Sterilization Of Medical Products Research Articles

Effects of gamma radiation on cyclic olefin copolymers with varied norbornene content: Impacts on structure and properties at sterilization doses

Cyclic olefin copolymer (COC) is a transparent amorphous plastic known for its chemically inertness, biocompatibility, low density, and easy processability. These qualities have led to its widespread adoption in various cutting-edge applications, including the medical, packaging, optical and microelectronics. Radiation sterilization, utilizing high-energy irradiation, is a method for achieving highly effective sterilization of medical products. However, this process can induce changes in the color and properties of the COC materials. In order to comprehend the effects of ionizing radiation on COC, it is crucial to investigate the underlying reaction mechanisms. In this work, the effects of γ-ray irradiation on COC with different norbornene contents were examined. The finding revealed that tertiary alkyl radical content and the degree of oxidative degradation increased with an increase in norbornene content. Furthermore, the macroscopic properties experienced notable shifts, including decreased thermal stability, lower glass transition temperature and the change in color from colorless and transparent to yellow-green. Analysis of the melt index indicated a dominance of cross-linking phenomena with increased absorbed dose for COC with a norbornene content of 35%, while the melt flow rate steadily accelerated with the increase of absorbed dose for COC with norbornene content of 46%, 52% and 57%, leading to a predominant cracking behavior. The variation in tensile properties of the four COCs before and after irradiation were minimal, not exceeding 3%. Overall, this investigation sheds light on the intricate effects of ionizing radiation on COC and highlights the importance of understanding these mechanisms for practical applications.

Dosimetry for low-energy electron beam applications at Fraunhofer FEP

Abstract Accelerating electrons to achieve chemical and biological effects is a well-established competence of Fraunhofer FEP. Today, there is a large variety of low-energy electron beam applications with a broad range of absorbed doses, e.g. modification of plastics, plasma-chemical syntheses, pollutant removal in wastewaters and exhaust gases, sterilization of medical products, disinfection of seeds, biocompatible functionalization of implants and stimulation of biotechnological processes. This calls for reliable, sensitive, and flexible methods for dosimetry. Radiochromic films are suitable tools to measure electron dose distributions for the characterization and quality control of Fraunhofer FEP’s irradiation facilities. Risø B3 radiochromic film from DTU Health Tech, the dosimeter of choice at FEP, reliably detects doses in the range of 10–100 kGy. However, with new upcoming applications, doses in the single-digit kGy range and even lower come to the fore. Hence, the palette of dosimeters at FEP must be extended. Gafchromic’s HD-V2 film is a welcome complement and widens the accessible dose range down to 10 Gy. Using a UV-VIS spectrophotometer for read-out of the films and custom analysis algorithms further increase the sensitivity of the dosimetric setup. Additionally, dosimeters based on the optically stimulated luminescence (OSL) of beryllium oxide offer a wide dose range and high sensitivity. They were used to measure doses induced by secondary X-ray components to gain more information about a specific radiation field. The work gives an overview of the dosimetric toolbox at Fraunhofer FEP and the efforts to implement new methods of detection for low-dose applications and X-ray dosimetry.

Effect of ionizing radiation on the physicochemical and functional properties of silicone rubber and silicone foley catheter

The utilization of ionizing radiation, such as gamma ray and electron beam, in medical product sterilization has seen significant growth in recent years, driven by concerns regarding the safety of ethylene oxide sterilization. This paper examines the effects of these radiation modalities on silicone rubber, and its applicability on a silicone rubber-containing medical device, specifically a silicone foley catheter, by assessing its functional properties before and after irradiation at varying absorbed doses.Analysis of the irradiated samples revealed the presence of carbonyl groups, indicating radiation-induced oxidation. Gamma irradiation did not exhibit fundamental changes in the polymer structure but showed degradation at higher temperatures due to oxidation mechanisms. Moreover, a significant decrease in elongation at break was observed indicating that the already highly crosslinked silicone rubber experienced additional crosslinking affecting its mechanical properties. In contrast, both irradiations led to degradation, as evidenced by a decrease in TG residue. However, the mechanical properties, including tensile strength and elongation at break, were less affected. This suggests limited crosslinking and fragmentation of the polymer backbone. At a lower dose, a decrease in both strength and elongation indicated the formation of branched structures, limiting mobility, introducing irregularities, and weakening the polymer's overall strength. Despite these effects, the functional properties of the silicone foley catheter were practically unaffected at low absorbed doses, except for the discoloration of the syringe ports. Overall, the study provides insights into the effects of ionizing radiation on silicone rubber, highlighting the complex interplay between crosslinking, chain scission, and oxidation mechanisms. The findings contribute to understanding the changes in the polymer's structure and properties under different radiation modalities and doses, facilitating the development of effective sterilization techniques for medical devices containing silicone rubber.

