Neutral Products Desorption from DNA Thin Films Induced by Low-Energy Electrons (0.5-20 eV)

International audienceLow-energy electrons (LEEs) are produced in great amount in the biological medium, when submitted to high-energy radiations. They have the ability to induce strand breaks in the DNA duplex, as proven by electrophoresis analysis of irradiated dry deposits. LEE interactions with target molecules induce the formation of different species such as anions, cations, radicals and neutrals. The desorption of anionic species from oligonucleotides and DNA under LEEs irradiation has been intensively explored. The involved mechanisms and sites were successfully identified, including the resonant formation of transient negative ions (TNI) below 15 eV. However, the desorption of neutral products was less explored [4], due to their difficult detection. Exploring this aspect will provide additional information and complete the picture of the dissociating pathways followed by TNIs

Gold Nanoparticle Uptake in Tumor Cells: Quantification and Size Distribution by sp-ICPMS

Gold nanoparticles (AuNPs) are increasingly studied for cancer treatment purposes, as they can potentially improve both control and efficiency of the treatment. Intensive research is conducted in vitro on rodent and human cell lines to objectify the gain of combining AuNPs with cancer treatment and to understand their mechanisms of action. However, using nanoparticles in such studies requires thorough knowledge of their cellular uptake. In this study, we optimized single particle ICPMS (sp-ICPMS) analysis to qualify and quantify intracellular AuNP content after exposure of in vitro human breast cancer cell lines. To this aim, cells were treated with an alkaline digestion method with 5% TMAH, allowing the detection of gold with a yield of 97% on average. Results showed that under our experimental conditions, the AuNP size distribution appeared to be unchanged after internalization and that the uptake of particles depended on the cell line and on the exposure duration. Finally, the comparison of the particle numbers per cell with the estimates based on the gold masses showed excellent agreement, confirming the validity of the sp-ICPMS particle measurements in such complex samples

La construction du site pédagogique numérique CHIMACTIV : analyse d'une coopération réussie entre enseignants

International audienceUn collectif d'enseignants inter-établissements s'est organisé pour concevoir et co-construire un site pédagogique numérique. L'équipe de conception initiale a fortement coopéré (au sein de chaque établissement et entre établissements) et interagi étroitement avec différents acteurs (cellules TICE, étudiants, prestataires externes) pour aboutir à une version bilingue du site. La volonté d'élargir et de diversifier le champ des utilisateurs (enseignants et étudiants) a conduit à ouvrir ce collectif à de nouveaux enseignants, afin de faire évoluer le site et compléter son contenu. Après une analyse de l'organisation mise en place, nous discuterons des obstacles à surmonter, des facteurs de réussite et du ressenti des enseignants ayant vécu cette coopération, avant de conclure sur ce qu'apporte l'aspect « numérique » des ressources développées dans la coopération entre enseignants sur la base de notre expérience

A comparison of the radiosensitisation ability of 22 different element metal oxide nanoparticles using clinical megavoltage X-rays

