Residual ethylene oxide in medical devices and device material

Development of the headspace gas chromatography-tandem mass spectrometry method for ethylene oxide and ethylene chlorohydrin residue in medical devices

RATIONALE

Ethylene oxide (EO) sterilization is commonly employed for the sterilization of medical devices and has a very high market share. However, EO and its metabolite ethylene chlorohydrin (ECH) are toxic to humans. In compliance with the classification and residue limits of medical devices defined by ISO 10993-7, our study established two extraction methods for the testing of EO and ECH.

METHODS

The first method involves simulated-use extraction using water as the extraction solvent. While the second, exhaustive extraction, directly extracts sample through headspace sampling analysis. Gas chromatography-tandem mass spectrometry in multiple reaction monitoring mode was utilized, requiring only 16 min. Then, the developed method was applied to assess 10 commercially available medical devices sterilized by EO.

RESULTS

In simulated-use extraction, calibration curves were evaluated in the range of 1-100 and 5-500 μg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 85.0% to 95.2% and from 94.8% to 102.4%. In exhaustive extraction, calibration curves spanned 0.5-50 and 2-200 μg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 101.6% to 102.1% for EO and from 98.1% to 102.2% for ECH. After analysis of the 10 commercially available medical devices, two cotton swabs were found to have ECH of 35.1 and 28.4 μg per device, and four medical devices were found to have EO with concentration below the limit of quantification. Meanwhile, we found that the EO internal standard (propylene oxide) recommended by ISO 10993-7 had interference problems with other similar substances and was not suitable as an internal standard for EO.

CONCLUSIONS

This study offers a sensitive and straightforward analytical approach to EO and ECH residues in a variety of medical devices. In addition, the results show that the EO or ECH content of these types of medical devices in our study falls below the regulatory limits, therefore instilling confidence among consumers regarding their safe use.

Effect of Sterilization Methods on Chemical and Physical-Mechanical Properties of Cotton Compresses

The aim of this work was to determine the changes in the chemical and physical-mechanical properties of gauze compresses under the influence of various sterilizations. Gauze compresses are made of cotton; therefore, all methods used focused on cotton. The methods used to test possible damage to cotton materials (pH value (pH paper, KI starch paper), yellowing test, Fehling reaction, reaction to the formation of Turnbull blue (Berlin blue), microscopic staining with methylene blue and swelling reaction with Na-zincate) did not show that the sterilizations affected the cotton compresses. The morphological characteristics were examined with a scanning electron microscope (SEM). The SEM images showed that there were no morphological changes in the cotton fibers. FTIR-ATR spectroscopy revealed that the sterilization processes did not alter the characteristic bands of the cotton. The length of the macromolecules was increased (DP), showing that the sterilization processes had affected the cotton. The results of the wet strength test followed. The samples showed values below 100%, with the exception of two samples. It is known from theory that the relative wet strength is less than 100% when the material is damaged. The t-test performed on the strength results showed that the p-value was greater than 0.05 for all samples tested, with the exception of one sample. The degree of swelling capacity was determined, with non-sterilized samples having the highest capacity, followed by samples sterilized with ethylene oxide and then samples sterilized by steam sterilization. The results obtained are a contribution to the innovation of the topic of this work and a scientific confirmation for manufacturers and anyone interested in the influence of the sterilization process on natural fibers (cotton).

Evaluation of an early-stage prototype polyurethane femoral head implant for hip arthroplasty

Introduction

Thi study evalautes a new bone-preserving femoral head cover that mimics the articular cartilage of the femoral head.

Methods

A specially developed polyurethane (PU) was evaluated in biocompatibility (cytotoxicity test) and mechanical response to tensile loading. In the cytotoxicity test, steam sterilized (SS) and ethylene oxide sterilized (EtO) PU samples were incubated separately in a cell culture medium. The seeded cell line MG-63 was then added to these sample-incubated cell culture mediums. One negative control group and one positive control group were also evaluated. The cells in each group were cultured for seven days before being quantified using the alamarBlue assay. In the mechanical test, the femoral head cover implants were separated into three groups of three samples. Each group represented a different implant insertion idea: direct insertion (uc sample) and another two insertion modes (is and ss samples) representing implants with enclosure mechanisms. The test consisted of distance-controlled cyclic tensile loadings followed by a failure test.

Results

The cytotoxicity test results show no significant difference in fluorescence intensity between the negative control, the three SS groups, and one EtO group (P > 0.05). However, the other two EtO groups exhibit significantly lower fluorescence intensity compared with the negative control (P < 0.05). In the mechanical test, the is samples have the highest cyclic loading force at 559.50 ± 51.41 N, while the uc samples exhibit the highest force in the failure test at 632.16 ± 50.55 N. There are no significant differences (P > 0.05) among the uc, is, and ss groups in terms of stiffness.

