Abstract
Fluorescence endomicroscopy provides quick access to molecular targets, while Raman spectroscopy allows the detection of multiple molecular targets. Using a simultaneous fluorescence-Raman endoscopic system (FRES), we herein demonstrate its potential in cancer diagnosis in an orthotopically induced colorectal cancer (CRC) xenograft model. In the model, epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) were targeted with antibody-conjugated fluorescence and surface-enhanced Raman scattering (F-SERS) dots. FRES demonstrated fast signal detection and multiplex targeting ability using fluorescence and Raman signals to detect the F-SERS dots. In addition, FRES showed a multiplex targeting ability even on a subcentimeter-sized CRC after spraying with a dose of 50 µg F-SERS dots. In conclusion, molecular characteristics of tumor cells (EGFR in cancer cell membranes) and tumor microenvironments (VEGF in the extracellular matrix) could be simultaneously investigated when performing a colonoscopy.
Highlights
If applied to endoscopy, molecular imaging provides an opportunity to detect specific molecular targets of colorectal cancer (CRC) early[6]
The F-surface-enhanced Raman scattering (SERS) dots were labeled with a single fluorescent dye (AF610) and two Raman active molecules: rhodamine B isothiocyanate (RITC) and fluorescein isothiocyanate (FITC) for F-SERS-A and -B dots, respectively
Fluorescence signals were represented as small bright dots, and Raman signals revealed the highest Raman band at 1648 cm−1 for RITC (EGFR-F-SERS-A dots) and at 1324 cm−1 for FITC (VEGF-F-SERS-B dots) (Fig. 2b)
Summary
Molecular imaging provides an opportunity to detect specific molecular targets of CRC early[6]. FBE provides microscopic images using fluorescent dyes at the subcellular level its use is limited to only one fluorescent dye at a time, which has limited the identification of potential multiple targets of a cancer[8] Another technique, Raman spectroscopy, has been introduced to discover the molecular characteristics of a cancer by distinguishing the inherent vibrational fingerprints of the cancer cells[9, 10]. Tumor cells are surrounded by various cells such as fibroblasts, immune and blood vessel cells, and extracellular matrices These are collectively called the tumor microenvironment in which its constitution is associated with the extent of tumor cell proliferation, angiogenesis, invasion, and patients’ survival; each constituent should be examined and its role understood[17]. Further to the validation of FRES/F-SERS endoscopy of EGFR/HER2, and once again in CRC, we validated the duplex targeting capability, the system’s detection limit (sensitivity) and reproducibility, and its capacity for quantification and real-time imaging using F-SERS dots for EGFR (the target of cetuximab) and VEGF (the target of bevacizumab)
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