Gadolinium-based nanoparticles to improve the hadrontherapy performances

Synergistic effect of Gemcitabin-loaded metal organic frameworks nanoparticles with particle therapy

Combination of nanoagents with radiations has opened up new perspectives in cancer treatment, improving both tumor diagnosis and therapeutic index. This work presents the first investigation of an innovative strategy that combines porous metal-organic frameworks (nanoMOFs) loaded with the anti-cancer drug Gemcitabine monophosphate (GemMP) and particle therapy-a globally emerging technique that offers more precise radiation targeting and enhanced biological efficacy compared to conventional radiotherapy. This radiochemotherapy has been confronted with two major obstacles limiting the efficacy of therapeutics when tested in vivo: (i) the presence of hypoxia, one of the most important causes for radiotherapy failure and (ii) the presence of a microenvironment, main biological barrier to the direct penetration of nanoparticles into cancer cells. On the one hand, this study explore the effects of hypoxia on drug delivery systems in combination with radiation, demonstrating that GemMP-loaded nanoMOFs significantly enhance the anticancer efficacy of particle therapy under both normoxic (pO2 = 20 %) and hypoxic (pO2 = 0.5 %) conditions. Notably, the presence of GemMP-loaded nanoMOFs allows the irradiation dose to be reduced by 1.4-fold in normoxia and at least 1.6-fold in hypoxia, achieving the same cytotoxic effect (SF=10 %) as carbon or helium ions alone. Synergistic effects between GemMP-loaded nanoMOFs and radiations have been observed and quantified. On the other hand, we also highlighted the ability of the nanoMOFs to diffuse through an extracellular matrix and accumulate in cells. An higher effect of the encapsulated GemMP than the free drug was observed, confirming the key role of the nanoMOFs in transporting the active substance to the cancer cells as a Trojan horse. This paves the way to the design of "all-in-one" nanodrugs where each component plays a role in the optimization of cancer therapy to maximize cytotoxic effects on hypoxic tumor cells while minimizing toxicity on healthy tissue.

A High-Sensitivity Benchtop X-Ray Fluorescence Emission Tomography (XFET) System With a Full-Ring of X-Ray Imaging-Spectrometers and a Compound-Eye Collimation Aperture

The advent of metal-based drugs and metal nanoparticles as therapeutic agents in anti-tumor treatment has motivated the advancement of X-ray fluorescence computed tomography (XFCT) techniques. An XFCT imaging modality can detect, quantify, and image the biodistribution of metal elements using the X-ray fluorescence signal emitted upon X-ray irradiation. However, the majority of XFCT imaging systems and instrumentation developed so far rely on a single or a small number of detectors. This work introduces the first full-ring benchtop X-ray fluorescence emission tomography (XFET) system equipped with 24 solid-state detectors arranged in a hexagonal geometry and a 96-pinhole compound-eye collimator. We experimentally demonstrate the system's sensitivity and its capability of multi-element detection and quantification by performing imaging studies on an animal-sized phantom. In our preliminary studies, the phantom was irradiated with a pencil beam of X-rays produced using a low-powered polychromatic X-ray source (90kVp and 60W max power). This investigation shows a significant enhancement in the detection limit of gadolinium to as low as 0.1 mg/mL concentration. The results also illustrate the unique capabilities of the XFET system to simultaneously determine the spatial distribution and accurately quantify the concentrations of multiple metal elements.

Radiation therapy-activated nanoparticle and immunotherapy: The next milestone in oncology?

Radiotherapy (RT) is a fundamental treatment at the locoregional or oligometastatic stages of cancer. In various tumors, RT effects may be optimized using synergistic combinations that enhance tumor response. Innovative strategies have been designed that explore the radiation mechanisms, at the physical, chemical and biological levels, to propose precision RT approaches. They consist in combining RT with immunotherapy to revert radiation immunosuppressive effects or to enhance radiation-induced immune defenses against the tumor to favor immunogenic cell death. Radiotherapy-activated nanoparticles are another innovation. By increasing radiation response in situ, nanoparticles improve tumor control locally, and can trigger systemic immune reactions that may be exploited to improve the systemic efficacy of RT. Strong clinical evidence of improved outcomes is now available for combinations of RT and immunotherapy on one hand and RT and nanoparticles on the other hand. The triple combination of RT, immunotherapy and nanoparticles is promising in terms of tolerance, local and systemic anti-tumor control. Yet, significant challenges remain to unravel the complexity of the multiscale mechanisms underlying response to this combination and their associated parameters. Such parameters include patient characteristics, tumor bulk and histology, radiation technique, energy, dose, fractionation, immunotherapy targets and predictive biomarkers, nanoparticle type, size, delivery (intratumoral/intravenous), distribution. The temporal combination is another critical parameter. The mechanisms of response of the combinatorial approaches are reviewed, with a focus on underlying mechanisms based on preclinical, translational and clinical studies. Opportunities for translation of current understanding into precision RT trials combined with immunotherapy and nanoparticles are also discussed.

Recent Advances in Metal-Based NanoEnhancers for Particle Therapy

Radiotherapy is one of the most common therapeutic regimens for cancer treatment. Over the past decade, proton therapy (PT) has emerged as an advanced type of radiotherapy (RT) that uses proton beams instead of conventional photon RT. Both PT and carbon-ion beam therapy (CIBT) exhibit excellent therapeutic results because of the physical characteristics of the resulting Bragg peaks, which has been exploited for cancer treatment in medical centers worldwide. Although particle therapies show significant advantages to photon RT by minimizing the radiation damage to normal tissue after the tumors, they still cause damage to normal tissue before the tumor. Since the physical mechanisms are different from particle therapy and photon RT, efforts have been made to ameliorate these effects by combining nanomaterials and particle therapies to improve tumor targeting by concentrating the radiation effects. Metallic nanoparticles (MNPs) exhibit many unique properties, such as strong X-ray absorption cross-sections and catalytic activity, and they are considered nano-radioenhancers (NREs) for RT. In this review, we systematically summarize the putative mechanisms involved in NRE-induced radioenhancement in particle therapy and the experimental results in in vitro and in vivo models. We also discuss the potential of translating preclinical metal-based NP-enhanced particle therapy studies into clinical practice using examples of several metal-based NREs, such as SPION, Abraxane, AGuIX, and NBTXR3. Furthermore, the future challenges and development of NREs for PT are presented for clinical translation. Finally, we propose a roadmap to pursue future studies to strengthen the interplay of particle therapy and nanomedicine.

Does particle radiation have superior radiobiological advantages for prostate cancer cells? A systematic review of in vitro studies

BACKGROUND

Charged particle beams from protons to carbon ions provide many significant physical benefits in radiation therapy. However, preclinical studies of charged particle therapy for prostate cancer are extremely limited. The aim of this study was to comprehensively investigate the biological effects of charged particles on prostate cancer from the perspective of in vitro studies.

METHODS

We conducted a systematic review by searching EMBASE (OVID), Medline (OVID), and Web of Science databases to identify the publications assessing the radiobiological effects of charged particle irradiation on prostate cancer cells. The data of relative biological effectiveness (RBE), surviving fraction (SF), standard enhancement ratio (SER) and oxygen enhancement ratio (OER) were extracted.

RESULTS

We found 12 studies met the eligible criteria. The relative biological effectiveness values of proton and carbon ion irradiation ranged from 0.94 to 1.52, and 1.67 to 3.7, respectively. Surviving fraction of 2 Gy were 0.17 ± 0.12, 0.55 ± 0.20 and 0.53 ± 0.16 in carbon ion, proton, and photon irradiation, respectively. PNKP inhibitor and gold nanoparticles were favorable sensitizing agents, while it was presented poorer performance in GANT61. The oxygen enhancement ratio values of photon and carbon ion irradiation were 2.32 ± 0.04, and 1.77 ± 0.13, respectively. Charged particle irradiation induced more G0-/G1- or G2-/M-phase arrest, more expression of γ-H2AX, more apoptosis, and lower motility and/or migration ability than photon irradiation.

