60Co Γ-rays Research Articles

Radiation-Induced Cross-Linking of Gelatin by Using γ-Rays: Insoluble Gelatin Hydrogel Formation

Abstract Gelatin hydrogels with various concentrations were cross-linked by the irradiation with 60Co γ-rays, and we investigated the radiation-induced cross-linking of gelatin hydrogels by estimating the physical properties of irradiated hydrogels. In case of the 1, 5, and 10% (w/v) gelatin solutions, the specific water content of the irradiated hydrogels, the index showing the extent of cross-linking depended on the absorbed dose, and that of the irradiated gelatin hydrogels with the lower concentration decreased drastically. The breaking strength correlated to the absorbed dose, irrespective of the initial gelatin concentration. More than 8 kGy irradiation induced insolubility due to the cross-linking of the gelatin hydrogels. Besides, γ-ray irradiation to gelatin with free amino acids revealed that amino acids, which have side chains of hydrocarbon groups that are more than two carbon atoms, obstructed the cross-linking of gelatin hydrogels. It is thought that the hydrocarbon groups, such as an alkyl or a phenyl group of the side chains, are the cross-linking sites of gelatin hydrogels.

Effects of lactic acid fermentation and gamma irradiation of barley on antinutrient contents and nutrient digestibility in mink (Mustela vison) with and without dietary enzyme supplement

The experiment was conducted to study the effects of fermentation of barley, using two different strains of lactic acid bacteria, a Lactobacillus plantarum/pentosus strain isolated from spontaneously fermented rye sourdough (AD2) and a starch-degrading Lactobacillus plantarum (AM4), on contents of mixed-linked (1 → 3) (1 → 4)-β-glucans, α-amylase inhibitor activity, inositol phosphates, and apparent digestibility of macronutrients in mink. Effects of fermentation were compared with effects of gamma irradiation (γ-irradiation: 60Co γ-rays at 25 kGy). The diets were fed to mink with and without a supplementary enzyme preparation. Both lactic acid fermentation and γ-irradiation followed by soaking and incubation, reduced concentrations of soluble β-glucans, phytate and α-amylase inhibitor activity. Dietary enzyme supplementation increased significantly digestibility of crude protein, fat, starch and crude carbohydrate (CHO). Fermentation of the barley increased digestibility of starch and CHO. Fermentation with lactic acid bacteria AD2 resulted in higher starch and CHO digestibility than strain AM4, and had greater effect than γ-irradiation, soaking and incubation. The highest digestibility of starch and CHO was obtained after AD2 fermentation followed by enzyme supplementation. It is concluded that both lactic acid fermentation of barley and enzyme supplementation have positive nutritional implications in the mink by limiting the effects of antinutrients and improving digestibility and energy utilization.

Synthesis and characterization of poly ( n-butyl acrylate)-poly (methyl methacrylate) latex interpenetrating polymer networks by radiation-induced seeded emulsion polymerization

A series of latex interpenetrating polymer networks (LIPNs) were prepared via a two-stage emulsion polymerization of methyl methacrylate (MMA) or mixture of MMA and n-butyl acrylate ( n-BA) on crosslinked poly( n-butyl acrylate)(PBA) seed latex using 60Co γ-ray radiation. The particles of resultant latex were produced with diameters between 150 and 250 nm. FTIR spectra identified the formation of crosslinked copolymers of PMMA or P(MMA- co-BA). Dynamic light scattering (DLS) showed that with increasing n-BA concentration in second-stage monomers, the particle size of LIPN increased. Transmission electron microscope(TEM) photographs showed that the morphology of resultant acrylate interpenetrating polymer network (IPN) latex varied from the distinct core-shell structure to homogenous particle structure with the increase of n-BA concentration, and the morphology was mainly controlled by the miscibility between crosslinked PBA seed and second-stage copolymers and polarity of P(MMA- co-BA)copolymers. In addition, differential scanning calorimeter (DSC) measurements indicated the existence of reinforced miscibility between PBA seed and P(MMA- co-BA)copolymer in prepared LIPNs.

