Furin‐Mediated Self‐Assembly of Olsalazine Nanoparticles for Targeted Raman Imaging of Tumors

Abstract Olsalazine (Olsa) is a broad‐spectrum anti‐cancer agent acting as a DNA‐methylation inhibitor. When conjugated to 2‐cyano‐6‐aminobenzothiazole and a peptide substrate specific for the tumor‐overexpressed enzyme furin, it can self‐assemble into nanoparticles that can be detected by chemical‐exchange saturation‐transfer magnetic‐resonance imaging (CEST MRI). We report here that these nano‐assemblies can also be detected with high specificity in furin‐overexpressing tumor cells by Raman spectroscopy with a distinct scattering signature and demonstrate the utility of this sensing mechanism in vitro and in vivo. Our findings suggest that Raman spectroscopy could be used for high‐resolution image‐guided surgery to precisely delineate tumor margins during and after resection in real‐time as well as to determine microscopic tumor invasion and multifocal locoregional tumor spread, which are currently impossible to visualize with available imaging technologies, including CEST MRI.