CONCLUSIONS

Both carbon ion and proton irradiation have advantages over photon irradiation in radiobiological effects on prostate cancer cell lines. Carbon ion irradiation seems to have further advantages over proton irradiation.

Nanoscopic biodosimetry using plasmid DNA in radiotherapy with metallic nanoparticles

Nanoscopic lesions (complex damages), are the most lethal lesions for the cells. As nanoparticles have become increasingly popular in radiation therapy and the importance of analyzing nanoscopic dose enhancement has increased, a reliable tool for nanodosimetry has become indispensable. In this regard, the DNA plasmid is a widely used tool as a nanodosimetry probe in radiobiology and nano-radiosensitization studies. This approach is helpful for unraveling the radiosensitization role of nanoparticles in terms of physical and physicochemical effects and for quantifying radiation-induced biological damage. This review discusses the potential of using plasmid DNA assays for assessing the relative effects of nano-radiosensitizers, which can provide a theoretical basis for the development of nanoscopic biodosimetry and nanoparticle-based radiotherapy.

Transforming Nuclear Medicine with Nanoradiopharmaceuticals

Nuclear medicine is expected to make major advances in cancer diagnosis and therapy; tumor-targeted radiopharmaceuticals preferentially eradicate tumors while causing minimal damage to healthy tissues. The current scope of nuclear medicine can be significantly expanded by integration with nanomedicine, which utilizes nanoparticles for cancer diagnosis and therapy by capitalizing on the increased surface area-to-volume ratio, the passive/active targeting ability and high loading capacity, the greater interaction cross section with biological tissues, the rich surface properties of nanomaterials, the facile decoration of nanomaterials with a plethora of functionalities, and the potential for multiplexing several functionalities within one construct. This review provides a comprehensive discussion of nuclear nanomedicine using tumor-targeted nanoparticles for cancer radiation therapy with either pre-embedded radionuclides or nonradioactive materials which can be extrinsically triggered using various external nuclear particle sources to produce in situ radioactivity. In addition, it describes the prospect of combining nuclear nanomedicine with other modalities to enable synergistically enhanced combination therapies. The review also discusses advances in the fabrication of radionuclides as well as describes laser ablation technologies for producing nanoradiopharmaceuticals, which combine the ease of production with exceptional purity and rapid biodegradability, along with additional imaging or therapeutic functionalities. From a practical standpoint, these attributes of nanoradiopharmaceuticals may provide distinct advantages in diagnostic/therapeutic sensitivity and specificity, imaging resolution, and scalability of turnkey platforms. Coupling image-guided targeted radiation therapy with the possibility of in situ activation of nanomaterials as well as combining with other therapeutic modalities using a multifunctional nanoplatform could herald an era of exciting technological and therapeutic advances to radically transform the landscape of nuclear medicine. The review concludes with a discussion of current challenges and presents the authors' views on future opportunities to stimulate further research in this rewarding field of high societal impact.

Proton Stimulation Targeting Plaque Magnetite Reduces Amyloid-β Plaque and Iron Redox Toxicity and Improves Memory in an Alzheimer's Disease Mouse Model

BACKGROUND

The coexistence of magnetite within protein aggregates in the brain is a typical pathologic feature of Alzheimer's disease (AD), and the formation of amyloid-β (Aβ) plaques induces critical impairment of cognitive function.

OBJECTIVE

This study aimed to investigate the therapeutic effect of proton stimulation (PS) targeting plaque magnetite in the transgenic AD mouse brain.

METHODS

A proton transmission beam was applied to the whole mouse brain at a single entrance dose of 2 or 4 Gy to test the effect of disruption of magnetite-containing Aβ plaques by electron emission from magnetite. The reduction in Aβ plaque burden and the cognitive function of the PS-treated mouse group were assayed by histochemical analysis and memory tests, respectively. Aβ-magnetite and Aβ fibrils were treated with PS to investigate the breakdown of the amyloid protein matrix.

RESULTS

Single PS induced a 48-87%reduction in both the amyloid plaque burden and ferrous-containing magnetite level in the early-onset AD mouse brain while saving normal tissue. The overall Aβ plaque burden (68-82%) and (94-97%) hippocampal magnetite levels were reduced in late onset AD mice that showed improvements in cognitive function after PS compared with untreated AD mice (p < 0.001). Analysis of amyloid fibrils after exposure to a single 2 or 4 Gy proton transmission beam demonstrated that the protein matrix was broken down only in magnetite-associated Aβ fibrils.

CONCLUSION

Single PS targeting plaque magnetite effectively decreases the amyloid plaque burden and the ferrous-containing magnetite level, and this effect is useful for memory recovery.

Application of Carbon Ion and Its Sensitizing Agent in Cancer Therapy: A Systematic Review

Carbon ion radiation therapy (CIRT) is the most advanced radiation therapy (RT) available and offers new opportunities to improve cancer treatment and research. CIRT has a unique physical and biological advantage that allow them to kill tumor cells more accurately and intensively. So far, CIRT has been used in almost all types of malignant tumors, and showed good feasibility, safety and acceptable toxicity, indicating that CIRT has a wide range of development and application prospects. In addition, in order to improve the biological effect of CIRT, scientists are also trying to investigate related sensitizing agents to enhance the killing ability of tumor cells, which has attracted extensive attention. In this review, we tried to systematically review the rationale, advantages and problems, the clinical applications and the sensitizing agents of the CIRT. At the same time, the prospects of the CIRT in were prospected. We hope that this review will help researchers interested in CIRT, sensitizing agents, and radiotherapy to understand their magic more systematically and faster, and provide data reference and support for bioanalysis, clinical medicine, radiotherapy, heavy ion therapy, and nanoparticle diagnostics.

Rapid Evaluation of Novel Therapeutic Strategies Using a 3D Collagen-Based Tissue-Like Model

2D cell cultures are commonly used to rapidly evaluate the therapeutic potential of various treatments on living cells. However, the effects of the extracellular matrix (ECM) including the 3D arrangement of cells and the complex physiology of native environment are missing, which makes these models far from in vivo conditions. 3D cell models have emerged in preclinical studies to simulate the impact of the ECM and partially bridge the gap between monolayer cultures and in vivo tissues. To date, the difficulty to handle the existing 3D models, the cost of their production and their poor reproducibility have hindered their use. Here, we present a reproducible and commercially available "3D cell collagen-based model" (3D-CCM) that allows to study the influence of the matrix on nanoagent uptake and radiation effects. The cell density in these samples is homogeneous. The oxygen concentration in the 3D-CCM is tunable, which opens the opportunity to investigate hypoxic effects. In addition, thanks to the intrinsic properties of the collagen, the second harmonic imaging microscopy may be used to probe the whole volume and visualize living cells in real-time. Thus, the architecture and composition of 3D-CCMs as well as the impact of various therapeutic strategies on cells embedded in the ECM is observed directly. Moreover, the disaggregation of the collagen matrix allows recovering of cells without damaging them. It is a major advantage that makes possible single cell analysis and quantification of treatment effects using clonogenic assay. In this work, 3D-CCMs were used to evaluate the correlative efficacies of nanodrug exposure and medical radiation on cells contained in a tumor like sample. A comparison with monolayer cell cultures was performed showing the advantageous outcome and the higher potential of 3D-CCMs. This cheap and easy to handle approach is more ethical than in vivo experiments, thus, giving a fast evaluation of cellular responses to various treatments.

