BACKGROUND AND OBJECTIVES:The use of numerical models to predict radiosensitizing properties induced by metal-based nanoparticles (NPs) remains a real challenge in oncology. As most of the interactions due to radiation in biological environments originate from the secondary particles produced, we aim to formalize the relationship between these secondary particles, the irradiation dose and the NP concentration, to optimize mathematical and numerical tools for assessing NP-induced radiosensitization. METHODS:GATE simulations were carried out to demonstrate a linear and affine relationship between specific radiophysical quantities, the irradiation dose and NP concentration. This research has led to an effective new method for predicting radiophysical events and the proposal of a new model for predicting cell death. This model was confirmed by experimental biological results obtained from a clonogenic assay performed on U251 and U87 glioblastoma cells after exposure to different concentrations of metal-based NPs. RESULTS:We achieved an efficient method for quantifying certain radiophysical species (number of ionizations, photo- and compton electrons, bremsstrahlung and deposited dose) in the presence of NPs and at different irradiation doses. These findings have enabled us to suggest an extension of the linear quadratic (LQ) cell survival model. The LQ extension model was compared with experimental data both obtained in the laboratory and extracted from the literature. CONCLUSIONS:Radiophysical events provide valuable information for predicting the radiobiological and radiosensitizing effects of metal-based NPs in the context of X-ray photon irradiation. The extension of the LQ model we developed enables cell death to be predicted for different NP concentrations based on concentration effects alone.

Photodynamic therapy is an accepted therapy cancer treatment. Its advantages encourage researchers to delve deeper. The use of nanoparticles in PDT has several advantages including the passive targeting of cancer cells. The aim of this article is to evaluate the effectiveness of AGuIX nanoparticles (activation and guiding of irradiation by X-ray) in the presence or absence of a photosensitizer, Photofrin, under illumination of 630 nm or under X-ray irradiation. The goal is to improve local tumor control by combining PDT with low-dose-X-ray-activated NPs in the treatment of locally advanced metastatic lung cancer. The study of the energy transfer, which occurs after excitation of Gd/Tb chelated in AGuIX in the presence of Photofrin, was carried out. We could observe the formation of singlet oxygen after the light or X-ray excitation of Gd and Tb that was not observed for AGuIX or Photofrin alone, proving that it is possible to realize energy transfer between both compounds.

Cerenkov-induced photodynamic therapy (CR-PDT) with the use of Gallium-68 (68Ga) as an unsealed radioactive source has been proposed as an alternative strategy to X-ray-induced photodynamic therapy (X-PDT). This new strategy still aims to produce a photodynamic effect with the use of nanoparticles, namely, AGuIX. Recently, we replaced Gd from the AGuIX@ platform with Terbium (Tb) as a nanoscintillator and added 5-(4-carboxyphenyl succinimide ester)-10,15,20-triphenylporphyrin (P1) as a photosensitizer (referred to as AGuIX@Tb-P1). Although Cerenkov luminescence from 68Ga positrons is involved in nanoscintillator and photosensitizer activation, the cytotoxic effect obtained by PDT remains controversial. Herein, we tested whether free 68Ga could substitute X-rays of X-PDT to obtain a cytotoxic phototherapeutic effect. Results were compared with those obtained with AGuIX@Gd-P1 nanoparticles. We showed, by Monte Carlo simulations, the contribution of Tb scintillation in P1 activation by an energy transfer between Tb and P1 after Cerenkov radiation, compared to the Gd-based nanoparticles. We confirmed the involvement of the type II PDT reaction during 68Ga-mediated Cerenkov luminescence, id est, the transfer of photon to AGuIX@Tb-P1 which, in turn, generated P1-mediated singlet oxygen. The effect of 68Ga on cell survival was studied by clonogenic assays using human glioblastoma U-251 MG cells. Exposure of pre-treated cells with AGuIX@Tb-P1 to 68Ga resulted in the decrease in cell clone formation, unlike AGuIX@Gd-P1. We conclude that CR-PDT could be an alternative of X-PDT.

X-ray-induced Photodynamic Therapy (X-PDT) is an alternative strategy to improve Photo Dynamic Therapy (PDT) for cancer treatment [1]. The X-PDT principle is based on the conversion of X-ray photons into visible photons, from nanoscintillator embedded in nanoparticles (NPs) and linked to the photosensitizer, which, in turn, produces singlet oxygen and reactive species. Recently, several lines of evidence demonstrated that radionuclides can be used instead of X-rays irradiation to produce similar photodynamic effect, using NPs containing both nanoscintillator and photosensitizer. [1]. The obtained results are related to the Cerenkov luminescence and it is based on the positrons emission along lifetime of the radionuclides [2].

