C.-G. Lin, ... Y.-F. Song, in
Advances in Inorganic Chemistry, 2017 Hydrogen peroxide (H2O2) is industrially used as antibacterial and sterilizing agent
(92). In addition, peroxides are released from many other industrial processes, and their environmental release needs to be strictly controlled (93). In 2009, Salimi et al. (94) developed a three component electrochemical peroxide sensor. A simple procedure gave access to glassy carbon (GC) electrodes modified with SWNTs, α-SiMo12O404− and the copper complex [Cu(bpy)2]Br2. The copper complex and POM were irreversibly and strongly adsorbed onto GC electrode. Compared with a non-POM-functionalized reference electrode (based on a GC electrode modified with
SWNTs and [Cu(bpy)2]Br2 only), the POM-modified system showed stable voltammetric response and gave excellent electrocatalytic activity toward H2O2 reduction (bromate reduction was also reported) at low overpotential. The system was able to detect nanomolar concentrations of H2O2 and bromate, highlighting the sensitivity which is associated with the highly dispersed POMs on the nanostructured conductive substrate. Recently, Gorton et al. (95) assembled a robust and stable film composed of the ionic liquid [C8Py][PF6] and PMo12 on MWNT-modified GC electrodes using a simple dip-coating technique. Efficient H2O2 and iodate detection at low overpotentials was found together with low detection limits, high sensitivity, short response time (< 2 s) and satisfactory linear concentration
range, illustrating that in principle the sensors can be assembled in the field and used for in situ pollutant benefits as their high conductivity presumably contributes to the electron transfer between POM and MWNT substrate. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/S0898883816300174 Washing techniques for denim jeansC.W. Kan, in Denim, 2015 11.2.12 Ozone fadingOzone typically acts as a mild bleaching agent as well as a sterilising agent. In this technique of denim washing, the garment is bleached with ozone dissolved in water in a washing machine. However, this technique can also be carried out in a closed chamber by using ozone gas. The advantages of this method are: (1) a minimum loss of strength and (2) it is a simple method that is environmentally friendly. The ozonised water after laundering can easily be deozonised by ultraviolet radiation. Nowadays, ozone fading can also be achieved by plasma equipment (Jeanologia, 2011; Cheung et al., 2013a,b). Under the influence of plasma treatment, high energy electrons are formed. Some of the high energy electrons react with moisture in air and a mixture of radicals is generated (Zhang et al., 2008). During the generation of ozone plasma, a combination of charged particles, free radicals and ultraviolet light is generated. The ultraviolet light, being the by-product of the plasma treatment process, also contributes to production of the •OH radical. Hydroxyl radical •OH is the most oxidative radical among radicals generated in the plasma process and is the main radical responsible for degradation of indigo dye in textile materials. The •OH can oxidise indigo dye molecules (RH) producing organic radicals R•, which are highly reactive and can be further oxidised (Khraisheh, 2003; Khan et al., 2010). As a result, the colour fading effect of the indigo dyed textile is achieved. The K/S (in which K is the absorption coefficient at a specific wavelength and S is the scattering coefficient) values of different treated denim fabrics are shown in Table 11.1 (Kan and Yuen, 2012). From the results, it is noted that the differently treated denim fabrics have lower K/S values than the untreated denim fabric. The K/S value is linearly related to concentration of the colourant in the medium and it can be concluded that a paler shade is obtained after different treatments. Without the cellulase treatment, the plasma induced ozone treated denim fabric has a paler shade than the enzyme desized denim fabric because during the plasma induced ozone treatment, ozone oxidises indigo dyes on the denim fabric surface leading to a colour fading effect (Ghoranneviss et al., 2006; Kan and Yuen, 2012). However, in the case of enzyme desizing, the enzyme only reacts with the sizing material at the fibre surface and no breakdown of indigo dyes molecules occurs. Therefore, no significant shade change takes place. In the case of cellulase treatment, cellulase in the aqueous medium can penetrate effectively into the denim fabric. The enzymatic hydrolysis induced by cellulase in the plasma induced ozone treated denim fabric is more severe than the enzyme desized denim fabric. As a result, the cellulase treatment for plasma induced ozone treated denim fabric gives a paler shade than the enzyme desized denim fabric. Table 11.1. Colour properties of different denim fabrics