Study of the intracellular nanoparticle-based radiosensitization mechanisms in F98 glioma cells treated with charged particle therapy through synchrotron-based infrared microspectroscopy

The use of nanoparticles (NP) as dose enhancers in radiotherapy (RT) is a growing research field. Recently, the use of NP has been extended to charged particle therapy in order to improve the performance in radioresistant tumors. However, the biological mechanisms underlying the synergistic effects involved in NP-RT approaches are not clearly understood. Here, we used the capabilities of synchrotron-based Fourier Transform Infrared Microspectroscopy (SR-FTIRM) as a bio-analytical tool to elucidate the NP-induced cellular damage at the molecular level and at a single-cell scale. F98 glioma cells doped with AuNP and GdNP were irradiated using several types of medical ion beams (proton, helium, carbon and oxygen). Differences in cell composition were analyzed in the nucleic acids, protein and lipid spectral regions using multivariate methods (Principal Component Analysis, PCA). Several NP-induced cellular modifications were detected, such as conformational changes in secondary protein structures, intensity variations in the lipid CHx stretching bands, as well as complex DNA rearrangements following charged particle therapy irradiations. These spectral features seem to be correlated with the already shown enhancement both in the DNA damage response and in the reactive oxygen species (ROS) production by the NP, which causes cell damage in the form of protein, lipid, and/or DNA oxidations. Vibrational features were NP-dependent due to the NP heterogeneous radiosensitization capability. Our results provided new insights into the molecular changes in response to NP-based RT treatments using ion beams, and highlighted the relevance of SR-FTIRM as a useful and precise technique for assessing cell response to innovative radiotherapy approaches.

Green One-Step Synthesis of Medical Nanoagents for Advanced Radiation Therapy

PURPOSE

Metal-based nanoparticles (M-NPs) have attracted great attention in nanomedicine due to their capacity to amplify and improve the tumor targeting of medical beams. However, their simple, efficient, high-yield and reproducible production remains a challenge. Currently, M-NPs are mainly synthesized by chemical methods or radiolysis using toxic reactants. The waste of time, loss of material and potential environmental hazards are major limitations.

MATERIALS AND METHODS

This work proposes a simple, fast and green strategy to synthesize small, non-toxic and stable NPs in water with a 100% production rate. Ionizing radiation is used to simultaneously synthesize and sterilize the containing NPs solutions. The synthesis of platinum nanoparticles (Pt NPs) coated with biocompatible poly(ethylene glycol) ligands (PEG) is presented as proof of concept. The physicochemical properties of NPs were studied by complementary specialized techniques. Their toxicity and radio-enhancing properties were evaluated in a cancerous in vitro model. Using plasmid nanoprobes, we investigated the elementary mechanisms underpinning radio-enhancement.

RESULTS AND DISCUSSION

Pt NPs showed nearly spherical-like shapes and an average hydrodynamic diameter of 9 nm. NPs are zero-valent platinum successfully coated with PEG. They were found non-toxic and have the singular property of amplifying cell killing induced by γ-rays (14%) and even more, the effects of carbon ions (44%) used in particle therapy. They induce nanosized-molecular damage, which is a major finding to potentially implement this protocol in treatment planning simulations.

CONCLUSION

This new eco-friendly, fast and simple proposed method opens a new era of engineering water-soluble biocompatible NPs and boosts the development of NP-aided radiation therapies.

[T1-weighted magnetic resonance imaging contrast agents and their theranostic nanoprobes]

Magnetic resonance imaging (MRI) is an important imaging modality for clinical disease diagnosis, and nearly 50% of clinical MRI examinations require contrast agents to enhance the diagnostic sensitivity. This review provides a summary of the major MRI contrast agents and their classification, and the advantages and limits of the commercially available MRI contrast agents, and elaborates on the exceedingly small magnetic iron oxide nanoparticles (ES-MIONs), dotted core-shell iron and gadolinium hybrid nanoparticles (FeGd-HN) and exceedingly small gadolinium oxide nanoparticles (ES-GON). These nanoparticles can greatly improve the efficiency of T₁-weighted MRI due to their high r₁ value and low r₂/r₁ ratio, and are expected to be translated into clinical contrast agents for T₁-weighted MRI. The authors also review the diagnostic and therapeutic integration system that combines MRI contrast agents with various tumor therapies, such as MRI-guided ferroptosis therapy, radiosensitization therapy, and photothermal therapy, which allow efficient treatment as well as real-time monitoring of tumors and serve as potential cancer therapy strategies. The possible future research directions in the field of MRI-based multifunctional diagnostic and therapeutic formulations are also discussed.

Uptake and excretion dynamics of gold nanoparticles in cancer cells and fibroblasts

Radiotherapy is one of the main treatments used to fight cancer. A major limitation of this modality is the lack of selectivity between cancerous and healthy tissues. One of the most promising strategies proposed in this last decade is the addition of nanoparticles with high-atomic number to enhance radiation effects in tumors. Gold nanoparticles (AuNPs) are considered as one of the best candidates because of their high radioenhancing property, simple synthesis and low toxicity. Ultra small AuNPs (core size of 2.4 nm and hydrodynamic diameter of 4.5 nm) covered with dithiolated diethylenetriaminepentaacetic acid (Au@DTDTPA) are of high interest because of their properties to bind MRI active or PET active compounds at their surface, to concentrate in some tumors and be eliminated via renal clearance thanks to their small size. These key figures make Au@DTDTPA the best candidate to develop image-guided radiotherapy. Surprisingly the capacity of the nanoparticles to penetrate cells, an important issue to predict radioenhancement, has not been established yet. Here, we report the uptake dynamics, internalization routes and excretion dynamics of Au@DTDTPA nanoparticles in various cancer cell lines including glioblastoma (U87-MG), chordoma (UM-Chor1), cervix (HeLa), prostate (PC3), and pancreatic (BxPC-3) cell lines as well as fibroblasts (Dermal fibroblasts). This study demonstrates a strong cell line dependence of the nanoparticle uptake and excretion dynamics. Different pathways of cell internalization evidenced here explain this dependence. As a major finding, the retention of Au@DTDTPA nanoparticles was found to be higher in cancer cells than in fibroblasts. This result strengthens the strategy of using nanoagents to improve tumor selectivity of radiation treatments. In particular Au@DTDTPA nanoparticles are good candidates to improve the treatment of radioresitant gliobastoma, pancreatic and prostate cancer in particular. In conclusion, the variability of cell-to-nanoparticle interaction is a new parameter to consider in the choice of nanoagents in a combined treatment.

Small-sized gadolinium oxide based nanoparticles for high-efficiency theranostics of orthotopic glioblastoma

Glioblastoma (GBM) is one of the most malignant tumors with poor prognosis and outcomes. Although smaller particle size can lead to higher blood-brain barrier (BBB)-permeability of the nanomaterials, most of the reported BBB-crossable nanomaterials for targeted GBM therapy are larger than 24 nm. To realize theranostics of GBM, co-loading of therapeutic and diagnostic agents on the same nanomaterials further results in larger particle size. In this study, we developed a kind of novel BBB-transportable nanomaterials smaller than 14 nm for high-efficiency theranostics of GBM (i.e., high contrast magnetic resonance imaging (MRI) and radiosensitization of GBM). Typically, poly(acrylic acid) (PAA) stabilized extremely small gadolinium oxide nanoparticles with modification of reductive bovine serum albumin (ES-GON-rBSA) was synthesized in water phase, resulting in excellent water-dispersibility. RGD dimer (RGD2, Glu-{Cyclo[Arg-Gly-Asp-(D-Phe)-Lys]}2) and lactoferrin (LF) were then conjugated to the ES-GON-rBSA to obtain composite nanoparticle ES-GON-rBSA-LF-RGD2 with extraordinary relaxivities (r1 = 60.8 mM-1 s-1, r2/r1 = 1.1). The maximum signal enhancement (ΔSNR) for T1-weighted MRI of tumors reached up to 423 ± 42% at 12 h post-injection of ES-GON-rBSA-LF-RGD2, which is much higher than commercial Gd-chelates (<80%). ES-GON-rBSA-LF-RGD2 exhibited high biocompatibility and can transport across the in vitro BBB model and the in vivo BBB of mice due to its small particle size (dh = 13.4 nm) and LF receptor mediated transcytosis. Orthotopic GBM studies reinforce that ES-GON-rBSA3-LF-RGD2 can accumulate in the orthotopic GBM and enhance the radiation therapy of GBM as an effective radiosensitizing agent.

