Synthesis and Application of a Glucoconjugated Organometallic Rhenium Complex as an IR Imaging Probe for Glycolytic Cancer Cells

Current tumor diagnostics rely on fluorodeoxyglucose (FDG)-PET imaging, but FDG's short half-life and high cost limit its widespread use. Infrared (IR) probes are emerging as non-radioactive alternatives to conventional tracers for tissue section and other in vitro imaging applications. Because cells and tissues are relatively free of absorption peaks between 1800 and 2200 cm-1, metal-carbonyl complexes, especially cyclopentadienylrhenium(I) tricarbonyl (Cp[Re(CO)3]) derivatives, absorb strongly in this window and provide robust platforms for bioconjugation. Furthermore, Cp[Re(CO)3] fragments can be introduced into organic substrates via an elegant three-component reaction that simultaneously forges the cyclopentadienyl-metal and cyclopentadienyl-substituent bonds. As a result, the functionalized half-sandwich complex is obtained in a single step without any special handling issues. We have therefore properly modified a glucose molecule with that complex and developed a novel glucoconjugated Cp[Re(CO)3] probe that enables IR-based visualization of diseased cells at 2100 cm-1, offering a non-invasive, non-radioactive histological tool and a promising basis for future medical imaging devices.