60Co Γ-irradiation Research Articles

Activity of glucose oxidase immobilized onto Fe3+ attached hydroxypropyl methylcellulose films

Hydroxypropyl methylcellulose (HMPC) insoluble films were prepared by 60Co-γ irradiation of 10% (w/w) aqueous solutions of hydroxypropyl methylcellulose. The adsorption of Fe3+ onto HPMC films was studied in the range of pH 3.0–7.0. The effect of initial concentrations of Fe3+ solutions on adsorption capacity was studied in the range of 100–1000ppm. Maximum adsorption capacity was found as 250mg Fe3+/g dry HPMC film at pH 5.0. The structure and the morphology of Fe3+-attached HPMC film were evaluated by using FTIR/ATR and SEM–EDX methods. Glucose oxidase (GOX) immobilization on both pristine HPMC and maximum Fe3+-attached HPMC film was investigated in aqueous solutions containing different amount of GOX and at different pHs. Maximum GOX adsorption capacity was found as 500mg/g Fe3+-attached HPMC film. Residual activity of GOX on pristine HPMC and Fe3+-attached HPMC films was investigated with changing pH. While maximum residual GOX activity was observed at pH 6.0 for free enzyme, it was obtained by HPMC and Fe3+-attached HPMC at pH 7.0. GOX desorption studies were achieved by using pH 6.0 buffer (I=0.02M) and 0.1M EDTA solutions. The long-term stability and activity studies of GOX, which is immobilized onto Fe3+-attached HPMC films are still under our investigation.

Reflectivity and absorption coefficient of a borosilicate glass during 60Co-γ irradiation calculated from data measured by an integrating sphere

Before and after 11 kGy 60Co-γ irradiation as well as after 150°C bleaching, reflectivity and absorption coefficient of a borosilicate glass were calculated from the intensity of transmitted light and the intensity of reflected light measured using an integrating sphere. The irradiation induced absorption in the studied wavelength range, while it only made the reflectivity change obviously in the range 4.5–5.6 eV (275–221 nm). The absorption coefficient spectrum and the reflectivity spectrum of the irradiated glass both recovered to a degree after 150°C bleaching. The relative error of irradiation-induced absorption coefficient calculated neglecting reflectivity change was studied, and the relative errors in the studied wavelength range theoretically increase when the thickness of glass sheet decreases, so if irradiation-induced absorption coefficients are studied using a thin glass sheet, reflectivity changes should be considered. The band gap of the glass was studied using Mott and Davis's theory, and it was found to reduce after irradiation, then after 150°C bleaching, it increased but still smaller than the one before irradiation.

Quantitative separation of radiation induced charges for gate controlled later PNP bipolar transistors

A new test structure of gate controlled lateral PNP bipolar transistors designed and fabricated. An independent gate terminal is patterned on the oxide layer above the active base region of normal lateral PNP bipolar transistors. According to the gate sweep technique, by sweeping the voltage applied to the gate terminal, one can obtain the characteristic of base current versus gate voltage. The quantitative variations of oxide trapped charges and interface traps are analytically estimated and numerically calculated, and the radiation induced defects in the gate controlled lateral PNP bipolar transistors during 60Co-γ irradiation and annealing at room temperature are separated independently. The test structures and measurements of the bipolar transistors used in the experiment are introduced in detail in this paper.

60Co γ-irradiation-initiated RAFT polymerization of VAc at room temperature

In this work, the reversible addition–fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using 60Co γ-irradiation as the initiation source. Under the dose rate of 10 Gy/min irradiation, the polymerization proceeded smoothly and converted approximately 90% of the monomer within 7 h. The molecular weight distribution ( M w/ M n) remained narrow ( M w/ M n < 1.35) up to 90% conversion. Compared to AIBN-initiated RAFT polymerization at 60 °C, 60Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molecular weight, especially at high conversion. The 1H NMR spectra and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that most of the chain ends of poly(VAc) (PVAc) from γ-irradiated RAFT polymerization were living and can be reactivated for chain-extension reactions. The microstructures of PVAc from 60Co γ-irradiated RAFT polymerization (almost head-to-tail addition) and AIBN-initiated RAFT polymerization (5% tail-to-tail addition) were different, as revealed by the 13C NMR spectra. For the first time, 60Co γ-irradiation was used as an initiation source for RAFT polymerization of VAc at room temperature.

