Ultrasmall AGuIX theranostic nanoparticles for vascular-targeted interstitial photodynamic therapy of glioblastoma

Abstract

Despite combined treatments, glioblastoma outcome remains poor with frequent local recurrences, indicating that a more efficient and local therapy is needed. In this way, vascular-targeted photodynamic therapy (VTP) could help tumor eradication by destroying its neovessels. In this study, we designed a polysiloxane-based nanoparticle (NP) combining a magnetic resonance imaging (MRI) contrast agent, a photosensitizer (PS) and a new ligand peptide motif (KDKPPR) targeting neuropilin-1 (NRP-1), a receptor overexpressed by angiogenic endothelial cells of the tumor vasculature. This structure achieves the detection of the tumor tissue and its proliferating part by MRI analysis, followed by its treatment by VTP. The photophysical properties of the PS and the peptide affinity for NRP-1 recombinant protein were preserved after the functionalization of NPs. Cellular uptake of NPs by human umbilical vein endothelial cells (HUVEC) was increased twice compared to NPs without the KDKPPR peptide moiety or conjugated with a scramble peptide. NPs induced no cytotoxicity without light exposure but conferred a photocytotoxic effect to cells after photodynamic therapy (PDT). The in vivo selectivity, evaluated using a skinfold chamber model in mice, confirms that the functionalized NPs with KDKPPR peptide moiety were localized in the tumor vessel wall.

New Targeted Gold Nanorods for the Treatment of Glioblastoma by Photodynamic Therapy

“…The results are displayed in Figure 5. Free H-KDKPPR-OH peptide succeeds to displace the binding of the biotinylated VEGF165 onto the receptor with an IC 50 = 2 µM [53]. This competitive binding study reveals that the conjugated MI-K(Pyro)DKPPR-OH peptide possesses a molecular affinity as good as that of free H-KDKPPR-OH with an inhibition concentration, IC 50 , of 1.5 µM.…”

“…The affinity of the compounds for NRP-1 was realized as previously described in terms of IC50 in a competition study [53]. Briefly, the surface of the high protein-binding capacity polystyrene 96 well ELISA plate (NUNC MaxiSorp™, Sigma-Aldrich, Saint-Quentin Fallavier, France) was coated with NRP-1 at a concentration of 2 µg·mL −1 in PBS and kept overnight at room temperature.…”

“…The obtained results were expressed as relative absorbance to wells containing only blocking buffer. For this assay, three wells were used per condition [53,54].…”

“…The PS (Pyro in our case) is coupled in the form of Fmoc-K(Pyro)-OH to the H-DKPPR-Wang growing peptide by classical Fmoc/tBu solid-phase synthesis, affording PP-PS (Scheme 2). This PP-PS conjugate was then grafted onto the surface of the nanorods through another click-chemistry reaction well-known as maleimido-thiol reaction [53]. The maleimide group reacts specifically with sulfhydryl groups when the pH of the reaction mixture is between 6.5 and 7.5; the result is the formation of a stable thioether linkage that is not reversible.…”

“…Neuropilin-1 (NRP-1) is a co-receptor of vascular endothelial growth factor receptors (VEGFR) localized not only on angiogenic endothelial cells but also onto tumoral cells such as glioblastoma cell lines (U87) [51]. In attempt to destroy glioblastoma, which is the most frequent and malignant brain tumor, several peptides were developed by our team [52][53][54] and other groups [55][56][57] that successfully targeted NRP-1. There are many publications dealing with PDT and gold nanoparticles.…”