Polymer-grafted gold nanoparticles for cancer treatment: synthesis and evaluation of their radiosensitizing properties

International audienceToday, even though treatments have much improved, cancer is still a leading cause of death in the world, being responsible for 1 death out of 6. Radiotherapy is widely used for tumor treatment, but suffers from side effects due to the irradiation of healthy surrounding tissues. Another issue is the radioresistance developed by some tumor cells, which implies to increase the involved doses. The challenge remains to deliver curative doses to tumor tissues while sparing sound ones. Hence the use of tumor-located radiosensitizers is a promising way to improve the efficacy of radiotherapy. High-Z materials have been known for several decades to amplify the damaging effects of both photon and ion radiations. Various nanoparticles have already been developed to take advantage of this property: gold, platinum and gadolinium are amongst the most investigated elements. A well-controlled synthesis is key to obtain stable and scalable nano-objects. Here, various polymers were grafted onto metallic nanoparticles to improve stability and biocompatibility and to facilitate subsequent functionalization. Advanced methods of characterization attested both robustness and reproducibility of the synthesis procedure. Moreover, promising results were obtained regarding the radioenhancing properties of these hybrid nanocompounds. Therefore, special attention has been given to the underlying mechanisms of the assessed radiosensitization, since they are not fully understood yet. Synthesis of polymer-grafted gold nanoparticles was performed through an in situ method, via the reduction of gold salts in the presence of polymeric ligands mainly prepared using controlled radical polymerization. The resulting nano-objects were fully characterized by thermogravimetric analysis, inductively coupled plasma mass spectrometry (ICP-MS), transmission electronic microscopy and small-angle x-ray and neutron scattering. Interactions between our nanocompounds and biological systems were studied in order to better understand the mechanisms at play. At the cellular scale, three aspects were examined for each type of nanoparticles: cellular uptake, cytotoxicity and radiosensitizing properties, through ICP-MS measurements, cell proliferation assays and clonogenic assays respectively. All irradiations were performed while keeping the delivered doses to low values (under 30 Gy) that are typical of clinic reality. Different types of radiations were tested, in order to compare their effects and their synergy with the nanocompounds. The synthesized nano-objects have shown great potential to enhance radiation cancer treatment. Their stability and controlled surface chemistry have allowed to develop multiple strategies in order to optimize their radiosensitizing effect and in vitro behavior

The consolidated European synthesis of CO2 emissions and removals for the European Union and United Kingdom: 1990–2020