Conclusion

The cytotoxicity test and the mechanical experiment provide initial assessments of the proposed PU femoral head cover implant. The evaluation outcomes of this study could serve as a foundation for developing more functional design and testing methods, utilizing numerical simulations, and developing animal/clinical trials in the future.

The presence of 3D printing in orthopedics: A clinical and material review

The field of additive manufacturing, 3D printing (3DP), has experienced an exponential growth over the past four decades, in part due to increased accessibility. Developments including computer-aided design and manufacturing, incorporation of more versatile materials, and improved printing techniques/equipment have stimulated growth of 3DP technologies within various industries, but most specifically the medical field. Alternatives to metals including ceramics and polymers have been garnering popularity due to their resorbable properties and physiologic similarity to extracellular matrix. 3DP has the capacity to utilize an assortment of materials and printing techniques for a multitude of indications, each with their own associated benefits. Within the field of medicine, advances in medical imaging have facilitated the integration of 3DP. In particular, the field of orthopedics has been one of the earliest medical specialties to implement 3DP. Current indications include education for patients, providers, and trainees, in addition to surgical planning. Moreover, further possibilities within orthopedic surgery continue to be explored, including the development of patient-specific implants. This review aims to highlight the use of current 3DP technology and materials by the orthopedic community, and includes comments on current trends and future direction(s) within the field.

Chemical Characterization and Non-targeted Analysis of Medical Device Extracts: A Review of Current Approaches, Gaps, and Emerging Practices

The developers of medical devices evaluate the biocompatibility of their device prior to FDA's review and subsequent introduction to the market. Chemical characterization, described in ISO 10993-18:2020, can generate information for toxicological risk assessment and is an alternative approach for addressing some biocompatibility end points (e.g., systemic toxicity, genotoxicity, carcinogenicity, reproductive/developmental toxicity) that can reduce the time and cost of testing and the need for animal testing. Additionally, chemical characterization can be used to determine whether modifications to the materials and manufacturing processes alter the chemistry of a patient-contacting device to an extent that could impact device safety. Extractables testing is one approach to chemical characterization that employs combinations of non-targeted analysis, non-targeted screening, and/or targeted analysis to establish the identities and quantities of the various chemical constituents that can be released from a device. Due to the difficulty in obtaining a priori information on all the constituents in finished devices, information generation strategies in the form of analytical chemistry testing are often used. Identified and quantified extractables are then assessed using toxicological risk assessment approaches to determine if reported quantities are sufficiently low to overcome the need for further chemical analysis, biological evaluation of select end points, or risk control. For extractables studies to be useful as a screening tool, comprehensive and reliable non-targeted methods are needed. Although non-targeted methods have been adopted by many laboratories, they are laboratory-specific and require expensive analytical instruments and advanced technical expertise to perform. In this Perspective, we describe the elements of extractables studies and provide an overview of the current practices, identified gaps, and emerging practices that may be adopted on a wider scale in the future. This Perspective is outlined according to the steps of an extractables study: information gathering, extraction, extract sample processing, system selection, qualification, quantification, and identification.

Defining a Path Toward the Use of Fast-Scan Cyclic Voltammetry in Human Studies

Fast Scan Cyclic Voltammetry (FSCV) has been used for decades as a neurochemical tool for in vivo detection of phasic changes in electroactive neurotransmitters in animal models. Recently, multiple research groups have initiated human neurochemical studies using FSCV or demonstrated interest in bringing FSCV into clinical use. However, there remain technical challenges that limit clinical implementation of FSCV by creating barriers to appropriate scientific rigor and patient safety. In order to progress with clinical FSCV, these limitations must be first addressed through (1) appropriate pre-clinical studies to ensure accurate measurement of neurotransmitters and (2) the application of a risk management framework to assess patient safety. The intent of this work is to bring awareness of the current issues associated with FSCV to the scientific, engineering, and clinical communities and encourage them to seek solutions or alternatives that ensure data accuracy, rigor and reproducibility, and patient safety.

The Emerging Role of Decellularized Plant-Based Scaffolds as a New Biomaterial

The decellularization of plant-based biomaterials to generate tissue-engineered substitutes or in vitro cellular models has significantly increased in recent years. These vegetal tissues can be sourced from plant leaves and stems or fruits and vegetables, making them a low-cost, accessible, and sustainable resource from which to generate three-dimensional scaffolds. Each construct is distinct, representing a wide range of architectural and mechanical properties as well as innate vasculature networks. Based on the rapid rise in interest, this review aims to detail the current state of the art and presents the future challenges and perspectives of these unique biomaterials. First, we consider the different existing decellularization techniques, including chemical, detergent-free, enzymatic, and supercritical fluid approaches that are used to generate such scaffolds and examine how these protocols can be selected based on plant cellularity. We next examine strategies for cell seeding onto the plant-derived constructs and the importance of the different functionalization methods used to assist in cell adhesion and promote cell viability. Finally, we discuss how their structural features, such as inherent vasculature, porosity, morphology, and mechanical properties (i.e., stiffness, elasticity, etc.) position plant-based scaffolds as a unique biomaterial and drive their use for specific downstream applications. The main challenges in the field are presented throughout the discussion, and future directions are proposed to help improve the development and use of vegetal constructs in biomedical research.

