Radiation effect studies on anticancer drugs, cyclophosphamide and doxorubicin for radiation sterilization

Two anticancer drugs, cyclophosphamide (CPH) and doxorubicin hydrochloride (DOXO), in powder form were exposed to a range of doses of ⁶⁰Co gamma and electron beam radiation to study the effects of ionizing radiation. Pharmacopoeia tests, discolouration, degradation products, effect of irradiation temperature and dose rate were investigated. CPH undergoes less than 2% degradation at 30 kGy. Chromatographic studies revealed formation of several trace level degradation products, discolouration and free radicals in the irradiated CPH. N,N-bis (2-chloroethyl) group in the molecule is particularly sensitive to radiation degradation. Irradiation to 5 kGy at low temperature (77 K) did not result in significant changes. DOXO was observed to be quite radiation resistant and did not undergo significant changes in its physico-chemical properties and degradation product profile. It can be radiation sterilized at normal sterilization dose of 25 kGy.     

The decontamination effects of gamma irradiation on the edible gelatin

The decontamination effects of gamma irradiation on the edible gelatin were studied. The results indicated that the bacterium and mold in the gelatin decreased significantly with the dose of 5 kGy treatment. However, the content of crude protein, microelement, amino acid in the gelatin remained unchanged under the irradiation of 4 and 8 kGy. The viscosity of the gelatin decreased with the increase of the irradiation dose, but the gelatin with a dose of 5 kGy treatment still accorded with the standard of the second-order class. These results suggested that the optimum irradiation dose for edible gelatin for the purpose of decontamination was in the range 3–5 kGy.     

Electron beam irradiated polyamide-6,6 films—II: mechanical and dynamic mechanical properties and water absorption behavior

Electron beam irradiation of poly(iminohexamethylene-iminoadipoyl) (Polyamide-6,6) films was carried out over a range of irradiation doses (20–500 kGy) in air. The mechanical properties were studied and the optimum radiation dose was 200 kGy, where the ultimate tensile stress (UTS), 10% modulus, elongation at break (EB) and toughness showed significant improvement over the unirradiated film. At a dose of 200 kGy, the UTS was improved by 19%, the 10% modulus by 9% and the EB by 200% over the control. The dynamic mechanical properties of the films were studied in the temperature region 303–473 K to observe the changes in the glass transition temperature (T_g) and loss tangent (tan δ) with radiation dose. The storage modulus of the film receiving a radiation dose of 200 kGy was higher than the unirradiated film. The water uptake characteristics of the Polyamide-6,6 films were investigated. The water uptake was less for the films that received a radiation dose of 200 and 500 kGy than the unirradiated film. The role of crystallinity, crosslinking and chain scission in affecting the tensile, dynamic mechanical and water absorption properties was discussed.     

Radiation effects on viscosimetry of protein based solutions

Due to their good functional properties allied to their excellent nutritional value, milk protein isolates and soy protein concentrates have gained a crescent interest. These proteins could have their structural properties improved when some treatments are applied, such as gamma irradiation, alone or in presence of other compounds, as a plasticizer. In this work, solutions of those proteins were mixed with a generally recognized as safe plasticizer, glycerol. These mixtures (8% protein (w/v) base) at two ratios 1:1 and 2:1 (protein:glycerol) were submitted to a gamma irradiation treatment (⁶⁰Co), at doses 0, 5, 15 and 25 kGy, and their rheological performance was studied. As irradiation dose increased viscosity measurements decayed significantly (p<0.05) for mixture soy/glycerol and calcium caseinate/glycerol. The mixture sodium caseinate/glycerol showed a trend to form aggregation of macromolecules with dose of 5 kGy, while the apparent viscosity for dispersions containing whey/glycerol remained almost constant as irradiation dose increases. In the case of soy protein isolate and sodium caseinate, a mixture of 2:1 showed a significant higher viscosity (p<0.05) than a mixture of 1:1.     