Radiation processing in India: The voyage and present status

Establishment of first gamma radiation facility for sterilization of medical products under auspices of UNDP by the Department of Atomic Energy (DAE) in the year 1974 gave a big boost to radiation related applied research activities in India. Today radiation related research is not confined to DAE units but it is being carried out in many universities and other institutes of India. A very positive outcome of this has been that, many industries are adopting radiation technologies. Presently 18 electron beams and 24 gamma processing plants are commercially operating in India. Radiation applications are being explored for radiolysis based advanced oxidation processes (AOPs) for treatment of waste water and treatment of dry sewage sludge, synthesis of grafted membranes for separation and energy storage purpose, synthesis of high recovery shape memory polymers, synthesis of chemi-resistive, electromechanical and peizo-resistive sensors and other applications. The article briefly describes various activities being presently being pursued or have been completed in recent past. Efforts have been put to guesstimate the direction of the near future activities in-view of the present activities.

An Overview of Electron Accelerator Applications in Environmental Protection with an Emerging Pollutants Decomposing approach

Bachground: In recent years, problems related to environmental damage and natural resource degradation are receiving increased attention from researchers throughout the world. This occurs mostly, through un-eco-friendly technology used to produce industrial products. Therefore, eco-friendly science and technology (green technology) which can empower and control the existing coal power plant for the virtue of society and the earth is required. Today, the design and application of electron accelerator has been well developed due to reliability, larger capacity, greater energy range, and cost reduction. Technologies that use particle accelerators are considered critical to advance high-tech processes in various economic fields, including material processing, sterilization of medical products, environmental protection, medicine, cargo inspection, chemical analysis, nuclear energy, etc. High-energy and high-power beams pose the ability to alter the physical, chemical, and biological properties of materials on an industrial scale. This technology has received more attention than other conventional treatment methods due to the need for smaller areas, high electrical efficiency, and production of by-products such as fertilizers. The electronic beam process in the treatment of off-gas, wastewater, and sludge, as well as the decomposition of emerging contaminants, is mentioned as a non-chemical, additive-free process that uses radiolysis to effectively decompose contaminants. The literature addresses various applications of electron accelerators in order to modify the physical, chemical, or biological properties of industrial pollutants in the liquid, solid, and gas phases through treatment by ionizing radiation to control environmental pollution. Many advantages can be achieved through this method, which is known as radiation processing.

THE POSSIBILITY OF APPLICATION OF PYROMETRIC METHOD IN INDUSTRIAL DOSIMETRY OF ELECTRON BEAM RADIATION

Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of material representative of the object to be processed. Commonly, such measurements are carried out using the disposable chemical dosimeters placed in the phantom at the nodes of the 3D grid. Such a procedure is very laborious and costly in terms of the consumption of dosimeters. In the work, we investigated the possibility of using pyrometric method for prompt mapping of the absorbed dose. The studies were carried out using a rectangular phantom in the form of a set of expanded polystyrene plates, which is exposed to a scanned electron beam. The temperature and absorbed dose distributions in the phantom were measured. A linear dependence between them has been established. The calculation of the absorbed dose profile was also performed by MC simulations. Satisfactory agreement of the calculated dose distribution with the measured one is shown. The limitations of applicability of the proposed method are determined.