Quantification of land surface–atmosphere fluxes of carbon dioxide (CO2) and their trends and uncertainties is essential for monitoring progress of the EU27+UK bloc as it strives to meet ambitious targets determined by both international agreements and internal regulation. This study provides a consolidated synthesis of fossil sources (CO2 fossil) and natural (including formally managed ecosystems) sources and sinks over land (CO2 land) using bottom-up (BU) and top-down (TD) approaches for the European Union and United Kingdom (EU27+UK), updating earlier syntheses (Petrescu et al., 2020, 2021). Given the wide scope of the work and the variety of approaches involved, this study aims to answer essential questions identified in the previous syntheses and understand the differences between datasets, particularly for poorly characterized fluxes from managed and unmanaged ecosystems. The work integrates updated emission inventory data, process-based model results, data-driven categorical model results, and inverse modeling estimates, extending the previous period 1990–2018 to the year 2020 to the extent possible. BU and TD products are compared with the European national greenhouse gas inventory (NGHGI) reported by parties including the year 2019 under the United Nations Framework Convention on Climate Change (UNFCCC). The uncertainties of the EU27+UK NGHGI were evaluated using the standard deviation reported by the EU member states following the guidelines of the Intergovernmental Panel on Climate Change (IPCC) and harmonized by gap-filling procedures. Variation in estimates produced with other methods, such as atmospheric inversion models (TD) or spatially disaggregated inventory datasets (BU), originate from within-model uncertainty related to parameterization as well as structural differences between models. By comparing the NGHGI with other approaches, key sources of differences between estimates arise primarily in activities. System boundaries and emission categories create differences in CO2 fossil datasets, while different land use definitions for reporting emissions from land use, land use change, and forestry (LULUCF) activities result in differences for CO2 land. The latter has important consequences for atmospheric inversions, leading to inversions reporting stronger sinks in vegetation and soils than are reported by the NGHGI. For CO2 fossil emissions, after harmonizing estimates based on common activities and selecting the most recent year available for all datasets, the UNFCCC NGHGI for the EU27+UK accounts for 926 ± 13 Tg C yr−1, while eight other BU sources report a mean value of 948 [937,961] Tg C yr−1 (25th, 75th percentiles). The sole top-down inversion of fossil emissions currently available accounts for 875 Tg C in this same year, a value outside the uncertainty of both the NGHGI and bottom-up ensemble estimates and for which uncertainty estimates are not currently available. For the net CO2 land fluxes, during the most recent 5-year period including the NGHGI estimates, the NGHGI accounted for −91 ± 32 Tg C yr−1, while six other BU approaches reported a mean sink of −62 [] Tg C yr−1, and a 15-member ensemble of dynamic global vegetation models (DGVMs) reported −69 [] Tg C yr−1. The 5-year mean of three TD regional ensembles combined with one non-ensemble inversion of −73 Tg C yr−1 has a slightly smaller spread (0th–100th percentiles of [] Tg C yr−1), and it was calculated after removing net land–atmosphere CO2 fluxes caused by lateral transport of carbon (crop trade, wood trade, river transport, and net uptake from inland water bodies), resulting in increased agreement with the NGHGI and bottom-up approaches. Results at the category level (Forest Land, Cropland, Grassland) generally show good agreement between the NGHGI and category-specific models, but results for DGVMs are mixed. Overall, for both CO2 fossil and net CO2 land fluxes, we find that current independent approaches are consistent with the NGHGI at the scale of the EU27+UK. We conclude that CO2 emissions from fossil sources have decreased over the past 30 years in the EU27+UK, while land fluxes are relatively stable: positive or negative trends larger (smaller) than 0.07 (−0.61) Tg C yr−2 can be ruled out for the NGHGI. In addition, a gap on the order of 1000 Tg C yr−1 between CO2 fossil emissions and net CO2 uptake by the land exists regardless of the type of approach (NGHGI, TD, BU), falling well outside all available estimates of uncertainties. However, uncertainties in top-down approaches to estimate CO2 fossil emissions remain uncharacterized and are likely substantial, in addition to known uncertainties in top-down estimates of the land fluxes. The data used to plot the figures are available at https://doi.org/10.5281/zenodo.8148461 (McGrath et al., 2023)

