CXCL12 and glioblastoma: Several initial mass loadings of CXCL12 tagged with a fluorescent dye (AlexaFluor® 647) were assessed, from 0.4 to 1.6 μg/mL (corresponding to 0.372 to 1.490 μg/mg NPs), which are representative of the concentration range required for therapeutic application targeting glioblastoma cells (Table 1).