Glioblastoma (GBM) is the most difficult brain cancer to treat, and photodynamic therapy (PDT) is emerging as a complementary approach to improve tumor eradication. Neuropilin-1 (NRP-1) protein expression plays a critical role in GBM progression and immune response. Moreover, various clinical databases highlight a relationship between NRP-1 and M2 macrophage infiltration. In order to induce a photodynamic effect, multifunctional AGuIX®-design nanoparticles were used in combination with a magnetic resonance imaging (MRI) contrast agent, as well as a porphyrin as the photosensitizer molecule and KDKPPR peptide ligand for targeting the NRP-1 receptor. The main objective of this study was to characterize the impact of macrophage NRP-1 protein expression on the uptake of functionalized AGuIX®-design nanoparticles in vitro and to describe the influence of GBM cell secretome post-PDT on the polarization of macrophages into M1 or M2 phenotypes. By using THP-1 human monocytes, successful polarization into the macrophage phenotypes was argued via specific morphological traits, discriminant nucleocytoplasmic ratio values, and different adhesion abilities based on real-time cell impedance measurements. In addition, macrophage polarization was confirmed via the transcript-level expression of TNFα, CXCL10, CD-80, CD-163, CD-206, and CCL22 markers. In relation to NRP-1 protein over-expression, we demonstrated a three-fold increase in functionalized nanoparticle uptake for the M2 macrophages compared to the M1 phenotype. The secretome of the post-PDT GBM cells led to nearly a three-fold increase in the over-expression of TNFα transcripts, confirming the polarization to the M1 phenotype. The in vivo relationship between post-PDT efficiency and the inflammatory effects points to the extensive involvement of macrophages in the tumor zone.

Rose Bengal is a well-known photosensitizer used in the treatment of several diseases [1, 2]. This photosensitizer produces a large amount of singlet oxygen upon specific illumination, which allows its use in photodynamic therapy [3]. The work to be presented highlights the passive tumor targeting by coupling Rose Bengal to nanoparticles in clinical phase 2 AGuIX chelated with lanthanides (Terbium or Gadolinium). One of the limitations of photodynamic therapy is the poor penetration of light into the tissues [4]. X-ray excitation of AGuIX(Ln)@RB overcomes this problem. Following the excitation of the lanthanide by X-ray, a FRET energy transfer from lanthanide to Rose Bengal takes place. Rose Bengal is then able to produce singlet oxygen. To enhance the targeting, peptide can be covalently couple to the nanoparticles [5]. Two types of peptide targeting NRP1 receptors over-expressed in neovessels were grafted on the nanoparticles. This presentation focuses on the synthesis, photophysical properties of these nanoparticles, physical characterization, the type of energy transfer between the species, and the in vitro PDT-X effect.

Rose Bengal (RB) is a photosensitizer (PS) used in anti-cancer and anti-bacterial photodynamic therapy (PDT). The specific excitation of this PS allows the production of singlet oxygen and oxygen reactive species that kill bacteria and tumor cells. In this review, we summarize the history of the use of RB as a PS coupled by chemical or physical means to nanoparticles (NPs). The studies are divided into PDT and PDT excited by X-rays (X-PDT), and subdivided on the basis of NP type. On the basis of the papers examined, it can be noted that RB used as a PS shows remarkable cytotoxicity under the effect of light, and RB loaded onto NPs is an excellent candidate for nanomedical applications in PDT and X-PDT.

Medulloblastoma (MB) is the most common pediatric malignant brain tumor. Despite current therapies, the morbidity and recurrent risk remains significant. Neuropilin-1 receptor (NRP1) has been implicated in the tumor progression of MB. Our recent study showed that NRP1 inhibition stimulated MB stem cells differentiation. Consequently, we hypothesized that targeting NRP1 in medulloblastoma could improve current treatments. NRP1 inhibition with a novel peptidomimetic agent, MR438, was evaluated with radiotherapy (RT) in MB models (DAOY, D283-Med and D341-Med) in vitro on cancer stem-like cells as well as in vivo on heterotopic and orthotopic xenografts. We show that NRP1 inhibition by MR438 radiosensitizes MB stem-like cells in vitro. In heterotopic DAOY models, MR438 improves RT efficacy as measured by tumor growth and mouse survival. In addition, clonogenic assays after tumor dissociation showed a significant reduction in cancer stem cells with the combination treatment. In the same way, a benefit of the combined therapy was observed in the orthotopic model only for a low cumulative irradiation dose of 10 Gy but not for 20 Gy. Finally, our results demonstrated that targeting NRP1 with MR438 could be a potential new strategy and could limit MB progression by decreasing the stem cell number while reducing the radiation dose.

