Gamma Radiation Sterilization Research Articles

Gamma Radiation Sterilization Dose of Adult Males in Asian Tiger Mosquito Pupae.

The pathogen-carrying tiger mosquito, Aedes albopictus, has spread from the Western Pacific and Southeast Asia to Europe, Africa, the Middle East, North and South America, and the Caribbean. This species of mosquito transmits arboviral infections, such as yellow fever, chikungunya, dengue, zika, and several encephalitides. The objective of this research was to provide a radiation dose inducing sterilization in adult male Ae. albopictus in the pupal stage. A cobalt-60 source of gamma radiation at a dose rate of 381 Gy/h was used. The pupae were irradiated with doses of 0 (control), 20, 30, 40, 50, and 60 Gy. Each treatment had a total of five replications using 60 pupae. After irradiation, the different phases of Ae. albopictus development (egg, larva, pupa, and adult) in the F1 generation were observed daily. Parameters such as viability, fertility, longevity, and mortality were recorded. The results from these studies showed that a dose of 60 Gy was necessary to sterilize 100% of the male Ae. albopictus pupae.

Influence of steam and pressure and gamma radiation sterilization on drug loaded intraocular lenses for endophthalmitis prevention

Influence of steam and pressure and gamma radiation sterilization on drug loaded intraocular lenses for endophthalmitis prevention

Survey of mushroom consumption and the possible use of gamma irradiation for sterilization of compost for its cultivation in Southern Ghana

BackgroundMushroom cultivation is increasingly becoming a serious agribusiness in Ghana, especially at the time when entrepreneurship is being encouraged to reduce the pressure of employment in the government sector and also due to its nutritional and medicinal attributes.MethodsA survey was carried out using the rapid appraisal method to review the existing methods of sterilization, use of gamma radiation in substrate sterilization and food preservation, preference of mushrooms in Ghana by consumers and nutritional and medicinal attributes of the mushroom.ResultsThe survey demonstrated the popularity of drum (moist heat) technique of sterilization in Ghana. Majority (64%) of the respondents were dissatisfied with the method of sterilization of compost and spawn substrate, while 36% indicated the method was alright by them. Majority (82%) of the respondents had never heard of sterilization of substrates for cultivation and its subsequent preservation of food or mushroom by gamma irradiation technique. All consumers (100%) desired to see their favorite mushroom produced all year round, and this constituted a significant (p < 0.05) viewpoint. Furthermore, a significant (p < 0.05) majority (90%) of the respondents were all for promotion of the consumption of mushroom, while a small percentage (10%) were noncommittal.ConclusionInformation and knowledge on the gamma irradiation technique for substrate production and consumption patterns of P.ostreatus mushrooms were not widely disseminated as anticipated.

Low-energy electron-beam treatment as alternative for on-site sterilization of highly functionalized medical products – A feasibility study

Over the last decades, the medical device industry has grown significantly. Complex and highly functionalized medical devices and implants are being developed to improve patient treatment and to enhance their health-related quality of life. However, medical devices from this new generation often cannot be sterilized by standard methods such as autoclaving or sterilizing gases, as they are temperature sensitive, containing electronic components like sensors and microchips, or consist of polymers. Gamma irradiation for sterilization of such products is also problematic due to long processing times under highly reactive conditions resulting in material degradation or loss of functionality. Low-energy electron-beam treatment could enable irradiation sterilization of medical surfaces within seconds. This method is very fast in comparison to gamma irradiation because of its high dose rate and therefore degradation processes of polymers can be reduced or even prevented. Additionally, electron penetration depth can be precisely controlled to prevent damage of sensitive components like electronics and semiconductors.The presented study focuses on two key aspects: 1.) Can new and highly functionalized medical products in future be sterilized using low-energy electron-beam irradiation; and 2.) Is the low-energy electron-beam technology suitable to be set up on-site to speed up sterilization processing or make it available “just-in-time”. To address these questions, different test specimens were chosen with complex geometry or electronic functional parts to gather information about the limitations and chances for this new approach. The test specimens were inoculated with clinical relevant test organisms (Pseudomonas aeruginosa) as well as with approved radiation resistant organisms (Deinococcus radiodurans and Bacillus pumilus) to prove the suitability of low-energy electron-beam treatment for the above-mentioned medical products. The calculation of the D10 value for B. pumilus revealed equal efficacy when compared to standard high-energy irradiation sterilization. All of the above-mentioned germs were successfully inactivated by low-energy electron-beam treatment when test specimens were inoculated with a germ load > 10^6 CFU and treated with doses ≥ 10 kGy (for B. pumilus and P. aeruginosa) and > 300 kGy (for D. radiodurans) respectively. As an example, for specialized electronic components to be sterilized, an impedance sensor for cell culture applications was sterilized and unimpaired functionality was demonstrated even after five repeated sterilization cycles to a total dose of 50 kGy. To address the second aspect of on-site suitability of this technology, the product handling for low-energy electron-beam treatment had to be adapted to minimize the size of the electron-beam facility. Therefore, a mini electron-beam source was used and a specialized sample holder and 3D-handling regime were developed to allow reproducible surface treatment for complex product geometries. Inactivation of B. pumilus inoculated medical screws (> 10^6 CFU) was successful using the developed handling procedure. In addition, a packaging material (PET12/PE50) for medical products was investigated for its suitability for low-energy irradiation sterilization. Biocompatibility assessment revealed the material to be eligible for this application as even overdoses did not impair the biocompatibility of the material.With these results, the principal suitability of low-energy electron-beam treatment for sterilization of medical products containing electronics like sensors is demonstrated. The low-energy technology and the specialized 3D-handling regime allow the on-site setup of the technology in hospitals, medical practices or any other point of care.

