Wednesday, September 21, 2016

DNA + Light: Talk by Carlos E. Crespo-Hernández

Talk sponsored by the Department of Chemistry and Biochemistry 
Thursday, September 22, 2016
4:45pm  Science Center A255

DNA + Light: From Nucleic Acid Bases to Modifications that Enable Damage to Carcinoma Cells

Carlos E. Crespo-Hernández, Department of Chemistry and Center for Chemical Dynamics, Case Western Reserve University, Cleveland, OH, United States.

Partial abstract: Photodynamic therapy (PDT) is an effective treatment option for a variety of skin cancers and diseases. Recently, the DNA analog 4‑thiothymidine (4tT) has demonstrated efficacy as a PDT agent against rapidly-dividing malignant cells while leaving normal cells unharmed. Its phototoxic activity and low off-target effects make this thiobase a highly promising PDT candidate. However, the depth of tissues able to be treated with 4tT is limited by its absorption cutoff at ~365 nm. A thiobase photosensitizer able to absorb longer wavelengths of light is needed because longer wavelengths are able to reach more invasive skin cancers and diseases. Recently, we found that doubling the sulfur substitution of the nucleobase increases its photoreactivity and simultaneously shifts its absorption spectrum into the near-visible region (~395 nm) where light can penetrate more than 100% deeper into tissues. In vitro screening experiments performed in our laboratory using epidermoid carcinoma cells (A431) have revealed several doubly-substituted thiobase derivatives that are effective photosensitizes.

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