Optical probes for bioimaging of tumor-infiltrating immune cells and their applications in cancer immunotherapy

The role of tumor-infiltrating immune cells (TIICs) in the tumor microenvironment (TME) is crucial in tumor development. The precise localization of TIICs within tumor tissues and the elucidation of their biological processes are critical for tumor diagnosis, treatment, and prognosis. Currently, optical probes with high specificity, sensitivity, and spatiotemporal resolution have emerged as powerful tools for the precise localization of TIICs and the investigation of their biological functions. In addition, the modifiability of optical biomaterials with these characteristics enables them to facilitate diverse and precise localization of TIICs and the monitoring of biological processes according to different design strategies. This review summarizes recent advancements in optical probes derived from optical biomaterials, including design strategies for TIIC-targeted optical probes, their applications in precise TIIC localization, and biological process monitoring. Furthermore, we emphasize the importance of their integration with immunotherapy, analyze the underlying factors contributing to the limited development of optical probes for regulatory T cells (Tregs), and systematically discuss the opportunities and challenges associated with their rapid advancement in tumor diagnosis and treatment.