Background: Local recurrences of glioblastoma (GBM) after heavy standard treatments remain frequent and lead to a poor prognostic. Major challenges are the infiltrative part of the tumor tissue which is the ultimate cause of recurrence. The therapeutic arsenal faces the difficulty of eradicating this infiltrating part of the tumor tissue while increasing the targeting of tumor and endogenous stromal cells such as angiogenic endothelial cells. In this aim, neuropilin-1 (NRP-1), a transmembrane receptor mainly overexpressed by endothelial cells of the tumor vascular system and associated with malignancy, proliferation and migration of GBM, highlighted to be a relevant molecular target to promote the anti-vascular effect of photodynamic therapy (VTP). Methods: The multiscale selectivity was investigated for KDKPPR peptide moiety targeting NRP-1 and a porphyrin molecule as photosensitizer (PS), both grafted onto original AGuIX design nanoparticle. AGuIX nanoparticle, currently in Phase II clinical trials for the treatment of brain metastases with radiotherapy, allows to achieve a real-time magnetic resonance imaging (MRI) and an accumulation in the tumor area by EPR (enhanced permeability and retention) effect. Using surface-plasmon resonance (SPR), we evaluated the affinities of KDKPPR and scramble free peptides, and also peptides-conjugated AGuIX nanoparticles to recombinant rat and human NRP-1 proteins. For in vivo selectivity, we used a cranial window model and parametric maps obtained from T2*-weighted perfusion MRI analysis. Results: The photophysical characteristics of the PS and KDKPPR molecular affinity for recombinant human NRP-1 proteins were maintained after the functionalization of AGuIX nanoparticle with a dissociation constant of 4.7 μM determined by SPR assays. Cranial window model and parametric maps, both revealed a prolonged retention in the vascular system of human xenotransplanted GBM. Thanks to the fluorescence of porphyrin by noninvasive imaging and the concentration of gadolinium evaluated after extraction of organs, we checked the absence of nanoparticle in the brains of tumor-free animals and highlighted elimination by renal excretion and hepatic metabolism. Conclusion: Post-VTP follow-ups demonstrated promising tumor responses with a prolonged delay in tumor growth accompanied by a decrease in tumor metabolism.

During last decade, special focus has been laid on ultrasmall nanoparticles for nanomedicine and eventual clinical translation. To achieve such translation, a lot of challenges have to be solved. Among them, size determination is a particularly tricky one. In this aim, we have developed a simple hyphenation between Taylor dispersion analysis and ICP-MS. This method was proven to allow the determination of the hydrodynamic radius of metal-containing nanoparticles, even for sizes under 5 nm, with a relative standard deviation below 10% (with a 95% confidence interval) and at low concentrations. Moreover, its specificity provides the opportunity to perform measurements in complex biological media. This was applied to the characterization of an ultrasmall gadolinium-containing nanoparticle, used as theranostic agent in cancer diseases. Hydrodynamic radii measured in urine, cerebrospinal fluid and undiluted serum demonstrated the absence of interaction between the particle and biological compounds such as proteins.

No abstract