Abstract Cancer is the second leading cause of death worldwide after cardiovascular disease. Depending on the type and the location of the tumor, several cancer treatments are implemented. Among these, the three most conventional therapies are surgery, radiotherapy and chemotherapy. However, there are other therapeutic approaches such as photodynamic therapy (PDT). PDT relies on the combined action of light, a photoactivable molecule called photosensitizer (PS) and molecular oxygen. Most of the PSs used for clinical applications are not cancer-cell specific. One of the solutions to overcome this problem is the use of nanoparticles (NPs) to induce a passive targeting. It is also possible to graft a vector onto the NPs to specifically target membrane receptors overexpressed in the tumor cells or neovessels surrounding the tumor. In this review, we focus on the NPs loaded with PSs and coupled to peptides for targeted PDT. We described nanosystems that targeted Neuropilin-1 (NRP-1), αvβ3 integrins, nucleolin membrane receptor, epidermal growth factor (EGF) receptor, protein-glutamine-gamma-glutamyltransferase (TGM2), p32, transferrin, PD-1, and mitochondrial membrane. The use of a cell absorbing-peptide is also described.

X-ray-induced photodynamic therapy is based on the energy transfer from a nanoscintillator to a photosensitizer molecule, whose activation leads to singlet oxygen and radical species generation, triggering cancer cells to cell death. Herein, we synthesized ultra-small nanoparticle chelated with Terbium (Tb) as a nanoscintillator and 5-(4-carboxyphenyl succinimide ester)-10,15,20-triphenyl porphyrin (P1) as a photosensitizer (AGuIX@Tb-P1). The synthesis was based on the AGuIX@ platform design. AGuIX@Tb-P1 was characterised for its photo-physical and physico-chemical properties. The effect of the nanoparticles was studied using human glioblastoma U-251 MG cells and was compared to treatment with AGuIX@ nanoparticles doped with Gadolinium (Gd) and P1 (AguIX@Gd-P1). We demonstrated that the AGuIX@Tb-P1 design was consistent with X-ray photon energy transfer from Terbium to P1. Both nanoparticles had similar dark cytotoxicity and they were absorbed in a similar rate within the cells. Pre-treated cells exposure to X-rays was related to reactive species production. Using clonogenic assays, establishment of survival curves allowed discrimination of the impact of radiation treatment from X-ray-induced photodynamic effect. We showed that cell growth arrest was increased (35%-increase) when cells were treated with AGuIX@Tb-P1 compared to the nanoparticle doped with Gd.

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 non-invasive 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.

This article highlights the performance measurements of an optical device which aims at upgrading preclinical irradiators. The evaluated device allows acquiring X-ray as well as bioluminescence images with a single sensor. The latter consists of a supercooled camera equipped with a 1024x1024 charge coupling device (each element measuring 13x13µm²). X-ray imaging is feasible, thanks to a conversion phosphor screen. Phantom acquisitions revealed a spatial resolution of 2.5 line pairs per millimetre (0.2mm) for Xray imaging and between 0.4 and 0.7mm for bioluminescence images. Image homogeneity was 0.8 for radiographic images with preclinical imaging parameters and higher than 0.9 for optical images. For functional imaging, contrast to noise ratio (CNR) ranged from 1.3 (for contrast of 2:1 and 0.1s acquisition) up to 253 (for contrast of 32:1 and 5s acquisition). CNR was related to acquisition duration. The device’s overall performance revealed that it is suitable to upgrade existing irradiators and improve laboratory capabilities toward image-guided radiotherapy.

Photodynamic therapy (PDT) is a promising therapeutic strategy for cancers where surgery and radiotherapy cannot be effective. PDT relies on the photoactivation of photosensitizers, most of the time by lasers to produced reactive oxygen species and notably singlet oxygen. The major drawback of this strategy is the weak light penetration in the tissues. To overcome this issue, recent studies proposed to generate visible light in situ with radioactive isotopes emitting charged particles able to produce Cerenkov radiation. In vitro and preclinical results are appealing, but the existence of a true, lethal phototherapeutic effect is still controversial. In this article, we have reviewed previous original works dealing with Cerenkov-induced PDT (CR-PDT). Moreover, we propose a simple analytical equation resolution to demonstrate that Cerenkov light can potentially generate a photo-therapeutic effect, although most of the Cerenkov photons are emitted in the UV-B and UV-C domains. We suggest that CR-PDT and direct UV-tissue interaction act synergistically to yield the therapeutic effect observed in the literature. Moreover, adding a nanoscintillator in the photosensitizer vicinity would increase the PDT efficacy, as it will convert Cerenkov UV photons to light absorbed by the photosensitizer.