A Facile One-Pot Synthesis of Versatile PEGylated Platinum Nanoflowers and Their Application in Radiation Therapy

Nanomedicine has stepped into the spotlight of radiation therapy over the last two decades. Nanoparticles (NPs), especially metallic NPs, can potentiate radiotherapy by specific accumulation into tumors, thus enhancing the efficacy while alleviating the toxicity of radiotherapy. Water radiolysis is a simple, fast and environmentally-friendly method to prepare highly controllable metallic nanoparticles in large scale. In this study, we used this method to prepare biocompatible PEGylated (with Poly(Ethylene Glycol) diamine) platinum nanoflowers (Pt NFs). These nanoagents provide unique surface chemistry, which allows functionalization with various molecules such as fluorescent markers, drugs or radionuclides. The Pt NFs were produced with a controlled aggregation of small Pt subunits through a combination of grafted polymers and radiation-induced polymer cross-linking. Confocal microscopy and fluorescence lifetime imaging microscopy revealed that Pt NFs were localized in the cytoplasm of cervical cancer cells (HeLa) but not in the nucleus. Clonogenic assays revealed that Pt NFs amplify the gamma rays induced killing of HeLa cells with a sensitizing enhancement ratio (SER) of 23%, thus making them promising candidates for future cancer radiation therapy. Furthermore, the efficiency of Pt NFs to induce nanoscopic biomolecular damage by interacting with gamma rays, was evaluated using plasmids as molecular probe. These findings show that the Pt NFs are efficient nano-radio-enhancers. Finally, these NFs could be used to improve not only the performances of radiation therapy treatments but also drug delivery and/or diagnosis when functionalized with various molecules.

Investigating the mechanisms behind extensive death in human cancer cells following nanoparticle assisted photo-thermo-radiotherapy

We have recently reported the synthesis and characterization of gold-coated iron oxide nanoparticle and demonstrated such a nanoparticle (Au@Fe₂O₃ NP) was able to significantly enhance the lethal effects of photo-thermo-radiotherapy. The purpose of this study was to determine the mechanisms behind such an enhancement by investigating the changes induced in cancer cell viability, proliferation, and morphology as well as monitoring the alteration of some genes which play important role in the process of cell death. Using MTT assay and transmission electron microscopy (TEM), the KB cells viability and morphology were assessed after treating with various combinations of NPs, photothermal therapy (PTT), and radiotherapy (RT). Clonogenic assay was used to assess the proliferation ability of treated KB cells. Nanoparticle internalization into the cells was investigated by TEM and inductively coupled plasma (ICP). During the treatment procedures, temperature changes were monitored using an IR-camera. Furthermore, the changes occurred in Bax, BCL2 and HSP70 genes expression level were measured using real-time PCR. The results showed that combination of NP, PTT, and RT caused more cell death compared to PTT or RT alone. Following such a combination therapy, massive cell injury was detected. We also observed an extensive increase in Bax/Bcl2 ratio and HSP70 expression for the KB cells treated by combination therapy procedure. Our results showed that massive cell injury and apoptosis induction are the main reasons of extensive cell death observed in cancer cells when a nanoparticle assisted photo-thermo-radiotherapy procedure is applied.

Radio-Enhancing Properties of Bimetallic Au:Pt Nanoparticles: Experimental and Theoretical Evidence

The use of nanoparticles, in combination with ionizing radiation, is considered a promising method to improve the performance of radiation therapies. In this work, we engineered mono- and bimetallic core-shell gold–platinum nanoparticles (NPs) grafted with poly (ethylene glycol) (PEG). Their radio-enhancing properties were investigated using plasmids as bio-nanomolecular probes and gamma radiation. We found that the presence of bimetallic Au:Pt-PEG NPs increased by 90% the induction of double-strand breaks, the signature of nanosize biodamage, and the most difficult cell lesion to repair. The radio-enhancement of Au:Pt-PEG NPs were found three times higher than that of Au-PEG NPs. This effect was scavenged by 80% in the presence of dimethyl sulfoxide, demonstrating the major role of hydroxyl radicals in the damage induction. Geant4-DNA Monte Carlo simulations were used to elucidate the physical processes involved in the radio-enhancement. We predicted enhancement factors of 40% and 45% for the induction of nanosize damage, respectively, for mono- and bimetallic nanoparticles, which is attributed to secondary electron impact processes. This work contributed to a better understanding of the interplay between energy deposition and the induction of nanosize biomolecular damage, being Monte Carlo simulations a simple method to guide the synthesis of new radio-enhancing agents.

Radiosensitizing Effect of Gadolinium Oxide Nanocrystals in NSCLC Cells Under Carbon Ion Irradiation

Gadolinium-based nanomaterials can not only serve as contrast agents but also contribute to sensitization in the radiotherapy of cancers. Among radiotherapies, carbon ion irradiation is considered one of the superior approaches with unique physical and biological advantages. However, only a few metallic nanoparticles have been used to improve carbon ion irradiation. In this study, gadolinium oxide nanocrystals (GONs) were synthesized using a polyol method to decipher the radiosensitizing mechanisms in non-small cell lung cancer (NSCLC) cell lines irradiated by carbon ions. The sensitizer enhancement ratio at the 10% survival level was correlated with the concentration of Gd in NSCLC cells. GONs elicited an increase in hydroxyl radical production in a concentration-dependent manner, and the yield of reactive oxygen species increased obviously in irradiated cells, which led to DNA damage and cell cycle arrest. Apoptosis and cytostatic autophagy were also significantly induced by GONs under carbon ion irradiation. The GONs may serve as an effective theranostic material in carbon ion radiotherapy for NSCLC.

Backscattered electron emission after proton impact on gold nanoparticles with and without polymer shell coating

This work aims at measuring experimentally proton induced secondary electron energy spectra after interaction with gold nano particles (GNPs) and polymer-coated GNPs. Backscattered electron energy spectra were collected over a 0 to 1000 eV energy range using a retarding field analyzer (RFA). This paper presents the spectra obtained for proton beam energies of 0.5 and 2 MeV and diameter 2.5 and 3.8 nm GNPs. The spectra were also measured for 3.8 nm GNPs after 5 and 10 MeV proton irradiations. GNPs were deposited on a 100 nm carbon film. Each experimental spectrum was compared with dedicated simulations based on existing numerical models used in the TRAX and Geant4 Monte Carlo codes. For 100 nm carbon target, good agreement between experimental, TRAX and Geant4 simulation results can be observed. For 3.8 nm GNPs, the TRAX simulations reproduce with good agreement the electron energy spectra produced after 0.5, 2, 5 and 10 MeV proton irradiations, while Geant4 spectra display a lower secondary electron yield at low energy (<600 eV) for all the studied energies. This underestimation can mostly be explained by the 790 eV threshold applied in the condensed history model used by Geant4 which impacts the secondary electron energy distribution. Results obtained for carbon and gold targets highlight the impact of the secondary electron production threshold for proton ionization process considered in condensed history models. The experimental results demonstrate that the single interaction approach used in TRAX is adapted to reproduce secondary electron emission from GNPs. On the other hand, the standard electron generation threshold implement in G4BetheBlochModel and G4BraggModel condensed-history models used in Geant4 is not adapted to reproduce low energy electron emission in gold targets. Finally, the results highlight that the GNP coating leads to a decrease of the electron yield and mostly affects low energy electrons (<500 eV) emitted from GNPs.