Effect of electron beam irradiation on filtering facepiece respirators integrity and filtering efficiency

Abstract The outbreak of the COVID-19 pandemic has shown that the demand for medical masks and respirators exceeds the current global stockpile of these items, and there is a dire need to increase the production capacity. Considering that ionizing radiation has been used for sterilization of medical products for many years and electron beam (EB) irradiation enables the treatment of huge quantities of disposable medical products in a short time this method should be tested for the mask’s decontamination. In this work, three different filtering facepiece respirators (FFRs) were irradiated with electron beams of 12 kGy and 25 kGy. The results confirmed that the decrease in filtration efficiency after irradiation of all respirators results from the elimination of the electric charge from the polypropylene (PP) fibers in the irradiation process. Moreover, the applied doses may affect the thermal stability of PP fabrics, while filtering materials structure and integrity have not changed after irradiation.

ESTIMATION OF BBU THRESHOLD CURRENT IN AN INHOMOGENEOUS ACCELERATING SECTION

In this work we describe the procedure of estimation of regenerative beam blowup threshold current in an inhomogeneous accelerating section. The self-consistent problem of transverse motion of particles in the field of dipole mode excited by the beam is solved. The distribution of dipole field near the structure axis and the energy variation of beam particles were calculated before simulating the transverse dynamics. The threshold current for S-band industrial linac designed for radiation sterilization of medical products is estimated.

Degradation studies of a commercial radiation‐resistant polypropylene sterilized by gamma and electron beam technology before and after subsequent accelerated aging cycles

ABSTRACTIrradiation is one of the most widely used technologies for sterilization of medical products. Unfortunately, some polymers in the medical field are susceptible to high‐energy radiation. In the case of polypropylene, this leads to yellowing and embrittlement due to degradation mechanisms. This study compares the impact of gamma and eBeam sterilizations at a dose of 45 kGy on a commercially available, radiation‐resistant polypropylene in combination with accelerated aging studies. Mechanical behavior as well as yellowing, accompanied by structural investigations like molar mass characterization and crystallinity analysis, have been investigated. It is shown that eBeam has less damaging effects compared with gamma irradiation. This is shown by an initial drop in elongation at break by 46% for gamma irradiated samples in contrast to 24% decrease using eBeam irradiation. Also, an initial drop in molar mass by 43% was found for gamma irradiated samples and by 27% for eBeam. Change in color was observed by an initial increase in the yellowness index of 42% at samples after gamma irradiation, respectively, of 22% for eBeam irradiated samples. Interestingly, molar mass remained constant during aging, whereas yellowing and Embrittlement further change. Additionally, empirical equations were found, which describe the experimental data. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48436.

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.

Sterility and Safety Validation for Transport Packaging of Organs and Tissues

The bags used in the transport of organs and tissues must be sterile, nontoxic, pyrogen free, and must serve as a barrier throughout their useful life. The goal of this study was to show the sterility, safety, and functionality of the bags subjected to irradiation, through validated procedures and techniques. The selected sterilization method was the use of gamma radiation. The sterilization dose was determined based on validated standards for the sterilization of medical products, ISO 11137-2: 2013 and ISO/TS 13004: 2013, using the Verification Dose Maximum method on samples belonging to 3 manufacturing lots. The ISO 10993-5: 2009 standard was used in the cytotoxicity tests, by means of extracts test and quantitative technique of MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The tests to determine the expiration date of the kit were performed by ASTM F1980, accelerated aging, and ASTM D3078 to evaluate hermeticity. The irradiation dose validated to reach the required sterility safety level was 22.5 kGy. The constituent materials and the sterilization method do not generated cellular toxicity, and the product was not modified during the simulated time of 5 years. Sterilization by irradiation is a method that leaves no residue, does not harm the properties of the material because it is conducted in cold, and as the sterilizing agent, the energy absorbed by the product is highly penetrating and can be treated in its final packaging, with no risk of postcontamination. It is for this reason that it is prioritized over other methods of sterilization.