A Preclinical Animal Model for the Study of Scaffold-Guided Breast Tissue Engineering

Scaffold-guided breast tissue engineering (SGBTE) has the potential to transform reconstructive breast surgery. Currently, there is a deficiency in clinically relevant animal models suitable for studying novel breast tissue engineering concepts. To date, only a small number of large animal studies have been conducted and characterization of these large animal models is poorly described in the literature. Addressing this gap in the literature, this publication comprehensively describes our original porcine model based on the current published literature and the experience gained from previous animal studies conducted by our research group. In a long-term experiment using our model, we investigated our SGBTE approach by implanting 60 additively manufactured bioresorbable scaffolds under the panniculus carnosus muscle along the flanks of 12 pigs over 12 months. Our model has the flexibility to compare multiple treatment modalities where we successfully investigated scaffolds filled with various treatments of immediate and delayed fat graft and augmentation with platelet rich plasma. No wound complications were observed using our animal model. We were able to grow clinically relevant volumes of soft tissue, which validates our model. Our preclinical large animal model is ideally suited to assess different scaffold or hydrogel-driven soft tissue regeneration strategies. Impact statement The ability to regenerate soft tissue through scaffold-guided tissue engineering concepts can transform breast reconstructive surgery. We describe an original preclinical large animal model to study controlled and reproducible scaffold-guided breast tissue engineering (SGBTE) concepts. This model features the flexibility to investigate multiple treatment conditions per animal, making it an efficient model. We have validated our model with a long-term experiment over 12 months, which exceeds other shorter published studies. Our SGBTE concept provides a more clinically relevant approach in terms of breast reconstruction. Future studies using this model will support the translation of SGBTE into clinical practice.

Effects of Two Melt Extrusion Based Additive Manufacturing Technologies and Common Sterilization Methods on the Properties of a Medical Grade PLGA Copolymer

Although bioabsorbable polymers have garnered increasing attention because of their potential in tissue engineering applications, to our knowledge there are only a few bioabsorbable 3D printed medical devices on the market thus far. In this study, we assessed the processability of medical grade Poly(lactic-co-glycolic) Acid (PLGA)85:15 via two additive manufacturing technologies: Fused Filament Fabrication (FFF) and Direct Pellet Printing (DPP) to highlight the least destructive technology towards PLGA. To quantify PLGA degradation, its molecular weight (gel permeation chromatography (GPC)) as well as its thermal properties (differential scanning calorimetry (DSC)) were evaluated at each processing step, including sterilization with conventional methods (ethylene oxide, gamma, and beta irradiation). Results show that 3D printing of PLGA on a DPP printer significantly decreased the number-average molecular weight (Mn) to the greatest extent (26% Mn loss, p < 0.0001) as it applies a longer residence time and higher shear stress compared to classic FFF (19% Mn loss, p < 0.0001). Among all sterilization methods tested, ethylene oxide seems to be the most appropriate, as it leads to no significant changes in PLGA properties. After sterilization, all samples were considered to be non-toxic, as cell viability was above 70% compared to the control, indicating that this manufacturing route could be used for the development of bioabsorbable medical devices. Based on our observations, we recommend using FFF printing and ethylene oxide sterilization to produce PLGA medical devices.

Reuse of Filtering Facepiece Respirators in the COVID-19 Era

The current COVID-19 pandemic has resulted in an immense and unforeseen increase in demand for personal protective equipment (PPE) for healthcare workers worldwide. Amongst other products, respirator masks are crucial to protect the users against transmission of the virus. Decontamination and reuse of the existing stock could be a solution to the shortage of new respirators. Based upon existing studies, it was found that (I) a solid quality control method is essential to test product reuse, (II) in-depth evaluation of the different parts of the filtering facepiece respirator (FFR) should be considered, and (III) communication of the reuse cycle is essential to take track of the amount of reuse, as this is limited to ensure quality. The goal of this paper is two-fold. First, we identify the impact of decontamination on the different parts of the FFRs and how the quality control should be performed. Two different types of FFRs are analysed within this paper, resulting in the recommendation of combining quantitative respirator mask fit testing with a thorough sensory evaluation of decontaminated FFRs to qualify them for reuse. Secondly, the possibilities of communication of this reuse to the eventual user are mapped through in-depth reasoning.

