Low-temperature Plasma Sterilization Research Articles

Analysis of sterilization efficiency and application cost of three low temperature sterilization methods.

This paper discusses the sterilization efficiency of three low temperature sterilization methods used in thermosensitive medical devices and makes a preliminary analysis of sterilization costs so as to provide the basis for reasonable selection of low temperature sterilizer in Central Sterile Supply Department. Medical devices compatible with the three sterilization methods were selected for sterilization, and two packaging materials were selected for the three low-temperature sterilization equipment according to the compatibility of the packaging materials. The equipment packed with the same packaging materials were sterilized for five times, and each low-temperature sterilizer was sterilized for a total of ten times. The sterilization effect, sterilization cycle time, energy consumption, and cost of the three sterilizers were compared. The cycle time of ethylene oxide sterilizer was 393.6min, and the cycle time of hydrogen peroxide low temperature plasma sterilizer was 56.1min. The cycle time of low temperature steam and formaldehyde sterilizer was 105.7min. The hydrogen peroxide low temperature plasma sterilizes single cycle power consumption at a maximum of 5 kWh. The single cycle energy consumption of compressed air ethylene oxide sterilizer is up to 12 l. In terms of sterilization application cost, hydrogen peroxide low temperature plasma sterilization has the highest cost, followed by ethylene oxide sterilization, and low temperature steam and formaldehyde sterilization is the lowest. The sterilization efficiency of hydrogen peroxide low temperature plasma sterilization is the highest, followed by low temperature steam and formaldehyde sterilization, and the lowest is ethylene oxide sterilization. The three low temperature sterilization methods can achieve effective sterilization of devices. Each hospital can choose an appropriate low temperature sterilization method according to the characteristics of thermosensitive instruments, turnover efficiency requirements, and financial status.

The influence of low-temperature sterilization procedures on piezoelectric ceramics for biomedical applications

Piezoelectric materials are intensively investigated for usage in biomedical applications ranging from in vivo sensors and energy harvesters to implants for bone and neural cell stimulation. Besides the high requirements for reliability and low cytotoxicity, implantable materials must be sterilizable without losing their functionality. In this study, we investigate the impact of low temperature plasma sterilization and the associated cleaning routines on the piezoelectric properties of PZT, BCZT and KNN bulk ceramics. The stability of the piezoelectric response strongly depends on the material system, with BCZT ceramics showing the strongest decline in properties. Several factors were identified to contribute to this reduction of the piezoelectric coefficient, the most important being mechanical stress due to sample handling as well as chemical reactions during cleaning, disinfection and sterilization. The study highlights the importance of evaluating the impact of all influencing factors along the pre-implantation handling chain in the material selection process.

The Investigation of the Influence of Low-Temperature Plasma and Steam Sterilization on the Properties of Track Membranes Made of Polyethylene Terephthalate

The influence of modification by low-temperature atmospheric-pressure plasma and steam sterilization on the properties of track membranes based on polyethylene terephthalate is studied. It is found that the action of hot steam under pressure changes the topography of the surface of the membranes with the formation of artifacts in the form of large oval-shaped protrusions with a height of 300–400 nm and a density of up to 0.007 protrusions/μm2 on the surface, increases the surface roughness by 40% and the wetting angle by 9°–18° for the initial membranes and by 36.8°–39.6° for the membranes modified in plasma, and decreases their surface energy to the initial value of 33 mJ/m2. Despite the morphological and structural changes in the surface, sterilization by hot steam under pressure does not lead to any noticeable change in the surface charge and ζ potential of the track membranes. Hot steam under pressure does not promote further crystallization of the membrane, keeping the polymer with a crystalline phase of 40–42%. Thus, to preserve the properties acquired by the membrane after the plasma treatment, it is necessary to search for a different sterilization method (gamma radiation, ethylene oxide sterilization).