Stochastic modelling of DSB repair after photon and ion irradiation

Purpose: To test the stochastic model for DNA double-strand break (DSB) repair via non-homologous end joining (NHEJ) implemented in the Monte Carlo code PARTRAC (PARticle TRACks) against measured repair kinetics after nitrogen ion and 60Co γ reference irradiation.Material and methods: By combining Monte Carlo track structure calculations with multi-scale models of cellular DNA, yields of DSB are calculated for N ion and 60Co γ-irradiation. The NHEJ model in PARTRAC is used to determine rejoining kinetics of the DNA ends and DNA fragment distributions after certain repair times. Model parameters are adapted to the measured rejoining kinetics for the different radiation types.Results: DSB rejoining kinetics after low- and high-linear energy transfer (LET) irradiation have been reproduced after refinements of the DNA repair model, in particular by considering an ongoing production of detectable DSB in the initial phase, e.g., by enzymatic processing of labile sites, and by assuming a limited availability of repair enzymes needed for processing complex lesions during the slow repair phase.Conclusions: The need for certain model refinements suggests mechanisms that may significantly contribute to the DSB rejoining kinetics during both initial and later phases of NHEJ.

Leaf Extract ofMoringa oleiferaPrevents Ionizing Radiation-Induced Oxidative Stress in Mice

The present study evaluated the hepatoprotective effect of aqueous ethanolic Moringa oleifera leaf extract (MoLE) against radiation-induced oxidative stress, which is assessed in terms of inflammation and lipid peroxidation. Swiss albino mice were administered MoLE (300 mg/kg of body weight) for 15 consecutive days before exposing them to a single dose of 5 Gy of ⁶⁰Co γ-irradiation. Mice were sacrificed at 4 hours after irradiation. Liver was collected for immunoblotting and biochemical tests for the detection of markers of hepatic oxidative stress. Nuclear translocation of nuclear factor kappa B (NF-κB) and lipid peroxidation were augmented, whereas the superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and ferric reducing antioxidant power (FRAP) values were decreased by radiation exposure. Translocation of NF-κB from cytoplasm to nucleus and lipid peroxidation were found to be inhibited, whereas increases in SOD, CAT, GSH, and FRAP were observed in the mice treated with MoLE prior to irradiation. Therefore pretreatment with MoLE protected against γ-radiation-induced liver damage. The protection may be attributed to the free radical scavenging activity of MoLE, through which it can ameliorate radiation-induced oxidative stress.

Anti-tumor effect of suicide gene therapy using chimeric promoter plus radiotherapy on cancer cell lines

To explore the synergistic anti-tumor effect of radiotherapy and horseradish peroxidase/prodrug indole-3-acetic acid (HRP/IAA) gene therapy system using chimeric hTERT promoter responsive to ionizing radiation. The synthetic hTERT promoters containing four tandem-repeat copies of radio-inducible CArG elements, and the chimeric promoter containing cytomegalovirus (CMV) early promoter were both constructed. The activities of the chimeric promoters in cancer cell lines (HeLa, A549, and MHCC97) and normal cell line (MRC-5) were detected using luciferase reporter gene expression analysis after a (60)Co γ-irradiation treatment at a series of doses(a single dose of 0 to 10 Gy). The anti-tumor effect of combining irradiation with HRP/IAA gene-directed enzyme prodrug therapy system controlled by the chimeric promoter was tested by colony formation assay, cell counting and apoptosis analysis. The chimeric promoters were ineffective in normal human cells, even after irradiation, but the expression of luciferase gene in tumor cells was significantly higher. The activity of the chimeric promoter in MRC-5 cells was 22.3%, 12.9% and 13.6% of that in HeLa, A549 and MHCC97 cells, respectively. After irradiation, the ratios were 11.7%, 8.7% and 8.8%, respectively. Furthermore, the chimeric promoters could successfully induce the expression of luciferase gene following different doses of radiation, with maximal inducible activity seen after 6 Gy irradiation. The chimeric promoter containing four tandem-repeat copies of radio-inducible CArG elements and CMV early promoter showed the highest activity with 6 Gy irradiation. The relative luciferase activities in HeLa, A549 and MHCC97 cells were 1.7 ± 0.2, 2.3 ± 0.2 and 2.3 ± 0.1, respectively. The chimeric promoter mediated suicide gene therapy system could increase radio-sensitivity in different cancer cells. Compared with the control system, it plus irradiation showed stronger cell proliferation inhibition, 67.3% vs. 26.1% in HeLa, 69.0% vs. 28.3% in A549, 64.6% vs. 20.8% in MHCC97 cells, and also higher apoptosis-inducing effect, 39.6% vs. 14.2% in HeLa, 33.0% vs. 12.4% in A549, and 33.2% vs. 14.2% in MHCC97 cells. Chimeric promoter containing hTERT promoter, CArG elements and CMV promoter preserve the tumor-specificity in telomerase-positive tumor cells, and irradiation-responsive to low dose of radiation. The suicide gene therapy using this promoter plus radiotherapy show a strong anti-tumor effect in vitro. It is expected to have a good potential for future application in gene radiotherapy.