Targeted delivery of hesperetin to cartilage attenuates osteoarthritis by bimodal imaging with Gd2(CO3)3@PDA nanoparticles via TLR-2/NF-κB/Akt signaling

The progressive degeneration of cartilage marks the advancement of osteoarthritis (OA), which requires specific targeted treatment for effective cartilage repair. However, there is still no efficient cartilage delivery system or novel magnetic resonance (MR) contrast agent (CA). Herein, we report the synthesis of a novel class of MR CA, Gd₂(CO₃)₃-based nanoparticles (NPs), from a simpler and "greener" approach than previous ones. After the coating of polydopamine (PDA) onto the Gd₂(CO₃)₃ core, we further anchored a cartilage-targeting peptide and loaded hesperetin (Hes) into NPs (Hes-Gd₂(CO₃)₃@PDA-PEG-DWpeptide, HGdPDW), showing excellent cartilage affinity and MR suitability. Additionally, the synthesized HGdPDW exerted significant protective effects against IL-1β stimulation, as shown by the decreased apoptosis and inflammation and increased maturation of chondrocytes in vitro. More importantly, RNA-seq analyses showed the significant reduction of TLR-2 in IL-1β-treated chondrocytes, and this reduction was followed by the inactivation of NF-κB/Akt signaling, leading to the protective effect of HGdPDW. By the establishment of anterior cruciate ligament transection (ACLT) OA mice, the bimodal MRI/IVIS imaging demonstrated the effective cartilage-binding ability of HGdPDW in OA knees with low cytotoxicity, which alleviated the gradual degeneration of articular cartilage in vivo by inhibiting TLR-2 in chondrocytes. Taken together, these results suggest that HGdPDW could target cartilage effectively, thereby protecting chondrocytes from apoptosis and inflammation via TLR-2/NF-κB/Akt signaling. We hope this new class of MRI CA could be applied in not only other fields using MRI technology but also the treatment of general cartilage-related diseases; this application will undoubtedly extend the treatment of OA clinically.

Experimental measurements validate the use of the binary encounter approximation model to accurately compute proton induced dose and radiolysis enhancement from gold nanoparticles

In protontherapy, it has been suggested that nanoparticles of high-Z material like gold (GNP) could be used as radiosensitizers. The origin of this enhancement phenomenon for proton radiation is not yet well understood and additional mechanistic insights are required. Previous works have highlighted the good capabilities of TRAX to reproduce secondary electron emission from gold material. Therefore, TRAX cross sections obtained with the binary encounter approximation (BEA) model for proton ionization were implemented within Geant4 for gold material. Based on the TRAX cross sections, improved Geant4 simulations have been developed to investigate the energy deposition and radical species production around a spherical gold nanoparticle (5 and 10 nm in diameter) placed in a water volume during proton irradiation. Simulations were performed for incident 2 MeV proton. The dose enhancement factor and the radiolysis enhancement factor were quantified. Results obtained with the BEA model were compared with results obtained with condensed-history models. Experimental irradiation of 200 nm gold films were performed to validate the secondary electron emission reproduction capabilities of physical models used in Monte Carlo (MC) simulations. TRAX simulations reproduced the experimental backscattered electron energy spectrum from gold film with better agreement than Geant4. Results on gold film obtained with the BEA model enabled to estimate the electron emission from GNPs. Results obtained in our study tend to support that the use of the BEA discrete model leads to a significant increase of the dose in the near vicinity of GNPs (<20 nm), while condensed history models used in Geant4 seem to overestimate the dose and the number of chemical species for increasing distances from the GNP. Based on discrete BEA model results, no enhancement effect due to secondary electron emitted from the GNP is expected if the GNP is not in close proximity to key cellular functional elements (DNA, mitochondria…).

Thioredoxin Reductase Activity Predicts Gold Nanoparticle Radiosensitization Effect

Gold nanoparticles (GNPs) have been shown to be effective contrast agents for imaging and emerge as powerful radiosensitizers, constituting a promising theranostic agent for cancer. Although the radiosensitization effect was initially attributed to a physical mechanism, an increasing number of studies challenge this mechanistic hypothesis and evidence the importance of oxidative stress in this process. This work evidences the central role played by thioredoxin reductase (TrxR) in the GNP-induced radiosensitization. A cell type-dependent reduction in TrxR activity was measured in five different cell lines incubated with GNPs leading to differences in cell response to X-ray irradiation. Correlation analyses demonstrated that GNP uptake and TrxR activity inhibition are associated to a GNP radiosensitization effect. Finally, Kaplan-Meier analyses suggested that high TrxR expression is correlated to low patient survival in four different types of cancer. Altogether, these results enable a better understanding of the GNP radiosensitization mechanism, which remains a mandatory step towards further use in clinic. Moreover, they highlight the potential application of this new treatment in a personalized medicine context.

Treatment of multiple brain metastases using gadolinium nanoparticles and radiotherapy: NANO-RAD, a phase I study protocol

INTRODUCTION

Occurrence of multiple brain metastases is a critical evolution of many cancers with significant neurological and overall survival consequences, despite new targeted therapy and standard whole brain radiotherapy (WBRT). A gadolinium-based nanoparticle, AGuIX, has recently demonstrated its effectiveness as theranostic and radiosensitiser agent in preclinical studies. The favourable toxicity profile in animals and its administration as a simple intravenous injection has motivated its use in patients with this first in human study.

METHODS AND ANALYSIS

The NANO-RAD study is a phase I, first in human injection, monocentric, open-label, dose-escalation study to investigate the safety, the tolerability and the spectrum of side effects of AGuIX in combination with WBRT (30 Gy, 10 fractions of 3 Gy) for patients with multiple brain metastases. Five dose escalation cohorts are planned: 15, 30, 50, 75 and 100 mg/kg. A total of 15-18 patients will be recruited into this trial. The primary objective is to determine the maximum-tolerated dose of AGuIX nanoparticles combined with WBRT for the treatment of multiple brain metastases. Toxicity will be assessed using the National Cancer Institute Common Toxicity Criteria V.4.03. Secondary objectives are pharmacokinetic profile, distribution of AGuIX in metastases and surrounding healthy tissue visualised by MRI, intracranial progression-free survival and overall survival. Intracranial response will be determined according to Response Evaluation Criteria in Solid Tumour Criteria V.1.1 comparing MRI performed prior to treatment and at each follow-up visits.

ETHICS AND DISSEMINATION

Approval was obtained from the ethics committee Sud Est V, France (Reference number 15-CHUG-48). The study was approved by the French National Agency for the Safety of Medicines and Health Products (ANSM) (Reference number 151519A-12). The results will be published in peer-reviewed journals or disseminated through national and international conferences.

TRIAL REGISTRATION NUMBER

NCT02820454; Pre-results.

Antibody-functionalized gold nanoparticles as tumor-targeting radiosensitizers for proton therapy

AIM

This study aimed at developing antibody-functionalized gold nanoparticles (AuNPs) to selectively target cancer cells and probing their potential radiosensitizing effects under proton irradiation.

MATERIALS & METHODS

AuNPs were conjugated with cetuximab (Ctxb-AuNPs). Ctxb-AuNP uptake was evaluated by transmission electron microscopy and atomic absorption spectroscopy. Radioenhancing effect was assessed using conventional clonogenic assay.

RESULTS & CONCLUSION

Ctxb-AuNPs specifically bound to and accumulated in EGFR-overexpressing A431 cells, compared with EGFR-negative MDA-MB-453 cells. Ctxb-AuNPs enhanced the effect of proton irradiation in A431 cells but not in MDA-MB-453 cells. These data indicate, for the first time, that combining enhanced uptake by specific targeting and radioenhancing effect, using conjugated AuNPs, is a promising strategy to increase cell killing by protontherapy.