The Effect of Different Sterilization Methods on Polypropylene Syringes

This presents the influence of gamma irradiation on Pharmacopeia specifications, mechanical and flow parameters of polypropylene (PP) syringes. There has been significant progress in the terminal sterilization of single-use, disposable medical devices with gamma radiation sterilization due to the growing awareness of toxic residues during the ethylene oxide (EtO) sterilization. PP is a widely used polymer for the production of syringes because of its excellent mechanical and thermal properties and has expanded continuously over the last decade. Although 25 kGy was generally recommended for the gamma radiation sterilization of medical products, this radiation dose is high enough to produce substantial damage. Electron spin resonance (ESR) characteristics of irradiated syringes were also studied at normal (25 °C, 60% relative humidity) and accelerated (40 °C, 75% relative humidity) stability test conditions. It was found that the chemical and radiolytic changes and sterility assurance levels (SAL) after gamma radiation sterilization were different in PP syringes. It was shown that for two commercial syringes, E1 and E3, a SAL of 10−4 could be attained with only 10 kGy, with there being less detrimental radiation effects on E1. The differences in the radiosensitivity of the propylene syringes could be due to the different formulations and manufacturing processes. The results indicated that a commercial syringe, identified as E1 could be safely sterilized with gamma irradiation as the radicals decay over a period of days under normal conditions and quenched much faster under stability conditions. Furthermore, ESR technique could be used successfully in monitoring the radiosterilization of this material. Additionally, the confirmation and validation of the SAL doses which are below 25 kGy, will decrease the time and cost of the sterilization with less damaging effects of ionizing irradiation.

Evaluation of multilayer film stability by Raman spectroscopy after gamma-irradiation sterilization process

Polymers such as polyethylene (PE) and ethylene vinyl alcohol (EVOH) are primary constituents of single use plastic systems in the biopharmaceutical and biotechnology industries. These devices are sterilized by gamma-irradiation prior to be used, the usual dose being between 25 and 45 kGy. Optical spectroscopies are of great interest for chemical analysis and are used to obtain information on the composition of materials such as polymers. Raman spectroscopy provides information on the fundamental vibrations of molecules, using excitation in the visible wavelength range. The purpose of this study is to unveil the impact of gamma-sterilization on polymers in industry-like experimental conditions. Cross-sections of films are analyzed before and after sterilization using different radiation doses: their compositions and chemical evolution of the material are examined using micro-Raman spectroscopy. As the chemical composition of the layers is complex, due to the presence of additive compounds, there is considerable overlap between the spectral data. In this case, the use of spectral curve resolution chemometric methods is unique for unravelling the complex identification of the layers and to study the degree of chemical modifications.

