Biomedical Instrumentation and Technology最新文献

When infectious misfolded proteins self-propagate, they cause transmissible spongiform encephalopathies (TSEs) or prion diseases. TSEs are rare, progressive neurodegenerative diseases with long incubation times and are always fatal. Iatrogenic transmission of these diseases is a major concern for human health, and existing methods of decontamination are either ineffective or require caustic chemical treatment followed by extended steam sterilization cycles. Research was undertaken to explore using enzymatic detergents to decontaminate prion-laden surgical devices, equipment, and stainless-steel tools using existing healthcare facility protocols, including cleaning followed by steam or low-temperature sterilization. Several formulations of enzymatic detergents were used to clean stainless steel wires contaminated with infected hamster brain homogenate. Buffering the solutions to achieve a final pH between 8.5 and 9 when diluted, followed by sonication at 45 to 60°C, was effective in rendering prions undetectable in Western blot images. Subsequent sterilization in an autoclave improved the results, causing further prion degradation. Protein misfolding cyclic amplification showed that adding a four-minute prevacuum auto-clave cycle produced a less than 5-log to 6-log reduction in infectious prion proteins using a multienzymatic detergent and a 6-log reduction using a protease enzyme detergent. Increasing the autoclave cycle to 18 minutes generated a consistent 6-log reduction for both formulations, which is the accepted benchmark for effective sterilization.

The temperature of the water used in vacuum pumps of steam sterilizers has the potential to cause failures in sterilization processes due to reduced efficiency and compromised vacuum levels. This study measured the impact of water temperature on a liquid ring vacuum pump (monobloc design) in a steam sterilizer. A sterilizer with a 566-L chamber was used for the tests. The water temperatures tested were 10°C, 20°C, 30°C, 40°C, and 50°C, and the following outcomes were analyzed: vacuum depth achieved in the drying phase (mbar), total cycle time (min), vacuum rate in the conditioning phase (mbar/s), and water consumption (L). Water temperature influenced the performance of the vacuum pump in all outcomes analyzed. Considering total cycle times, the performance with water at 10°C can be up to 50% better compared with performance with water at 50°C. The highest vacuum rates were obtained with water between 10°C and 20°C (up to 13 and 20.24 mbar/s, respectively). In cycles performed at 10°C, average water consumption was 33.3 L. In contrast, for cycles carried out at 50°C, the average water consumption increased to 94.2 L. The temperature of the water used in vacuum pumps influences the efficiency of sterilization cycles, which can result in longer cycles and higher water consumption.

Protein assays commonly used to evaluate reusable device cleanliness do not always accurately measure the low concentrations of protein that are expected on reusable medical devices after processing. Methods often are adapted to provide an estimation of protein concentration; however, sensitivity issues in the portion of standard curves at the acceptance criteria of 6.4 μg/cm² protein have been reported. Using analytical validation criteria, method improvements for the micro-bicinchoninic acid assay for protein residuals are demonstrated by incorporating a standard addition method, increasing the well volume, and changing the working reagent ratio. These improvements increased method sensitivity and accuracy in the reliable detection of protein levels for device cleaning validations.

Saturated steam (SS) is used for sterilizing many medical devices. Exposure to SS for appropriate temperature/time combinations creates a microbicidal environment that renders product sterile. Superheated steam (SHS) has been heated beyond its saturation point and is less microbicidal, compromising process efficacy. Sterilization monitoring systems should detect SHS. One method is to use biological indicators (BIs; e.g., rapid-readout self-contained BIs [RRSCBIs]). The purpose of this study was to determine if RRSCBIs can detect SHS. Pressurizing the boiler to 4,700 mB, manifold to 4,000 mB, and chamber jacket to 3,600 mB and heating the viewing window to 150°C in a 10-L BI evaluation resistometer vessel allowed approximately 12°C and 4.5°C of superheat in a nominal 121.75 ± 0.25°C and 132.5 ± 0.25°C cycle, respectively, to be reproducibly achieved. Replicate tests using multiple RRSCBIs from different batches were exposed vertically (cap up), inverted (cap down), and horizontally to SS and SHS. RRSCBI viability was determined using a fluorescent readout method. RRSCBIs exposed to SS at 121.75 ± 0.25°C for 7 or 14 minutes were negative. A total of 135 type A RRSCBIs were exposed to SHS (12°C) at 121.75 ± 0.25°C for 14 minutes. Zero of 45 RRSCBIs mounted vertically showed a positive fluorescent result, 26 of 45 mounted inverted were positive, and 45 of 45 mounted horizontally were positive. A total of 135 type B RRSCBIs were exposed to SHS (12°C) at 121.75 ± 0.25°C for 7 minutes. Twenty-four of 45 mounted vertically were positive, 41 of 45 mounted inverted were positive, and 45 of 45 mounted horizontally were positive. RRSCBIs detected SHS, but this was orientation dependent. Further work is required to establish the application of these findings in healthcare facility settings.