Evaluation of Sterilization Performance for Vaporized-Hydrogen-Peroxide-Based Sterilizer with Diverse Controlled Parameters

Hydrogen-peroxide-based low-temperature sterilization is a new sterilization technology for temperature-dependent medical devices. The effect of the process parameters of hydrogen-peroxide-based sterilizer on the sterilization performance of process challenge devices (PCDs) needs to be investigated. Sterilant amount, operating temperature, vacuum pressure, diffusion time, and chamber loading of the sterilizer on the sterilization performance of PCDs were adjusted. Seven PCDs with various morphologies and material containing biological indicators (BI) (EZTest, Geobacillus stearothermophilus) were used to evaluate the sterilization performance. The sterilization success rates of PCDs were 86, 71, and 57% with controlled temperature and pressure, diffusion time, and sterilant volume injection, respectively. The PCD material and structure also obviously affected sterilization performance. The sterilization of PCD A is the least successful for all parameters. Meanwhile, the sterilization of PCD B was influenced by the diffusion time and the sterilant injection volume. PCD B and PCD C were successfully sterilized by controlling the temperature and pressure. The weights and volume of the sterilization loading chamber resulted in a different sterilization performance. Sterilization performances of PCD 1, PCD 2, and PCD 3 were <70, <90, and 100%, respectively. Sterilant volume, sterilant diffusion time, pressure, temperature, PCD types, and chamber loading were proven to be important process parameters of sterilizer that affect the sterilization performance of vaporized-hydrogen-peroxide-based sterilizers.

Application of Gamma Radiation on Hard Gelatin Capsules as Sterilization Technique and Its Consequences on the Chemical Structure of the Material

Hard capsules are made from gelatin, an organic polymer obtained through the hydrolysis of collagen present in animal tissues. Gelatin can be degraded by microorganisms and some strategies can be used to control contaminating micro-organisms. Gamma irradiation is considered as an effective sterilization method; however, its application can alter the chemical structure of the irradiated product. Samples of hard gelatin capsules were irradiated at doses of 5, 15, and 25 kGy at room temperature. The characterizations of the physical and chemical effects were evaluated by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry techniques. Furthermore, hard gelatin capsule samples were dissolved and inoculated with Bacillus subtilis, a Gram-positive spore-forming bacterium, to evaluate the effect of gamma ray radiation on bacterial counts. The results showed that gamma radiation did not interfere on physical parameters of the capsule, such as moisture content, mass, body and cap length, and disintegration time. Nevertheless, differential scanning calorimetry results demonstrated changes in the glass transition temperature, indicating the formation of crosslinking in irradiated capsules. It was observed that there were significant reductions on the inoculated bacterial population starting from the lowest irradiation dose and there was no detection of bacterial growth from the 15 kGy dose, while in the non-irradiated samples were found with 10⁴ CFU mL^-1 of bacteria. Therefore, this work concludes that the gamma radiation is effective on the reduction of the microbial population, cause discrete physical-chemical alterations, and could be used as a hard capsule sterilization technique.

Identification and quantification of ethylene oxide in sterilized medical devices using multiple headspace GC/MS measurement

This manuscript, based on the ISO 10993-7 approach, describes a multiple HS-GC measurement of residual EO present in sterilized plastic samples. The quantification of EO is done, according to the ISO standard, by addition of EO amounts extracted for each repeated extraction. During the method development, the specificity of the detection of EO regarding acetaldehyde (structural isomer of EO) which may be formed from EO has been ensured and different tests were performed to check a possible influence of the sample preparation. Assays to maximize EO extraction were performed for different materials (Cyclo-olefine Copolymer (COC), Cyclo-olefine Polymer (COP), Silicon, Polyurethane (PUR)) changing extraction temperatures and times for the headspace and the pre-thermal treatment. Results highlight that depending on the material, EO can be more or less retained and thus thermal extraction conditions to maximize the amount of extractible EO from plastics may change accordingly. For COC syringes a validation according to ICH guidelines and an inter-laboratories study were performed. The method has been used for a market survey of EO sterilized medical devices, results obtained are reported in this manuscript.

Solvent or thermal extraction of ethylene oxide from polymeric materials: Medical device considerations

Ethylene oxide (EO) gas is commonly used to sterilize medical devices. Bioavailable residual EO, however, presents a significant toxicity risk to patients. Residual EO is assessed using international standards describing extraction conditions for different medical device applications. We examine a series of polymers and explore different extraction conditions to determine residual EO. Materials were sterilized with EO and exhaustively extracted in water, in one of three organic solvents, or in air using thermal desorption. The EO exhaustively extracted varies significantly and is dictated by two factors: the EO that permeates the material during sterilization; and the effectiveness of the extraction protocol in flushing residual EO from the material. Extracted EO is maximized by a close matches between Hildebrand solubility parameters δ_polymer , δ_EO , and δ_solvent . There remain complexities to resolve, however, because maximized EO uptake and detection are accompanied by great variability. These observations may inform protocols for material selection, sterilization, and EO extraction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2455-2463, 2018.