Preparation of polymeric nanocapsules by radiation induced miniemulsion polymerization

In this research, polystyrene (PSt) nanocapsules with liquid cores were prepared by 60Co γ-ray radiation induced miniemulsion polymerization, in which N-vinyl pyrrolidone (NVP) was used as the polar monomer. The characterization of polymer was carried out by 1H NMR. It was verified that during polymerization, graft copolymerization between poly (pyrrolidone) (PVP) and PSt had taken place instead of random copolymerization. The interfacial tension between polymer and water was reduced because of the grafting reaction that had occurred, which was helpful to form nanocapsules. The influence of the ratio of St to NVP, the type and amount of the surfactant and the monomer/dodocane ratio on the particle morphology was studied by TEM. Finally, the releasing process of the synthesized nanoparticles was monitored by UV–vis measurement.

Cell killing, nuclear damage and apoptosis in Chinese hamster V79 cells after irradiation with heavy-ion beams of 16O, 12C and 7Li

Chinese hamster V79 cells were exposed to high LET (linear energy transfer) 16O-beam (625 keV/μm) radiation in the dose range of 0–9.83 Gy. Cell survival, micronuclei (MN), chromosomal aberrations (CA) and induction of apoptosis were studied as a follow up of our earlier study on high LET radiations ( 7Li-beam of 60 keV/μm and 12C-beam of 295 keV/μm) as well as 60Co γ-rays. Dose dependent decline in surviving fraction was noticed along with the increase of MN frequency, CA frequency as well as percentage of apoptosis as detected by nuclear fragmentation assay. The relative intensity of DNA ladder, which is a useful marker for the determination of the extent of apoptosis induction, was also increased in a dose dependent manner. Additionally, expression of tyrosine kinase lck-1 gene, which plays an important role in response to ionizing radiation induced apoptosis, was increased with the increase of radiation doses and also with incubation time. The present study showed that all the high LET radiations were generally more effective in cell killing and inflicting other cytogenetic damages than that of low LET γ-rays. The dose response curves revealed that 7Li-beam was most effective in cell killing as well as inducing other nuclear damages followed by 12C, 16O and 60Co γ-rays, in that order. The result of this study may have some application in biological dosimetry for assessment of genotoxicity in heavy ion exposed subjects and in determining suitable doses for radiotherapy in cancer patients where various species of heavy ions are now being generally used.

60Co γ-ray irradiation effects on dielectric characteristics of tin oxide films of different thicknesses on n-type Si(1 1 1) substrates

We have tried to determine the effects of 60Co gamma irradiation on properties of Au/SnO 2/n-Si (MOS) structures such as dielectric constant ( ε′), dielectric loss ( ε″), tangent loss (tan δ) and ac conductivity ( σ ac). Three samples were fabricated with different deposition time. The samples were irradiated using a 60Co γ-ray source irradiation with the total dose range of 0–500 kGy at room temperature. Capacitance and conductance ( C– G– V) measurements were performed at a frequency of 500 kHz in the dark and at room temperature before and after irradiation. The experimental data were analyzed using complex permittivity and electric modulus. The values of ε′, ε″, tan δ and σ ac showed a strong dependence on the applied voltage and irradiation dose. The dielectric properties of MOS structures have been found to be strongly influenced by the presence of dominant radiation-induced defects. Experimental results show that the interfacial polarization contributes to the improvement of dielectric properties of Au/SnO 2/n-Si (MOS) Schottky diodes.

Radiation hardness test of preamplifier circuits composed of commercial bipolar transistors

In general, radiation-hardened transistors are very expensive and it is sometimes not easy to acquire proper ones for application. In this study, we designed a front-end electronic circuit for high-rate neutron counters installed in a high-level γ-radiation hot cell. All the transistors adopted for this circuit are not radiation-hardened ones, i.e. commercial ones not specifically processed for a radiation resistance. The aim of our study was to seek more radiation-resistant transistors from among the commercial ones and to verify the radiation hardness of the circuit composed of these transistors. The circuit includes a preamplifier, a comparator, and a monostable multivibrator. To realize the radiation hardness of this circuit with commercial transistors, the transistors were categorized into two groups: general speed and high-speed transistors. After a 100 Mrad irradiation from a 60Co γ-ray source, the reduction of the current gain of the general speed transistors was over 80% and that of the high-speed transistors was below 68%. The signal-to-noise ( S/ N) ratio of the preamplifier output voltage was reduced by 66% for the former and by 36% for the latter.