Kan and Yuen (2012). Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780857098436000111 Reproductive and Endocrine ToxicologyE.A. Whelan, in Comprehensive Toxicology, 2010 11.27.2.2.5 Exposures in the health care settingChemicals that are widely used in the health care industry, such as anesthetic gases, antineoplastic agents, and sterilizing agents, have been linked to adverse reproductive outcomes. Early studies of anesthetic gases were generally based on self-reported exposure and outcome data and have, therefore, been questioned by many reviewers. One study reported an association of anesthetic gas exposure with spontaneous abortion and congenital malformations (Guirguis et al. 1990), but may have also suffered from recall and reporting bias. Studies in Finland have reported associations between exposure to antineoplastic drugs and the risk of spontaneous abortion (Selevan et al. 1985; Taskinen et al. 1986, 1994). Other outcomes such as ectopic pregnancy (Saurel-Cubizolles et al. 1993) and decreased birth weight (Stucker 1993) have also been associated with exposure to these agents. Chemical sterilants, such as ethylene oxide and glutaraldehyde, have been associated with spontaneous abortion in a Finnish study (Hemminki et al. 1982). Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780080468846011325 Beta-PropiolactoneA. de Peyster, in Encyclopedia of Toxicology (Third Edition), 2014 HumansBeing so unstable, beta-propiolactone reacts with tissues of the body that it comes in contact with. Acute administration of beta-propiolactone as a sterilizing agent in sera has induced signs of inoculation-area skin irritation in people. Skin exposure to a 40% (or greater) solution of beta-propiolactone in water for 20 min has caused skin burns. The vapor of beta-propiolactone is unbearable to human beings at concentrations greater than 0.1 mg l−1 of air, a level considerably lower than workplace air standards in the United States. The immediate respiratory irritation felt upon exposure appears to be great enough to prevent most people from working in the presence of vapor concentrations that might be injurious. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123864543011684 Ensuring fabrics survive sterilisationM.J.A.M. Abreu, in Textiles for Hygiene and Infection Control, 2011 9.2 Purpose and importance of sterilisationIt was Louis Pasteur and then Robert Koch who first postulated the link between micro-organisms and infection. Ever since this link was established, man has developed many procedures to reduce the risk of disease caused by microorganisms, including topical, systemic antimicrobial chemicals, physical barriers and sterilisation of clinical materials (Walker, 1997). Accordingly, Massey (1994) stated that the primary purpose of sterilising an item is to render it safe for use by destroying all living microscopic organisms. Transmissible agents (such as spores, bacteria and viruses) can be eliminated through sterilisation. This is different from disinfection, where only organisms that can cause disease are removed (Eurotherm, 2011). Abreu et al. (2004a) has pointed out that because bacteria multiply very quickly, the sterilisation process must be absolute. Even a few organisms invading the patient’s body during a surgical procedure can reproduce rapidly and contribute to post-operative complications. So, an object can never be ‘almost’, ‘partially’ or ‘practically’ sterilised – it is either sterilised or not sterilised. The European Norm 556-1 2001: Sterilisation of Medical Devices – Requirements for Medical Devices to be Designated Sterile – Part 1, defines sterility as the state of being free from viable micro-organisms (≤ 1 × 10– 6) and defines sterilisation as the process used to inactivate microbiological contaminants and thereby transform the non-sterile items into sterile ones. This definition is, however, very simplistic, because the probability of survival is determined by the number and resistance of the micro-organisms and by the environment in which the organisms exist during treatment, the bioburden of raw materials, the subsequent storage and the control of the environment in which the product is manufactured, assembled and packaged. 9.2.1 Sterilising requirements for single-use and reusable textile fabricsThe products are either used once (sterilised single-use fabrics) or are laundered and afterwards sterilised again and used multiple times (life cycle is a maximum of 50 uses). In the USA, single-use dominates the market, with 90% of drapes and gowns being single-use. In Europe, the situation is very different, with single-use accounting for less than 50%. These numbers differ significantly throughout Europe. In southern Europe and the UK, the penetration of single-use is much lower than in the Scandinavian countries, where the single-use penetration is over 80% (Abreu et al., 2006a). A product (single-use or reusable) that is designed successfully, could, after a sterilisation process, be transformed into an unrecognisable piece of material. This sterilisation process can induce some positive changes in the product, such as improved strength and tear resistance while some sterilisation procedures could restrict the product’s use for defined applications, causing brittleness for example (Abreu et al., 2004a). To achieve sterilisation by any available method, Walker (1997) has indicated a number of required key parameters: (i)achieve intimate contact between the individual micro-organism and the sterilising agent used; (ii)deliver the required quantity of sterilising agent to each individual microorganism; (iii)maintain the required quantity for the required time period to achieve inacti-vation of the micro-organism; (iv)remove sterilising agent residues from the product to a pre-determined acceptable level. Specifically, textile fabrics contain interstices that can entrap gases and liquids used for sterilisation. This entrapment of gases and liquids can shelter microorganisms on the surface and in the interior of the fabric, which will restrain the intimate contact between the sterilising agent and each individual micro-organism and the entrapment of sterilisation residues will increase the difficulties in achieve the removal of sterilising agent residues from the product to a pre-determined acceptable level. 9.2.2 Common types of sterilisation methodsFour common types of sterilisation are in use today: gas, irradiation, steam autoclave and dry heat. The first two types of sterilisation are also called low-temperature sterilisation methods, applied mostly to single-use products. The latter two types are also called high-temperature sterilisation methods, and are applied to reusable products. Many sterilisers, such as those used in hospitals, use saturated steam and dry heat, but these methods are not practical for some plastics and other synthetic materials because high temperatures damage them. These materials require low-temperature sterilisation (Abreu, 2004). New procedures such as those using plasma and X-rays are also increasingly used for a variety of applications. Table 9.1 summarises the advantages and disadvantages of the most common sterilisation methods. Table 9.1. Advantages and disadvantages of the most common sterilisation methods
Gamma and electron beam irradiationIrradiation is an effective sterilisation method, but it is limited to commercial use only. Radiation sterilisation can be accomplished using one of two forms of radiation, either gamma radiation (electromagnetic radiation) from 60Co or 137Cs, or electron beam radiation from accelerated electrons (particle radiation). These high-energy particles or electromagnetic radiation exert their sterilising effect by inducing ionising events in the materials. The released energetic electrons collide with neighbouring atoms and create a shower of secondary electrons. These energetic electrons bombard DNA molecules in the harmful micro-organisms and induce irreversible damage to inactivate them. On the other hand, the same energetic electron shower can also induce severe damage to the material and cause mechanical or biocompatibility failures. Table 9.2 compares the two ionising energy sources (Woo and Purohit, 2002). Table 9.2. Properties of ionising energy sources
c = speed of light. Source: Woo and Purohit (2002). Gamma radiation. Gamma radiation is the result of transition of an atomic nucleus from an excited state to a ground state, as in certain radioactive materials. It involves the bombardment of photons and has considerable penetrating power emitted from a 60Co source. It is characterised by deep penetration and low dose rates (Massey, 2005). Gamma rays thus are electromagnetic waves. They have the capability of penetrating to a much greater distance than electron beam rays before losing their energy from collision. Because they travel at the speed of light, they must pass through a thickness measuring several feet before making sufficient collisions to lose all of their energy. 60Co is the most common source of irradiation used for sterilisation. The product must be exposed to radiation for 10 to 20 hours, depending on the strength of the source (URMC, 2010). Electron beam radiation. Electron beam radiation consists of electrons with a single negative charge and a low mass, generated from a linear accelerator. In this method, sterilisation is quick, but with limited penetration. Electrons normally cannot penetrate materials deeply, but when produced in man-made machines they can be accelerated to high energies with a subsequent improvement in penetrating ability (Block, 2001). Recent advances in electron beam technology have made it a worthy competitor to traditional gamma sterilisation. Increased power, compact design, improved reliability and a power source that does not deplete with time, in addition to security issues, are contributing to E-beam technology’s gains for medical device sterilisation (Woo and Purohit, 2002). Ethylene oxideEthylene oxide (EtO) gas sterilisation was introduced in the 1950s, and is an effective, low-temperature chemical sterilisation method. It takes longer than steam sterilisation, typically 16–18 hours for a complete cycle. Temperatures reached during sterilisation are usually in the 50–60 °C range (Patel, 2003). EtO is a colourless gas; it is an eye and skin irritant, and a suspected human carcinogen (Massey, 2005). Due to EtO being highly flammable and explosive in air, it must be