Ethylene Oxide Gas Sterilization of Medical Devices

　Ethylene oxide gas is an agent in the sterilization of medical devices due to its effectiveness and compatibility with most materials. The advantages and disadvantages, as well as its recommended uses, are explored in this review article. The variables and their relevance on process optimization are described, the types of processing cycles are detailed and emphasis is given to the design and validation of the sterilization process.

Use of a gelatin hydrogel membrane containing β-tricalcium phosphate for guided bone regeneration enhances rapid bone formation

The purpose of this study was to evaluate a thin gelatin hydrogel membrane containing β-tricalcium phosphate (G-TCP) for use in guided bone regeneration, a technique that we developed. G-TCP membranes were fabricated from gelatin and β-TCP powder, freezedried, and cross-linked by heating. The resulting G-TCP membranes were as thin as collagen membranes, with high mechanical integrity. Proliferation and differentiation of rat bone marrow stromal cells (BMSCs) on G-TCP and collagen membranes were examined. On both membranes, BMSCs proliferated well and expressed alkaline phosphatase. However, more bone-like mineralized tissue formed on G-TCP membranes than on collagen membranes at 4 weeks. The effects of G-TCP and collagen membranes on bone regeneration in rat parietal bone defects were histologically examined. Bone bridges with mature uniform bone were observed under G-TCP membranes as early as 2 weeks. These results indicate that G-TCP is a GBR membrane that is comparable or superior to collagen membrane.

Opportunities and challenges for the development of polymer-based biomaterials and medical devices

Biomaterials and medical devices are broadly used in the diagnosis, treatment, repair, replacement or enhancing functions of human tissues or organs. Although the living conditions of human beings have been steadily improved in most parts of the world, the incidence of major human’s diseases is still rapidly growing mainly because of the growth and aging of population. The compound annual growth rate of biomaterials and medical devices is projected to maintain around 10% in the next 10 years; and the global market sale of biomaterials and medical devices is estimated to reach $400 billion in 2020. In particular, the annual consumption of polymeric biomaterials is tremendous, more than 8000 kilotons. The compound annual growth rate of polymeric biomaterials and medical devices will be up to 15–30%. As a result, it is critical to address some widespread concerns that are associated with the biosafety of the polymer-based biomaterials and medical devices. Our group has been actively worked in this direction for the past two decades. In this review, some key research results will be highlighted.

Antimicrobial peptide melimine coating for titanium and its in vivo antibacterial activity in rodent subcutaneous infection models

Implant-associated infections represent a significant health problem and financial burden on healthcare systems. Current strategies for the treatment or prevention of such infections are still inadequate and new strategies are needed in this era of antibiotic resistance. Melimine, a synthetic antimicrobial peptide with broad spectrum activity against bacteria, fungi and protozoa, has been shown to be a promising candidate for development as antimicrobial coating for biomedical devices and implants. In this study, the in vitro and in vivo antimicrobial activity of melimine-coated titanium was tested. The titanium surface was amine-functionalised with 3-aminopropyltriethoxysilane (APTES) followed by reaction with a bifunctional linker 4-(N-maleimidomethyl)cyclohexane-1-carboxylic 3-sulfo-n-hydroxysuccinimide ester (Sulfo-SMCC) to yield a maleimide functionalised surface. Melimine was then tethered to the surface via a thioether linkage through a Michael addition reaction of the cysteine at its N-terminus with the maleimide moiety. Melimine coating significantly reduced in vitro adhesion and biofilm formation of Pseudomonas aeruginosa by up to 62% and Staphylococcus aureus by up to 84% on the titanium substrates compared to the blank (p < 0.05). The activity was maintained after ethylene oxide gas sterilisation. The coating was also challenged in both mouse and rat subcutaneous infection models and was able to reduce the bacterial load by up to 2 log10 compared to the uncoated surface (p < 0.05). Melimine coating is a promising candidate for development as a surface antimicrobial that can withstand industrial sterilisation while showing good biocompatibility.

Chemical modifications of therapeutic proteins induced by residual ethylene oxide

Ethylene oxide (EtO) is widely used in sterilization of drug product primary containers and medical devices. The impact of residual EtO on protein therapeutics is of significant interest in the biopharmaceutical industry. The potential for EtO to modify individual amino acids in proteins has been previously reported. However, specific identification of EtO adducts in proteins and the effect of residual EtO on the stability of therapeutic proteins has not been reported to date. This paper describes studies of residual EtO with two therapeutic proteins, a PEGylated form of the recombinant human granulocyte colony-stimulating factor (Peg-GCSF) and recombinant human erythropoietin (EPO) formulated with human serum albumin (HSA). Peg-GCSF was filled in an EtO sterilized delivery device and incubated at accelerated stress conditions. Glu-C peptide mapping and LC-MS analyses revealed residual EtO reacted with Peg-GCSF and resulted in EtO modifications at two methionine residues (Met-127 and Met-138). In addition, tryptic peptide mapping and LC-MS analyses revealed residual EtO in plastic vials reacted with HSA in EPO formulation at Met-328 and Cys-34. This paper details the work conducted to understand the effects of residual EtO on the chemical stability of protein therapeutics.

