The implementation of molecularly targeted imaging modalities has progressed considerably in recent years. Fluorophores in the near-IR range are of particular interest for in vivo optical imaging due to the significant tissue penetration of light in this range. One such agent, indocyanine green, is FDA approved and currently involved in over 100 active clinical trials, including over 30 for cancer diagnosis. Despite a central role in modern biology and medicine, the compounds employed in near-IR fluorescence techniques have changed little in recent decades. Using molecular design concepts borrowed from related fields (e.g. medicinal chemistry and complex molecule synthesis), we seek to develop new agents with improved utility for cancer-related imaging. The long-term goal is to identify readily synthesized, stable, and bright fluorophores with optimal properties for biomedical imaging. Our current efforts in this area are split in two aims.
Aim 1 - Synthetic methods to prepare heptamethine cyanine fluorophores. The heptamethine cyanine class of near-IR fluorophores are used for many applications, including for fluorescence-guided surgery. We have developed a new rearrangement reaction that enables the synthesis of previously inaccessible variants. Compared to existing agents, the compounds we have prepared exhibited improved optical properties and, most importantly, significantly greater chemical stability to biological nucleophiles. We have shown that these new agents can be conjugated to the anti-HER2 antibody, trastuzumab, and exhibit excellent fluorescence properties in microscopy experiments. Ongoing efforts are centered on employing these readily synthesized compounds in a variety of applications, including for in vivo animal studies.
Aim 2 - Synthesis and evaluation of fluorescent natural products. Many natural products have evolved to, at least in part, interact with light, and derivatives of some, such as umbelliferone, are important fluorophores. My lab is particularly interested in a natural product with structural similarity to cyanine fluorophores. We anticipate this compound may exhibit useful optical switching properties with utility for certain microscopy applications. At this stage, we are developing a concise synthesis to provide access to this promising compound.
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