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Khosravifarsani M, Ait-Mohand S, Paquette B, Sanche L, Guérin B. High Cytotoxic Effect by Combining Copper-64 with a NOTA-Terpyridine Platinum Conjugate. J Med Chem 2021; 64:6765-6776. [PMID: 33909440 DOI: 10.1021/acs.jmedchem.1c00039] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Terpyridine platinum (TP)-based chemotherapeutic agents target three-dimensional structures on DNA known as G-quadruplexes. We report the rational design and synthesis of a TP conjugate combined with copper-64 (64Cu), the decay characteristics of which include emission of β- and Auger electrons for radiotherapy and β+ particles for positron emission tomography (PET) imaging. The present experimental studies show that the novel [64Cu]Cu-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA)-TP is stable, permitting selective killing of cancer cells. The antitumor activity of [64Cu]Cu-NOTA-TP at high apparent molar activity is in the low nanomolar range and 27,800-fold greater than that of natCu-NOTA-TP at 24 h post treatment. These results suggest that this combination of a cytotoxic TP agent with 64Cu has considerable potential for cancer treatment and PET imaging.
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Affiliation(s)
- Meysam Khosravifarsani
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Samia Ait-Mohand
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Benoit Paquette
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Léon Sanche
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - Brigitte Guérin
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.,Sherbrooke Molecular Imaging Center (CIMS), CRCHUS, 3001, 12e Avenue Nord, Sherbrooke, Québec J1H 5N4, Canada
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2
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Gilles M, Brun E, Sicard-Roselli C. Quantification of hydroxyl radicals and solvated electrons produced by irradiated gold nanoparticles suggests a crucial role of interfacial water. J Colloid Interface Sci 2018; 525:31-38. [DOI: 10.1016/j.jcis.2018.04.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 03/09/2018] [Accepted: 04/04/2018] [Indexed: 12/26/2022]
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3
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Bouhier M, Vigneron G, Ngono-Ravache Y, Shirdhonkar M, Renault JP, Le Caër S. In situ and time-resolved infrared detection of the reactivity induced by electrons in polymer films. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2017; 88:034102. [PMID: 28372418 DOI: 10.1063/1.4978442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The real time and in situ analysis of chemical reactions such as polymerization reactions, polymer degradation, and oxidation of polymers is of utmost importance. Surprisingly, only few experimental tools allowing this are available. To bridge this gap, we have developed a new experimental setup coupling a 60 keV electron gun with an infrared spectrometer operating in the mid-IR region (800-4000 cm-1) and associated with the rapid scan mode. The measurements are performed using the infrared reflection absorption spectroscopy approach. We worked here with 0.5-25 ms pulses for which the dose per pulse ranges from 4 to 200 kGy. Combining pulse electrons with rapid scan analysis enables performing experiments with a time resolution of 80 ms (and above). Therefore, this new platform can, for instance, give direct insights into reaction mechanisms at stake during the degradation of polymers. First results on a bisphenol A polycarbonate irradiated under vacuum enabling the validation of this new setup and also the recording of time-resolved spectra are presented. Reaction mechanisms are then proposed.