Sublethal irradiation promotes migration and invasiveness of prostate cancer PC-3 cells:Implications for radiotherapy of human prostate cancer

Objective To study the changes in the matrix metalloproteinases-2 and 9 (MMP2, MMP9) induced by 60Co γ-ray external irradiation of human prostate cancer PC-3 cells.

On the interface trap density and series resistance of tin oxide film prepared on n-type Si (1 1 1) substrate: Frequency dependent effects before and after 60Co γ-ray irradiation

We report the first investigation of the frequency dependent effects of gamma irradiation on interface state density and series resistance determined from capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics in SnO2/n-Si structures prepared by spray deposition method. The samples were irradiated using a 60Co γ-ray source at 500kGy at room temperature. The C–V and G–V measurements of the samples were performed in the voltage range −6V to 2V and at 10kHz, 100kHz, 500kHz and 1MHz at room temperature before and after 500kGy irradiation. The measurement capacitance and conductance are corrected for series resistance. It has been seen that the value of the series resistance Rs of sample decreases from 204Ω to 55.4Ω with increasing the frequency before irradiation while it decreases from 248Ω to 60Ω with increasing frequency at 500kGy irradiation. It has been found that and Dit values of MOS structure increases up to 100kHz and then decreases up to 1MHz while the Rs increases with increasing irradiation dose for our sample. The interface state density Dit ranges from 1.83×1013cm−2eV−1 for before irradiation to 1.54×1013cm−2eV−1 for 500kGy irradiation dose at 500kHz and decreases with increasing frequency.

The effect of 60Co (γ-ray) irradiation on the electrical characteristics of Au/SnO 2/n-Si (MIS) structures

The effect of 60Co (γ-ray) irradiation on the electrical properties of Au/SnO 2/n-Si (MIS) structures has been investigated using the capacitance–voltage ( C– V) and conductance–voltage ( G/ ω− V) measurements in the frequency range 1 kHz to 1 MHz at room temperature. The MIS structures were exposed to γ-rays at a dose rate of 2.12 kGy/h in water and the range of total dose was 0–500 kGy. It was found that the C– V and G/ ω− V curves were strongly influenced with both frequency and the presence of the dominant radiation-induced defects, and the series resistance was increased with increasing dose. Also, the radiation-induced threshold voltage shift (Δ V T) strongly depended on radiation dose and frequency, and the density of interface states N ss by Hill–Coleman method decreases with increasing radiation dose.

Formation of Intrinsic Point Defects in Fluorine-doped Synthetic SiO2Glass by60Co γ-ray Irradiation

Intrinsic point defect formation in a fluorine-doped synthetic silica (SiO2) glass by 60Co γ-ray irradiation was examined. The most abundantly formed defects are oxygen vacancies (Si–Si bonds). The concentrations of Si–Si bonds and interstitial oxygen molecules increase almost linearly with the γ-ray dose. These observations indicate that the primarily intrinsic defect process in SiO2 glass irradiated with 60Co γ-rays is the Frenkel pair formation, rather than a simple cleavage of an Si–O bond into a pair of silicon and oxygen dangling bonds.

Synergetic degradation of chitosan with gamma radiation and hydrogen peroxide

Chitosan samples were irradiated by 60Co γ-rays in the presence of hydrogen peroxide with radiation dose from 10 kGy to 100 kGy. The degradation was monitored by gel permeation chromatography (GPC), revealing the existence of a synergetic effect on the degradation. Structures of the degraded products were characterized with Fourier-transform infrared spectra (FT-IR), ultraviolet–visible spectral (UV–vis) analysis, and X-ray diffraction (XRD). Results showed that the crystallinity of chitosan decreases with degradation, and the crystalline state of water-soluble chitosan is entirely different from that of water-insoluble chitosan. An elemental analysis method was employed to investigate changes in the element content of chitosan after degradation. Mechanism of chitosan radiation degradation with and without hydrogen peroxide was also discussed.