Hybrid and polymer nano-objects under irradiation

Les nano-objets hybrides ou polymères connaissent un intérêt grandissant depuis plusieurs années mais peu sont étudiés sous irradiation. Dans ce travail, différents nano-objets ont été synthétisés et étudiés pour comprendre leur stabilité face à des rayonnements ionisants. Nous avons étudié l’effet de l’irradiation sur des copolymères à blocs amphiphiles pouvant s’organiser en micelles dans l’eau. Les objets varient par la nature de leur polymère hydrophobe et leur sensibilité aux rayonnements ionisants. Dans un cas, des polyméthacrylates ont été copolymérisés par ATRP à partir d’un PEG macro-amorceur. Dans un autre cas, pour accentuer l’effet de l’irradiation, un polysulfone aliphatique plus radiosensible, a été synthétisé via une polyaddition thiol-ène. Après nanoprécipitation, les objets ont été caractérisés avant et après irradiation par des techniques de diffusion et de chromatographie. En parallèle, on s’est intéressés également à des nanoparticules métalliques connues pour augmenter l’effet de l’irradiation. Des nanoparticules d’or greffées de polymères ont été synthétisées par voie « grafting to » après synthèse de macro-ligands par polymérisation radicalaire contrôlée. Après une caractérisation fine des objets, l’effet de l’irradiation a été étudié à la fois sur la taille des objets et la masse des polymères afin de déterminer la nature des phénomènes mis en jeu.Hybrid and polymer nano-objects have known a growing interest these last years but few are studied under irradiation. In the present work, different nano-objects have been synthetized and studied to understand their stability towards ionizing rays. We have studied the effect of irradiation onto amphiphilic bloc copolymer that form micelles in water. Objects were varied by the nature of their hydrophobic bloc and their sensibility to ionizing rays. First, methacrylates were copolymerized by ATRP with a PEG macro-initiator. Secondly, to improve radiation effect, a more radiosensitive polymer, a polyolefinsulfone, was synthetized by a thiol-ene polyaddition. After nanoprecipitation, objects were caracterized before and after irradiation by scattering and chromatography techniques. In parallel we also studied metallic nanoparticles well known for improving irradiation effect. Polymer-grafted gold nanoparticles were synthetized via a “grafting to” technique, after the synthesis of macro-ligands by controlled radical polymerization. After a precise characterization of these objects, irradiation effect has been studied via changes in size and polymer mass. This will permit to determine the nature of induced phenomena

Nano-objets hybrides et polymères sous irradiation

Hybrid and polymer nano-objects have known a growing interest these last years but few are studied under irradiation. In the present work, different nano-objects have been synthetized and studied to understand their stability towards ionizing rays. We have studied the effect of irradiation onto amphiphilic bloc copolymer that form micelles in water. Objects were varied by the nature of their hydrophobic bloc and their sensibility to ionizing rays. First, methacrylates were copolymerized by ATRP with a PEG macro-initiator. Secondly, to improve radiation effect, a more radiosensitive polymer, a polyolefinsulfone, was synthetized by a thiol-ene polyaddition. After nanoprecipitation, objects were caracterized before and after irradiation by scattering and chromatography techniques. In parallel we also studied metallic nanoparticles well known for improving irradiation effect. Polymer-grafted gold nanoparticles were synthetized via a “grafting to” technique, after the synthesis of macro-ligands by controlled radical polymerization. After a precise characterization of these objects, irradiation effect has been studied via changes in size and polymer mass. This will permit to determine the nature of induced phenomena.Les nano-objets hybrides ou polymères connaissent un intérêt grandissant depuis plusieurs années mais peu sont étudiés sous irradiation. Dans ce travail, différents nano-objets ont été synthétisés et étudiés pour comprendre leur stabilité face à des rayonnements ionisants. Nous avons étudié l’effet de l’irradiation sur des copolymères à blocs amphiphiles pouvant s’organiser en micelles dans l’eau. Les objets varient par la nature de leur polymère hydrophobe et leur sensibilité aux rayonnements ionisants. Dans un cas, des polyméthacrylates ont été copolymérisés par ATRP à partir d’un PEG macro-amorceur. Dans un autre cas, pour accentuer l’effet de l’irradiation, un polysulfone aliphatique plus radiosensible, a été synthétisé via une polyaddition thiol-ène. Après nanoprécipitation, les objets ont été caractérisés avant et après irradiation par des techniques de diffusion et de chromatographie. En parallèle, on s’est intéressés également à des nanoparticules métalliques connues pour augmenter l’effet de l’irradiation. Des nanoparticules d’or greffées de polymères ont été synthétisées par voie « grafting to » après synthèse de macro-ligands par polymérisation radicalaire contrôlée. Après une caractérisation fine des objets, l’effet de l’irradiation a été étudié à la fois sur la taille des objets et la masse des polymères afin de déterminer la nature des phénomènes mis en jeu

Hybrid metal-polymer nanoparticles as promising radiosensitizers for cancer treatment

