Gold-Nanorod-Assisted Live Cell Nuclear Imaging Based on Near-Infrared II Dark-Field Microscopy

SIMPLE SUMMARY: Colorectal cancer cells exhibited superior dark-field imaging results in the near-infrared II (NIR-II) wavelength range (900–1880 nm) compared to the visible light region. Subsequently, we synthesized gold nanorods (GNRs) for dark-field scattering imaging of colorectal cancer cells in the NIR-II spectrum. The results demonstrated that imaging with GNRs significantly improved the signal-to-background ratio (SBR) and showed enhanced performance, particularly in the 1425–1475 nm wavelength range. Finally, we conducted dark-field imaging of cell nuclei in the NIR-II range utilizing GNRs for specific labeling of colorectal cancer cell nuclei. The resulting nuclear images were highly accurate in localization and exhibited higher SBR compared to non-specifically-labeled cell imaging. ABSTRACT: Dark-field microscopy offers several advantages, including high image contrast, minimal cell damage, and the absence of photobleaching of nanoprobes, which make it highly advantageous for cell imaging. The NIR-II window has emerged as a prominent research focus in optical imaging in recent years, with its low autofluorescence background in biological samples and high imaging SBR. In this study, we initially compared dark-field imaging results of colorectal cancer cells in both visible and NIR-II wavelengths, confirming the superior performance of NIR-II imaging. Subsequently, we synthesized gold nanorods with localized surface plasmon resonance (LSPR) absorption peaks in the NIR-II window. After bio-compatible modification, we non-specifically labeled colorectal cancer cells for NIR-II dark-field scattering imaging. The imaging results revealed a sixfold increase in SBR, especially in the 1425–1475 nm wavelength range. Finally, we applied this imaging system to perform dark-field imaging of cell nuclei in the NIR-II region and used GNRs for specific nuclear labeling in colorectal cancer cells. The resulting images exhibited higher SBR than non-specifically-labeled cell imaging, and the probe’s labeling was precise, confirming the potential application of this system in photothermal therapy and drug delivery for cancer cells.