Radiation-optical characteristics of quartz glass and sapphire

The systems registering plasma radiation comprise optical elements, which may distort a diagnostic signal if they are not radiation resistant. The work was aimed at experimental study of optical absorption and γ-induced luminescence of KU-1 quartz glass and sapphire crystals in the range of 200–900nm, which were irradiated in the 60Co γ-ray source of 6.7Gys−1 up to the dose of 108Gy and in the water cooled nuclear reactor of WWR-SM type with neutron fluences of 1017–1020cm−2, in order to imitate plasma effect. The transparency window (minimal optical losses) and the intrinsic luminescence bands were determined in the studied materials. The advantages of KU-1 type glass over sapphire as optical elements at 300–350K have been demonstrated.

A novel methodology for characterizing strand-break termini and damaged bases in plasmid DNA exposed to ionizing radiation

We have developed a de novo methodology to characterize radiation damage in DNA. An enzyme system consisting of the 3′→5′ exonuclease snake venom phosphodiesterase (SVPD) and calf intestine alkaline phosphatase (CIAP) was used to examine the 3′ termini of strand-break sites. In this study, we hypothesized that the strand-break termini can be divided into two categories: CIAP-independent SVPD sites and CIAP-dependent SVPD sites. The former consists of strand-break termini that can be recognized directly and digested by SVPD without CIAP pretreatment, whereas the latter includes the termini that cannot be digested by SVPD without CIAP pretreatment. In addition, the apparent radiation–chemical yield ( G value) can be estimated using the level of intact 2′-deoxynucleotides produced during a 15-min incubation with SVPD. The G value for total strand breaks in fully dried DNA irradiated with 60Co γ-rays was estimated to be 0.1 μmol/J. Moreover, the G values of CIAP-dependent and CIAP-independent SVPD sites were estimated to be 0.078 and 0.024 μmol/J, respectively. These values suggest that 3′-phosphate termini are more likely to be produced than 3′ termini without phosphate. Furthermore, piperidine-treated irradiated plasmid DNA was also treated with the same enzyme system to examine the piperidine-labile sites. As a result of the treatment, the G value of the CIAP-dependent SVPD sites increased to 0.16 μmol/J, whereas no significant increase was seen in the G value of the CIAP-independent SVPD sites. This observation implies that most piperidine-labile damaged bases can be eliminated to form apurinic/apyrimidinic sites, which are completely removed by piperidine treatment to form 3′ phosphate termini, and that prompt CIAP-independent SVPD sites are piperidine resistant.

Metal-mediated reactivity in the organic solid state: from self-assembled complexes to metal–organic frameworks

The purpose of this tutorial review is to address the use of metal ions to mediate reactions in the organic solid state. We describe metal complexes and coordination networks that facilitate dimerizations, oligomerizations and polymerizations of olefins and acetylenes via irradiation (e.g. ultraviolet (UV) and (60)Co gamma-rays) and thermal annealing. We show how metal ions can be utilized to direct the formation of polymers and molecules. We also describe how supramolecular chemistry has recently influenced dimerization processes in self-assembled metal-organic solids.

RBE and genetic susceptibility of mouse and rat spermatogonial stem cells to protons, heavy charged particles and 1.5 MeV neutrons

The main purpose of the present study is to provide data on RBE and genetic susceptibility in the mouse and the rat when exposed to protons, HZE particles and neutrons. Genetic damage from exposure to 50 MeV and 9 GeV protons, 4 GeV/nucleon helium ions, 4 GeV/nucleon carbon ions and 1.5 MeV neutrons was studied in adult (CBA × C57Bl/6J) F1 mice. Damage from 9 GeV protons and 4 GeV helium ions was studied in adult Wistar rats. The incidence of reciprocal translocations (RT) induced in the spermatogonial stem cells of each species was recorded. RBE values were derived by comparing linear regression coefficients from dose–responses within the same dose-range for each of the radiation types tested and 60Co γ-rays or by means of a direct nonparametric method. RT yields measured after mouse and rat spermatogonial irradiation with protons, heavy charged particles and neutrons fit the linear model of the dose–response relationship. Relative to 60Co γ-rays, RBE values are as follows for mouse spermatogonia: 0.9 for 50 MeV protons; 1.3 for 9 GeV protons; 0.7 for 4 GeV helium ions; and 1.3 for 4 GeV carbon ions. For rat spermatogonia, values were: 1.7 for 9 GeV protons and 1.3 for helium ions. Compared to mice irradiated using the same experimental design, rats were more susceptible to high-LET radiations, with susceptibility assessed by genetic damage to their spermatogonial stem cells. The RBE of 1.5 MeV neutron is about 6.6.