International audienceNanotechnologies are being widely studied for medical applications, both diagnosis and treatment. They have already shown great promise, especially to treat cancer through various strategies such as chemotherapy, photothermal therapy or radiation therapies. High-Z elements nanoparticles are of particular interest for the latter, considering their ability to amplify the damaging effects of both photon and ion radiations: gold, platinum and gadolinium are amongst the most investigated elements. A well-controlled synthesis is key to obtain stable and scalable nano-objects. Here, various polymers were grafted onto metallic nanoparticles to improve stability and biocompatibility and to facilitate subsequent functionalization. Advanced methods of characterization attested to the robustness and reproducibility of the synthesis procedure. Moreover, promising results were obtained regarding the radioenhancing properties of these hybrid nanocompounds. Polymers mainly synthesized via controlled radical polymerization were grafted onto gold and platinum nanoparticles by a "grafting to" or "grafting from" method. Subsequent grafting of a chemotherapy drug onto the polymer corona was also successfully carried out. The resulting nano-objects were fully characterized by thermogravimetric analysis, transmission electronic microscopy and small-angle x-ray scattering. Small-angle neutron scattering was also performed, taking advantage of possible contrast matching. The impact of various radiation doses on the nanoparticles structure was studied. Finally, radiosensitizing effects were investigated through in vitro tests. Under irradiation, uncoupling and cleavage of polymer chains were demonstrated, leading to an overall size reduction of the hybrid nano-objects. The location of target sites during irradiation was determined and helped to better understand the underlying mechanism of the radiosensitization assessed by the in vitro results. The synthesized nano-objects have therefore shown great potential to enhance radiation cancer treatment. Their stability and controlled surface chemistry will allow to develop multiple strategies to further improve their radiosensitizing effect and in vitro behavior. In vivo tests are currently under study, as well as experiments regarding radioenhancement for proton therapy

Ligand-free synthesis of gold nanoparticles incorporated within oriented cylindrical block copolymer films : towards optical metamaterials

We report a method to incorporate non-functionalized gold nanoparticles (AuNPs) in oriented cylindrical phases of poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP) block copolymers, perpendicular to a substrate. The combination of AFM, TEM, GISAXS and spectroscopy allows complete characterization of the nanocomposites. AuNPs are produced by the ultra-sound reduction of a gold salt in the copolymer solution, prior to the deposition of the films by spin-coating. The AuNPs are found to be located within the PVP cylinders exclusively. The seeded-growth of these pre-formed AuNPs by a further ultra-sound treatment produced plasmonic AuNPs (up to d =10 nm). For perpendicular cylinders, the PVP domains are swollen without any change in their orientation. Ellipsometric optical properties of these plasmonic AuNPs embeded into oriented cylinders show a definite extinction in reflectivity at a precise energy and incidence angle

Ligand-free synthesis of gold nanoparticles included within cylindrical blocl copolymer films

International audienceWe report a method to include non-functionalized gold nanoparticles (AuNPs) in oriented cylindrical phases of poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP) block copolymers, perpendicular or parallel to a substrate. The combination of AFM, TEM, GISAXS and spectroscopy allows a complete characterization of the nanocomposite. AuNPs are produced by the ultra-sound reduction of a gold salt in the copolymer solution, prior to the deposition of the film by spin-coating. The AuNPs are found to be located within the PVP cylinders exclusively. Sizes from 2 to 4 nm are tuned as a function of the initial gold salt concentration. A seeded-growth of these pre-formed AuNPs was also achieved by a further ultra-sound treatment to produce larger AuNPs (up to d=10 nm) with plasmon resonance properties. For parallel cylinders, the presence of AuNPs in the PVP domains disturbs the organization, while, for perpendicular cylinders, the PVP domains are swollen without any change in their orientation. The synthesis of AuNPs inside the copolymer was also performed by radiolysis, through the irradiation of the copolymer solution or the copolymer film, both containing the gold salt. In these cases, the presence of plasmonic AuNPs was also evidenced. Offering a control of the AuNPs size (< 2 nm to 10 nm) and location, the presented method is a unique way of inserting plasmonic AuNPs into oriented cylinders for reaching anisotropic geometries of valuable interest for optic