Noninvasively Real‐Time Monitoring In‐Vivo Immune Cell and Tumor Cell Interaction by NIR‐II Nanosensor

Immunocytotherapy holds significant promise as a novel cancer treatment, but its effectiveness is often hindered by delayed responses, requiring evaluations every 2-3 weeks based on current diagnostic methods. Early assessment of immune cell-tumor cell interactions could provide more timely insights into therapeutic efficacy, enabling adjustments to treatment plans. In this study, a noninvasive nanosensor (C8R-DSNP) for real-time monitoring of in vivo immune cell activities in the second near-infrared long-wavelength (NIR-II-L) window (1500-1900 nm), which offers deep tissue transparency, is reported. The C8R-DSNP responds rapidly to caspase-8, a key apoptotic signaling molecule generated during interactions between natural killer (NK-92) cells and tumor cells. Using ratiometric NIR-II-L fluorescence imaging, dynamic in vivo observations of NK-92 cells' engagement with tumor cells in a mouse model are captured. These results demonstrate tumor cells apoptosis that happens as early as 4.5 h after NK-92 cells infusion. Additionally, in vitro urine imaging confirmed the initiation of apoptosis via cleaved fluorescent small molecules, while single-cell tracking within blood vessels and tumors further elucidated immune cell dynamics. This real-time NIR-II-L monitoring approach offers valuable insights for optimizing immunocytotherapy strategies.