IMPROVEMENT OF RADIOSENSITIVE LIQUID-CORE MICROCAPSULES BY YTTRIUM POLYMERIZATION

Microcapsules comprising alginate and hyaluronic acid that can be decomposed by radiation are under development. Previously, we observed that radiation efficiently decomposes microcapsules comprising alginate and hyaluronic acid in the ratio 2:1 by weight. In this study, Yttrium ( Y ) was added to these microcapsules to improve their decomposition by radiation. Hyaluronic acid solutions (0.1% weight/volume) were mixed into 0.2% alginate solution, and carboplatin (0.2 mmol) was added; the resultant was used for capsule preparation. Capsules were prepared by spraying the material into mixtures of 4.34% CaCl 2 solution supplemented with Y at final concentrations from 0 to 1.0 × 10−2%. These capsules were irradiated by a single dose of 0.5, 1.0, 1.5, or 2 Gy with 60Co γ-rays. Immediately after irradiation, we observed the release of the core contents of the microcapsule using a micro Particle Induced X-ray Emission (PIXE) camera. The mean diameter of the microcapsules was 37.3 ± 7.8 μm . Maximum content of radiation-induced release was observed for liquid-core microcapsules prepared by polymerization in a 4.34% CaCl 2 solution supplemented with 5.5 × 10−3% Y .

60Co γ-ray irradiation effects on the interface traps density of tin oxide films of different thicknesses on n-type Si (1 1 1) substrates

We report the first investigation of the gamma irradiation effects on interface state density and series resistance determined from capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics in Au/SnO2/n-Si (MOS) structures prepared at various SnO2 layer thicknesses by spray deposition technique. It was fabricated three samples depending on deposition time. The samples were irradiated using a 60Co γ-ray source irradiation with the total dose range was 0–500kGy at room temperature. The C–V and G–V measurements of the samples were performed at high frequency (500kHz) at room temperature before and after irradiation. The measurement capacitance and conductance are corrected for series resistance. The thicknesses of SnO2 films obtained from the measurement of the oxide capacitance in the accumulation region for MOS Schottky diodes were 19, 52, 191Å, for D1, D2 and D3 samples, respectively. It has been seen that the value of the series resistance Rs of samples D1 (50Ω), D2 (66Ω) and D3 (157Ω) increases with increasing the oxide layer thickness and increases from 50Ω to 62.7Ω with increasing irradiation dose. The single frequency method of Hill-Coleman was used to determine the interface state density (Dit).

The mechanism of 60Co γ-ray radiation induced interfacial redox reaction in inverse emulsion and its application in the synthesis of polymer microcapsules

The motivation of this work is to explore the formation mechanism of polymer microcapsules via γ-ray radiation in W/O inverse emulsion system. Utilizing the strong reducing radical (eaq−, hydrated electron) and oxidant radical (OH, hydroxyl radical) produced in the aqueous phase by the 60Co γ-ray radiation, two interfacial redox initiation systems were proposed and applied to the preparation of polymer microcapsules. In this work, BPO (benzoyl peroxide)–eaq− and DMA (N,N-dimethyl aniline)–OH were used to control the polymerization position at the water–oil interface. Finally, polystyrene (PS) microcapsules were synthesized successfully. From the kinetic curves of monomer conversion, the mechanism of radiation induced interfacial reaction was determined and this method can be extended to synthesize polymer capsules and composite spheres.

The biological effectiveness of antiproton irradiation

Background and purpose Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons. Materials and methods V79 cells were suspended in a semi-solid matrix and irradiated with 46.7 MeV antiprotons, 48 MeV protons, or 60Co γ-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness. Results Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was ∼3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE). Conclusion We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.