ESR investigations of gamma irradiated medical devices

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) biomaterials have been employed in recent years for periodontal procedures. In the present study, widely used dental GTR/GBR biomaterials (grafts: G1, G2, G3 and membranes: M1, M2, M3, M4) were exposed to gamma irradiation at an absorbed dose range of 0–50kGy and the radiolytic intermediates that have been created in the samples upon irradiation were characterized in detail by Electron Spin Resonance (ESR) spectroscopy. We aimed to standardize the measurement conditions for practical applications of gamma radiation sterilization of GTR/GBR biomaterials. We investigated the characteristic features of free radicals in gamma irradiated GTR/GBR biomaterials and examined the stability of the induced radicals at room temperature and accelerated stability conditions with ESR spectroscopy including dose-response curves, microwave power studies, dosimetric features of the biomaterials, variations of the peak heights with temperature, and long term stabilities of the radical species. Long-term stability studies have shown that G1 is quite stable even in accelerated storage conditions. The signal intensities of graft-type GTR/GBR biomaterials stored in normal and stability conditions have decreased very rapidly even only a few days after gamma irradiation sterilization. Thus, those samples indicating relatively low stability features can be very good candidates for the radiosterilization process. The beta-tricalcium phosphate and PLGA containing G1 and M1 respectively have found to be the most gamma stable bone substitute biomaterials and be safely sterilized by gamma radiation. ESR spectroscopy is an appropriate technique in giving important detailed spectroscopic findings in the gamma radiation sterilization studies of GTR/GBR biomaterials.

Nano drug delivery systems and gamma radiation sterilization

In recent years, drug delivery systems such as liposomes and microparticles have been used in clinic for the treatment of different diseases and from a regulatory point of view, a parenterally applied drug and drug delivery systems must be sterile and pyrogen free. Radiation sterilization is a method recognized by pharmacopoeias to achieve sterility criteria of parenterals. It has the ability to kill microorganisms in therapeutic products. The ability of, however, irradiation might also affect the performance of drug delivery systems. One of the most critical points is irradiation dose, because certain undesirable chemical and physical changes may accompany with the irradiation, especially with the traditionally applied dose of 25 kGy. Its ionizing property may cause fragmentation of covalent bond. The care must be paid to the applied dose. In this research, the effects of gamma irradiation on different drug delivery systems such as chitosan microparticles, liposomes, niosomes and sphingosomes were investigated. According to the experimental data, it can be concluded that gamma irradiation can be a suitable sterilization technique for liposome, niosome and sphingosome dispersions. When all irradiated drug carrier systems were taken into consideration, chitosan glutamate microparticles were found as the most radioresistant drug delivery system among the others.

In vitro characterization of design and compressive properties of 3D-biofabricated/decellularized hybrid grafts for tracheal tissue engineering

Infection or damage to the trachea, a thin walled and cartilage reinforced conduit that connects the pharynx and larynx to the lungs, leads to serious respiratory medical conditions which can often prove fatal. Current clinical strategies for complex tracheal reconstruction are of limited availability and efficacy, but tissue engineering and regenerative medicine approaches may provide viable alternatives. In this study, we have developed a new “hybrid graft” approach that utilizes decellularized tracheal tissue along with a resorbable polymer scaffold, and holds promise for potential clinical applications. First, we evaluated the effect of our decellularization process on the compression properties of porcine tracheal segments, and noted approximately 63% decrease in resistance to compression following decellularization. Next we developed four C-shape scaffold designs by varying the base geometry and thickness, and fabricated polycaprolactone scaffolds using a combination of 3D-Bioplotting and thermally-assisted forming. All scaffolds designs were evaluated in vitro under three different environmental testing conditions to determine the design that offered the best resistance to compression. These were further studied to determine the effect of gamma radiation sterilization and cyclic compression loading. Finally, hybrid grafts were developed by securing these optimal design scaffolds to decellularized tracheal segments and evaluated in vitro under physiological testing conditions. Results show that the resistance to compression offered by the hybrid grafts created using gamma radiation sterilized scaffolds was comparable to that of fresh tracheal segments. Given that current clinical attempts at tracheal transplantation using decellularized tissue have been fraught with luminal collapse and complications, our data support the possibility that future embodiments using a hybrid graft approach may reduce the need for intraluminal stenting in tracheal transplant recipients.

CORR Insights(®): Gamma Radiation Sterilization Reduces the High-cycle Fatigue Life of Allograft Bone.