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Affiliation(s)
- M Bouhier
- LIONS, NIMBE, UMR 3685, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette Cedex, France
| | - G Vigneron
- LIONS, NIMBE, UMR 3685, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette Cedex, France
| | - Y Ngono-Ravache
- DRF/IRAMIS/CIMAP, UMR 6252, BP 5133, F-14070 Caen Cedex 5, France
| | - M Shirdhonkar
- LIONS, NIMBE, UMR 3685, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette Cedex, France
| | - J P Renault
- LIONS, NIMBE, UMR 3685, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette Cedex, France
| | - S Le Caër
- LIONS, NIMBE, UMR 3685, CEA, CNRS, Université Paris Saclay, F-91191 Gif-sur-Yvette Cedex, France
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Rakowski JT, Laha SS, Snyder MG, Buczek MG, Tucker MA, Liu F, Mao G, Hillman Y, Lawes G. Measurement of gold nanofilm dose enhancement using unlaminated radiochromic film. Med Phys 2015; 42:5937-44. [DOI: 10.1118/1.4931054] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Ounoughi N, Mavon C, Belafrites A, Fromm M. Spatial distribution of air kerma rate and impact of accelerating voltage on the quality of an ultra soft X-ray beam generated by a cold cathode tube in air. RADIAT MEAS 2015. [DOI: 10.1016/j.radmeas.2015.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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6
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Alizadeh E, Sanz AG, Madugundu GS, García G, Wagner JR, Sanche L. Thymidine Decomposition Induced by Low-Energy Electrons and Soft X Rays under N2and O2Atmospheres. Radiat Res 2014; 181:629-40. [DOI: 10.1667/rr13584.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Koulouklidis AD, Cohen S, Kalef-Ezra J. Thermochromic phase-transitions of GafChromic films studied by z
-scan and temperature-dependent absorbance measurements. Med Phys 2013; 40:112701. [DOI: 10.1118/1.4823761] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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8
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Molecularly targeted gold nanoparticles enhance the radiation response of breast cancer cells and tumor xenografts to X-radiation. Breast Cancer Res Treat 2012; 137:81-91. [PMID: 23160926 DOI: 10.1007/s10549-012-2338-4] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 11/04/2012] [Indexed: 01/16/2023]
Abstract
The purpose of this study was to evaluate the effect of molecularly targeted gold nanoparticles (AuNPs) on tumor radiosensitization both in vitro and in vivo. Human Epidermal Growth Factor Receptor-2 (HER-2)-targeted AuNPs (Au-T) were synthesized by conjugating trastuzumab (Herceptin) to 30 nm AuNPs. In vitro, the cytotoxicity of Au-T or non-targeted AuNPs (Au-P) was assessed by γ-H2AX immunofluorescence microscopy for DNA damage and clonogenic survival assays. In vivo, athymic mice bearing subcutaneous MDA-MB-361 xenografts were treated with a single dose of 11 Gy of 100 kVp X-rays 24 h after intratumoral injection of Au-T (~0.8 mg of Au) or no X-radiation. Normal tissue toxicity was determined by hematology or biochemistry parameters. The combination of Au-P or Au-T with X-ray exposure increased the formation of γ-H2AX foci by 1.7 (P = 0.054) and 3.3 (P = 0.024) fold in comparison to X-radiation alone, respectively. The clonogenic survival of cells exposed to Au-T and X-rays was significantly lower from that of cells exposed to X-radiation alone, which translated to a dose enhancement factor of 1.6. In contrast, survival of cells exposed to Au-P and X-rays versus X-radiation alone were not significantly different. In vivo, the combination of Au-T and X-radiation resulted in regression of MDA-MB-361 tumors by 46 % as compared to treatment with X-radiation (16.0 % increase in tumor volume). No significant normal tissue toxicity was observed. Radiosensitization of breast cancer to X-radiation with AuNPs was successfully achieved with an optimized therapeutic strategy of molecular targeting of HER-2 and intratumoral administration.
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Martínez-Rovira I, Sempau J, Prezado Y. Monte Carlo-based treatment planning system calculation engine for microbeam radiation therapy. Med Phys 2012; 39:2829-38. [DOI: 10.1118/1.4705351] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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10
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Alizadeh E, Sanche L. Induction of Strand Breaks in DNA films by Low Energy Electrons and Soft X-ray under Nitrous Oxide Atmosphere. Radiat Phys Chem Oxf Engl 1993 2012; 81:33-39. [PMID: 24976692 DOI: 10.1016/j.radphyschem.2011.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Five-monolayer (5ML) plasmid DNA films deposited on glass and tantalum substrates were exposed to Al Kα X-rays of 1.5 keV under gaseous nitrous oxide (N2O) at atmospheric pressure and temperature. Whereas the damage yields for DNA deposited on glass are due to soft X-rays, those arising from DNA on tantalum are due to both the interaction of low energy photoelectrons from the metal and X-rays. Then, the differences in the yields of damage on glass and tantalum substrates, essentially arises from interaction of essentially low-energy electrons (LEEs) with DNA molecules and the surrounding atmosphere. The G-values (i.e., the number of moles of product per Joule of energy absorbed) for DNA strand breaks induced by LEEs (GLEE) and the lower limit of G-values for soft X-ray photons (GXL) were calculated and the results compared to those from previous studies under atmospheric conditions and other ambient gases, such as N2 and O2. Under N2O, the G-values for loss of supercoiled DNA are 103±15 nmol/J for X-rays, and 737±110 nmol/J for LEEs. Compared to corresponding values in an O2 atmosphere, the effectiveness of X-rays to damage DNA in N2O is less, but the G value for LEEs in N2O is more than twice the corresponding value for an oxygenated environment. This result indicates a higher effectiveness for LEEs relative to N2 and O2 environments in causing SSB and DSB in an N2O environment. Thus, the previously observed radiosensitization of cells by N2O may not be only due to OH• radicals but also to the reaction of LEE with N2O molecules near DNA. The previous experiments with N2 and O2 and the present one demonstrate the possibility to investigate damage induced by LEEs to biomolecules under various type of surrounding atmospheres.