The role of thioredoxin reductase in gold nanoparticle radiosensitization effects

Aim: To identify new mechanisms responsible for the radiosensitization effect of gold nanoparticles (GNPs). Materials & methods: A549 lung carcinoma cells were incubated with 10-nm GNPs during 6 or 24 h before to be exposed to 25 keV/μm protons or 225 kV x-rays. Results: GNP incubation led to a time-dependent mitochondria membrane depolarization, oxidative stress and to x-ray and proton radiosensitization. Moreover, a marked inhibition of thioredoxin reductase was observed. Irradiation of cells invalidated for thioredoxin reductase evidenced a radiosensitization effect, suggesting that this enzyme is a potential GNP target. Conclusion: We suggest that GNPs play a radiosensitizer role by weakening detoxification systems. Altogether, these results open up promising novel strategies for the development of nanotechnologies associated to radiotherapy.

Track analysis of a synchrotron X-ray photoelectric nanoradiator by in situ fluorescence imaging of reactive oxygen species: comparative study of gold and iron oxide nanoparticles

The emission of fluorescent X-rays and low-energy electrons by mid-/high-Z nanoparticles upon irradiation with either X-ray photons or high-energy ion beams is referred to as the nanoradiator effect (NRE). A track analysis of NRE was performed using reactive oxygen species (ROS) gels, to which macrophages containing gold nanoparticles (AuNPs) were attached, together with single-cell irradiation of the intracellular nanoparticles from a microbeam of synchrotron X-rays, and the range and distribution of ^\bulletOH and O₂^{ \bullet - } produced were compared with those of the Fe-nanoradiator by magnetite nanoparticles (FeONP, Fe₃O₄). The Au-nanoradiator generated ROS fluorescence to a greater depth and wider angle with respect to the incident X-rays than that of the Fe-nanoradiator. The ROS-oxidant fluorescence intensity ratios of ^\bulletOH to O₂^{ \bullet - } were different for the AuNPs and FeONPs, reflecting different relative yields of electrons and fluorescent X-rays from NRE. In the region immediately (<100 µm) below the irradiated cell, ^\bulletOH-radicals were distributed mainly along two or three tracks in the depth direction in the FeONP- or AuNP-ROS gel. In contrast, O₂^{ \bullet - } was scattered more abundantly in random directions in the AuNP-ROS gel than in the FeONP-ROS gel. Track analysis of X-ray photoelectric nanoradiator radiation showed a different range of dose distribution and relative emission compositions between Au- and Fe-nanoradiators, suggesting more extensive damage beyond a single cell containing AuNPs than one containing FeONPs.

AGuIX® from bench to bedside-Transfer of an ultrasmall theranostic gadolinium-based nanoparticle to clinical medicine

AGuIX^® are sub-5 nm nanoparticles made of a polysiloxane matrix and gadolinium chelates. This nanoparticle has been recently accepted in clinical trials in association with radiotherapy. This review will summarize the principal preclinical results that have led to first in man administration. No evidence of toxicity has been observed during regulatory toxicity tests on two animal species (rodents and monkeys). Biodistributions on different animal models have shown passive uptake in tumours due to enhanced permeability and retention effect combined with renal elimination of the nanoparticles after intravenous administration. High radiosensitizing effect has been observed with different types of irradiations in vitro and in vivo on a large number of cancer types (brain, lung, melanoma, head and neck…). The review concludes with the second generation of AGuIX nanoparticles and the first preliminary results on human.

Metal-based NanoEnhancers for Future Radiotherapy: Radiosensitizing and Synergistic Effects on Tumor Cells

Radiotherapy is one of the major therapeutic strategies for cancer treatment. In the past decade, there has been growing interest in using high Z (atomic number) elements (materials) as radiosensitizers. New strategies in nanomedicine could help to improve cancer diagnosis and therapy at cellular and molecular levels. Metal-based nanoparticles usually exhibit chemical inertness in cellular and subcellular systems and may play a role in radiosensitization and synergistic cell-killing effects for radiation therapy. This review summarizes the efficacy of metal-based NanoEnhancers against cancers in both in vitro and in vivo systems for a range of ionizing radiations including gamma-rays, X-rays, and charged particles. The potential of translating preclinical studies on metal-based nanoparticles-enhanced radiation therapy into clinical practice is also discussed using examples of several metal-based NanoEnhancers (such as CYT-6091, AGuIX, and NBTXR3). Also, a few general examples of theranostic multimetallic nanocomposites are presented, and the related biological mechanisms are discussed.

Dose enhancement effects of gold nanoparticles specifically targeting RNA in breast cancer cells

Localization microscopy has shown to be capable of systematic investigations on the arrangement and counting of cellular uptake of gold nanoparticles (GNP) with nanometer resolution. In this article, we show that the application of specially modified RNA targeting gold nanoparticles ("SmartFlares") can result in ring like shaped GNP arrangements around the cell nucleus. Transmission electron microscopy revealed GNP accumulation in vicinity to the intracellular membrane structures including them of the endoplasmatic reticulum. A quantification of the radio therapeutic dose enhancement as a proof of principle was conducted with γH2AX foci analysis: The application of both-SmartFlares and unmodified GNPs-lead to a significant dose enhancement with a factor of up to 1.2 times the dose deposition compared to non-treated breast cancer cells. This enhancement effect was even more pronounced for SmartFlares. Furthermore, it was shown that a magnetic field of 1 Tesla simultaneously applied during irradiation has no detectable influence on neither the structure nor the dose enhancement dealt by gold nanoparticles.

Nanoparticle radio-enhancement: principles, progress and application to cancer treatment

Enhancement of radiation effects by high-atomic number nanoparticles (NPs) has been increasingly studied for its potential to improve radiotherapeutic efficacy. The underlying principle of NP radio-enhancement is the potential to release copious electrons into a nanoscale volume, thereby amplifying radiation-induced biological damage. While the vast majority of studies to date have focused on gold nanoparticles with photon radiation, an increasing number of experimental, theoretical and simulation studies have explored opportunities offered by other NPs (e.g. gadolinium, platinum, iron oxide, hafnium) and other therapeutic radiation sources such as ion beams. It is thus of interest to the research community to consolidate findings from the different studies and summarise progress to date, as well as to identify strategies that offer promising opportunities for clinical translation. This is the purpose of this Topical Review.

AS1411 aptamer conjugated gold nanoclusters as a targeted radiosensitizer for megavoltage radiation therapy of 4T1 breast cancer cells

In the present study, AS1411 aptamer conjugated gold nanoclusters (GNCs) have been introduced as a targeted radiosensitizer for enhancing megavoltage radiation therapy efficacy.

Particle therapy and nanomedicine: state of art and research perspectives

Cancer radiation therapy with charged particle beams, called particle therapy, is a new therapeutic treatment presenting major advantages when compared to conventional radiotherapy. Because ions have specific ballistic properties and a higher biological effectiveness, they are superior to x-rays. Numerous medical centres are starting in the world using mostly protons but also carbon ions as medical beams. Several investigations are attempting to reduce the cost/benefit ratio and enlarge the range of therapeutic indications. A major limitation of particle therapy is the presence of low but significant damage induced in healthy tissues located at the entrance of the ion track prior to reaching the tumour. It is thus a major challenge to improve the targeting of the tumours, concentrating radiation effects in the malignance. A novel strategy, based on the addition of nanoparticles targeting the tumour, was suggested over a decade ago to improve the performance of conventional photon therapy. Recently, similar developments have emerged for particle therapy and the amount of research is now exploding. In this paper, we review the experimental results, as well as theoretical and simulation studies that shed light in the promising outcomes of this strategy and in the underpinning mechanisms. Several experiments provide consistent evidence of significant enhancement of ion radiation effects in the presence of nanoparticles. In view of implementing this strategy for cancer treatment, simulation studies have begun to establish the rationale and the specificity of this effect. In addition, these studies will help to outline a list of possible mechanisms and to predict the impact of ion beams and nanoparticle characteristics. Many questions remain unsolved, but the findings of these first studies are encouraging and open new challenges. After summarizing the main results in the field, we propose a roadmap to pursue future research with the aim to strengthen the potential interplay between particle therapy and nanomedicine.