Исследование влияния низкотемпературной плазмы и паровой стерилизации на свойства трековых мембран из полиэтилентерефталата

Исследование влияния низкотемпературной плазмы и паровой стерилизации на свойства трековых мембран из полиэтилентерефталата

Splint Sterilization—A Potential Registration Hazard in Computer-Assisted Surgery

Registration of preoperative targeting information for the intraoperative situation is a crucial step in computer-assisted surgical interventions. Point-to-point registration using acrylic splints is among the most frequently used procedures. There are, however, no generally accepted recommendations for sterilization of the splint. An appropriate method for the thermolabile splint would be hydrogen peroxide-based plasma sterilization. This study evaluated the potential deformation of the splint undergoing such sterilization. Deformation was quantified using image-processing methods applied to computed tomographic (CT) volumes before and after sterilization. An acrylic navigation splint was used as the study object. Eight metallic markers placed in the splint were used for registration. Six steel spheres in the mouthpiece were used as targets. Two CT volumes of the splint were acquired before and after 5 sterilization cycles using a hydrogen peroxide sterilizer. Point-to-point registration was applied, and fiducial and target registration errors were computed. Surfaces were extracted from CT scans and Hausdorff distances were derived. Effectiveness of sterilization was determined using Geobacillus stearothermophilus. Fiducial-based registration of CT scans before and after sterilization resulted in a mean fiducial registration error of 0.74 mm; the target registration error in the mouthpiece was 0.15 mm. The Hausdorff distance, describing the maximal deformation of the splint, was 2.51 mm. Ninety percent of point-surface distances were shorter than 0.61 mm, and 95% were shorter than 0.73 mm. No bacterial growth was found after the sterilization process. Hydrogen peroxide-based low-temperature plasma sterilization does not deform the splint, which is the base for correct computer-navigated surgery.

Comparison of Point-to-Plane and Point-to-Point Corona Discharge for the Decontamination or Sterilization of Surfaces and Liquids

We studied the decontamination of surfaces and inactivation of bacteria and yeast in liquids by low-temperature plasma generated in the DC corona discharge of an open- air type in the point-to-plane or point-to-point arrangement. We found that the inactivation in liquid suspensions is slightly more ef fi cient with the point-to-plane discharge in comparison with the point-to-point one. In the case of agar surface decontamination, two types of inhibi- tion zones were observed, which indicates the different mechanism of action for the point-to- point and point-to-plane dicharges. This knowledge may be important in the future selection of microbicidal agents and in the development of ef fi cient methods for low-temperature plasma decontamination or sterilization.

Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air

The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma in atmospheric humid air was investigated in order to develop a low-temperature, low-cost, and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of B. atrophaeus spores was found to be dependent strongly on humidity, and was completed within 15 min at a relative humidity of 90% and a temperature of 30 °C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. The inactivation rates depend on not only relative humidity but also temperature, so that water content in air could determine the generation of reactive species such as hydroxyl radicals that are effective for the inactivation of B. atrophaeus spores.

Effect of Sterilization on Non‐woven Polyethylene Terephthalate Fiber Structures for Vascular Grafts

Non-woven polyethylene terephthalate (PET) fibers produced via melt blowing and compounded into a 6 mm diameter 3D tubular scaffold were developed with artery matching mechanical properties. This work compares the effects of ethylene oxide (EtO) and low temperature plasma (LTP) sterilization on PET surface chemistry and biocompatibility. As seen through X-ray photoelectron spectroscopy (XPS) analysis, LTP sterilization led to an increase in overall oxygen content and the creation of new hydroxyl groups. EtO sterilization induced alkylation of the PET polymer. The in vitro cytotoxicity showed similar fibroblastic viability on LTP- and EtO-treated PET fibers. However, TNF-α release levels, indicative of macrophage activation, were significantly higher when macrophages were incubated on EtO-treated PET fibers. Subcutaneous mice implantation revealed an inflammatory response with foreign body reaction to PET grafts independent of the sterilization procedure.

Response of Deinococcus radiodurans to low-pressure low-temperature plasma sterilization processes

Characterize the response of Deinococcus radiodurans R1 cells to low-pressure low-temperature nitrogen-oxygen microwave plasma and identify repair processes during recovery. Cells coated onto glass slides exhibited a biphasic plasma inactivation kinetics. Treatment with various plasmas and subsequent incubation in recovery medium prolonged the lag phase in a part of the survivors, during which the ability to grow on stress medium was recovered. This recovery strongly depended on transcriptional and translational processes and cell wall synthesis, as revealed by addition of specific inhibitors to the recovery medium. Genes involved in DNA repair, oxidative stress response, and cell wall synthesis were induced during recovery, as determined by quantitative RT-PCR. Damage to chromosomal DNA caused by plasma agents and repair during recovery was directly shown by quantitative PCR. Plasmas with less UV radiation emission were also effective in killing D. radiodurans cells but resulted in less DNA damage and lower induction of the investigated genes. The response of D. radiodurans to plasma indicates that DNA, proteins, and cell wall are primary targets of plasma finally leading to the cell death. Protein oxidation is more important for killing of D. radiodurans cells than of Bacillus subtilis spores. Thus, the contaminating biological material affects the plasma composition to be used for sterilization. The results in this study provide new insight into the interaction of plasma with bacterial cells. This knowledge contributes to the definition of useful parameters for novel plasma sterilization equipment to control process safety.