Effective gamma-ray sterilization and characterization of conductive polypyrrole biomaterials

Conductive polymers, including polypyrrole (PPy), have been extensively explored to fabricate electrically conductive biomaterials for bioelectrodes and tissue engineering scaffolds. For their in vivo uses, a sterilization method without severe impairment of original material properties and performance is necessary. Gamma-ray radiation has been commonly applied for sterilization of medical products because of its simple and uniform sterilization without heat generation. Herein we describe the first study on gamma-ray sterilization of PPy bioelectrodes and its effects on their characteristics. We irradiated PPy bioelectrodes with different doses (0–75 kGy) of gamma-rays. Gamma-ray irradiation of the PPy (γ-PPy) increased the oxygenation and hydrophilicity of the surfaces. Interestingly, gamma-ray irradiation did not alter the electrical impedances and conductivities of the PPy substrates. Additionally, γ-PPy prepared with various dopants (e.g., para-toluene sulfonate, polystyrene sulfonate, and chlorine) showed the electrochemical properties similar to the non-irradiated control. Gamma-ray irradiation at doses of ≥15 kGy was required for effective sterilization as evidenced by complete eradication of gram positive and negative bacteria. γ-PPy substrates also showed cytocompatibility similar to untreated control PPy, indicating no substantial alteration of cytocompatibility. In conclusion, gamma ray sterilization is a viable method of sterilization of conducting polymer-based biomaterials for biomedical applications.

Professor Glyn O. Phillip's legacy within the IAEA programme on radiation and tissue banking.

Professor Phillips began his involvement in the implementation of this important IAEA programme, insisting that there were advantages to be gained by using the ionizing radiation technique to sterilize human and animal tissues, based on the IAEA experience gained in the sterilization of medical products. The outcome of the implementation of the IAEA programme on radiation and tissue banking demonstrated that Professor Phillips was right in his opinion.

Electron beam induced modifications in flexible biaxially oriented polyethylene terephthalate sheets: Improved mechanical and electrical properties

In the present work, we have studied the effects of electron beam irradiation (with dose ranging from 2 to 32 kGy) on mechanical and electrical properties of biaxially oriented polyethylene terephthalate (BOPET) sheets. The sol-gel analysis, Fourier transformation infra-red (FTIR), X-ray photoelectron spectroscopy (XPS) characterizations of the irradiated BOPET sheets suggest partial cross-linking of PET chains through the diethylene glycol (DEG). The mechanical properties of BOPET, such as, tensile strength, Young's modulus and electrical resistivity shows improvement with increasing dose and saturate for doses >10 kGy. The improved mechanical properties and high electrical resistivity of electron beam modified BOPET sheets may have additional advantages in applications, such as, packaging materials for food irradiation, medical product sterilization and electronic industries.

ILU industrial electron accelerators for medical-product sterilization and food treatment

Pulse linear electron accelerators of the ILU type have been developed and produced by the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, for more than 30 years. Their distinctive features are simplicity of design, convenience in operation, and reliability during long work under conditions of industrial production. ILU accelerators have a range of energy of 0.7–10 MeV at a power of accelerated beam of up to 100 kW and they are optimally suitable for use as universal sterilizing complexes. The scientific novelty of these accelerators consists of their capability to work both in the electron-treatment mode of production and in the bremsstrahlung generation mode, which has high penetrating power.

Electroresponsive Supramolecular Graphene Oxide Hydrogels for Active Bacteria Adsorption and Removal

Bacteria contamination in drinking water and medical products can cause severe health problems. However, currently available sterilization methods, mainly based on the size-exclusion mechanism, are typically slow and require the entire contaminated water to pass through the filter. Here, we present an electroresponsive hydrogel based approach for bacteria adsorption and removal. We successfully engineered a series of graphene oxide hydrogels using redox-active ruthenium complexes as noncovalent cross-linkers. The resulting hydrogels can reversibly switch their physical properties in response to the applied electric field along with the changes of oxidation states of the ruthenium ions. The hydrogels display strong bacteria adsorbing capability. A hydrogel of 1 cm(3) can adsorb a maximum of 1 × 10(8) E. coli. The adsorbed bacteria in the hydrogels can then be inactivated by a high voltage electric pulse and removed from the hydrogels subsequently. Owing to the high bacteria removal rate, reusability, and low production cost, these hydrogels represent promising candidates for the emergent sterilization of medical products or large-scale purification of drinking water.