used in an explosion-proof sterilising chamber in a controlled environment. EtO sterilisation is used mainly to sterilise medical products that cannot support conventional high-temperature steam sterilisation – such as devices that incorporate electronic components, plastic packaging or plastic containers. EtO gas infiltrates packages, as well as products themselves, to kill micro-organisms that are left during production or packaging processes. Most EtO sterilisation lines involve three stages. These different stages depend on the size or number of devices to be treated. The stages are as follows: (i)pre-conditioning (ii)sterilising (iii)aeration (Eurotherm, 2011). During the second stage, sterilisation depends on four parameters: (i)EtO gas concentration (ii)temperature (iii)humidity (iv)exposure time. Each parameter may be varied. Consequently, EtO sterilisation is a complex multiparameter process, where each parameter affects the other dependent parameters (URMC, 2010). EtO is still a dominant sterilisation technique, but general use is declining for the following reasons: (i)changes in the physical properties of the polymers due to the reactivity of the gas; (ii)length of degassing time, product aeration and elimination of gas toxic residues; (iii)absorption and adsorption of the gas, leaving residues and damaging the optical properties of the polymer; (iv)the Environmental Protection Agency has found EtO to be mutagenic and has initiated steps to restrict its use; (v)operator safety (because of toxic gas residues). Nevertheless, EtO is the least aggressive form of sterilisation for many materials. In addition, the replacement of the most common EtO carrier gas (CFC-12, Freon) with non-ozone-depleting alternatives, such as carbon dioxide and chloral-tetrafluoroethane, will ensure EtO remains a viable choice for many users of sterilisation services (Abreu et al., 2003). Saturated steamSteam autoclaving is the oldest, safest and most cost-effective method of sterilisation. The definition given by Massey (2005) is ‘sterilisation by steam under pressure in an autoclave’. In the steam autoclaving process, micro-organisms are killed by heat and this is accelerated by the addition of moisture. Steam, by itself, is not sufficient for sterilisation. To be effective against spore-forming bacteria and viruses, autoclaves need to: (i)have steam in direct contact with the material being sterilised (i.e. loading of items is very important); (ii)create vacuum in order to displace all the air initially present in the autoclave and replace it with steam; (iii)implement a well-designed control scheme for steam evacuation and cooling so that the load does not perish. The efficiency of the sterilisation process depends on two major factors. One of them is the thermal death time, i.e. the time for which microbes must be exposed at a particular temperature before they are all dead. The second factor is the thermal death point or temperature at which all microbes in a sample are killed. Any living thing will be killed when exposed to saturated steam at 120° longer than 15 minutes. As temperature is increased, time may be decreased (Eurotherm, 2011). Heat by itself can, of course, also readily kill bacteria, but because saturated steam can circulate and penetrate porous items in the steriliser chamber, it substantially reduces the time required for sterilisation. Like all gases, saturated steam cannot undergo a reduction in temperature without a reduction in pressure. Conversely, it cannot undergo a reduction in pressure unless the temperature is proportionately lowered. An excellent demonstration of this phenomenon is seen in locations that are subject to unusual levels of atmospheric pressure. In those areas, changes in steam pressure are required to achieve the minimum temperatures required for sterilisation. Dry heatDeath of microbial life by dry heat is a physical oxidation or slow-burning process of coagulating the protein in the cells. In the absence of moisture, higher temperatures are required than when moisture is present, because micro-organisms are destroyed through a very slow process of heat absorption by conduction (URMC, 2010). The disadvantages of dry heat sterilisation are given below. (i)Heating is slow. Diffusion and penetration of heat are slow because the heat transfer medium is poor and there is a distinct lack of available heat compared with steam in particular. (ii)It requires long sterilising periods. Long exposure times are required because the killing rate by dry heat is slow, as is heat absorption. (iii)It requires high temperatures. These temperatures may be harmful to materials. (iv)Materials are damaged. Deterioration of materials occurs with oxidation. Killing by dry heat is an oxidation process and the medium that facilitates this killing action also augments its harmful effects. (Block, 2001). Other sterilisation methodsPlasma. Low-temperature plasma sterilisation was introduced to fill the gap between autoclave: high-temperature steam sterilisation (safest, fastest and least expensive) and EtO gas sterilisation, which