Autoimmune hemolytic anemia and thrombocytopenia attributed to an intrauterine contraceptive device

BACKGROUND

Evans syndrome is a rare condition manifested by combined autoimmune hemolytic anemia (AIHA) and thrombocytopenia or neutropenia. It is often associated with other autoimmune disorders, immunodeficiencies, and non-Hodgkin's lymphoma.

CASE REPORT

We describe a patient with Evans syndrome that may have been related to exposure to a polyethylene-based intrauterine contraceptive device (IUD). A 26-year-old white female presented with severe, symptomatic AIHA and subsequently developed severe thrombocytopenia. She had a refractory course resistant to multiple treatments including corticosteroids, intravenous immune globulin, rituximab, splenectomy, cyclophosphamide, cyclosporine, eculizumab, and plasma exchange. It was then noticed that her serum autoantibody agglutinated red blood cells (RBCs) in the presence of polyethylene glycol (PEG) but not in the absence of PEG nor when an alternative agglutination enhancing technique, low-ionic-strength solution, was used. Therefore, her polyethylene-containing IUD, which was a polyethylene frame with a levonorgestrel-releasing device, was removed. Norgestrel-dependent, platelet (PLT)-reactive antibodies were not identified by either flow cytometry or in vivo in a NOD/SCID mouse. Testing for PEG-dependent antibodies was not possible. Remission, with no requirement for RBC or PLT transfusions and return of her hemoglobin and PLT counts to normal, followed removal of the IUD.

CONCLUSION

The patient's recovery after removal of the IUD and the PEG dependence of RBC agglutination suggested a possibility that the IUD may have been a contributing factor to the etiology of Evans syndrome in this patient.

Evaluation of intraocular reactivity to metallic and ethylene oxide contaminants of medical devices in a rabbit model

OBJECTIVE

To evaluate the intraocular reactivity to metallic and ethylene oxide (EO) contaminants of ophthalmic devices in rabbits.

DESIGN

Two experimental animal studies.

PARTICIPANTS

Thirty-five New Zealand white rabbits.

METHODS

A metallic exposure study and an EO exposure study were performed. In the first study, both eyes of 25 rabbits were equally allocated to intracameral injections of alumina 0.2 μg, alumina 20 μg, copper sulfate 0.4 μg, copper sulfate 20 μg, or an aqueous control. In the second study, 10 rabbits were allocated (5 per group) to receive intracamerally an ophthalmic viscosurgical device (OVD) exposed to EO or not exposed to EO (control). All eyes were examined by slit lamp at baseline and 3, 6, 9, 24, 48, and 72 hours after exposure, with dilated indirect ophthalmoscopy being performed at 24 and 72 hours. Tonometry was performed only in the first study.

MAIN OUTCOME MEASURES

Grade of corneal clouding, anterior chamber (AC) flare, AC cells, AC fibrin, iridal hyperemia, cell and fibrin on the lens surface, vitreous haze and cells, lens opacities, intraocular pressure, and onset time.

RESULTS

For metallic compounds at the study's low doses, mean inflammatory grades were 0.2 or less above the control for all responses at all time points. For the high-dose alumina, mean inflammatory grades peaked at 6 to 9 hours at 0.5 to 0.7 above the control responses for conjunctival congestion, iris hyperemia, AC cells, flare, and fibrin and declined over the remaining time points. For the high-dose copper sulfate, mean inflammatory grades peaked between 3 and 24 hours at 1.2 to 1.8 above the control responses for conjunctival congestion, iris hyperemia, AC cells, flare, fibrin, and corneal clouding, then subsequently declined. The intraocular pressure changes appeared significant for only high-dose copper sulfate, with mean declines of 4.3 to 7.5 mmHg at 6 to 72 hours. No clinically meaningful differences in ocular inflammation were observed between the OVD exposed to EO and the OVD not exposed to EO.

CONCLUSIONS

Alumina and copper sulfate did not cause clinically meaningful ocular inflammation at the low study levels (levels expected with ophthalmic devices). Ethylene oxide exposure of an OVD was not associated with inflammation.

Sterilization of heat-sensitive silicone implant material by low-pressure gas plasma

BACKGROUND

In recent years, plasma treatment of medical devices and implant materials has gained more and more acceptance. Inactivation of microorganisms by exposure to ultraviolet (UV) radiation produced by plasma discharges and sterilization of medical implants and instruments is one possible application of this technique. The aim of this study was to evaluate the effectiveness of this sterilization technique on silicone implant material.