Endotoxins are high-molecular-weight complexes that contain lipopolysaccharide, protein, and phospholipid originating from the outer membrane of gram-negative bacteria. As gram-negative bacteria are naturally present in a variety of sources, endotoxins are commonly identified as contaminants in manufacturing environments. In industrial applications, endotoxin often is considered difficult to inactivate and to have a strong affinity with surfaces resulting from its hydrophobic chemical structure. This article describes the investigation of the true affinity of endotoxin, from various microbial sources in solution, for medical device material surfaces. In addition, endotoxin reduction was investigated with commonly used sterilization methods such as those based on ionizing radiation, dry and moist heat, and ethylene oxide sterilization. Endotoxin activity was found to be reduced following exposure to a range of sterilization modalities with the degree of activity reduction related to the source of endotoxin and the substrate material upon which it was present.

Polytetrafluoroethylene (PTFE) is a common polymer used in medical devices due to its exceptional properties (e.g., biocompatibility, inertness, chemical stability, low coefficient of friction). However, as a result of molecular weight reduction caused by the process of chain scission, it is known to be susceptible to radiation exposure and can rapidly lose strength and integrity. In this design of experiments study, the goal was to determine whether an operating window of conditions exist for electron beam (E-beam) radiation sterilization in which the degradation of PTFE is acceptably low. PTFE was tested for yield stress after exposure to radiation under different parameters (total dose [15-60 kGy], packaging atmosphere [air/nitrogen], and poststerilization accelerated aging [real-time equivalent of 1 and 3 years]). The results showed that total dose and packaging atmosphere were significant factors and indicated that the use of modified atmosphere packaging (vacuum sealing with nitrogen gas purge) can be a useful approach in increasing the stability of PTFE toward E-beam sterilization.

While selecting the test variables for a cleaning validation for reusable medical devices, the manufacturer must provide a simulative and clinically representative challenge for the device. An appropriate challenge must be identified with care so as not to overchallenge the cleaning process by selecting the worst case for every variable, thus leading to an impossible validation or unrealistic processing requirements. To appropriately select the testing variables, an understanding of the challenge to the cleaning process is important. The relationship among device material, test soil, and application method was investigated by testing 140 variable combinations, including seven materials (stainless steel, polyoxymethylene, polyether ether ketone, nitinol, aluminum, titanium, and silicone), four test soils (defibrinated blood soil, coagulated blood, modified coagulated blood, and Miles soil), and five soil application methods (pipetting neat, pipetting spreader, painting, handling with soiled gloves, and immersion). Stainless steel was the only material that showed consistent soil application in a thickness (at ~6 μL/cm²) that fully covered the test surface without some element of pooling, cracking, flaking, or soil migration with all test soils and application methods. The data collected using solubility testing indicated that a complex relationship for material adherence may exist between device materials and test soil. Stainless steel was the most challenging material tested.

Parametric release, which relies on use of process data for product release, provides many benefits. However, adoption by the sterilization industry has been slow, with release typically involving biological indicator (BI) growth responses/ dosimetry readings. The current article highlights how the data provided by the process (described through examples for ethylene oxide [EO], vaporized hydrogen peroxide [VHP], and radiation) may be better used to inform parametric release implementation. The examples involving EO and VHP demonstrated the ability of the sterilization equipment to deliver validated parameters repeatedly after the load presented was validated. For instances in which load variability has not been addressed in performance qualification, BI testing or even measurement of EO concentration cannot reliably or fully inform the impact of such variance on the validated process. "Direct" monitoring of EO concentration is a current requirement in ISO 11135:2014. Nonetheless, the findings presented here show that EO and VHP concentrations can be determined by the calculated method, rendering the use of a concentration measurement probe somewhat superfluous. In alignment with European Union good manufacturing practice Annex 17, a key requirement of parametric release is to have sufficient data to demonstrate the repeatability of the validated process. Similar to gas technologies, radiation processing strives to implement parametric release but is limited by the currently available means of measuring all critical parameters, such as photon delivery.

The identification of worst-case device (or device set) features has been a well-established validation approach in many areas (e.g., terminal sterilization) for determining process effectiveness and requirements, including for reusable medical devices. A device feature approach for cleaning validations has many advantages, representing a more conservative approach compared with the alternative compendial method of testing the entirety of the device. By focusing on the device feature(s), the most challenging validation variables can be isolated to and studied at the most difficult-to-clean feature(s). The device feature approach can be used to develop a design feature database that can be used to design and validate device cleanliness. It can also be used to commensurately develop a quantitative cleaning classification system that will augment and innovate the effectiveness of the Spaulding classification for microbial risk reduction. The current study investigated this validation approach to verify the efficacy of device cleaning procedures and mitigate patient risk. This feature categorization approach will help to close the existing patient safety gap at the important interface between device manufacturers and healthcare facilities for the effective and reliable processing of reusable medical devices. A total of 56,000 flushes of the device features were conducted, highlighting the rigor associated with the validation. Generating information from design features as a critical control point for cleaning and microbiological quality will inform future digital transformation of the medical device industry and healthcare delivery, including automation.