Inactivation of Animal and Human Prions by Hydrogen Peroxide Gas Plasma Sterilization

Prions cause various transmissible spongiform encephalopathies. They are highly resistant to the chemical and physical decontamination and sterilization procedures routinely used in healthcare facilities. The decontamination procedures recommended for the inactivation of prions are often incompatible with the materials used in medical devices. In this study, we evaluated the use of low-temperature hydrogen peroxide gas plasma sterilization systems and other instrument-processing procedures for inactivating human and animal prions. We provide new data concerning the efficacy of hydrogen peroxide against prions from in vitro or in vivo tests, focusing on the following: the efficiency of hydrogen peroxide sterilization and possible interactions with enzymatic or alkaline detergents, differences in the efficiency of this treatment against different prion strains, and the influence of contaminating lipids. We found that gaseous hydrogen peroxide decreased the infectivity of prions and/or the level of the protease-resistant form of the prion protein on different surface materials. However, the efficiency of this treatment depended strongly on the concentration of hydrogen peroxide and the delivery system used in medical devices, because these effects were more pronounced for the new generation of Sterrad technology. The Sterrad NX sterilizer is 100% efficient (0% transmission and no protease-resistant form of the prion protein signal detected on the surface of the material for the mouse-adapted bovine spongiform encephalopathy 6PB1 strain and a variant Creutzfeldt-Jakob disease strain). Thus, gaseous or vaporized hydrogen peroxide efficiently inactivates prions on the surfaces of medical devices.

欧州における滅菌の最新事情と新型過酸化水素低温プラズマ滅菌装置の位置付け(第82回日本医科器械学会大会ランチョンセミナー5記録)

欧州における滅菌の最新事情と新型過酸化水素低温プラズマ滅菌装置の位置付け(第82回日本医科器械学会大会ランチョンセミナー5記録)

Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization

The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 × 106 and 3.0 × 106 were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 °C below that of CW SWPs under the same average microwave power.

Comparison of low-temperature hydrogen peroxide gas plasma sterilization for endoscopes using various Sterrad™ models

This study compared the effectiveness of sterilizing four types of endoscope using different models of the Sterrad system (Sterrad 50, 100, 100S and 200). Sterilization levels meeting international requirements were attained in all cases with carriers inoculated with Geobacillus stearothermophilus spores. The endoscopes were tested in half cycles ('overkill'). This is the first study to compare the Sterrad models marketed to date in terms of effective sterilization of endoscopes with narrow lumens.

In vitro cytotoxicity testing of AB‐polymer networks based on oligo(ϵ‐caprolactone) segments after different sterilization techniques

Recently developed versatile biodegradable polymeric biomaterial offer new therapeutic options in numerous medical fields. Biocompatibility is a crucial requirement for the biomedical application of biomaterials, including the sterilization of these materials with the use of accepted protocols. Ethylene-oxide (EO) and low-temperature plasma (LTP) sterilization are frequently used low-temperature sterilization technologies for heat-sensitive materials. The agarose diffusion assay is a recommended cell-screening test to assess the cytotoxicity of biomaterials in vitro. The sensitivity of the agarose assay can be increased by using a modified computer-based image-analysis system. The influence of EO and LTP sterilization on the cytotoxicity of a versatile polymer system of shape-memory polymer networks based on oligo (epsilon-caprolactone) dimethacrylate and n-butyl acrylate was investigated. Statistically significant differences in the rate of cell lysis after EO and LTP sterilization of the polymer samples were detected by using this modified quantification system. The influence of the different sterilization techniques on the cytotoxicity of the polymeric material, as well as the clinical relevance of the described differences, are discussed.

