LGMN and central nervous system cancer: The overexpression of legumain in a glioma site led to the selective accumulation of AuNP-Cy5.5-A&C, and fluorescence signal of AuNP-Cy5.5-A&C began emerging in the glioma site with an increasing intensity over time and obtained a high G/B ratio (the ratio of fluorescence at the glioma site to fluorescence at the normal brain site).