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Affiliation(s)
- Elahe Alizadeh
- Groupe en science des radiations, Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, J1H 5N4, Sherbrooke, Canada
| | - Léon Sanche
- Groupe en science des radiations, Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, J1H 5N4, Sherbrooke, Canada
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11
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Alizadeh E, Cloutier P, Hunting D, Sanche L. Soft X-ray and low energy electron-induced damage to DNA under N2 and O2 atmospheres. J Phys Chem B 2011; 115:4523-31. [PMID: 21452797 PMCID: PMC3846624 DOI: 10.1021/jp200947g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
DNA damage induced by low energy electrons (LEEs) and soft X-rays is measured under dry nitrogen and oxygen at atmospheric pressure and temperature. Five-monolayer plasmid DNA films deposited on tantalum and glass substrates are exposed to Al K(α) X-rays of 1.5 keV in the two different environments. From the damage yields for DNA, G values are extracted for X-rays and LEEs. The G values for LEEs are 3.5 and 3.4 higher than those for X-ray photons under N(2) and O(2) atmospheres, respectively. Because most of the measured damage is in the form of single strand breaks (SSB), this result indicates a much higher effectiveness for LEEs relative to X-rays in causing SSB in both environments. The results indicate that the oxygen fixation mechanism, which is highly effective in increasing radiobiological effectiveness, under aerobic conditions, is operative on the type of damage created at the early stage of DNA radiolysis by LEEs.
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Affiliation(s)
- Elahe Alizadeh
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
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12
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Sato K, Nishikino M, Okano Y, Ohshima S, Hasegawa N, Ishino M, Kawachi T, Numasaki H, Teshima T, Nishimura H. γ-H2AX and phosphorylated ATM focus formation in cancer cells after laser plasma X irradiation. Radiat Res 2010; 174:436-45. [PMID: 20718602 DOI: 10.1667/rr2178.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The usefulness of laser plasma X-ray pulses for medical and radiation biological studies was investigated, and the effects of laser plasma X rays were compared with those of conventional sources such as a linear accelerator. A cell irradiation system was developed that used copper-Kα (8 keV) lines from an ultrashort high-intensity laser to produce plasma. The absorbed dose of the 8 keV laser plasma X-ray pulse was estimated accurately with Gafchromic® EBT film. When the cells were irradiated with approximately 2 Gy of laser plasma X rays, the circular regions on γ-H2AX-positive cells could be clearly identified. Moreover, the numbers of γ-H2AX and phosphorylated ataxia telangiectasia mutated (ATM) foci induced by 8 keV laser plasma X rays were comparable to those induced by 4 MV X rays. These results indicate that the laser plasma X ray source may be useful for radiation biology studies.
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Affiliation(s)
- Katsutoshi Sato
- Department of Medical Physics and Engineering, Graduated School of Medicine, Osaka University, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan
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13
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Nishikino M, Sato K, Hasegawa N, Ishino M, Ohshima S, Okano Y, Kawachi T, Numasaki H, Teshima T, Nishimura H. Note: Application of laser produced plasma K alpha x-ray probe in radiation biology. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:026107. [PMID: 20192524 DOI: 10.1063/1.3302827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A dedicated radiation biology x-ray generation and exposure system has been developed. 8.0 keV in energy x-ray pulses generated with a femtosecond-laser pulse was used to irradiate sample cells through a custom-made culture dish with a silicon nitride membrane. The x-ray irradiation resulted in DNA double-strand breaks in the nucleus of a culture cell that were similar to those obtained with a conventional x-ray source, thus demonstrating the feasibility of radiobiological studies utilizing a single burst of x-rays focused on single cell specimens.