Pectin- and gelatin-based film: effect of gamma irradiation on the mechanical properties and biodegradation

Agricultural by-products, pectin and gelatin, were used to prepare a biodegradable film. The film casting solution including the pectin and gelatin was irradiated at 0, 10, 20, and 30 kGy to investigate the irradiation effect on the mechanical properties of the film. The tensile strength of the 10 kGy-irradiated film was the highest among the treatments but the elongation at break, water vapour permeability, and swelling ratio were the lowest. Hunter color L^*- and a^*-values decreased but the b^*-value increased as the irradiation dose increased. The total organic carbon content produced from the Paenibacillus polymyxa and Pseudomonas aeruginosa also showed that the film of 10 kGy-irradiated was lower than those of 0, 20, and 30 kGy-irradiated films. In conclusion, irradiation of the film casting solution at 10 kGy increased the mechanical properties of the pectin and gelatin based film. To manufacture the film by agricultural by-products, however, the irradiation dose of the film casting solution should be determined to achieve better mechanical properties.     

Detergent Powder: Investigation for Feasible Retrospective Dosimetry Using ESR Technique

An Electron Spin Resonance (ESR) study of radiation induced free radicals in the commonly used detergent powder (Surf), was conducted to examine its potential application for retrospective/high level dosimetry, including possible dating of the accidents. The radical ions present in the irradiated detergent powder were identified as arising predominantly from sodium tri poly phosphate (Na₃P₅O₁₀) and sodium sulphate (Na₂SO₄). The physical mixture of sodium tri poly phosphate and sodium sulphate in 4:1 ratio was found to give an ESR response, similar to that of the detergent powder. These results suggest that the detergent powder can be used as a dosimeter in the 20 Gy to 18 kGy dose range, spanning over 3 orders of magnitude. The second derivative ESR spectra of the detergent powder irradiated to different doses showed that the relative yield of the radicals is independent of irradiation dose. The decay pattern of radicals when followed as a function of post irradiation days, lead to the idea about the contrasting decay characteristics of the radicals. From the ESR signals of the irradiated detergent samples, it is shown that radiation dose can be evaluated and the radiation incident can be dated with an accuracy of ±10%.     

Threonine-FX dosimeter for food irradiation

A detailed study for the spectrophotometric readout method for L-threonine powder, [CH₃CH(OH)CH(NH₂)COOH], was done. In this method, 400 mg unirradiated/irradiated L-threonine powder was dissolved in 10 ml of a solution which contains 3×10⁻⁴ mol dm⁻³ ferrous ammonium sulphate and 1.7×10⁻⁴ mol dm⁻³ xylenol orange (XO) in aerated aqueous 0.17 mol dm⁻³ sulphuric acid (FX). The peroxy radicals produced from irradiated threonine oxidize ferrous ions and XO forms a complex with ferric ions as well as controls the chain length of ferrous ion oxidation. The plot of absorbance at 556 nm against dose is linear in the dose range 20–400 Gy and doses down to about 1 Gy can be measured using 10-cm path cells. Response of the dosimeter is independent of irradiation temperature above 20. A dose of 50 Gy–10 kGy can be measured dissolving 50 mg threonine powder in 10 ml of a solution which contains 3×10⁻⁴ mol dm⁻³ ferrous ammonium sulphate and 1.3×10⁻⁴ mol dm⁻³ XO in aerated aqueous 0.06 mol dm⁻³ sulphuric acid (FX). The plot of absorbance at 552 nm against dose is non-linear. However dosimeter shows linear dose response up to 1000 Gy. Irradiated threonine powder is stable for about 3 months. The reproducibility of the method is better than ±2%. This dosimeter is very useful as transfer dosimeter for food irradiation programme.     

Radiation Graft Copolymerization of a Mixture of Styrene and n-Butyl Acrylate on Natural Rubber Latex

The radiation graft copolymerization of a mixture of styrene (St) and n-butyl acrylate (NBA) monomers on natural rubber (NR) latex has been studied. An irradiation dose of about 18 kGy was needed to attain a conversion of about 80%. The tensile strength of the grafted NR film increases with increasing irradiation dose. A film tensile strength of about 155 kg/cm² was attained by irradiation of a mixture of St, NBA, and NR latex with a dose of about 14 kGy. At low concentrations of monomer in the latex, the Mooney viscosity of the film increases with increasing irradiation dose. At higher monomer concentration, grafting and homopolymerization proceed more favorably than crosslinking, and thus the Mooney viscosity decreases with increasing dose. Thermal analysis of the film showed that the grafted NR was more heat resistant than ungrafted NR.     

