X-ray and NIR Induced Photochemistry in UV-Vis Opaque Media

In this project, funded by the Chemical Mechanism, Function, and Properties Program of the Chemistry Division, Professor Vladimir Popik of the Department of Chemistry at the University of Georgia is developing a novel strategy for selective activation of bioactive compounds using Near Infrared (NIR) light or low level X-ray radiation. While a significant fraction of diseases is localized in some organ or tissue, the treatment is often systemic, causing undesirable off-target effects. Most obvious example of such complications is the toxic effects of anti-cancer drugs, but even treatment of arthritic inflammation with nonsteroidal anti-inflammatory drugs (NSAIDs) increases the chances of a heart attack or stomach ulcer. The use of tissue-penetrating X-ray or NIR for drug activation may allow for the selective treatment of localized malignancies, while sparing the rest of the organism from harmful side effects. This project studies the fundamental feasibility of such an approach and its potential impact in photochemistry. The project provides students with an interdisciplinary training at the interface of synthetic and physical organic chemistry, as well as photochemistry, biochemistry, and nano-technology. High school students conducting summer internships in the Professor Popik's laboratory via the University of Georgia Young Dawgs Program will be exposed to modern scientific research.

While photomedicine offers high spatiotemporal selectivity in the treatment of various malignancies, the majority of the photo-activation strategies require UV-Vis irradiation. The high absorbance and the strong scattering of light below 650 nm in mammalian tissues limit the utility of current photomedicine mostly to subcutaneous and ophthalmic applications. The main goal of this project is the exploration of the feasibility of the induction of photochemical reactions in UV-Vis opaque mediums employing X-ray and NIR radiation. Since the X-ray absorption cross-section of organic molecules is very small, Professor Popik plans to explore the use of X-ray scintillating nanoparticles as localized light sources and gold nanoparticles as emitters of high energy electrons. The NIR light within the so-called photo-therapeutic window (650 - 950 nm) penetrates deep into the tissues, but carries insufficient energy to achieve photo-activation. Upconverting nanoparticles that emit UV-Vis light upon NIR excitation may circumvent this problem. Alternatively, the enhancement of two-photon cross-section in nanocrystalline states due to quantum chain reactions will be explored. Nanocrystals of photoactivated drugs have additional advantages as drug delivery vehicles: they contain more active material per weight than other nano-carriers, as no inert core or membrane is required.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Award Number: 2451821
Principal Investigator: Vladimir Popik
Funds Obligated: $380,000
State: GA