Optical imaging has the potential to improve the efficacy of surgical and endoscopic approaches to
cancer treatment; however, the optimal type of
fluorescent probe has not yet been established. It is well-known that
rhodamine-core-derived fluorophores offer a combination of desirable properties such as good photostability, high extinction coefficient, and high fluorescence quantum yield. However, despite the ubiquitous use of
rhodamine fluorophores for in vivo optical imaging, it remains to be determined if unique chemical properties among individual
rhodamine core family members affect fluorophore parameters critical to in vivo optical imaging applications. These parameters include preserved fluorescence intensity in low pH environments, similar to that of the endolysosome; efficient fluorescence signal despite conformational changes to targeting
proteins as may occur in harsh subcellular environments; persistence of fluorescence after cellular internalization; and sufficient signal-to-background ratios to permit the identification of fluorophore-targeted
tumors. In the present study, we conjugated 4 common
rhodamine-core based
fluorescent dyes to a clinically feasible and quickly internalizing
D-galactose receptor targeting
reagent,
galactosamine serum albumin (GmSA), and conducted a series of in vitro and in vivo experiments using a metastatic
ovarian cancer mouse model to determine if differences in optical imaging properties exist among
rhodamine fluorophores and if so, which
rhodamine core possesses optimal characteristics for in vivo imaging applications. Herein, we demonstrate that the
rhodamine-fluorophore, TAMRA, is the most robust of the 4 common
rhodamine fluorophores for in vivo optical imaging of
ovarian cancer metastases to the peritoneum.