Synthesis and properties of sodium alginate/Na +rectorite grafted acrylic acid composite superabsorbent via 60Coγ irradiation

Sodium alginate/Na +rectorite-graft-poly acrylic acid (SA/Na +REC-g-PAA) composite superabsorbent was prepared via 60Coγ irradiation in methanol solution and nitrogen protection. The effect of the preparation conditions on graft ratio, graft efficiency and absorption of water were investigated. The structure and morphology were analyzed by IR, XRD, TEM and SEM. The results showed that the optimal condition was that the amount of Na +REC was 2 wt%, the ratio of SA/Na +REC to AA was 10 wt%, total dose was 9.0 kGy and volume ratio of methanol to water was 8:2. SEM showed that it is much easier to obtain porous products through 60Coγ irradiation than chemical initiator. The mechanism of graft copolymerization via 60Coγ irradiation was discussed. The water absorption of the graft copolymer in salt solutions of different ionic strengths was also measured, from which the superabsorbent properties are found to be saline sensitive. Ionic strength markedly decreased the water absorption of the sodium alginate grafted superabsorbent composites.

Stereospecific solid-state cyclodimerization of bis(trans-2-butenoato)calcium and triaquabis(trans-2-butenoato)magnesium

60Co γ-irradiation of bis(trans-2-butenoato)calcium (4) and triaquabis(trans-2-butenoato)magnesium (11) affords cyclodimerization products cis,trans- and trans,trans-nepetic acids (5 and 15), respectively. The products are produced in high yield, based upon conversion, by a γ-ray induced radical chain pathway and provide unprecedented, stereospecific, one-pot syntheses of two of the four possible nepetic acid diastereomers, adding significant generality to the synthetic scope of the γ-ray induced reactions of crystalline metal trans-2-butenoates. Stereochemical analysis of the products from the analogous trans-2-butenoato-3-d complexes 19 and 27 establishes unequivocally that hydrogen atom transfer is also stereospecific and not part of a random process. The stereochemistry of the diastereomers is that predicted by the analysis of crystal packing, consistent with the least-motion principles of the topochemical postulate. Analysis of the crystal structures, with respect to the nearest neighbors, is consistent with the hypothesis that the formation of both carbon–carbon bonds and hydrogen atom transfer are topochemical and controlled by the crystal lattice. Analysis of the packing diagrams provides a pathway for chain propagation throughout the crystal that consumes all the molecules in the unit cell.

Chemo- and stereospecific solid-state dimerization of lithium trans-2-butenoate and lithium trans-2-butenoate formamide solvate

