PDCD1 and neoplasm: Meanwhile, the average Ce6 fluorescence intensity in tumors in the LEH-CSPC group under norm or FMD conditions was much higher than that of other organs, and the tumor accumulation was significantly improved compared with the free PD-1 and Ce6 group after 24 h (Fig. 3D to F), verifying that this delivery system could enhance the accumulation of free drugs in tumor sites; however, this result indicates that the FMD condition cannot enhance the tumor accumulation of LEH-CSPC nanoparticles.