Steam Sterilization Conditions Research Articles

Highly stable, fluorescent, artificial lipoprotein nanoparticles.

Here, we report a novel kind of protein nanoparticles of 11 nm in size, which have a central protein core surrounded by two layers of lipid. One layer of the lipid was covalently attached to the protein, while the other layer has been physically assembled around the protein core. Particle synthesis is highly modular, while both the size and charge of the protein nanoparticles are controlled in a predictable manner. Circular dichroism studies of the conjugate showed that the protein secondary structure is retained, while biophysical characterizations indicated the particle purity, size, and charge. The conjugate had a high thermal stability to steam sterilization conditions at 121°C (17 psi). After labeling the protein core with few different fluorescent dyes, they were strongly fluorescent with the corresponding colors independent of their size, unlike quantum dots. They are readily digested by proteases, and these water-soluble, non-toxic, highly stable, biocompatible, and biodegradable conjugates are suitable for cell imaging and drug delivery applications.

Improving parametric load release for steam sterilization

Current standards and procedures for parametric load release are based on technologies from the 1960s, are consensus based and are often not supported by scientific evidence. In the literature, however, methods are reported which can fairly easily be implemented and improve current parametric load release for steam sterilization. To implement an improved parametric load release procedure, exceeding the current standards and methods for monitoring steam sterilization processes. Implementation of the procedure should be feasible for all interested end-users. The steam sterilization criteria specified in the literature were used to define a set of steam sterilization conditions. A search for commercially available devices and methods which can assess these conditions parametrically was performed. After selecting a method, a field study was carried out. Two devices were identified which could be used to improve parametric load release after a steam sterilization process. A comparison showed that a permanently installed device which - independent from the sterilizer - measures the temperature, the steam composition in the chamber and the time for every steam sterilization process, offers the most advantages. The selected method has been implemented and tested on 51 steam sterilizers. The selected method makes steam sterilization safer, more sustainable, and more cost effective. It can be implemented by all interested end-users.

Evaluating the sterilization effect of wheat flour treated with continuous high-speed-stirring superheated steam

In this study, the response surface methodology (RSM) was used to optimize the superheated steam sterilization conditions of wheat flour. Moreover; the impact of different treatment conditions on the physicochemical and structure of starch and protein in wheat flour was investigated. The three response variables (the total plate count, peak viscosity, and SDS sedimentation value) were determined to be most dependent on treatment time levels followed by moisture content and treatment temperature. Multiple-response optimization results showed that the treatment temperature 150 °C for 6 s at 13.5% moisture content was an optimal condition. In this case, the peak viscosity of wheat flour increased to 2560 cP, and enthalpy of gelatinization (ΔH) decreased to 5.67 J/g, while the crystalline structure and granular microstructure of starch were well maintained, and the ordering of protein was improved. Based on the optimized conditions, further increasing the treatment temperature, time, and moisture content, respectively, would destroy the physicochemical properties, among which the treatment time had the greatest effect.

Steam sterilization chemical indicators are not adequate for monitoring real steam sterilization cycles.

Chemical indicators are commonly used in hospitals to monitor steam sterilization conditions, indicating that medical devices are safe to be used. The results are stored for future evidence in the event of an infection incident root cause analysis. This type of indicator is also becoming an option for cycle monitoring in pharmaceutical steam sterilizers, improving cycle control. They are constructed and tested according to published standards, but contradictory results between chemical indicators and cycle printouts have a critical impact on process control. We found that type 6 chemical indicators used in steam sterilizer cycles did not perform according to their intended use, showing an ″approved″ result in a ″failed″ cycle (a false positive). This study demonstrated that type 6 chemical indicator specifications are not adequate for monitoring steam sterilizers. A change in standards is therefore needed.