60Co γ-irradiation of both lithium trans-2-butenoate (11) and lithium trans-2-butenoate·formamide (12) affords the same dimer, dilithium trans-5-methyl-2-heptenedioate (13). However, stereochemical analysis of products 22 and 24 from the analogous trans-2-butenoate-2-d salts 21 and 23 established that C–C and C–H bond formation occur stereospecifically by syn addition to the double bond in lithiumtrans-2-butenoates 11 and 21 and anti addition to the double bond in lithium trans-2-butenoate·formamide complexes 12 and 23. These reactions, which provide an unprecedented, chemospecific one step synthesis of dicarboxylate 13, add significantly to the synthetic scope of the γ-ray induced reactions of crystalline metal trans-2-butenoates that lead to cyclic and acyclic dimers and acyclic trimers by γ-ray initiated radical chain reactions. The stereochemistry of products 22 and 24 is that predicted by analysis of crystal packing, consistent with least-motion principles of the topochemical postulate as shown in Fig. 12 and 13. Analysis of the crystal structures, with respect to nearest neighbors, is consistent with the hypothesis that formation of carbon–carbon bonds in propagation step 1 and hydrogen atom transfer in propagation step 2 are topochemical and controlled by the crystal lattice. Analysis of the packing diagrams provides a pathway for chain propagation throughout the crystal that consumes all the molecules in the unit cell. The dimerization of 12 is much more rapid and proceeds in much higher yield than that of 11, probably as a result of significantly shorter C⋯C contacts and a more robust pathway for hydrogen transfer.

Protective effect of flavonoids from Astragalus complanatus on radiation induced damages in mice

This study aimed to evaluate the radioprotective effect of flavonoids extracted from the seeds of Astragalus complanatus R.Br. (FAC) and their protective mechanism against radiation damage. FAC increased the survival rate of mice and made the damaged organ injured by 60Co γ-irradiation recovered to normal appearance with the mechanism of enhancing immune function and blood-producing function in vivo. The molecule mechanism of FAC against radiation is involved in the reduction of DNA injury and mutation in vitro. Eleven monomers of the FAC were analyzed by HPLC. These results seem to support the use of FAC in relieving radiation damage.

Poly(BMA-co-NVP)/NiS core-shell hybrid materials via Interfacial-initiated miniemulsion copolymerization and gamma-irradiation

In this work, N-butyl methacrylate (BMA)/N-vinyl-2-pyrrilidone (NVP) amphiphilic core-shell nanoparticles were successfully prepared via miniemulsion copolymerization, the emulsion was initiated by the redox initiation couple of cumene hydroperoxide (CHPO) and ferrous sulfate hydrate (FS). The synthetic waterborne polyurethane (WPU) was used as surfactant and hexadecane (HD) as co-stabilizer, respectively. FTIR and XPS were used to confirm the occurrence of copolymerization between two monomers. TEM and DLS were used to observe the particle morphology and determine the particle size and its polydispersity index (PDI). It was found that the core-shell poly(BMA-co-NVP) nanoparticles prepared via interfacial-initiated miniemulsion copolymerization (IMEP) had relatively small diameters (40–120 nm) and narrowly particle size distribution (0.066–0.243). Only about 2 wt% surfactants based on the solution was enough to prepare a stable miniemulsion. The results demonstrated that IMEP prompted the copolymerization of water-soluble NVP monomer with oil-soluble BMA monomer to form core-shell nanoparticles. The effects of surfactant and co-stabilizer affect on the miniemulsion copolymerization were discussed. All the results indicate that the fabrication amphiphilic core-shell nanoparticles via IMEP were successful. Then the poly(BMA-co-NVP)/NiS hybrid materials were fabricate via the reaction of NiSO4 and CH3CSNH2 on the copolymers surface under 60Co γ-irradiation at room temperature and ambient pressure. The hybrid materials were characterized by FESEM.

Effects of homogeneous and inhomogeneous static magnetic fields combined with gamma radiation on DNA and DNA repair

The aim of this study was to reveal whether static magnetic fields (SMFs) influence the repair of radiation-damaged DNA on leukocytes or has any effect on DNA. After 4 Gy of (60)Co-gamma irradiation, some of the samples were exposed to inhomogeneous SMFs with a lateral magnetic flux density gradient of 47.7, 1.2, or 0.3 T/m by 10 mm lateral periodicity, while other samples were exposed to homogeneous SMF of 159.2 +/- 13.4 mT magnetic flux density for a time period of 0.5 min, 1, 2, 4, 6, 18, 20, or 24 h. Another set of samples was exposed to the aforementioned SMFs before gamma irradiation. The following three groups were examined: (i) exposed to SMF only, (ii) exposed to SMF following irradiation by (60)Co-gamma, and (iii) exposed to SMF before (60)Co-gamma irradiation. The analysis of the DNA damage was made by single-cell gel electrophoresis technique (comet assay). Statistically significant differences were found at 1 h (iSMF), 4 h (hSMF), and 18 h (hSMF) if samples were exposed to only SMF, compared to control. When the SMF exposure followed the (60)Co-gamma irradiation, statistically significant differences were found at 1 h (iSMF) and 4 h (hSMF). If exposure to SMF preceded (60)Co-gamma irradiation, no statistically significant difference was found compared to 4 Gy gamma-irradiated group.

