Cancer stem cell labeling using poly(l-lysine)-modified iron oxide nanoparticles

Cell labeling using magnetic nanoparticles is an increasingly used approach in noninvasive behavior tracking, in vitro separation of cancer stem cells (CSCs), and CSC-based research in cancer therapy. However, the impact of magnetic labeling on the biological properties of targeted CSCs, such as self-renewal, proliferation, multi-differentiation, cell cycle, and apoptosis, remains elusive. The present study sought to explore the potential effects on biological behavior when CSCs are labeled with superparamagnetic iron oxide (SPIO) nanoparticles in vitro. The glioblastoma CSCs derived from U251 glioblastoma multiforme were labeled with poly(l-lysine) (PLL)-modified γ-Fe2O3 nanoparticles. The iron uptake of glioblastoma CSCs was confirmed through prussian blue staining, and was further quantified using atomic absorption spectrometry. The cellular viability of the SPIO-labeled glioblastoma CSCs was assessed using a fluorescein diacetate and propidium iodide double-staining protocol. The expressed specific markers and multi-differentiation of SPIO-labeled glioblastoma CSCs were comparatively assessed by immunocytochemistry and semi-quantitative RT-PCR. The effects of magnetic labeling on cell cycle and apoptosis rate of glioblastoma CSCs and their differentiated progenies were assayed using a flow cytometer. The results demonstrated that the cell viability and proliferation capacity of glioblastoma CSCs and their differentiated progenies were not affected by SPIO labeling compared with their unlabeled counterparts. Moreover, the magnetically labeled CSCs displayed an intact multi-differentiation potential, and could be sub-cultured to form new tumor spheres, which indicates the CSCs capacity for self-renewal. In addition, cell cycle distribution, apoptosis rate of the magnetically labeled glioblastoma CSCs, and their differentiated progenies were not impaired. Therefore, the SPIO-labeled CSCs could be a feasible approach in conducting further functional analysis of targeted CSCs.