leaves toxic residuals. It is a low-temperature, non-toxic, but fairly expensive sterilisation method. Plasma is ionised gas made up of ions and electrons, and it is distinguishable from solid, liquid or gas phases. Plasma is often referred to as the fourth state of matter. The Sterrad system is a hydrogen peroxide gas plasma sterilisation system with an operating temperature range of 45–50 °C. Operating cycle times range from 45 to 70 minutes, depending on the size of system. This sterilisation system uses a combination of hydrogen peroxide and low-temperature gas plasma to quickly sterilise, for example, most medical instruments and materials without leaving any toxic residues. Hydrogen peroxide is a known antimicrobial agent that is capable of inactivating resistant bacterial spores. Sterilisation by this method occurs in a low-moisture environment (Patel, 2003). This sterilisation method can be produced through the action of either a strong electric or magnetic field, somewhat like a neon light. The cloud of plasma created consists of ions, electrons and neutral atomic particles that produce a visible glow. Free radicals of the hydrogen peroxide in the cloud interact with the cell membranes, enzymes or nucleic acids to disrupt life functions of micro-organisms (URMC, 2010). X-ray sterilisation. This is a new, developing process that is based on obtaining X-rays through conversion of electron beams. The X-rays produced have the same penetrating properties as the rays produced by Cobalt-60, but this treatment is faster, more flexible, and more environmentally friendly. X-rays offer excellent product penetration in sterilisation, thoroughly treating the surface and interior of a product (Patel, 2003). Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845696368500098 Methods of AnalysisF. Topuz, ... J. Groll, in Comprehensive Biomaterials, 2011 3.329.3.1.1.5 Hydrogen peroxideHydrogen peroxide is the product of reactions of oxidative metabolism catalyzed by oxidases and its detection is prominent in environmental, clinical, and biological studies due to its applications in many industrial processes as an oxidizing, bleaching, and sterilizing agent.119 A lot of work has been done for the determination of hydrogen peroxide via different methods like titrimetry, electrochemistry, and UV spectrophotometry.120 Peroxidases (POD) are generally used in these constructions to convert hydrogen peroxide into radicals. The sensitivity of the determination of hydrogen peroxide via peroxidase enzyme depends on the ability of the immobilizing matrix to retain the functional conformation of the enzyme for a long time. Through the last decade, an impressive number of inventive designs for hydrogen peroxide determination have appeared. Here, we focus on some illustrative example studies of hydrogel-based hydrogen peroxide detection, generally based on the electrochemical sensing system. The detection of H2O2 is based on the intracellular optical sensor reported by Kim et al.121 They established optical nanosensor based on PEG hydrogel spheres containing the enzyme horseradish peroxidase (HRP) for hydrogen peroxide detection. HRP was encapsulated in PEG hydrogel spheres by reverse emulsion photopolymerization without losing activity. Afterward, the fluorescence emission response of these hydrogel spheres changed as a function of H2O2 concentration in the presence of Amplex Red, and no leaching of HRP was observed from the spheres. The HRP-loaded hydrogel spheres were introduced via phagocytosis inside macrophages and were found to respond to both exogenous and endogenous sources of oxidative stress. Varma and Mattiasson developed a simple amperometric biosensor for the detection of hydrogen peroxide in aqueous and organic solvents.122 Therefore, they entrapped catalase in 30% polyacrylamide gels and created a two-electrode system. By studying the kinetics of the catalase-modified electrode by cyclic voltammetry (CV) and coupling it to a flow injection analysis (FIA) setup, it was possible to create a sensing system that could monitor a broad range of hydrogen peroxide concentrations (0.5–100 mM) in different solvents. As mentioned previously, amperometric detection of H2O2 has been achieved via immobilization of HRP in cross-linked films of ferrocene-modified linear poly(ethylenimine).118 When a small amount of H2O2 was added to the solution, oxidation peaks disappeared and reduction peaks increased due to an increase in redox polymer mediation of the HRP-catalyzed reduction of H2O2. A new-type sol–gel/hydrogel composite-based hydrogen peroxide biosensor based on silica sol and a graft copolymer of poly vinyl alcohol with 4-vinyl pyridine was fabricated by Wang et al.123 The film was characterized by FT-IR spectroscopy and optimum analytical performance was obtained depending on the pH and electrochemical behavior of the biosensor using potassium hexacyanoferrate(II) as a mediator. This system exhibited high sensitivity (15 μA mM−1) and a low detection limit of 5 × 10−7 M. Optical-based local detection of H2O2 secreted by stimulated macrophages was performed using an enzyme-based biosensor by Yan et al.124 Photolithographic patterning of hydrogel based on PEG with incorporation of horseradish peroxidase (HRP) applied to construct microstructures, use as sensing agent (Figure 9). They used a special organic molecule, called Amplex Red, which became fluorescent in the presence of H2O2 and HRP, and was either immobilized inside hydrogel elements alongside enzyme molecules or added into the cell culture media during cell activation. The production of H2O2 after mitogenic stimulation of macrophages resulted in the appearance of fluorescence in the HRP-containing hydrogel microstructures.  