The researchers working on the project were from the University of Notre Dame (Notre Dame, IL, USA) and the Washington University School of Medicine (St. Louis, MO, USA). Bradley D. Smith, a professor of chemistry and biochemistry at Notre Dame, points out that the group of researchers had previously discovered that synthetic zinc (II)-dipicolylamine (Zn-DPA) coordination complexes can selectively target the outer surfaces of anionic cell membranes. Furthermore, fluorescent versions of these Zn-DPA complexes act as imaging probes that can distinguish dead and dying mammalian cells from healthy cells in a cell culture and also selectively target bacteria in contaminated samples.

The researchers also recently demonstrated that a fluorescent near-infrared (NIR) probe referred to as PSS-794 can be used to image bacterial infections in mice, indicating that PSS-794 has a notable ability to selectively target anionic cells in living animals.

In the new study, the researchers revealed a significant expansion of the animal imaging capability of PSS-794 by showing that it can target the anionic dead and dying cells within tumors in rat and mouse models. The research is an important step toward the development of optical imaging probes that could determine, noninvasively, the amount and type of cell death in tumors. Such imaging techniques could help clinicians accurately determine the grade of tumors and the stage of cancers, as well as to measure the effectiveness of treatments.

The researchers also believe that analogous probes can be developed that would allow for deep tissue imaging of cancers in humans. Prof. Smith pointed out that although the study focused on mammary and prostate tumors, imaging of cell death is also useful for treatment of numerous conditions, including cardiovascular disease, neurology, renal disease, and even transplant rejection.

The research was published online December 2009 in the Journal of the American Chemical Society (JACS).

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University of Notre Dame
Washington University School of Medicine