Contamination of bronchoscopes with Mycobacterium tuberculosis and successful sterilization by low-temperature hydrogen peroxide plasma sterilization

Background: The transmission of mycobacteria by bronchoscopes has been reported several times in the last years. To explore methods to prevent transmission of tuberculosis in this way, we sterilized contaminated bronchoscopes with low-temperature hydrogen peroxide gas plasma sterilization. Methods: Bronchoscopes were contaminated with Mycobacterium tuberculosis and decontaminated with a washer/disinfecter (“normal washing”). Some were additionally disinfected with glutaraldehyde (“intensive washing”). Afterward the bronchoscopes were sterilized by low-temperature hydrogen peroxide plasma sterilization. Results: After normal washing, 8/17 samples had positive results by culture, and 7/17 had positive results by nucleic acid amplification technique. After intensive washing, all samples had negative results by culture, and 10/25 had positive results by nucleic acid amplification technique; after sterilization with low-temperature hydrogen peroxide plasma sterilization, all samples had negative results by culture and nucleic acid amplification technique. Conclusion: Washing of bronchoscopes, as performed normally, is not sufficient for decontamination of bronchoscopes. Additional disinfection is recommended. If the nucleic acid amplification technique is used for diagnostic procedures, sterilization by low-temperature hydrogen peroxide plasma sterilization is recommended to avoid false-positive results.

Effect of gas-plasma sterilization on the osteoinductive capacity of demineralized bone matrix.

The current study evaluated the effect of low-temperature hydrogen peroxide gas plasma sterilization on the osteoinductive capability of human demineralized bone matrix using a rat model. Twelve athymic rats received three separate implants consisting of steam-sterilized demineralized bone matrix (negative control), sterile-harvest demineralized bone matrix (positive control), and gas-plasma-sterilized demineralized bone matrix. A demineralized bone matrix pellet from each sterilization group was placed individually into one of three separate soft tissue pockets created in the epaxial musculature of each rat. All 12 rats were euthanized 9 weeks after implantation. Each implantation site was removed along with 0.5-cm normal tissue around the implant. Histologic examination was done on each implant site to determine the presence or absence of new bone, cartilage, or bone marrow elements. All 12 sterile harvest demineralized bone matrix sites histologically contained new bone elements, whereas none of the negative control or gas plasma sterilized demineralized bone matrix sites contained any of these same elements. The results of this study indicate that demineralized bone matrix sterilized with low-temperature, gas-plasma sterilization loses its osteoinductive capacity in a manner similar to that of steam-sterilized demineralized bone matrix, making low-temperature, gas- plasma sterilization unsuitable as a method of secondary sterilization of demineralized bone matrix.

低温プラズマ滅菌装置の普及と問題点(<特集>医療機器の消毒と滅菌)

低温プラズマ滅菌装置の普及と問題点(<特集>医療機器の消毒と滅菌)

Costs of low-temperature plasma sterilization compared with other sterilization methods

Plasma sterilization is a new technique for decontaminating thermolabile products without the severe drawbacks associated with gas sterilization methods (residues, environment compatibility). The actual costs, per sterilization unit, of three sterilization techniques — plasma, ethylene oxide and formaldehyde — were compared. As plasma sterilization is an alternative to steam sterilization for sterilizing thermostable but easily corroding products or electronic instruments, costs for steam sterilization were calculated and compared as well. If one considers only the cost of the sterilization procedure itself, without taking into account the time-saving element of plasma sterilization, then ethylene oxide sterilization proves to be the most expensive procedure, followed by plasma sterilization; sterilization with formaldehyde was the least expensive. Inclusion of the time required to sterilize an instrument, however, altered the relative costs of the three methods. Because plasma sterilization takes less time to perform than either ethylene oxide or formaldehyde sterilization, fewer instruments need be procured. In order to measure and compare the time-saving advantage that plasma sterilization affords, five groups of instruments were assembled and the total cost of sterilizing an instrument of each group was calculated. The five groups included (1) disposable, (2) electronic, (3) endoscopic, (4) sharp and (5) standard instruments. In all cases, ethylene oxide sterilization was the most expensive method. Formaldehyde sterilization was, in four out of five cases, more expensive than plasma sterilization. Steam sterilization proved to be the cheapest method of sterilizing a laparoscopic set, even when costs due to damage inflicted on the optical instruments were calculated. In the case of a vitrectome, however, plasma sterilization costs were nearly the same as steam sterilization when the lower rate of damage by plasma sterilization was taken into account.

Low Temperature Plasma Sterilization and Peracetic Acid Sterilant/Disinfectant(Special Issue : Prevention of Infection Caused by Medical Instruments and Devices (1))

Low Temperature Plasma Sterilization and Peracetic Acid Sterilant/Disinfectant(Special Issue : Prevention of Infection Caused by Medical Instruments and Devices (1))