Comparison of steam sterilization conditions efficiency in the treatment of Infectious Health Care Waste

Many studies show that the treatment of Infectious Health Care Waste (IHCW) in steam sterilization devices at usual operating standards does not allow for proper treatment of Infectious Health Care Waste (IHCW). Including a grinding component before sterilization allows better waste sterilization, but any hard metal object in the waste can damage the shredder. The first objective of the study is to verify that efficient IHCW treatment can occur at standard operating parameters defined by the contact time–temperature couple in steam treatment systems without a pre-mixing/fragmenting or pre-shredding step. The second objective is to establish scientifically whether the standard operation conditions for a steam treatment system including a step of pre-mixing/fragmenting were sufficient to destroy the bacterial spores in IHCW known to be the most difficult to treat. Results show that for efficient sterilization of dialysis cartridges in a pilot 60L steam treatment system, the process would require more than 20min at 144°C without a pre-mixing/fragmenting step.In a 720L steam treatment system including pre-mixing/fragmenting paddles, only 10min at 144°C are required to sterilize IHCW proved to be sterilization challenges such as dialysis cartridges and diapers in normal conditions of rolling.

"Stable-on-the-Table" Biosensors: Hemoglobin-Poly (Acrylic Acid) Nanogel BioElectrodes with High Thermal Stability and Enhanced Electroactivity.

In our efforts toward producing environmentally responsible but highly stable bioelectrodes with high electroactivities, we report here a simple, inexpensive, autoclavable high sensitivity biosensor based on enzyme-polymer nanogels. Met-hemoglobin (Hb) is stabilized by wrapping it in high molecular weight poly(acrylic acid) (PAA, MW 450k), and the resulting nanogels abbreviated as Hb-PAA-450k, withstood exposure to high temperatures for extended periods under steam sterilization conditions (122 °C, 10 min, 17–20 psi) without loss of Hb structure or its peroxidase-like activities. The bioelectrodes prepared by coating Hb-PAA-450k nanogels on glassy carbon showed well-defined quasi-reversible redox peaks at −0.279 and −0.334 V in cyclic voltammetry (CV) and retained >95% electroactivity after storing for 14 days at room temperature. Similarly, the bioelectrode showed ~90% retention in electrochemical properties after autoclaving under steam sterilization conditions. The ultra stable bioelectrode was used to detect hydrogen peroxide and demonstrated an excellent detection limit of 0.5 μM, the best among the Hb-based electrochemical biosensors. This is the first electrochemical demonstration of steam-sterilizable, storable, modular bioelectrode that undergoes reversible-thermal denaturation and retains electroactivity for protein based electrochemical applications.

Case study on the orientation of phaco hand pieces during steam sterilization processes

Steam sterilization is an essential part of infection prevention. The literature shows that sterilization of medical instruments containing channels is not trivial. Phaco hand pieces have a simple configuration: a device contains a channel with a constant radius. No literature was found indicating whether the sterilization conditions on the inner surface of a phaco hand piece are influenced by the orientation of the hand piece. To determine whether the orientation of a phaco hand piece influences the results of a sterilization process of this device. A qualitative case study, including experiments, is performed with a protocolled combination of steam sterilizer, process, phaco hand piece, orientation of the phaco hand piece, and wrapping. In this specific case, the orientation of the hand piece influenced the result of the steam sterilization process; in vertically (upright) oriented phaco hand pieces with free water drainage, sterilization conditions are reproducibly established. In the same process, in horizontally oriented or vertically oriented hand pieces without free drainage, these conditions are not established in a reproducible way. In the investigated combination of sterilizer, process, load, loading pattern and wrapping, phaco hand pieces have to be oriented vertically (upright) with free water drainage to obtain steam sterilization conditions on the inner surface. It is likely that instruments with comparable configuration and dimensions will yield comparable results. It is therefore recommended that this issue is considered during the development of medical instruments and during performance qualifications of such instruments.

Measuring non-condensable gases in steam

In surgery, medical devices that are used should be sterilized. To obtain surface steam sterilization conditions, not only in the sterilizer chamber itself but also in the loads to be sterilized, the amount of non-condensable gases (NCGs), for instance air, should be very low. Even rather small fractions of NCGs (below 1%) seriously hamper steam penetration in porous materials or devices with hollow channels (e.g., endoscopes). A recently developed instrument which might detect the presence of residual NCGs in a reliable and reproducible way is the 3M(TM) Electronic Test System (ETS). In this paper, a physical model is presented that describes the behavior of this instrument. This model has been validated by experiments in which known fractions of NCGs were introduced in a sterilizer chamber in which an ETS was placed. Despite several approximations made in the model, a good agreement is found between the model predictions and the experimental results. The basic principle of the ETS, measuring the heat transfer by condensation on a cooled surface, permits a very sensitive detection of NCGs in harsh environments like water vapor at high temperatures and pressures. Our model may serve to develop adapted and optimized versions of this instrument for use outside the field of sterilization, e.g., in heat exchangers based on steam condensation.

