Cancer Cell Membrane-Biomimetic Nanobubbles Carrying Indocyanine Green for Ultrasound/Fluorescence Bimodal Imaging of Colorectal Cancer

Abstract The aim of this study was to construct cancer cell membrane-coated and Indocyanine green-loaded nanobubbles for targeted ultrasound/fluorescence bimodal imaging of colorectal cancer (CRC). ICG-loaded nanobubbles (ICG-NBs) and CT26 (a murine CRC cell line) cancer cell membrane-camouflaged and ICG-NBs (ICG-MNBs) were synthesized via mechanical oscillation. Physicochemical characterization included particle size and zeta potential, and in vitro ultrasound and fluorescence imaging were performed. The binding specificity of ICG-MNBs and ICG-NBs to CT26 cells was evaluated using confocal laser scanning microscopy (CLSM) and flow cytometry. Comparative bimodal imaging (ultrasound and fluorescence) of ICG-MNBs and ICG-NBs was performed in subcutaneous xenograft tumor models. Under a light and transmission electron microscope, ICG-MNBs were uniformly distributed and similar in size and shape. The addition of the cancer cell membrane reduced the particle size (p = 0.039) and decreased the zeta potential (p < 0.001). Both SDS-PAGE and CLSM results confirmed the successful hybridization of lipid and cell membranes (CM). CLSM and flow cytometry confirmed significantly enhanced binding specificity of ICG-MNBs to CT26 cells compared to that of ICG-NBs. In vitro ICG-MNBs and ICG-NBs imaging demonstrated concentration-dependent enhancements in ultrasound and fluorescence signal intensity. For in vivo imaging, compared with ICG-NBs, the signal intensity of tumors injected with ICG-MNBs was higher. Both results indicated that the modification of cancer CM can significantly enhance the targeted accumulation of nanobubbles to the corresponding tumor and improve the display ability of contrast-enhanced ultrasound and fluorescence imaging for the corresponding tumors. A safety study showed the certain biosafety of ICG-MNBs and that they could be used as a relatively safe ultrasound/fluorescence imaging contrast agent. This study demonstrates that ICG-MNBs represent a promising bimodal contrast agent for the precise diagnosis of CRC.