Where Are We Now? Viral transmission from allograft tissue is rare, but when it occurs, it can be a life-threatening complication. Bacterial infections following allograft reconstructions are both common and limb-threatening. Minimizing the risks are crucial for patient safety. Therefore, any attention we can focus on graft sterilization is effort well spent. The sterilization process—cleaning, defatting, and storing the allograft—must be safe, efficient, and effective. Currently, sterilization generally uses ionizing radiation. Ethylene oxide and autoclave treatments are no longer used because of toxicity, loss of strength of the material, and loss of osteoinductive properties caused by the denaturation of proteins or the alkylation of amino acids [1, 2, 4-6]. Instead, the current standard is gamma-radiation sterilization because of its convenience and effectiveness both against bacterial contaminants as well as viral transmission (HIV and Hepatitis C). However, irradiation damages the collagenous fiber system by cracking the polymer chains and alkylation of free radicals. Crosslinking or free radical scavenging could reduce the damage caused by irradiation. Since both are achieved with chemical solutions, it is important to validate the penetration depth of the chemicals applied. Where Do We Need To Go? In order to achieve safe and efficient graft sterilization, we must combine different treatments. The combination of the safest chemical treatment with the lowest irradiation dose can balance the disadvantages of each of those two approaches. The collagenous fibers resist ice crystal damage, the ground substance, however, not, resulting in loss of tension of the fiber pattern. This is well known from electron microscopy and can be counteracted by antifreezing solutions like dimethylsulfoxide [3]. How Do We Get There? Because most of the radioprotective treatments include chemical solutions, it is important to understand how fast and how deep the radioprotectives can penetrate mineralized bone. Scanning electron microscopy, in combination with a fatigue test, may yield valuable information regarding the integrity of collagenous fiber pattern. Finally, mechanical strength should be compared across the various processing approaches, particularly focusing on fatigue strength, since that is the mode of failure of greatest clinical relevance.

Gamma Radiation Sterilization Reduces the High-cycle Fatigue Life of Allograft Bone.

Sterilization by gamma radiation impairs the mechanical properties of bone allografts. Previous work related to radiation-induced embrittlement of bone tissue has been limited mostly to monotonic testing which does not necessarily predict the high-cycle fatigue life of allografts in vivo. We designed a custom rotating-bending fatigue device to answer the following questions: (1) Does gamma radiation sterilization affect the high-cycle fatigue behavior of cortical bone; and (2) how does the fatigue life change with cyclic stress level? The high-cycle fatigue behavior of human cortical bone specimens was examined at stress levels related to physiologic levels using a custom-designed rotating-bending fatigue device. Test specimens were distributed among two treatment groups (n = 6/group); control and irradiated. Samples were tested until failure at stress levels of 25, 35, and 45 MPa. At 25 MPa, 83% of control samples survived 30 million cycles (run-out) whereas 83% of irradiated samples survived only 0.5 million cycles. At 35 MPa, irradiated samples showed an approximately 19-fold reduction in fatigue life compared with control samples (12.2 × 10(6) ± 12.3 × 10(6) versus 6.38 × 10(5) ± 6.81 × 10(5); p = 0.046), and in the case of 45 MPa, this reduction was approximately 17.5-fold (7.31 × 10(5) ± 6.39 × 10(5) versus 4.17 × 10(4) ± 1.91 × 10(4); p = 0.025). Equations to estimate high-cycle fatigue life of irradiated and control cortical bone allograft at a certain stress level were derived. Gamma radiation sterilization severely impairs the high cycle fatigue life of structural allograft bone tissues, more so than the decline that has been reported for monotonic mechanical properties. Therefore, clinicians need to be conservative in the expectation of the fatigue life of structural allograft bone tissues. Methods to preserve the fatigue strength of nonirradiated allograft bone tissue are needed. As opposed to what monotonic tests might suggest, the cyclic fatigue life of radiation-sterilized structural allografts is likely severely compromised relative to the nonirradiated condition and therefore should be taken into consideration. Methods to reduce the effect of irradiation or to recover structural allograft bone tissue fatigue strength are important to pursue.