Comparison of gadolinium nanoparticles and molecular contrast agents for radiation therapy-enhancement

PURPOSE

Nanoparticles appear as a novel tool to enhance the effectiveness of radiotherapy in cancer treatments. Many parameters influence their efficacy, such as their size, concentration, composition, their cellular localization, as well as the photon source energy. The current Monte Carlo study aims at comparing the dose-enhancement in presence of gadolinium (Gd), either as isolated atoms or atoms clustered in nanoparticles (NPs), by investigating the role played by these physical parameters at the cellular and the nanometer scale. In parallel, in vitro assays were performed in presence of either the gadolinium contrast agent (GdCA) Magnevist^® or ultrasmall gadolinium NPs (GdNPs, 3 nm) for comparison with the simulations.

METHODS

PENELOPE Monte Carlo Code was used for in silico dose calculations. Monochromatic photon beams were used to calculate dose enhancements in different cell compartments and low-energy secondary electron spectra dependence with energy. Particular attention has been placed on the interplay between the X-ray beam energy, the Gd localization and its distance from cellular targets. Clonogenic assays were used to quantify F98 rat glioma cell survival after irradiation in the presence of GdNPs or GdCA, using monochromatic X-rays with energies in the 30 keV-80 keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. The simulations that correspond to the experimental conditions were compared with the experimental results.

RESULTS

In silico, a highly heterogeneous and clustered Gd-atom distribution, a massive production of low energy electrons around GdNPs and an optimal X-ray beam energy, above the Gd K-edge, were key factors found to increase microscopic doses, which could potentially induce cell death. The different Gd localizations studied all resulted in a lower dose enhancement for the nucleus component than for cytoplasm or membrane compartments, with a maximum dose-enhancement factor (DEF) found at 65 keV and 58 keV, respectively. In vitro, radiosensitization was observed with GdNPs incubated 5 h with the cells (2.1 mg Gd/mL) at all energies. Experimental DEFs were found to be greater than computational DEFs but follow a similar trend with irradiation energy. However, an important radiosensitivity was observed experimentally with GdNPs at high energy (1.25 MeV), whereas no effect was expected from modeling. This effect was correlated with GdNPs incubation time. In vitro, GdCA provided no dose enhancement at 1.25 MeV energies, in agreement with computed data.

CONCLUSIONS

These results provide a foundation on which to base optimizations of the physical parameters in Gd radiation-enhanced therapy. Strong evidence was provided that GdCA or GdNPs could both be used for radiation dose-enhancement therapy. There in vivo biological distribution, in the tumor volume and at the cellular scale, will be the key factor for providing large dose enhancements and determine their therapeutic efficacy.

Reactive oxygen species-based measurement of the dependence of the Coulomb nanoradiator effect on proton energy and atomic Z value

PURPOSE

The Coulomb nanoradiator (CNR) effect produces the dose enhancement effects from high-Z nanoparticles under irradiation with a high-energy ion beam. To gain insight into the radiation dose and biological significance of the CNR effect, the enhancement of reactive oxygen species (ROS) production from iron oxide or gold NPs (IONs or AuNPs, respectively) in water was investigated using traversing proton beams.

METHODS AND MATERIALS

The dependence of nanoradiator-enhanced ROS production on the atomic Z value and proton energy was investigated. Two biologically important ROS species were measured using fluorescent probes specific to •OH or [Formula: see text] in a series of water phantoms containing either AuNPs or IONs under irradiation with a 45- or 100-MeV proton beam.

RESULTS

The enhanced generation of hydroxyl radicals (•OH) and superoxide anions ([Formula: see text]) was determined to be caused by the dependence on the NP concentration and proton energy. The proton-induced Au or iron oxide nanoradiators exhibited different ROS enhancement rates depending on the proton energy, suggesting that the CNR radiation varied. The curve of the superoxide anion production from the Au-nanoradiator showed strong non-linearity, unlike the linear behavior observed for hydroxyl radical production and the X-ray photoelectric nanoradiator. In addition, the 45-MeV proton-induced Au nanoradiator exhibited an ROS enhancement ratio of 8.54/1.50 ([Formula: see text] / •OH), similar to that of the 100-KeV X-ray photoelectric Au nanoradiator (7.68/1.46).

CONCLUSIONS

The ROS-based detection of the CNR effect revealed its dependence on the proton beam energy, dose and atomic Z value and provided insight into the low-linear energy transfer (LET) CNR radiation, suggesting that these factors may influence the therapeutic efficacy via chemical reactivities, transport behaviors, and intracellular oxidative stress.

Pinhole X-ray fluorescence imaging of gadolinium and gold nanoparticles using polychromatic X-rays: a Monte Carlo study

This work aims to develop a Monte Carlo (MC) model for pinhole K-shell X-ray fluorescence (XRF) imaging of metal nanoparticles using polychromatic X-rays. The MC model consisted of two-dimensional (2D) position-sensitive detectors and fan-beam X-rays used to stimulate the emission of XRF photons from gadolinium (Gd) or gold (Au) nanoparticles. Four cylindrical columns containing different concentrations of nanoparticles ranging from 0.01% to 0.09% by weight (wt%) were placed in a 5 cm diameter cylindrical water phantom. The images of the columns had detectable contrast-to-noise ratios (CNRs) of 5.7 and 4.3 for 0.01 wt% Gd and for 0.03 wt% Au, respectively. Higher concentrations of nanoparticles yielded higher CNR. For 1×10¹¹ incident particles, the radiation dose to the phantom was 19.9 mGy for 110 kVp X-rays (Gd imaging) and 26.1 mGy for 140 kVp X-rays (Au imaging). The MC model of a pinhole XRF can acquire direct 2D slice images of the object without image reconstruction. The MC model demonstrated that the pinhole XRF imaging system could be a potential bioimaging modality for nanomedicine.

Gadolinium-based nanoparticles as sensitizing agents to carbon ions in head and neck tumor cells

Hadrontherapy presents the major advantage of improving tumor sterilization while sparing surrounding healthy tissues because of the particular ballistic (Bragg peak) of carbon ions. However, its efficacy is still limited in the most resistant cancers, such as grade III-IV head and neck squamous cell carcinoma (HNSCC), in which the association of carbon ions with gadolinium-based nanoparticles (AGuIX^®) could be used as a Trojan horse. We report for the first time the radioenhancing effect of AGuIX^® when combined with carbon ion irradiation in human tumor cells. An increase in relative biological effectiveness (1.7) in three HNSCC cell lines (SQ20B, FaDu, and Cal33) was associated with a significant reduction in the radiation dose needed for killing cells. Radiosensitization goes through a higher number of unrepaired DNA double-strand breaks. These results underline the strong potential of AGuIX^® in sensitizing aggressive tumors to hadrontherapy and, therefore, improving local control while lowering acute/late toxicity.

Platinum nanoparticles: an exquisite tool to overcome radioresistance

Backgroud

Small metallic nanoparticles are proposed as potential nanodrugs to optimize the performances of radiotherapy. This strategy, based on the enrichment of tumours with nanoparticles to amplify radiation effects in the tumour, aims at increasing the cytopathic effect in tumours while healthy tissue is preserved, an important challenge in radiotherapy. Another major cause of radiotherapy failure is the radioresistance of certain cancers. Surprisingly, the use of nanoparticles to overcome radioresistance has not, to the best of our knowledge, been extensively investigated. The mechanisms of radioresistance have been extensively studied using Deinococcus radiodurans, the most radioresistant organism ever reported, as a model.

Methods

In this work, we investigated the impact of ultra-small platinum nanoparticles (1.7 nm) on this organism, including uptake, toxicity, and effects on radiation responses.

Results

We showed that the nanoparticles penetrate D. radiodurans cells, despite the 150 nm cell wall thickness with a minimal inhibition concentration on the order of 4.8 mg L⁻¹. We also found that the nanoparticles amplify gamma ray radiation effects by >40%.