High-dose electron beam sterilization of soft-tissue grafts maintains significantly improved biomechanical properties compared to standard gamma treatment.

Allografts have gained increasing popularity in anterior cruciate ligament (ACL) reconstruction. However, one of the major concerns regarding allografts is the possibility of disease transmission. Electron beam (Ebeam) and Gamma radiation have been proven to be successful in sterilization of medical products. In soft tissue sterilization high dosages of gamma irradiation have been shown to be detrimental to biomechanical properties of grafts. Therefore, it was the objective of this study to compare the biomechanical properties of human bone-patellar tendon-bone (BPTB) grafts after ebeam with standard gamma irradiation at medium (25 kGy) and high doses (34 kGy). We hypothesized that the biomechanical properties of Ebeam irradiated grafts would be superior to gamma irradiated grafts. Paired 10 mm-wide human BPTB grafts were harvested from 20 donors split into four groups following irradiation with either gamma or Ebeam (each n = 10): (A) Ebeam 25 kGy, (B) Gamma 25 kGy, (C) Ebeam 34 kGy (D) Gamma 34 kGy and ten non-irradiated BPTB grafts were used as controls. All grafts underwent biomechanical testing which included preconditioning (ten cycles, 0-20 N); cyclic loading (200 cycles, 20-200 N) and a load-to-failure (LTF) test. Stiffness of non-irradiated controls (199.6 ± 59.1 N/mm) and Ebeam sterilized grafts did not significantly differ (152.0 ± 37.0 N/mm; 192.8 ± 58.0 N/mm), while Gamma-irradiated grafts had significantly lower stiffness than controls at both irradiation dosages (25 kGy: 126.1 ± 45.4 N/mm; 34 kGy: 170.6 ± 58.2 N/mm) (p < 0.05). Failure loads at 25 kGy were significantly lower in the gamma group (1,009 ± 400 N), while the failure load was significantly lower in both study groups at high dose irradiation with 34 kGy (Ebeam: 1,139 ± 445 N, Gamma: 1,073 ± 617 N) compared to controls (1,741 ± 304 N) (p < 0.05). Creep was significantly larger in the gamma irradiated groups (25 kGy: 0.96 ± 1.34 mm; 34 kGy: 1.06 ± 0.58 mm) than in the Ebeam (25 kGy: 0.50 ± 0.34 mm; 34 kGy: 0.26 ± 0.24 mm) and control (0.20 ± 0.18 mm) group that did not differ significantly. Strain difference was not different between either control or study groups (controls: 1.0 ± 0.03; Ebeam 34 kGy 1.04 ± 0.018; Gamma 34 kGy 1.0 ± 0.028; 25 kGy: 1.4 ± 2,0; 34 kGy: 1.1 ± 1.1). The most important result of this study was that ebeam irradiation showed significantly less impairment of the biomechanical properties than gamma irradiation. Considering the results of this study and the improved control of irradiation application with electronic beam, this technique might be a promising alternative in soft-tissue sterilization.

Sterilization of Medical Products from Collagen by Means of Supercritical CO2

AbstractCollagen is increasingly used as material for medical devices because of its excellent biocompatibility. To achieve long‐term durability, the collagen materials are dried and subsequently sterilized. Most common sterilization methods are unsuitable as they cause denaturation. Currently, only ethylenoxide or γ irradiation preserves the microscopic and macroscopic collagen structure. However, both methods require high safety standards and include the risk of uncontrolled crosslinking or cleavage of protein chains. Here, supercritical carbon dioxide is used for the sterilization of different collagen devices. Thereby, the influence of pressure, temperature, sterilization aid and dosage, and different operation modes is determined. The method is a promising alternative to existing sterilization techniques.

P195: Orthopedic surgical infections caused by rapidly growing mycobacteria: integrative review of literature

Infections due to rapidly growing mycobacteria (RGM) are strongly related to failures in the processes of cleaning, disinfection and sterilization of medical products.