Evaluating the Effect of Gamma Irradiation and Steam Sterilization on the Survival and Growth of Composted Sawdust Fungi in Ghana

The growth and survival of some fungi associated with composted and pretreated sawdust particularly for mushroom cultivation were investigated on two growth media; Cooke’s and Oxytetracycline Glucose Yeast Extract (OGYE). Some fungi were isolated during the composting of sawdust over a period of 28 days as well as after pretreatment with gamma irradiation doses of 5, 10, 15, 20, 25 and 32 kGy and moist heat of 100±2oC for 2.5 hours. Fungal counts ranged 4.725.77 log10 CFU/g and 3.44.1 log10 CFU/g respectively for both media. Both pretreatment methods effectively reduced (p<0.05) fungal counts by an average of 1.48 (irradiation) and 2.22 (steam) log-cycle reductions on OGYE while there was an average of 3.13 (irradiation) and 1.10 (steam) Original Research Article Kortei et al.; BMRJ, 7(4): 180-192, 2015; Article no.BMRJ.2015.110 181 log-cycle reduction on Cooke’s. Corresponding radiation sensitivities (D10 values) of 5.94±2.06 kGy and 5.64±1.12 kGy were recorded for fungi on both media respectively. Five species belonging to three genera were isolated on OGYE and among the fungi were Aspergillus niger, Aspergillus fumigatus, Aspergillus ustus, Mucor racemosus and Rhizopus stolonifer. Ten species belonging to four genera were also isolated on Cooke’s medium included Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, Aspergillus ustus, Aspergillus terreus, Aspergillus parasiticus, Aspergillus alutaceus, Rhizopus stolonifer, Fusarium oxysporum and Mucor racemosus. There was an observed reduction (p<0.05) in species diversity after pretreatment. The presence of these microorganisms on sawdust also has serious repercussions on animal and human health.

Mechanical properties of acellular mouse lungs after sterilization by gamma irradiation

Lung bioengineering using decellularized organ scaffolds is a potential alternative for lung transplantation. Clinical application will require donor scaffold sterilization. As gamma-irradiation is a conventional method for sterilizing tissue preparations for clinical application, the aim of this study was to evaluate the effects of lung scaffold sterilization by gamma irradiation on the mechanical properties of the acellular lung when subjected to the artificial ventilation maneuvers typical within bioreactors. Twenty-six mouse lungs were decellularized by a sodium dodecyl sulfate detergent protocol. Eight lungs were used as controls and 18 of them were submitted to a 31kGy gamma irradiation sterilization process (9 kept frozen in dry ice and 9 at room temperature). Mechanical properties of acellular lungs were measured before and after irradiation. Lung resistance (RL) and elastance (EL) were computed by linear regression fitting of recorded signals during mechanical ventilation (tracheal pressure, flow and volume). Static (Est) and dynamic (Edyn) elastances were obtained by the end-inspiratory occlusion method. After irradiation lungs presented higher values of resistance and elastance than before irradiation: RL increased by 41.1% (room temperature irradiation) and 32.8% (frozen irradiation) and EL increased by 41.8% (room temperature irradiation) and 31.8% (frozen irradiation). Similar increases were induced by irradiation in Est and Edyn. Scanning electron microscopy showed slight structural changes after irradiation, particularly those kept frozen. Sterilization by gamma irradiation at a conventional dose to ensure sterilization modifies acellular lung mechanics, with potential implications for lung bioengineering.

The effect of gamma radiation sterilization on dental biomaterials

Biomaterials are used in the field of bone and tissue engineering, orthopaedics and dentistry. Dental biomaterials including commercially available biodegradable materials act as physical barriers to help quicker healing while stimulating the regeneration of periodontal tissues, which is defined as Guided Tissue Regeneration (GTR). Amongst natural and synthetic biomaterials, collagen and aliphatic polyesters, such as polylactic acid (PLA) and poly (lactic-co-glycolic) acid (PLGA) are the most frequently used biomaterials for regenerative therapies due to their excellent biocompatibility and biodegradability. Due to their resorption in the body and interaction with biological systems, the GTR membranes must be sterile and pyrogen free. The sterility and apyrogenicity of the GTR membranes before human use is a regulatory requirement, however the sterilization of biomaterials is challenging due to the physicochemical changes and toxic residues with the commonly used sterilization techniques. The purpose of the present study was to evaluate the effect of gamma radiation and ethylene oxide sterilization on dental biomaterials with analytical, microbiological and histological examinations. PLGA-based GTR dental biomaterial is selected as the most gamma stable membrane according to the FTIR, DSC, TGA, and SEM results. This dental membrane was sterilized with ethylene oxide (EtO) and the effect of sterilization method on PLGA-based membrane was also investigated. Animal experiments were carried out to evaluate the regenerative properties and inflammatory responses of gamma and EtO sterilized PLGA-based GTR membrane after implantation. Histological examinations showed that resorption and bone formation of gamma sterilized PLGA-based GTR membrane was completed in 12 weeks without any inflammatory response; while only 60.095 ± 2.019% of new bone formation was observed with EtO sterilized one. Gamma sterilized PLGA membrane had significantly faster (P < 0.05) resorption and bone formation in comparison with EtO sterilization. In conclusion, the PLGA-based biomaterials could be sterilized safely and time- and cost-effectively with validated radiation doses for the tissue engineering applications.