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Affiliation(s)
- Masaharu Nishikino
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Advanced Photon Research Center, 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215, Japan.
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14
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Brun E, Cloutier P, Sicard-Roselli C, Fromm M, Sanche L. Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions. J Phys Chem B 2009; 113:10008-13. [PMID: 19603845 DOI: 10.1021/jp902540k] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In 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.
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Affiliation(s)
- Emilie Brun
- Laboratoire de Chimie Physique, CNRS UMR 8000, Université Paris-Sud 11, Bat. 350, 91405 Orsay Cedex, France
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Zheng Y, Sanche L. Gold nanoparticles enhance DNA damage induced by anti-cancer drugs and radiation. Radiat Res 2009; 172:114-9. [PMID: 19580513 DOI: 10.1667/rr1689.1] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The chemotherapeutic agent cisplatin was chemically linked to pGEM-3Zf(-) plasmid DNA to produce a cisplatin-DNA complex, Gold nanoparticles, which bind electrostatically to pure DNA, could also be added to this complex. Dry films of pure plasmid DNA and DNA-cisplatin, DNA-gold nanoparticles and DNA-cisplatin-gold nanoparticles complexes were bombarded by 60 keV electrons. The yields of single- and double-strand breaks were measured as a function of exposure by electrophoresis. From a comparison of such yields from the different type of films, we found that the binding of only one gold nanoparticle to a plasmid-cisplatin complex containing 3197 base pairs increases by a factor of 3 the efficiency of the chemotherapeutic agent cisplatin to produce double-strand breaks in irradiated DNA. Furthermore, adding two cisplatin molecules and one gold nanoparticle to DNA enhances radiation-induced DSBs by a factor of 7.5. A number of phenomena could contribute to this huge enhancement, including the higher density of low-energy electrons and reactive species around the gold nanoparticles and the weakening of bonds adjacent to cisplatin in the DNA backbone. The addition of gold nanoparticles to cisplatin and other platinum agents may therefore provide interesting avenues of research to improve the treatment of cancer by concomitant chemoradiation.
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Affiliation(s)
- Yi Zheng
- Groupe en sciences des radiations, Faculté de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Brun E, Duchambon P, Blouquit Y, Keller G, Sanche L, Sicard-Roselli C. Gold nanoparticles enhance the X-ray-induced degradation of human centrin 2 protein. Radiat Phys Chem Oxf Engl 1993 2009. [DOI: 10.1016/j.radphyschem.2008.11.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Zheng Y, Cloutier P, Hunting DJ, Sanche L. Radiosensitization by Gold Nanoparticles: Comparison of DNA Damage Induced by Low and High-Energy Electrons. J Biomed Nanotechnol 2008. [DOI: 10.1166/jbn.2008.3282] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Our previous studies on high energy (60 keV) electron bombardment of thin films of pGEM-3Zf(-) plasmid DNA with and without bound gold nanoparticles (GNP) showed that the presence of these particles greatly increases the formation of single-(SSB) and double-strand (DSB) breaks. To study
the basic mechanisms underlying this DNA sensitization, we performed similar experiments with low energy (1, 10, 100 eV) and 60 keV electrons. The exposure response curves were recorded for the formation of SSB, DSB and loss of supercoiled DNA. The yields of SSB and DSB for pure DNA, salted
DNA and GNP-DNA complexes with a molecular ratio of 1:1 were measured by agarose gel electrophoresis. The yields recorded for the GNP-DNA complexes were consistently enhanced by a factor of about 2 or more compared to those obtained with the salted DNA sample. Furthermore, the yields for low-energy
electron damage were at least one order of magnitude larger than those produced by high-energy electrons. The results suggest that the radiosensitizing action of GNP takes place via two mechanisms: (1) an increase of the absorption of ionizing radiation close to the DNA, which in turns leads
to a considerable increase in the production of short range secondary electrons that have a high probability of damaging DNA, and (2) an increase in the sensitivity of DNA to fragmentation induced by low energy electron impact near the site of binding of the GNP.