Proteomic Alterations in Progeny of Irradiated Human Liver Cells

This study was designed to characterize the differential protein expression in the progeny of human liver cells surviving exposure to ionizing radiation. The progeny of irradiated cells were derived from a human liver cell line exposed to 0, 2, 4, or 6 Gy of 60Co γ-irradiation. Total protein of the cells was extracted by two-dimensional electrophoresis (2-DE) and analyzed with ImageMaster 2D Platinum software. In total, 42 differentially expressed proteins from the progeny of irradiated cells were screened, of which 17 were identified by matrix assistant laser desorption ion-top flight-mass spectrometry (MALDI-TOF-MS) analysis. There were 4 upregulated and 13 downregulated proteins detected. The upregulated expression of two proteins, mitochondrial heat-shock 60-kD protein (HSP60) and globin transcription factor 1 (GATA-1), was further confirmed by immunoblotting. Database search revealed that these differentially expressed proteins may function in cell cycle regulation, cytoskeleton maintenance, stress response, and tumor metastasis, indicating an effect of radiation-induced genomic instability (RIGI) in the progeny of irradiated cells. Analysis on functional roles of the screened proteins may provide insight into further mechanistic investigations underlying molecular events induced by RIGI.

60Co γ-irradiation effects on electrical properties of a rectifying diode based on a novel macrocyclic Zn octaamide complex

C 36H 28N 12O 8ZnCl 2·9/2H 2O, Zn-octaamide (ZnOA) macrocyclic compound was synthesized to be used in the fabrication of electronic and photoelectronic devices. The structure of new compound was identified by using 1H NMR, 13C NMR, IR, UV–vis and LC–MS spectroscopic methods. The Sn/ZnOA/n-Si/Au structure was engineered by forming a thin macrocyclic organic compound layer on n-Si inorganic substrate and then by evaporating Sn metal on the organic layer. It was seen that the device had a good rectifying behaviour and showed Schottky diode properties. The diode was irradiated under 60Co γ-source at room temperature. Characteristic parameters of the diode were determined from its current–voltage ( I– V) and capacitance voltage ( C– V) measurements before and after irradiation. It was observed that γ-irradiation had clear effects on I–V and C–V properties. Also, it was seen that the barrier height, the ideality factor and the series resistance values decreased after the applied radiation, while the saturation current value increased.

Investigation of nanostructure of konjac-based water absorbents with atomic force microscopy

Atomic force microscopy technology is gradually spreading to almost all aspects, including food science and technology, since it was first invented in 1986. In this study, this powerful instrument was applied to image nanostructures of three water absorbents-original konjac powder, konjac powder grafted with acrylic acid using 60Co γ-irradiation and regenerated grafted powder. Water absorption capacities and the rates of the three absorbents were also determined in this work. Original konjac powder could only absorb 60 times (w/w) of water, while 270 times for the grafted absorbent and 360 times for the regenerated absorbent. The initial water absorption rates in both tap and distilled water were high, but the rate decreased steeply as time elapsed. After 20 min, the absorbent was close to saturated status. These physical properties were in accordance with the nanostructures of these three water absorbents.

Differential radio-sensitivities of human chromosomes 1 and 2 in one donor in interphase- and metaphase-spreads after 60Co γ-irradiation