Thermal analysis on phase sensitive granisetron in situ forming implants

In this study effect of gamma irradiation sterilization and storage conditions on thermal properties of phase sensitive granisetron in situ forming implant (ISFI) was investigated. ISFI was prepared by mixing Poly(DL-lactide-co-glycolide) (PLGA) with dimethylsulfoxide (DMSO):propylene carbonate (PC) (1:1) solvent combination then granisetron HCl was added and homogenized. Following application of gamma irradiation, ISFI was stored at 25oC for 4 months. Differential Scanning Calorimeter (DSC) and Thermogravimetric Analysis-Differential Thermal Analysis (TGA-DTA) analysis were carried out on fresh, irradiated and aged forms of granisetron ISFI. According to DSC and TGA-DTA thermograms and mass loss results application of gamma irradiation and storage of irradiated ISFI at 25oC for 4 months have not significant effect on thermal stability of ISFI.

Effects of gamma radiation sterilization and strain rate on compressive behavior of equine cortical bone

ObjectivesGamma radiation has been widely used for sterilization of bone allograft. However, sterilization by gamma radiation damages the material properties of bone which is a major clinical concern since bone allograft is used in load bearing applications. While the degree of this damage is well investigated for quasi-static and cyclic loading conditions, there does not appear any information on mechanical behavior of gamma-irradiated cortical bone at high speed loading conditions. In this study, the effects of gamma irradiation on high strain rate compressive behavior of equine cortical bone were investigated using a Split Hopkinson Pressure Bar (SHPB). Quasi-static compression testing was also performed. MethodsEquine cortical bone tissue from 8year old retired racehorses was divided into two groups: non-irradiated and gamma-irradiated at 30kGy. Quasi-static and high strain rate compression tests were performed at average strain rates of 0.0045/s and 725/s, respectively. ResultsAgreeing with previous results on the embrittlement of cortical bone when gamma-irradiated, the quasi-static results showed that gamma-irradiation significantly decreased ultimate strength (9%), ultimate strain (27%) and toughness (41%), while not having significant effect on modulus of elasticity, yield strain and resilience. More importantly, contrary to what is typically observed in quasi-static loading, the gamma-irradiated bone under high speed loading showed significantly higher modulus of elasticity (45%), ultimate strength (24%) and toughness (26%) than those of non-irradiated bone, although the failure was at a similar strain. SignificanceUnder high speed loading, the mechanical properties of bone allografts were not degraded by irradiation, in contrast to the degradation measured in this and prior studies under quasi-static loading. This result calls into question the assumption that bone allograft is always degraded by gamma irradiation, regardless of loading conditions. However, it needs further investigation to be translated positively in a clinical setting.

Bone embrittlement and collagen modifications due to high-dose gamma-irradiation sterilization