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Zheng Y, Hunting DJ, Ayotte P, Sanche L. Radiosensitization of DNA by Gold Nanoparticles Irradiated with High-Energy Electrons. Radiat Res 2008; 169:19-27. [PMID: 18159957 DOI: 10.1667/rr1080.1] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Accepted: 08/14/2007] [Indexed: 11/03/2022]
Affiliation(s)
- Yi Zheng
- Département de Chimie, Faculté des Sciences, , Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
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Cai Z, Cloutier P, Hunting D, Sanche L. Comparison between X-ray photon and secondary electron damage to DNA in vacuum. J Phys Chem B 2007; 109:4796-800. [PMID: 16851564 DOI: 10.1021/jp0459458] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Both monolayer and thick (20 microm) films of dry pGEM-3Zf(-) plasmid DNA deposited on tantalum foil were exposed to Al Kalpha X-rays (1.5 keV) for various times in an ultrahigh vacuum chamber. For monolayer DNA, the damage was induced mainly by low energy secondary electrons (SEs) emitted from the tantalum. For the thick films, DNA damage was induced chiefly by X-ray photons. Different forms of plasmid DNA were separated and quantified by agarose gel electrophoresis. The exposure curves for the formation of nicked circular (single strand break, SSB), linear (double strand break, DSB), and interduplex cross-link forms 1 and 2 were obtained for both monolayer and thick films of DNA, respectively. The lower limits of G values for SSB and DSB induced by SEs were derived to be 86 +/- 2 and 8 +/- 2 nmol J(-1), respectively. These values are 1.5 and 1.6 times larger than those obtained with 1.5 keV photons. The projected X-ray energy dependence of the low energy electron (LEE) enhancement factor for the SSB and DSB in monolayer DNA is also discussed. This new method of investigation of the SE-induced damage to large biomolecules allows direct comparison of the yield of products induced by high energy photons and LEEs under identical experimental conditions.
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Affiliation(s)
- Zhongli Cai
- Faculté de médecine, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
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Hupe O, Brunzendorf J. A novel method of radiochromic film dosimetry using a color scanner. Med Phys 2006; 33:4085-94. [PMID: 17153388 DOI: 10.1118/1.2357019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A procedure that allows the improved extraction of the dose information based on the multicolor scanning of the radiochromic film is presented. The basic principle is the determination of the dose values from each color channel of the digital film image in RGB format by applying a nonlinear calibration function. The best estimate of the dose is then a weighted mean of the dose values derived from each color channel. The weighting factors are determined in such a way that the noise in the two-dimensional dose profile is at the minimum. The calculation of the weighting factors is presented; they are chosen to be proportional to the signal-to-noise ratio, Si/v(i)2, in all three color channels, i=red, green, or blue. The data reduction can be fully computerized, including the "cleaning" of the digital image from dust and scratches. It is highly reproducible, which is important for quality assurance, and easy to use. Our novel evaluation procedure combines the good response in the low dose range of the red color with the extended dose range of the blue and green color channels (response up to 10,000 Gy), making use of one single, steady evaluation function. Therefore, a smooth evaluation is possible in a wide dose range. For the interpretation of measurements with the radiochromic films the spatial inhomogeneity of the film's response to ionizing radiation is very important. Investigations on both film types, HS and MD55-2, as well as on the new EBT film have been carried out.
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Affiliation(s)
- Oliver Hupe
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
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21
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Rampado O, Garelli E, Deagostini S, Ropolo R. Dose and energy dependence of response of Gafchromic XR-QA film for kilovoltage x-ray beams. Phys Med Biol 2006; 51:2871-81. [PMID: 16723772 DOI: 10.1088/0031-9155/51/11/013] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
There is a growing interest in Gafchromic films for patient dosimetry in radiotherapy and in radiology. A new model (XR-QA) with high sensitivity to low dose was tested in this study. The response of the film to different x-ray beam energies (range 28-145 kVp with various filtrations, dose range 0-100 mGy) and to visible light was investigated, together with the after exposure darkening properties. Exposed films were digitized with a commercially available, optical flatbed scanner. A single functional form for dose versus net pixel value variation has been determined for all the obtained calibration curves, with a unique fit parameter different for each of the used x-ray beams. The film response was dependent on beam energy, with higher colour variations for the beams in the range 80-140 kVp. Different sources of uncertainties in dose measurements, governed by the digitalization process, the film response uniformity and the calibration curve fit procedure, have been considered. The overall one-sigma dose measurement uncertainty depended on the beam energy and decreased with increasing absorbed dose. For doses above 10 mGy and beam energies in the range 80-140 kVp the total uncertainty was less than 5%, whereas for the 28 kVp beam the total uncertainty at 10 mGy was about 10%. The post-exposure colour variation was not negligible in the first 24 h after the exposure, with a consequent increase in the calculated dose of about 10%. Results of the analysis of the sensitivity to visible light indicated that a short exposure of this film to ambient and scanner light during the measurements will not have a significant impact on the radiation dosimetry.
