Abstract
BackgroundTargeted superparamagnetic iron oxide (SPIO) nanoparticles have emerged as a promising biomarker detection tool for molecular magnetic resonance (MR) image diagnosis. To identify patients who could benefit from Epidermal growth factor receptor (EGFR)-targeted therapies, we introduce lipid-encapsulated SPIO nanoparticles and hypothesized that anti-EGFR antibody cetuximab conjugated of such nanoparticles can be used to identify EGFR-positive glioblastomas in non-invasive T2 MR image assays. The newly introduced lipid-coated SPIOs, which imitate biological cell surface and thus inherited innate nonfouling property, were utilized to reduce nonspecific binding to off-targeted cells and prevent agglomeration that commonly occurs in nanoparticles.ResultsThe synthesized targeted EGFR-antibody-conjugated SPIO (EGFR-SPIO) nanoparticles were characterized using dynamic light scattering, zeta potential assays, gel electrophoresis mobility shift assays, transmission electron microscopy (TEM) images, and cell line affinity assays, and the results showed that the conjugation was successful. The targeting efficiency of the synthesized EGFR-SPIO nanoparticles was confirmed through Prussian blue staining and TEM images by using glioblastoma cell lines with high or low EGFR expression levels. The EGFR-SPIO nanoparticles preferentially targeted U-251 cells, which have high EGFR expression, and were internalized by cells in a prolonged incubation condition. Moreover, the T2 MR relaxation time of EGFR-SPIO nanoparticles could be used for successfully identifying glioblastoma cells with elevated EGFR expression in vitro and distinguishing U-251 cells from U-87MG cells, which have low EFGR expression.ConclusionThese findings reveal that the lipid-encapsulated EGFR-SPIO nanoparticles can specifically target cells with elevated EGFR expression in the three tested human glioblastoma cell lines. The results of this study can be used for noninvasive molecular MR image diagnosis in the future.
Highlights
Targeted superparamagnetic iron oxide (SPIO) nanoparticles have emerged as a promising biomarker detection tool for molecular magnetic resonance (MR) image diagnosis
Epidermal growth factor receptor (EGFR) expression profile in human glioblastoma multiforme (GBM) cell lines To identify tumor cells with elevated EGFR expression in heterogeneous GBMs and select suitable models for evaluating targeting efficiency, the human GBM cell lines U-87MG, U-251, and DBTRG-05MG were used for evaluating the EGFR expression profile through Western blotting, flow cytometry, and IF staining
Flow cytometry analysis indicated that U-251 and DBTRG-05MG had 86.80 ± 16.52% and 87.18 ± 14.77% cells detected EGFR positive, which are significantly higher compared with the U-87MG (29.80 ± 15.95%), as detected using the anti-EGFR monoclonal antibody cetuximab (Fig. 1b)
Summary
Targeted superparamagnetic iron oxide (SPIO) nanoparticles have emerged as a promising biomarker detection tool for molecular magnetic resonance (MR) image diagnosis. Approximately 250,000 individuals are diagnosed with brain and nervous tumors worldwide [1] Among these tumors, glioblastoma (formerly glioblastoma multiforme; GBM) is the most common and lethal [1]. The binding of ligands to their ectodomain of the receptor promotes homodimer and heterodimer formation between receptors [8], which is essential for the activation of the intracellular tyrosine kinase domain and phosphorylation of the C-terminal tail [9]. These signaling processes influence downstream cellular processes, including cell proliferation, survival, angiogenesis, metabolism, and cell differentiation
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