Conclusions

Finally, this study demonstrates the capacity of metallic nanoparticles to amplify radiation in radioresistant organisms, thus opening the perspective to use nanoparticles not only to improve tumour targeting but also to overcome radioresistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12645-017-0028-y) contains supplementary material, which is available to authorized users.

An overview of current practice in external beam radiation oncology with consideration to potential benefits and challenges for nanotechnology

Over the past two decades, there has been a significant evolution in the technologies and techniques employed within the radiation oncology environment. Over the same period, extensive research into the use of nanotechnology in medicine has highlighted a range of potential benefits to its incorporation into clinical radiation oncology. This short communication describes key tools and techniques that have recently been introduced into specific stages of a patient’s radiotherapy pathway, including diagnosis, external beam treatment and subsequent follow-up. At each pathway stage, consideration is given towards how nanotechnology may be combined with clinical developments to further enhance their benefit, with some potential opportunities for future research also highlighted. Prospective challenges that may influence the introduction of nanotechnology into clinical radiotherapy are also discussed, indicating the need for close collaboration between academic and clinical staff to realise the full clinical benefit of this exciting technology.

Coulomb nanoradiator-mediated, site-specific thrombolytic proton treatment with a traversing pristine Bragg peak

Traversing proton beam-irradiated, mid/high-Z nanoparticles produce site-specific enhancement of X-ray photon-electron emission via the Coulomb nanoradiator (CNR) effect, resulting in a nano- to micro-scale therapeutic effect at the nanoparticle-uptake target site. Here, we demonstrate the uptake of iron oxide nanoparticles (IONs) and nanoradiator-mediated, site-specific thrombolysis without damaging the vascular endothelium in an arterial thrombosis mouse model. The enhancement of low-energy electron (LEE) emission and reactive oxygen species (ROS) production from traversing proton beam-irradiated IONs was examined. Flow recovery was only observed in CNR-treated mice, and greater than 50% removal of the thrombus was achieved. A 2.5-fold greater reduction in the thrombus-enabled flow recovery was observed in the CNR group compared with that observed in the untreated ION-only and proton-only control groups (p < 0.01). Enhancement of the X-ray photon-electron emission was evident from both the pronounced Shirley background in the electron yield and the 1.2- to 2.5-fold enhanced production of ROS by the proton-irradiated IONs, which suggests chemical degradation of the thrombus without potent emboli.

LET-dependent radiosensitization effects of gold nanoparticles for proton irradiation

The development of new modalities and protocols is of major interest to improve the outcome of cancer treatment. Given the appealing physical properties of protons and the emerging evidence of biological relevance of the use of gold nanoparticles (GNPs), the radiosensitization effects of GNPs (5 or 10 nm) have been investigated in vitro in combination with a proton beam of different linear energy transfer (LET). After the incubation with GNPs for 24 h, nanoparticles were observed in the cytoplasm of A431 cells exposed to 10 nm GNPs, and in the cytoplasm as well as the nucleus of cells exposed to 5 nm GNPs. Cell uptake of 0.05 mg ml^-1 of GNPs led to 0.78 pg Au/cell and 0.30 pg Au/cell after 24 h incubation for 10 and 5 nm GNPs respectively. A marked radiosensitization effect of GNPs was observed with 25 keV μm^-1 protons, but not with 10 keV μm^-1 protons. This effect was more pronounced for 10 nm GNPs than for 5 nm GNPs. By using a radical scavenger, a major role of reactive oxygen species in the amplification of the death of irradiated cell was identified. All together, these results open up novel perspectives for using high-Z metallic NPs in protontherapy.

Gold nanoparticles for cancer radiotherapy: a review

Radiotherapy is currently used in around 50% of cancer treatments and relies on the deposition of energy directly into tumour tissue. Although it is generally effective, some of the deposited energy can adversely affect healthy tissue outside the tumour volume, especially in the case of photon radiation (gamma and X-rays). Improved radiotherapy outcomes can be achieved by employing ion beams due to the characteristic energy deposition curve which culminates in a localised, high radiation dose (in form of a Bragg peak). In addition to ion radiotherapy, novel sensitisers, such as nanoparticles, have shown to locally increase the damaging effect of both photon and ion radiation, when both are applied to the tumour area. Amongst the available nanoparticle systems, gold nanoparticles have become particularly popular due to several advantages: biocompatibility, well-established methods for synthesis in a wide range of sizes, and the possibility of coating of their surface with a large number of different molecules to provide partial control of, for example, surface charge or interaction with serum proteins. This gives a full range of options for design parameter combinations, in which the optimal choice is not always clear, partially due to a lack of understanding of many processes that take place upon irradiation of such complicated systems. In this review, we summarise the mechanisms of action of radiation therapy with photons and ions in the presence and absence of nanoparticles, as well as the influence of some of the core and coating design parameters of nanoparticles on their radiosensitisation capabilities.

Effect of gadolinium-based nanoparticles on nuclear DNA damage and repair in glioblastoma tumor cells

Background

Tumor targeting of radiotherapy represents a great challenge. The addition of multimodal nanoparticles, such as 3 nm gadolinium-based nanoparticles (GdBNs), has been proposed as a promising strategy to amplify the effects of radiation in tumors and improve diagnostics using the same agents. This singular property named theranostic is a unique advantage of GdBNs. It has been established that the amplification of radiation effects by GdBNs appears due to fast electronic processes. However, the influence of these nanoparticles on cells is not yet understood. In particular, it remains dubious how nanoparticles activated by ionizing radiation interact with cells and their constituents. A crucial question remains open of whether damage to the nucleus is necessary for the radiosensitization exerted by GdBNs (and other nanoparticles).

Methods

We studied the effect of GdBNs on the induction and repair of DNA double-strand breaks (DSBs) in the nuclear DNA of U87 tumor cells irradiated with γ-rays. For this purpose, we used currently the most sensitive method of DSBs detection based on high-resolution confocal fluorescence microscopy coupled with immunodetection of two independent DSBs markers.

Results

We show that, in the conditions where GdBNs amplify radiation effects, they remain localized in the cytoplasm, i.e. do not penetrate into the nucleus. In addition, the presence of GdBNs in the cytoplasm neither increases induction of DSBs by γ-rays in the nuclear DNA nor affects their consequent repair.

Conclusions

Our results suggest that the radiosensitization mediated by GdBNs is a cytoplasmic event that is independent of the nuclear DNA breakage, a phenomenon commonly accepted as the explanation of biological radiation effects. Considering our earlier recognized colocalization of GdBNs with the lysosomes and endosomes, we revolutionary hypothesize here about these organelles as potential targets for (some) nanoparticles. If confirmed, this finding of cytoplasmically determined radiosensitization opens new perspectives of using nano-radioenhancers to improve radiotherapy without escalating the risk of pathologies related to genetic damage.

3D Imaging of Nanoparticle Distribution in Biological Tissue by Laser-Induced Breakdown Spectroscopy

Nanomaterials represent a rapidly expanding area of research with huge potential for future medical applications. Nanotechnology indeed promises to revolutionize diagnostics, drug delivery, gene therapy, and many other areas of research. For any biological investigation involving nanomaterials, it is crucial to study the behavior of such nano-objects within tissues to evaluate both their efficacy and their toxicity. Here, we provide the first account of 3D label-free nanoparticle imaging at the entire-organ scale. The technology used is known as laser-induced breakdown spectroscopy (LIBS) and possesses several advantages such as speed of operation, ease of use and full compatibility with optical microscopy. We then used two different but complementary approaches to achieve 3D elemental imaging with LIBS: a volume reconstruction of a sliced organ and in-depth analysis. This proof-of-concept study demonstrates the quantitative imaging of both endogenous and exogenous elements within entire organs and paves the way for innumerable applications.