Enhanced Detection of Malignant Glioma Xenograft by Fluorescein–Human Serum Albumin Conjugate

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Abstract
Object: During the surgical resection of malignant gliomas, it is important to make clear the border zone between the tumor tissue and normal brain tissue. For this purpose, we conjugated fluorescein and human serum albumin (FLS-HSA) and compared its effectiveness against that of fluorescein-sodium (FLS-Na) alone in detecting human glioma xenografts in SCID mice through a fluorescence microscope. Methods: We made FLS-HSA conjugate using carbodiimide as a linking reagent. SCID mice, with U251MG cells transplanted subcutaneously, were prepared as tumor models. The animals were sacrificed 15, 30, 60, 180, 360, or 720 min after the intravenous administration of either the FLS-HSA conjugate or FLS-Na alone (n = 3). Fluorescence images were taken with a digital camera, and the brightness of the tumor and that of the peripheral tissue in each image were quantified. In the group of tumor-bearing mice that received FLS-Na, the fluorescence of tumor tissue disappeared 60 min after the reagent was administered, and there was no significant difference in brightness between the tumor and peripheral tissue at any time point. On the other hand, injection of FLS-HSA revealed relative tumor-selective brightness and sufficient contrast between the tumor and surrounding tissue 60 and 360 min after administration. Conclusion: FLS-HSA has the advantages of specificity and persistence of fluorescence over FLS-Na for the purpose of identifying glioma nodules in xenogenic subcutaneous tumor transplantation models.