METHODS

Bacillus atrophaeus spores (10(6) colony-forming units [CFUs]) were sprayed on the surfaces of 12 silicone implant material samples. Four plasma sets with different gas mixtures (argon [Ar], argon-oxygen [Ar:O(2)], argon-hydrogen [Ar:H(2)] and argon-nitrogen [Ar:N(2)]) were tested for their antimicrobial properties. Post-sterilization mechanical testing of the implant material was performed in order to evaluate possible plasma-induced structural damage.

RESULTS

The inductively coupled low-pressure plasma technique can achieve fast and efficient sterilization of silicone implant material without adverse materials effects. All four gas mixtures led to a significant spore reduction, and no structural damage to the implant material could be observed.

Sterilization of medical devices by ethylene oxide, determination of the dissipation of residues, and use of Green Fluorescent Protein as an indicator of process control

Ethylene oxide (EO) is used to sterilize Oxygenator and Tubing applied to heart surgery. Residual levels of EO and its derivatives, ethylene chlorohydrin (ECH) and ethylene glycol (EG), may be hazardous to the patients. Therefore, it must be removed by the aeration process. This study aimed to estimate the minimum aeration time for these devices to attain safe limits for use (avoiding excessive aeration time) and to evaluate the Green Fluorescent Protein (GFP) as a biosensor capable of best indicating the distribution and penetration of EO gas throughout the sterilization chamber. Sterilization cycles of 2, 4, and 8 h were monitored by Bacillus atrophaeus ATCC 9372 as a biological indicator (BI) and by the GFP. Residual levels of EO, ECH, and EG were determined by gas chromatography (GC), and the residual dissipation was studied. Safe limits were reached right after the sterilization process for Oxygenator and after 204 h of aeration for Tubing. In the 2 h cycle, the GFP concentration decreased from 4.8 (+/-3.2)% to 7.5 (+/-2.5)%. For the 4 h cycle, the GFP concentration decreased from 17.4 (+/-3.0)% to 21.5 (+/-6.8)%, and in the 8 h cycle, it decreased from 22.5 (+/-3.2)% to 23.9 (+/-3.9)%. This finding showed the potentiality for GFP applications as an EO biosensor.

Emission characteristics of plastic syringes sterilized with ethylene oxide--a controlled study

OBJECTIVES

This study examined the emission characteristics of ethylene oxide (EO)-sterilized syringes under various environmental conditions, aiming to develop control strategies to minimize worker exposure.

METHODS

Experiments were performed in a facility in which temperature, relative humidity (RH), and air change rate (ACR) were controlled.

RESULTS

Analytical results indicate that the main effects of the four test variables on kinetic parameters were statistically significant (p < 0.05), except for the effect of the product on the decay rate constant, the effect of ACR on maximum EO concentration, and effect of RH on the area under the curve-days 1 and 2. The interactive effects among test variables were also evident, indicating complex emission behaviors. The mean EO emission factors during the days 1 and 2 and at the 48th hour for the 1- and 30-ml products were 2302, 1301, and 1031 mg/m(3)/h, and 871, 490, and 381 mg/m(3)/h, respectively. The times required for air EO concentrations from tested products to return to approximately 0 and 1 ppm (permissible limit) were 417 and 218 h, respectively.

CONCLUSIONS

Plastic content, temperature, RH, and ACR affected EO emissions. ACR is an achievable means of control; however, the aeration area/system should be isolated to ensure adequate ventilation is achieved.

An Evaluation of Sterilisation Processes

A sterile environment is one of the basic elements of in vitro cell culture. When choosing an appropriate sterilisation method, the possibility that the physical and chemical properties of the sterilised material could be altered by the sterilisation process itself, should be considered. Avoiding any potential problems of toxicity arising as a consequence of the sterilisation process is essential, not only in in vitro cell culture procedures, but especially in the case of the sterilisation of medical devices which come into contact with human tissue (e.g. catheters, surgical tools, and containers used for transplant preparation and storage). As it is not possible to predict the potential effects of every combination of test material and sterilisation process, we have designed a simple test, which can be easily performed to ensure the absence of cytotoxicity. The test involves the culturing of a non-adherent cell line in direct contact with the test material, in micro-wells attached to the surface of the test device. By using this novel test method, three sterilisation procedures were compared for each material. The results indicated that, neither ionising irradiation nor ethylene oxide left toxic residues on the surface of polystyrene; and that, in the case of steel, neither steam sterilisation nor ethylene oxide left toxic residues on the metal. The cold plasma system, which left toxic residues on the surface of both materials, required a post-sterilisation period of 24 hours in the case of steel, and 10 days in the case of polystyrene, in order to eliminate toxic residues prior to their use.

