Penetration into Solid Tumor Tissue of Fluorescent Latex Microspheres: A Mimic of Liposome Particles

Background: Using liposomes as a vehicle to transport anticancer drugs to cancer cells, to increase their effectiveness and decrease their toxicity, has been studied for many years. However, due to technical difficulties, the path of penetration for liposome particles into solid tumor tissue is still not clear. Materials and Methods: In this report, rhodamine-labeled fluorescent latex microspheres were used as a model of liposome particles, combined with fluorescent staining of blood vessel CD31 and tumor cell nuclei. The penetration of microspheres from blood vessels in L1210JF solid tumors of mice was observed. After fluorescent latex microspheres were injected into tail vein, tumor tissue samples were collected at various times and cryosections were then made for fluorescent staining. Results: Under fluorescence microscopy, the red fluorescent latex microspheres, the green fluorescent blood vessels and the blue tumor cells in the cancer tissue were seen clearly. The leaking of microspheres out from blood vessels was seen directly. Conclusion: The results confirmed that the tiny particles can only leak out through the holes of the broken blood vessels and spread out through the space in between the cells of the solid tumor.