Radiation polymerization of thermo-sensitive poly (N-vinylcaprolactam)

Temperature-sensitive poly (N-vinylcaprolactam) both in water-soluble state and in gel was prepared by γ-radiation polymerization. The effects of radiation dose, radiation dose rate and monomer concentration on polymerization and the low critical solution temperature characteristics of the polymer were studied. The results show that the polymer prepared within certain radiation dose (beyond 2 kGy) and dose rate range (2–14 Gy/min) has good temperature sensitivity and uniformity.     

Effect of dose rate on inactivation of microorganisms in spices by electron-beams and gamma-rays irradiation

Total aerobic bacteria in spices used in this study were determined to be 1 × 10⁶ to 6 × 10⁷ per gram. A study on the inactivation of microorganisms in spices showed that doses of 6–9kGy of EB (electron-beams) or γ-irradiation were required to reduce the total aerobic bacteria in many However, a little increase of resistance was observed on the inactivation of total aerobic bacteria in many spices in case of EB irradiation. These difference of radiation sensitivities between EB and γ-rays was explained by dose rate effect on oxidation damage to microorganisms from the results of radiation sensitivities of Bacillus pumilus and B. megaterium spores at dry conditions. On the other hand, these high dose rate of EB irradiation suppressed the increase of peroxide values in spices at high dose irradiation up to 80 kGy. However, components of essential oils in spices were not changed even irradiated up to 50 kGy with EB and γ-rays.     

Dose response and post-irradiation characteristics of the Sunna 535-nm photo-fluorescent film dosimeter

Results of characterization studies on one of the first versions of the Sunna photo-fluorescent dosimeter™ have previously been reported, and the performance of the red fluorescence component described. This present paper describes dose response and post-irradiation characteristics of the green fluorescence component from the same dosimeter film (Sunna Model γ), which is manufactured using the injection molding technique. This production method may supply batch sizes on the order of 1 million dosimeter film elements while maintaining a signal precision (1σ) on the order of ±1% without the need to correct for variability of film thickness. The dosimeter is a 1 cm×3 cm polymeric film of 0.5-mm thickness that emits green fluorescence at intensities increasing almost linearly with dose. The data presented include dose response, post-irradiation growth, heat treatment, dosimeter aging, dose rate dependence, energy dependence, dose fractionation, variation of response within a batch, and the stability of the fluorimeter response. The results indicate that, as a routine dosimeter, the green signal provides a broad range of response at food irradiation (0.3–5 kGy), medical sterilization (5–40 kGy), and polymer cross-linking (40–250 kGy) dose levels.     

Effect of gamma radiation on growth and survival of common seed-borne fungi in India

The present work describes radiation-induced effects of major seeds like Oryza sativa Cv-2233, Oryza sativa Cv-Shankar, Cicer arietinum Cv-local and seed-borne fungi like Alternaria sp., Aspergillus sp., Trichoderma sp. and Curvularia sp. ⁶⁰Co gamma source at 25 °C emitting gamma ray at 1173 and 1332 keV energy was used for irradiation. Dose of gamma irradiation up to 3 kGy (0.12 kGy/h) was applied for exposing the seed and fungal spores. Significant depletion of the fungal population was noted with irradiation at 1–2 kGy, whereas germinating potential of the treated grain did not alter significantly. However, significant differential radiation response in delayed seed germination, colony formation of the fungal spores and their depletion of growth were noticed in a dose-dependent manner. The depletion of the fungal viability (germination) was noted within the irradiation dose range of 1–2 kGy for Alternaria sp. and Aspergillus sp., while 0.5–1 kGy for Trichoderma sp. and Curvularia sp. However, complete inhibition of all the selected fungi was observed above 2.5 kGy.     