[A double inductively coupled low-pressure plasma for sterilization of medical implant materials]

The potential of plasma treatment in medicine is only slowly gaining acceptance. Inactivation of germs through exposure to UV radiation produced by plasma discharges and sterilization of medical implant devices and instruments is one possible application of this technique. In addition, due to the manifold possibilities of coating through plasma processes, quick sterilization-coating combinations of medical implant devices are possible. To analyze the effectiveness of this sterilization process on different material surfaces, three different alloys (X2CrNiMo18-15-3, Ti6Al7Nb and Ti6Al4V) and one thermoplastic material (ultra-high molecular weight polyethylene, UHMWPE), commonly used in medical implant devices, were examined in the presented study. After spraying Bacillus atrophaeus spores (10(6) CFU) on the surfaces of four different implant materials tested in this study (X2CrNiMo18-15-3, UHMWPE, Ti6Al7Nb and Ti6Al4V), it was demonstrated in each of four gas mixtures used (Ar, Ar:O2, Ar:H2 and Ar:N2) that due to the application of inductively coupled low-pressure plasma technique, plain medical implant materials can be sterilized rapidly, and can be protective and efficient.

Extraction and stability of ethylene oxide residue in medical devices

Ethylene oxide (EO) gas is commonly used to sterilize medical devices. A major concern is the amount of residue that may remain on or in the device and be available in the body. Some standards (ASTMF619 and ISO 10993-12) recommend using two different extraction solutions (one polar, one nonpolar), for sample preparation prior to testing medical devices. However, ISO 10993-7 recommends water to process medical devices to determine EO residual levels. To address this, EO residual levels were examined in different extraction solutions. EO residual levels from devices and materials extracted with different solutions were evaluated. Results from this study indicate little difference between extraction solutions of water, cell culture media, and serum (less than 30% difference). Given the increased cost and increased background noise of media or serum over water, using only water to process medical devices and materials for EO residues appears adequate.

Ethylene oxide sterilization in the medical-supply manufacturing industry: assessment and control of worker exposure

OBJECTIVE

In 2005, the Taiwan Institute of Occupational Safety and Health started an on-site consulting program for the medical supplies manufacturing industry, which use ethylene oxide (EO) as a sterilant, with the goal of enhancing occupational hygiene practices and controlling EO-related risks. This study presents EO exposure assessment results and examines the effectiveness of control measures.

METHODS

Detailed surveys, including exposure monitoring, were conducted at 10 factories. Airborne EO was collected using an HBr-coated charcoal tube and analyzed using GC/MS.

RESULTS

Sterilizer operators had an average short-term EO exposure level of 27.61 ppm during unloading; mean time-weighted average workshift exposure was 7.35 ppm. High EO concentrations were also present throughout the facilities. Specifically, mean EO concentrations in the aeration area, near the sterilizer and in the warehouse were 10.19, 5.75, and 8.78 ppm, respectively. These findings indicate that immediate controls are needed, and that EO emissions from sterilized products during storage cannot be overlooked. Worker short-term exposures during unloading was inversely correlated (p < 0.05) with the numbers of poststerilization purge cycle applied. The specific controls implemented and their usefulness is discussed.

CONCLUSION

Increasing the number of poststerilization purge cycles is a simple approach to eliminating extremely high exposure during unloading. Improvements to ventilation, particularly in the aeration area and warehouse, were also effective in minimizing worker exposures. Use of effective respirator is recommended until the EO exposure levels, averaging 3.41 ppm after the controls, fall below the permissible exposure limit.

Assessing the residual antibacterial activity of clinical materials disinfected with glutaraldehyde, o-phthalaldehyde, hydrogen peroxide or 2-bromo-2-nitro-1,3-propanediol by means of a bacterial toxicity assay

This study investigated the use of a rapid bacterial toxicity test for detecting disinfectant residues released by disinfected materials. The test substances included an environmental disinfectant used in hospitals in high-risk areas, such as critical care units or emergency services, and three disinfectants used on clinical devices when a high level of disinfection is required. The test materials were polyurethane, polypropylene, glass, latex and cotton from different instruments and utensils used in hospitals. Of the four test disinfectants, o-phthalaldehyde (OPA) and 2-bromo-2-nitro-1,3-propanediol (BNP) showed the greatest inhibitory activity (as much as 300-fold greater than hydrogen peroxide in the case of OPA) according to the toxicity text. However, with the exception of hydrogen peroxide on latex, it was the most porous test materials, namely latex and cotton, that accumulated the least residue. BNP was the disinfectant that left the least residue on the five test materials, while the greatest residual concentration was left by hydrogen peroxide on latex (as much as 5 microg/cm2). The biotest used in this study permitted the detection of disinfectant residues released by different types of previously disinfected clinical materials, and can be adapted to simulate elution conditions similar to those existing in routine hospital practice.