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Affiliation(s)
- O Rampado
- Struttura Complessa Fisica Sanitaria, Azienda Ospedaliera San Giovanni Battista, Corso Bramante 88, 10126 Torino, Italy.
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Cai Z, Cloutier P, Hunting D, Sanche L. Enhanced DNA damage induced by secondary electron emission from a tantalum surface exposed to soft x rays. Radiat Res 2006; 165:365-71. [PMID: 16494526 DOI: 10.1667/rr3509.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Both thick and thin films of pGEMR-3Zf- plasmid DNA deposited on a tantalum foil were exposed to soft X rays (effective energy of 14.8 keV) for various times in air under a relative humidity of 45% (Gamma approximately 6, where Gamma is the number of water molecules per nucleotide) and 84% (Gamma approximately 21), respectively. For a thick film, the DNA damage was induced chiefly by X-ray photons. For a thin film of DNA, X-ray-induced secondary electrons emitted from the tantalum result in a substantial increase in DNA damages. Different forms of plasmid DNA were separated and quantified by agarose gel electrophoresis and laser scanning. The exposure curves for the formation of nicked circular (single-strand break, SSB), linear (double-strand break, DSB), and interduplex crosslink forms 1 and 2 were obtained for both thick and thin films of DNA. The secondary electron enhancement factor for SSBs, DSBs and crosslinks of the thin film of DNA were derived to be 3.8 +/- 0.5, 2.9 +/- 0.7 and 7 +/- 3 at Gamma approximately 6 and 6.0 +/- 0.8, 7 +/- 1 and 3.9 +/- 0.9 at Gamma approximately 21, respectively. This study provides a molecular basis for understanding the enhanced biological effects at interfaces during diagnostic X-ray examination and radiotherapy.
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Affiliation(s)
- Zhongli Cai
- Faculté de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada
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Cai Z, Cloutier P, Sanche L, Hunting D. DNA Interduplex Crosslinks Induced by AlKαX Rays under Vacuum. Radiat Res 2005; 164:173-9. [PMID: 16038588 DOI: 10.1667/rr3408] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Dry pGEM-3Zf(-) plasmid DNA was exposed to Al(kalpha) X rays (1.5 keV) for various times in an ultra-high vacuum chamber with mean absorbed dose rates ranging from 1.8 to 41.7 Gy s(-1). The different forms of plasmid DNA were separated by neutral agarose gel electrophoresis and quantified by staining and laser scanning. In addition to the bands for supercoiled, nicked circular, linear and concatameric forms of plasmid DNA, two additional bands were observed in X-irradiated samples; these migrated at rates similar to those for 8-kb and >10-kb linear double-stranded DNA. Digestion of irradiated DNA with the restriction enzymes EcoR1 and PvuI suggested that the two slowly migrating bands were interduplex crosslinked DNA. Alkaline agarose gel electrophoresis of irradiated DNA digested with EcoR1 confirmed that the interduplex crosslink was covalent. Exposure-response curves were determined for the formation of nicked circular, linear and interduplex crosslinked DNA as well as for the loss of supercoiled and concatameric DNA. Formation and loss of these species were independent of absorbed dose rate over a 20-fold range. The G values for DNA single-strand breaks, double-strand breaks and crosslinks were determined to be 62 +/- 6, 5.6 +/- 0.6 and 16 +/- 4 nmol J(-1), respectively. The formation of DNA interduplex crosslinks appears to be due to single event. The mechanism responsible for the formation of DNA interduplex crosslinks is discussed with emphasis on its implications in vivo.
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Affiliation(s)
- Zhongli Cai
- Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada
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