Radiation-induced crosslinking of collagen gelatin into a stable hydrogel

Gelatin, the low molecular weight collagen derivative from porcine skin was transformed into a stable permanent hydrogel by γ-radiation. A series of samples with 3% gelatin solution in water were irradiated at doses of 12, 25, 50, 100, 150, 200 kGy at room temperature in the absence of air with a dose rate of 2.2 kGy/h. At low dose gelatin hydrogels incorporating all the available water were obtained. At higher doses above 50 kGy, the gelatin hydrogel samples show a curious shrinking phenomenon due to the relatively high crosslinking density level achieved, so part of the available water is squeezed out from the gel cage. The gelatin hydrogel samples were studied by mass fractionation analysis, by spectrophotometric and polarimetric analysis. Further characterization was made by FT-IR spectroscopy and by thermal analysis (DSC, DTA and TGA) of the dried gelatin samples after irradiation in comparison to a reference untreated sample.     

EPR and UV spectral study of gamma-irradiated white and burned sugar, fructose and glucose

The EPR and UV spectral properties of gamma-irradiated white and burned sugar, fructose and glucose are studied with the accent on their suitability as dosimetric materials. It is shown that gamma-irradiation of solid samples of white sugar and fructose yields stable EPR spectra whereas glucose signal remains time-dependent even 11 months later. Sugar and glucose exhibit linear EPR dose response in the region 0.44-21 kGy and fructose only up to ca. 10 kGy. The relative radiation sensitivity obtained for sugar and fructose is up to 10 kGy and slightly lower for glucose. Burned saccharides provide 2-3 orders of magnitude lower EPR radiation sensitivity making them not suitable for the proposed designation. According to the UV spectra water solutions of gamma-irradiated solid white saccharides show well pronounced absorption bands at 267 and 286 nm for sugar and fructose with time-dependent intensities reaching steady values ca. 11 days after dissolution. The intensities of these absorption bands are in linear relation with the absorbed dose of gamma-radiation. Glucose shows low sensitively because irradiation with 5.5 kGy yields only a shoulder at about 260-280 nm with decreasing to ca. 40% intensity in the first few days after dissolution. Excellent correlation between the intensities of the EPR- and UV-absorbed dose response is found for sugar and fructose in the region 0.44-10 kGy. This opens new possibilities for independent calibration the EPR dose response. Finally, the comparison suggests sugar as the best, universal material for EPR- and/or UV-dosimetry in the region 0.44-160 kGy.     

The use of ESR spectroscopy for the investigation of dosimetric properties of egg shells

Electron spin resonance (ESR) spectroscopy was used to investigate the dosimetric properties of chicken egg shells. The ESR spectra of the irradiated egg shell were found to have an asymmetric absorption characterized by a major resonance at g=2.0019 and a minor resonance at g_||=1.9980. The study was carried out on g=2.0019 signal because of the accuracy of measurements and the possibility of using it as ESR dosimeter. The activation energy (E), frequency factor (k₀) and mean-life (τ) were calculated to be 1.50±0.10 eV, 2×10¹³ s⁻¹ and (4.4±0.4)×10⁴ year respectively. Dose–response was investigated between dose ranges of 1 Gy and 10 kGy for ⁶⁰Co γ-rays. Dose–response was found to be appropriate for dosimetry in the range 3 Gy to 10 kGy. The lower limit of observable doses for egg shell sample was about 3 Gy. The other ESR dosimetric parameters of egg shell samples, fading characteristic, light effect, dose-rate dependence and energy dependence, have also been studied in detail. Apart from its non-tissue equivalence, egg shell has very good dosimetric properties with insignificant fading, light independence, linearity in dose–response (3 Gy–10 kGy), dose-rate independence and independence from energy above 500 keV. It suggests that egg shell may be used as a retrospective γ radiation dosimetry after nuclear accidents or other short accidental radiation events.     

Applicability study on existing dosimetry systems to high-power Bremsstrahlung irradiation

Applicability of the existing dosimetry systems to high-power Bremsstrahlung irradiation was investigated through a dose intercomparison study, where several dosimeters were irradiated in the dose range 4–12 kGy in identical polyethylene phantoms in a Bremsstrahlung beam obtained from a 5-MeV electron accelerator. Included in the study were alanine dosimeters molded by three different binders, three types of liquid dosimeters—ceric-cerous, dichromate and ethanol-chlorobenzen (ECB), and glutamine powder. The dosimeter responses for Bremsstrahlung radiation were analyzed at the issuing laboratories, and the dose values determined using calibration based on cobalt-60 gamma-ray irradiation. Dose values for all the three dose levels for all dosimetry systems were in good agreement—better than 3%. The results of the study demonstrate that these existing dosimetry systems have a potential for application to high-power Bremsstrahlung irradiation.     

