In Vivo Nerve-Specificity of Rhodamines and Si-rhodamines

Accidental nerve damage or transection of vital nerve structures remains an unfortunate reality that is often associated with surgery. Despite the existence of nerve-sparing techniques, the success of such procedures is not only complicated by anatomical variance across patients but is also highly dependent on a surgeon's first-hand experience that is acquired over numerous procedures through trial and error, often with highly variable success rates. Fluorescent small molecules, such as rhodamines and fluoresceins have proven incredibly useful for biological imaging in the life sciences, and they appeared to have potential in illuminating vital nerve structures during surgical procedures. In order to make use of the current clinically relevant imaging systems and to provide surgeons with fluorescent contrast largely free from the interference of hemoglobin and water, it was first necessary to spectrally tune known fluorescent scaffolds towards near infrared (NIR) wavelengths. To determine whether the well-documented Si-substitution strategy could be applied towards developing a NIR fluorophore that retained nerve-specific properties of candidate molecules, an in vivo comparison was made between two compounds previously shown to highlight nervous structures - TMR and Rhodamine B - and their Si-substituted derivatives.