The current clinical study is aimed at evaluating the clinical relevance of an innovative device (called CyPaM2 device) that for the first time provides urologists with (i) a panoramic image of the bladder inner wall within the surgery time, and with (ii) a simultaneous (bimodal) display of fluorescence and white-light video streams during the fluorescence assisted-transurethral resection of bladder cancers procedure. The clinical relevance of this CyPaM2 device was evaluated on 10 patients according to three criteria (image quality, fluorescent lesions detection relevance, and ergonomics) compared with a reference medical device. Innovative features displayed by the CyPaM2 device were evaluated without any possible comparison: (i) simultaneous bimodal display of white-light and fluorescence video streams, (ii) remote light control, and (iii) time delay for the panoramic image building. The results highlight the progress to achieve in order to obtain a fully mature device ready for commercialization and the relevance of the innovative features proposed by the CyPaM2 device confirming their interest.

In recent years, the use of gold-based nanoparticles in radiotherapy has been extensively studied, and the associated radiosensitization mechanism has been evaluated in a variety of in vitro studies. Given that mitotic catastrophe is widely involved in radiation-induced cell death, we evaluated the effect of gold nanoparticles on this key event. Most of the methods currently used to visualize and quantify morphological changes and multinucleation are manual. To circumvent this time-consuming step, we developed and optimized an image processing workflow (based on freely accessible software and plugins) for the automated quantification of mitotic catastrophes. We validated this approach in three cell lines by comparing the number of radiation-induced mitotic catastrophes detected using the automated and manual methods in the presence and absence of nanoparticles. With the Bland-Altman analysis, the automated and manual counting methods were found to be fully interchangeable. The ultimate goal of this work was to determine whether mitotic catastrophe was critically involved in radiationinduced cell death after prior exposure to gold nanoparticles. In the radioresistant U87 cell line, exposure to gold nanoparticles was associated with a shorter time course for the events related to mitotic catastrophe, which peaked at 96 h postirradiation. Mitotic catastrophe was dose-dependent in both the presence and absence of gold nanoparticles. These results demonstrate that cell exposure to gold nanoparticles led to an increase in mitotic catastrophe events, and confirm the marked radiosensitizing effect observed in clonogenic assays.

Introduction Metal-based nanoparticles with radiosensitizing aim have promising prospects in the field of radiotherapy. Due to their high X-ray absorption capacity, nanomaterials with high atomic number may indeed improve radiation therapy efficacy in cancer treatment. Clinical trials are ongoing to evaluate the benefit of nanoparticle enhanced radiotherapy. The objective of the present study was to validate the potential of gold nanoparticle enhanced radiotherapy to treat glioblastoma using in silico , in vitro and in vivo approaches. Material and methods Among a panel of 5 gold nanoparticles (AuNPs), an innovative Monte Carlo simulation approach was used to rank the most promising nanoparticles according to their theoretical radiosensitizing effect. In U87-MG glioblastoma cells, the radiosensitizing effect of the selected nano-objects was confirmed by clonogenic assays and cell death processes such as apoptosis, senescence, and mitotic catastrophes were investigated. A brain tumour window model, allowing fluorescence-based imaging was used to evaluate the tumour tissue selectivity of Cy5-labelled nanoparticles. Results and discussions A radiosensitizing effect was determined for 3 among 5 tested AuNPs with a dose modifying factor (DMF) from 0.4 to 0.5 ( i.e. a DMF equal to 0.5 means the treatment is twice as efficient). Our results showed an inverse relationship between the radiosensitizing effects and the AuNPs sizes. Moreover, the nature of the coating influences the triggered cell death process. In case of PVP-coated AuNPs, the cell death was characterised by a radio-induced senescence in relation with a 1.5-fold increase of the reactive oxygen species production. In contrast, smallest PEG-coated AuNPs triggered post-RX mitotic catastrophes, leading to a delayed cell death. For in vivo experiments, a most promising AuNP ( i.e. Au@DTDTPA:Gd) was selected, showing an interesting U87-tumour tissue selectivity. Conclusion After validating the in vitro radiosensitizing effect of small-sized AuNPs, an innovative design was selected for in vivo experiments. Tumour tissue accumulation and selectivity were evidenced for this innovative nanoparticle. We still have to validate the in vivo radiosensitizing effect using an orthotopic U87 model. We will suggest optimised treatment modalities.