Field evaluations of the VDmax approach for substantiation of a 25 kGy sterilization dose and its application to other preselected doses

The International and European standards for radiation sterilization require evidence of the effectiveness of a minimum sterilization dose of 25 kGy but do not provide detailed guidance on how this evidence can be generated. An approach, designated VD_max, has recently been described and computer evaluated to provide safe and unambiguous substantiation of a 25 kGy sterilization dose. The approach has been further developed into a practical method, which has been subjected to field evaluations at three manufacturing facilities which produce different types of medical devices. The three facilities each used a different overall evaluation strategy: Facility A used VD_max for quarterly dose audits; Facility B compared VD_max and Method 1 in side-by-side parallel experiments; and Facility C, a new facility at start-up, used VD_max for initial substantiation of 25 kGy and subsequent quarterly dose audits. A common element at all three facilities was the use of 10 product units for irradiation in the verification dose experiment.

The field evaluations of the VD_max method were successful at all three facilities; they included many different types of medical devices/product families with a wide range of average bioburden and sample item portion values used in the verification dose experiments. Overall, around 500 verification dose experiments were performed and no failures were observed. In the side-by-side parallel experiments, the outcomes of the VD_max experiments were consistent with the outcomes observed with Method 1.

The VD_max approach has been extended to sterilization doses >25 and <25 kGy; verification doses have been derived for sterilization doses of 15, 20, 30, and 35 kGy. Widespread application of the VD_max method for doses other than 25 kGy must await controlled field evaluations and the development of appropriate specifications/standards.     

Ultra-sensitive mass spectrometric and other methods applied to environmental problems

Summary The radiation stability of UNEX stripping solutions containing water, methylamine carbonate, nitrilotriacetic acid, and metal salts was experimentally studied. The decomposition of the methylamine carbonate and nitrilotriacetic acid under gamma irradiation (dose: 0.29 kGy) is lower than 0.5 molecules per 100 eV or about 7.2E-04% and 0.047%, respectively. The decomposition products do not adversely affect the UNEX process up to a 3 MGy absorbed dose. The stripping solutions can be regenerated and reused.     

Radiation yield of oxygen-based radicals in hyperquenched glassy water gamma-irradiated at 77 K

Hyperquenching of liquid water with cooling rates of 10⁶–10⁷ K s⁻¹ yields glassy water. Upon γ-irradiation at 77 K, the only paramagnetic species accumulating in hyperquenched glassy water are the hydroxyl and hydroperoxyl radicals. There are no hydrogen atoms or electrons seen by the ESR technique. For irradiation doses up to about 70 kGy, the relative contributions of hydroxyl and hydroperoxyl radicals to the total amount of paramagnetic species remain virtually constant. The total amount of paramagnetic species, n, is sublinear in dose, d, well approximated by n=8.55×10¹⁶d^0.8 for n in spin g⁻¹ and d in kGy.     

Preservation of fresh noodles by irradiation

At the present paper, it is studied to preserve fresh noodles by irradiation. The noodles which were irradiated by 10 kGy of ⁶⁰Co-γ rays and stored at room temperature (18–24°C). The appearance of the noodles was observed, the bacteria in the noodles were examines, and the acidity of the noodles was measured during 10 days after irradiation. The results showed that the number of bacteria and the extent of acidification of the noodles were in inverse proportion to radiation dose. When the absorbed dose was less than 8 kGy, the residual bacteria in the noodles could proliferate massively in several days and acidified the noodles. The pH of these noodles decreased from 6.2 to 5.0 or less and the noodles turned into sticky during storage. When the absorbed dose reached 8–10 kGy, most of bacteria were killed and the acidity of the noodles kept about pH 6.0. The appearance of the noodles looks fresh within 10 days after irradiation. They smelled as good as fresh ones.