luminescent biological probes and sensors
  • Photodynamic therapy of tumors
  • Solar energy conversion and storage

Some specific examples of ongoing research are described below.

Biomedical Imaging

Figure 1. Schematic representation of multifunctional detection system coupled to tumor-seeking antibody

Advanced materials for the multifunctional detection of cancer tissue are being prepared by the Turro group. These materials combine MRI contrast agents with molecules that are highly emissive in the near-IR range, where tissue penetration of light is maximized. As schematically shown in Figure 1, these materials are covalently linked to tumor-seeking antibodies, such that after administration to the patient, the dye/contrast agent-antibody conjugate localizes selectively on cancer cells. In collaboration with oncology surgeons and engineers, the team will use these new systems to detect cancer tissue before and during surgery.

Oncology surgeons require an intraoperative real-time hand-held probe in the operating room to image occult tumors that have “normal” tissue appearance. Such detection is critical to performing oncologically sound cancer operations to attain complete tumor removal, thus preventing subsequent local recurrences and distant metastases. The fluorescence detection method coupled to tumor-seeking antibodies represents a unique manner in which to achieve the requirements of the surgeons. In addition, a single molecule can be used as both an intraoperative probe and as contrast agent, thus providing multifunctional use.

Photodynamic Therapy

Figure 2. (a) DNA binding by cisplatin and (b) photochemical ligand loss by metal complexes

Transition metal complexes that are nontoxic in the dark and become highly toxic upon irradiation with visible or near-IR light are ideal for photodynamic therapy (PDT). PDT agents currently in use require oxygen for activity, which represents a drawback since malignant tumors often have low levels of oxygen. Complexes that are able to damage or covalently bind to DNA or other biomolecules upon irradiation with visible light are currently being investigated as potential PDT agents in the Turro group.

Cisplatin is a powerful chemotherapy drug currently in use. As shown in Figure 2a, the platinum atom covalently binds to DNA after thermal ligand exchange. This irreversible binding disrupts cellular function, ultimately resulting in cell death. However, cisplatin is not selective toward cancer cells, such that thermal ligand exchange also takes place in healthy tissue. Complexes that are able to undergo ligand-loss upon excitation with low energy light with high quantum yield can also bind to DNA (Figure 2b). These systems provide selectivity toward tumor tissue, since DNA binding only takes place in the irradiated areas. Complexes of ruthenium and rhodium have been shown to work well, with toxicity lower than that of cisplatin in the dark and up to 34-fold increase in toxicity upon irradiation with visible light.

Selected Recent Publications

“Ultrafast Ligand Exchange:  Detection of a Pentacoordinate Ru(II) Intermediate and Product Formation” Yao Liu, David Turner, Tanya N. Singh, Abdelatif Chouai, Kim R. Dunbar, and Claudia Turro, J. Am. Chem. Soc. 2009, 131, 26-27.

“Ru(II) Complexes of New Tridentate Ligands:  DNA Photocleavage and Unexpected High Yield of Sensitized 1O2” Yao Liu, Richard Hammitt, Daniel A. Lutterman, Joyce, L. E.; Randolph P. Thummel, Claudia Turro, Inorg. Chem. 2009, 48, 375-385.

“The Remarkable Influence of M2 s to Thienyl π Conjugation in Oligothiophenes Incorporating MM Quadruply Bonds” Burdzinski, G., Chisholm, M. H.; Chou, P.-T.; Feil, F.; Chou, Y.-H.; Gallucci, J.; Ghosh, Y.; Gustafson, T.; Ho, M.-N.; Liu, Y.; Ramnauth, R.; Turro, C. Proc. Natl. Acad. Sci., 2008, 105, 15247-15252.

“DNA Light-Switch Behavior Observed for a Non-Intercalating Complex” Daniel A. Lutterman, Abdellatif Chouai, Yujie Sun, Cristina D. Stewart, Kim R. Dunbar, and Claudia Turro, J. Am. Chem. Soc. 2008, 30, 1163-1170.

“cis-[Rh2(m-O2CCH3)2(CH3CN)6]2+ as a Photoactivated Cisplatin Analog” Lutterman, Daniel A.; Fu, Patty K.-L.; Turro, J. Am. Chem. Soc. 2006, 128, 738-739