Penetration of water vapour into narrow channels during steam sterilization processes

In surgery medical devices are used that should be sterile. To obtain surface steam sterilization conditions in hollow medical devices (e.g. endoscopes), sufficient water vapour should be present in the narrow channels in these devices during sterilization. In this paper, a model to calculate the water vapour distribution in narrow channels during steam sterilization processes is presented. The narrow channels in the devices are modelled as tubes with one open and one closed end. The model is restricted to isothermal situations in which no condensation takes place. To validate the model, the time evolution of the water vapour density at the closed end of a test tube is quantified by a pilot experiment based on infrared light absorption measurements. A stainless-steel test tube was used with a length of 54 cm, a radius of 1.5 mm and a wall thickness of 0.5 mm. These dimensions are comparable to the channels in medical instruments. Both the model calculations and the experiments show that for a wide range of sterilization process parameters the vapour density near the closed end of the tube is insufficient for steam sterilization. Despite the simplicity of the model, a fair overall agreement is found between the model predictions and the experimental results. This agreement can be improved significantly by an empirical modification of the boundary conditions at the open end of the tube. Our calculations show that the tube length is the most important parameter. Some possible changes in the process parameters to increase the water vapour concentration at the closed end of the tube are addressed briefly.

Ultra-stable hemoglobin–poly(acrylic acid) conjugates

Stabilization of proteins against thermal deactivation is a major challenge, and a simple, facile, novel chemical approach is described here to overcome this hurdle. We report here, for the first time, the successful synthesis of ultrastable protein nanoparticles consisting of met-hemoglobin (Hb) conjugated with low molecular weight polyacrylic acid (PAA, Mw 8000) to form discrete nanoparticles. Hb–PAA nanoparticles were not deactivated when subjected to prolonged thermal treatment such as steam sterilization conditions (122 °C, 40 minutes, 17–20 psi), while the unprotected Hb lost most of its activity when subjected to the same heating conditions. Several Hb–PAA derivatives which resist thermal inactivation, in a similar manner, are produced and characterized. Interestingly, the highest activity retention, after the above thermal treatment, was ∼100% for the untreated samples. This resistance to heat is attributed to the enhanced thermodynamic stability of the Hb–PAA conjugate and improved re-folding of the denatured state to the native form, facilitated by PAA conjugation to Hb. This is a unique approach to stabilize Hb against thermal inactivation, and it is a major breakthrough in the production of stable Hb-based nanomaterials that can be safely sterilized in an autoclave for biomedical/in vivo applications.

Physical stability of ethyl diatrizoate nanocrystalline suspension in steam sterilization.

To study the effects of formulation variables on the physical stability of a submicron crystal (nanocrystal) suspension under steam sterilization conditions. Suspensions of ethyl diatrizoate nanocrystals were prepared by wet milling in the presence of the surfactant poloxamine 908. Particle size distribution and zeta potential were measured by photon correlation spectroscopy. On heating, the mean particle size of the nanocrystal suspension remained essentially unchanged up to 110 degrees C, the cloud point of the stabilizing surfactant, but increased significantly above that temperature. The increase in particle size was a result of particle aggregation rather than crystal growth. Adding a cloud point booster to the suspension significantly minimized the particle aggregation at high temperatures. The purity of poloxamine 908 and the tonicity agent and buffer salt used also affected the heat stability of the suspension, the latter agents apparently through altering the surfactant cloud point. The aggregation of the ethyl diatrizoate nanocrystalline suspension under steam sterilization conditions was a result of phase separation of the stabilizing surfactant at its cloud point. When formulated with a cloud point booster to prevent the phase-separation, the suspension maintained its physical stability under steam sterilization without any significant change in particle size distribution.