Figure 9. Top: Fluorescence images of hydrogel microstructures after 5 min incubation with 5 μM H2O2 (b) and 20 μM H2O2 (c) in the presence of Amplex Red. Bottom: Culturing cells with sensing hydrogel micropatterns. HRP-containing PEG hydrogel micropatterns are fabricated on glass substrate (a), encapsulation of enzyme molecules does not diminish cell-resistive properties of PEG hydrogel. When incubated with micropatterned substrates, macrophages attach next to sensing hydrogel structures (b) and macrophages release H2O2 upon mitogenic stimulation (c). Reproduced from Yan, J.; Sun, Y.; Zhu, H.; Marcu, L.; Revzin, A. Biosens. Bioelectron. 2009, 24(8), 2604–2610, with permission from Elsevier.Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780080552941001197 Plasma Processes for Life SciencesIlaria Trizio, ... Pietro Favia, in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, 2018 Dental TreatmentsOral infections, including dental caries, periodontal and intraoral diseases, are caused by bacteria and may result in tooth destruction.236 Teeth brushing, fluoride uptake, antibiotics, and vaccines have been used as treatment for oral disease, but with limitations.237 Heat kills bacteria, but the application of this method to living tissues is dangerous. Sterilizing agents or antibiotics are used to treat human tissues that are infected by pathogens, but this may lead to pain and antibiotic resistance. Today, multidisciplinary joint competences (physicists, engineers, and dentist surgeons) have been involved in investigating the possible application of plasma processing in dentistry. Preliminary results indicate that this approach can be highly efficient in killing bacteria in an inexpensive manner,238 therefore, potentially this could eliminate the problems associated with use of heat and antibiotics. Nowadays, cold AP plasmas are being exploited for treating caries, teeth whitening, malodor caring but also for treating herpetic wounds and oral cancer already mentioned in the previous paragraph.234 Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780124095472122711 Future trends for the sterilisation of biomaterials and medical devicesA. Simmons, in Sterilisation of Biomaterials and Medical Devices, 2012 11.2.4 Gas plasma sterilisationGas plasma sterilisation is a promising alternative for low-temperature sterilisation of medical devices. Although penetration is reduced compared with traditional EO, gas plasma offers generally good material compatibility and shorter cycle times. Cold plasma is a partially ionised gas comprising ions, electrons, ultraviolet photons and reactive neutrals such as radicals, excited and ground-state molecules. It is created by the application of an electric or magnetic field to a sterilising agent such as hydrogen peroxide (H2O2) or H2O2/peracetic acid (PAA). One procedure comprises a 45 min cycle during which vapourised H2O2 is diffused through the treatment chamber, after which 300 watts of radio-frequency power are applied at a pressure of 0.5 Torr to create the plasma. The plasma is maintained for a period sufficient to ensure complete sterilisation with a standard phase lasting 15 min. The total procedure takes approximately 1 h.25 Another process uses PAA and H2O2 vapour treatment, which is alternated with downstream plasma treatment by microwave excitation of the low-pressure gas mixture comprising oxygen, hydrogen and argon. The equipment operates by vapourising the chemical agents and diffusing the vapour into the chamber, alternating with the plasma. At the end of sterilisation, the reactive species combine to form water and oxygen, eliminating the need for aeration.8 H2O2 works by the production of destructive hydroxyl free radicals, which can attack membrane lipids, DNA and other essential cell components. 26 Inactivation of micro-organisms is dependent on time, temperature and concentration. PAA is an oxidising agent that denatures protein, disrupts cell wall permeability and oxidises sulphur bonds in proteins, enzymes and other metabolites.26 Gas plasma sterilisation is reported to be suitable for the sterilisation of metals, natural rubber, silicone and various polymers such as polyvinyl chloride, polyethylene and polyurethane.8,10 However, the process uses strongly oxidative chemical sterilising agents and it is well known that these agents can induce surface oxidation of some biomedical elastomers.2,19,27,28 Gas plasma is not suitable with liquids, oils, powders, biological tissues, paper, cotton and linen. It has inferior penetrating ability compared with EO, but both PAA and H2O2 perform more effectively than EO in terms of biological kill and sterilant removal.7 Other advantages of plasma sterilisation are that it is a fast, low-temperature process with no requirement for aeration. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845699321500118 EquipmentLars Hagel, ... Gail Sofer, in Handbook of Process Chromatography (Second Edition), 2008 11.1.5 Hygienic designSolvent compatibility of equipment and the hygienic design of chromatographic systems have become more obvious with the introduction of resins that withstand strong alkaline solutions suitable for CIP (for further details see Chapter 6). In principle, it is possible to sterilize a chromatographic system in-line. In reality, however, the geometry of the equipment may not allow the sterilizing agent to flush all parts of the system. Equipment should be chosen that does not create stagnant zones. For example, the geometry of a membrane valve allows for free liquid flow over the whole internal surface. Best practices for hygienic design are summarized by the ASME BioProcessing Equipment (ASME BPE) Standard, which is followed by many equipment suppliers. But it is not always possible to find hygienically designed equipment. For example, a small-scale ultraviolet (UV) monitor flow cell with laboratory types of non-sanitary, threaded connections might be needed in the system. It is still possible to achieve good process hygiene, however, by regularly opening the flow cell and cleaning it outside the system. For production systems, flow cells are machined or welded stainless steel or polypropylene with no threaded pieces and tri-clamp connections to the process line. Good hygiene in process chromatography depends on using hygienically designed equipment where available, 0.2 micron-filtered solutions coming into the system, a method for in-line cleaning and sanitization. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123740236500130 Ethylene oxide (EO) sterilization of healthcare productsG.C. Mendes, ... C.L.M. Silva, in Sterilisation of Biomaterials and Medical Devices, 2012 4.1 IntroductionUsed as a fumigant for insects in the early twentieth century, ethylene oxide (EO) was recognized as an anti-bacterial agent around 1929. Initially it was used for sterilization of spices, and in the 1940s it started being used as a low-temperature sterilizing agent for healthcare products (Rogers, 2005). Nowadays, ethylene oxide is still a dominant sterilization agent used in the medical device (MD) industry, with a continuous growth tendency, especially due to its effectiveness and compatibility with most materials. It is widely used, because it avoids heat and radiolytic stress often associated to sterilization with steam or radiation. This last point is especially important due to the diversity of developed products, designs, type of materials and packaging configurations demanded by the current market. This technique also has disadvantages, related to EO toxicity, that require special care for the protection of workers and patients, which has led several countries to limit its use, especially in healthcare centers. This topic will be further explored. This chapter provides a framework for understanding the basic principles of EO sterilization. The advantages and the disadvantages of this sterilization methodology and its recommended uses are described. The EO sterilization mechanism is explained and the variables that influence process lethality are discussed, as well as their relevance to process optimization. The EO processing cycles are detailed and emphasis is given to the design and validation of the sterilization process, including the microbiological assessment, which is the most challenging in the validation context. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781845699321500040 What solution is used for sterilization?The process involves the use of formalin, which is vaporized into a formaldehyde gas that is admitted into the sterilization chamber. A formaldehyde concentration of 8-16 mg/l is generated at an operating temperature of 70-75°C.
What chemical is used for sterilization and disinfection?These include alcohols, chlorine and chlorine compounds, formaldehyde, glutaraldehyde, ortho-phthalaldehyde, hydrogen peroxide, iodophors, peracetic acid, phenolics, and quaternary ammonium compounds.
What is used for sterilizing materials?Sterilization is the complete removal or destruction of all forms of microbial life, including bacteria, viruses, fungi and spores. Sterilization is achieved by steam, dry heat, ethylene oxide gas and liquid chemosterilizers. item is contaminated. A SAL of 6 is acceptable for a critical item.
What are the 4 types of sterilization?4 Main Methods of Sterilization | Organisms | Microbiology. Physical Methods: ... . Radiation Method: ... . Ultrasonic Method: ... . Chemical Method:. |
What agent is used for sterilization?
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