BackgroundRadiation-induced chromosome aberrations lead to a plethora of detrimental effects at cellular level. Chromosome aberrations provide broad spectrum of information ranging from probability of malignant transformation to assessment of absorbed dose. Studies mapping differences in radiation sensitivities between human chromosomes are seldom undertaken. Consequently, health risk assessment based on radio-sensitivities of individual chromosomes may be erroneous. Our efforts in this article, attempt to demonstrate differences in radio-sensitivities of human chromosome-1 and/or -2, both in interphase and metaphase spreads.MethodsUpon blood collection, dosimetry and irradiation were performed. Lymphocytes were isolated after whole-blood irradiation with 60Co γ-rays in the dose range of 0–5 Gy for both interphase, and metaphase aberration studies. Induction of premature chromosome condensation in interphase cells was accomplished using a phosphatase inhibitor, calyculin-A. Metaphase spreads were harvested from short-term peripheral blood lymphocyte cultures following colcemid arrest and using an automated metaphase harvester and spreader. Aberration analysis in both interphase and metaphase spreads were done using FISH.ResultsIn interphase, aberrant cell and aberration frequency involving chromosome 1 and/or 2 increased linearly with radiation dose. In metaphase, aberrations increased in a linear-quadratic manner with dose. Our studies ascertain that chromosome-2 is more radio-sensitive than chromosome-1 in both interphase and metaphase stages, albeit the DNA content of chromosome-2 is lesser than chromosome-1 by almost 10 million base pairs.ConclusionDifferences in radio-sensitivities of chromosomes have implications in genetic damage, chromosome organization, and chromosome function. Designing research experiments based on our vital findings may bring benefit to radiation-induced risk assessment, therapeutics and development of chromosome specific biomarkers.

Characterisation of flavour compounds formed by γ-irradiation of polypropylene

Sterilisation of plastic packaging materials for food, pharmaceutical or cosmetic products with 60Co γ-irradiation in the presence of oxygen can result in the formation of volatile substances. These may subsequently induce off-odours in these materials that might be regarded as negative by the consumers. Trace volatiles and odorous substances of polypropylene, irradiated with 60Co γ rays at 10 and 20 kGy, respectively, were collected and analysed by gas chromatography–olfactometry (GC–O), GC–MS and GC–GC–MS. The methodology was successfully applied for identification of 29 characteristic odorants in a non-irradiated control sample and 38 odorants in γ-irradiated polypropylene samples. Selected odour-active compounds were quantified using GC–GC–MS in combination with stable isotope dilution assays. The quantitative data mirrors the compositional changes in volatile odorous substances from polypropylene during treatment with ionising γ rays in a 60Co-irradiation plant.

Electron-induced damage to NPN transistors under different fluxes

Radiation damage of NPN transistors under different fluxes with electron energy of 1.5 MeV was investigated in this article. It has been shown that when NPN transistors were irradiated to a given fluence at different electron fluxes, the shift of base current was dependent on flux. With electron flux decreasing, the shift of base current becomes larger, while collector current almost keeps constant. Thus, more degradation of NPN transistors could be caused by low-electron-flux irradiation, similar to enhanced low-dose-rate sensitivity (ELDRS) of transistors under 60Co γ-irradiation. Finally, the underlying mechanisms were discussed here.

Assessment of genetic damage in peripheral blood of human volunteers exposed (whole-body) to a 200 μT, 60 Hz magnetic field

Aim: To investigate the extent of damage in nucleated cells in peripheral blood of healthy human volunteers exposed to a whole-body 60 Hz, 200 μT magnetic field.Materials and methods: In this study, 10 male and 10 female healthy human volunteers received a 4 h whole-body exposure to a 200 μT, 60 Hz magnetic field. In addition, five males and five females were treated in a similar fashion, but were exposed to sham conditions. For each subject, a blood sample was obtained prior to the exposure period and aliquots were used as negative- (pre-exposure) and positive- [1.5 Gray (Gy) 60Cobalt (60Co) γ-irradiation] controls. At the end of the 4 h exposure period, a second blood sample was obtained. The extent of DNA damage was assessed in peripheral human blood leukocytes from all samples using the alkaline comet assay. To detect possible clastogenic effects, the incidence of micronuclei was assessed in phytohemagglutinin (PHA)-stimulated lymphocytes using the cytokinesis-block micronucleus assay.Results: There was no evidence of either increased DNA damage, as indicated by the alkaline comet assay, or increased incidence of micronuclei (MN) in the magnetic field exposed group. However, an in vitro exposure of 1.5 Gy γ-irradiation caused a significant increase in both DNA damage and MN induction.Conclusions: This study found no evidence that an acute, whole-body exposure to a 200 μT, 60 Hz magnetic field for 4 hours could cause DNA damage in human blood.