Bone allografts are often used in orthopedic reconstruction of skeletal defects resulting from trauma, bone cancer or revision of joint arthroplasty. γ-Irradiation sterilization is a widely-used biological safety measure; however it is known to embrittle bone. Irradiation has been shown to affect the post-yield properties, which are attributed to the collagen component of bone. In order to find a solution to the loss of toughness in irradiated bone allografts, it is important to fully understand the effects of irradiation on bone collagen. The objective of this study was to evaluate changes in the structure and integrity of bone collagen as a result of γ-irradiation, with the hypothesis that irradiation fragments collagen molecules leading to a loss of collagen network connectivity and therefore loss of toughness.Using cortical bone from bovine tibiae, sample beams irradiated at 33kGy on dry ice were compared to native bone beams (paired controls). All beams were subjected to three-point bend testing to failure followed by characterization of the decalcified bone collagen, using differential scanning calorimetry (DSC), hydrothermal isometric tension testing (HIT), high performance liquid chromatography (HPLC) and gel electrophoresis (SDS-PAGE). The carbonyl content of demineralized bone collagen was also measured chemically to assess oxidative damage. Barium sulfate staining after single edge notch bending (SEN(B)) fracture testing was also performed on bovine tibia bone beams with a machined and sharpened notch to evaluate the fracture toughness and ability of irradiated bone to form micro-damage during fracture.Irradiation resulted in a 62% loss of work-to-fracture (p≤0.001). There was significantly less micro-damage formed during fracture propagation in the irradiated bone. HPLC showed no significant effect on pentosidine, pyridinoline, or hydroxypyridinoline levels suggesting that the loss of toughness is not due to changes in these stable crosslinks. For DSC, there was a 20% decrease in thermal stability (p<0.001) with a 100% increase (p<0.001) in enthalpy of denaturation (melting). HIT testing also showed a decrease in thermal stability (20% lower denaturation temperature, p<0.001) and greatly reduced measures of collagen network connectivity (p<0.001). Interestingly, the increase in enthalpy of denaturation suggests that irradiated collagen requires more energy to denature (melt), perhaps a result of alterations in the hydrogen bonding sites (increased carbonyl content detected in the insoluble collagen) on the irradiated bone collagen.Altogether, this new data strongly indicates that a large loss of overall collagen connectivity due to collagen fragmentation resulting from γ-irradiation sterilization leads to inferior cortical bone toughness. In addition, notable changes in the thermal denaturation of the bone collagen along with chemical indicators of oxidative modification of the bone collagen indicate that the embrittlement may be a function not only of collagen fragmentation but also of changes in bonding.

Gamma Irradiation and Autoclave Sterilization Peat and Compost as the Carrier for Rhizobial Inoculant Production

Rhizobium is a biofertilizer for leguminous crops. To formulate this form of fertilizer, the suitable sterilization processes of carrier are important. Therefore, the aim of this research was to elucidate the process of gamma irradiation and autoclaving on peat and compost based carriers for rhizobial inoculant production. Carriers with 10% moisture content packing in polyethylene bag could be efficiently sterilized by irradiation at 10-20 kGy, or by autoclaving with tyndallization approach (autoclaving two times in a row at 121ºC for 60 min, with waiting period of 18 hours after each time of autoclaving). The number of Bradyrhizobium sp. PRC008 was in the range of 108-109 cfu/g in both irradiated and autoclaved peat after 6 months storage. However, the numbers of bradyrhizobial cell were reduced in compost sterilized by both methods after one month storage. These results indicated that carrier material had an important influence on inoculant quality, while sterilization processes using gamma irradiation and autoclaving with tyndallization approach could be used for efficient rhizobial inoculant production with peat based carrier.

Sterilization treatments on polysaccharides: Effects and side effects on pectin

Thermal and irradiation treatments represent techniques used for a wide range of materials intended for different applications in the food and medical industry aimed to decontamination and sterilization of different technologic processes. Traditional treatments with vapor combined with pressure, reactive gases, and radiation can be used for sterilization of medical implants and to prevent food deterioration. On the other side, these treatments can be employed to obtain a controlled distribution of molecular weight of polymers, as reported by literature.Pectin, as many polysaccharides, may be susceptible to side effects and modifications caused by the sterilization treatments. In this perspective, physico-chemical and biological properties of pectin powders and solutions were investigated after sterilization. Traditional methods, i.e., ethylene oxide, gamma irradiation and moist heat sterilization, were compared and their effects on pectin structure were evaluated. Results indicate that each sterilization procedure affected pectin powders and solutions, resulting in a decrease of viscosity, molecular weight and rheological properties with respect of non-sterilized samples. For sterilized powders properties were better retained than for sterilized solutions, being EtO the optimal method for pectin powders and gamma rays, especially at low doses, for pectin solutions, independently of their structure and initial degree of esterification. Moist heat sterilization was found to significantly depolymerize pectin chains in solution, with the production of cytotoxic residues.

Gamma Radiation Sterilization Leads to Tibial Insert Damage

Gamma Radiation Sterilization Leads to Tibial Insert Damage