Background: A wide range of nanoparticles (NPs), composed of different elements and their compounds, are being developed by several groups as possible radiosensitisers, with some already in clinical trials. However, no systematic experimental survey of the clinical X-ray radiosensitising potential of different element nanoparticles has been made. Here, we directly compare the irradiation-induced (10 Gy of 6-MV X-ray photon) production of hydroxyl radicals, superoxide anion radicals and singlet oxygen in aqueous solutions of the following metal oxide nanoparticles: Al2O3, SiO2, Sc2O3, TiO2, V2O5, Cr2O3, MnO2, Fe3O4, CoO, NiO, CuO, ZnO, ZrO2, MoO3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb4O7, Dy2O3, Er2O3 and HfO2. We also examine DNA damage due to these NPs in unirradiated and irradiated conditions. Results: Without any X-rays, several NPs produced more radicals than water alone. Thus, V2O5 NPs produced around 5-times more hydroxyl radicals and superoxide radicals. MnO2 NPs produced around 10-times more superoxide anions and Tb4O7 produced around 3-times more singlet oxygen. Lanthanides produce fewer hydroxyl radicals than water. Following irradiation, V2O5 NPs produced nearly 10-times more hydroxyl radicals than water. Changes in radical concentrations were determined by subtracting unirradiated values from irradiated values. These were then compared with irradiation-induced changes in water only. Irradiation-specific increases in hydroxyl radical were seen with most NPs, but these were only significantly above the values of water for V2O5, while the Lanthanides showed irradiation-specific decreases in hydroxyl radical, compared to water. Only TiO2 showed a trend of irradiation-specific increase in superoxides, while V2O5, MnO2, CoO, CuO, MoO3 and Tb4O7 all demonstrated significant irradiation-specific decreases in superoxide, compared to water. No irradiation-specific increases in singlet oxygen were seen, but V2O5, NiO, CuO, MoO3 and the lanthanides demonstrated irradiation-specific decreases in singlet oxygen, compared to water. MoO3 and CuO produced DNA damage in the absence of radiation, while the highest irradiation-specific DNA damage was observed with CuO. In contrast, MnO2, Fe3O4 and CoO were slightly protective against irradiation-induced DNA damage. Conclusions: Beyond identifying promising metal oxide NP radiosensitisers and radioprotectors, our broad comparisons reveal unexpected differences that suggest the surface chemistry of NP radiosensitisers is an important criterion for their success

Vers la compréhension de l effet radiosensibilisateur de nanoparticules d or soumises à un rayonnement X

La radiothérapie est l une des stratégies thérapeutiques parmi les plus répandues dans la lutte contre le cancer mais son efficacité est limitée par la tolérance des tissus sains. De fait, son association avec des agents radiosensibilisants vise à accroître son efficacité en augmentant spécifiquement les dommages aux cellules tumorales. C est dans ce cadre que nous avons étudié la radiosensibilisation par des nanoparticules d or (NPo) associées à un rayonnement X in vitro. Ce travail de thèse a connu trois temps. Le premier a consisté en la mise en place des outils nécessaires à cette étude, à savoir la synthèse et la caractérisation de NPo ainsi que des différentes sources de rayonnement utilisées. Puis nous avons démontré la radiosensibilisation par les NPo combinées aux rayons X de trois cibles cellulaires potentielles : la membrane, les protéines et l ADN. Nous avons alors montré que la concentration des NPo, leur taille et l énergie des rayons X incidents étaient trois paramètres gouvernant cet effet radiosensibilisateur. Enfin, nous nous sommes intéressés aux mécanismes à l origine de cet effet : une surproduction de radicaux hydroxyle a été observée en présence de NPo et l effet direct des électrons émis par l or semble perdurer en solution. Nous avons également évalué les conditions de transposition de cette radiosensibilisation du in vitro au in vivo.Radiotherapy is one of the most widespread cancer treatments but it suffers from its lack of selectivity. That s why associated with a radiosensitizing agent that specifically enhances the radiation effect in the tumour, it could be more efficient. In this context, we studied the radiosensitization by gold nanoparticles (NPo) submitted to X-rays in vitro. Three steps could be distinguished in this work. The first one consisted in implementing the mandatory tools, namely NPo synthesis and characterization and calibration of the different irradiation sources. Then we demonstrated the radiosensitization by NPo combined to X-rays of three potential cellular targets: membrane, protein and DNA. We showed that NPo concentration, size and X-ray energy were three parameters governing this effect. Finally, we got interested in the underlying mechanisms: hydroxyle radicals overproduction was observed in the presence of NPo and direct effect from electrons emitted by gold seems to still occur in solution. Besides, we assessed the conditions required for the translation of this fundamental research topic to clinical applications.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Low-Energy (3-24 eV) electron damage to the peptide backbone

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Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions.

International audienceIn this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively