Sterilization by radiation

The irradiation of polymers is widespread in many industries. For example, microlithography is an essential process in the fabrication of integrated circuits that involves the modification of the solubility or volatility of thin polymer resist films by radiation. The sterilization by radiation of medical and pharmaceutical items, many of which are manufactured from polymeric materials, is increasing. This trend arises from both the convenience of the process and the concern about the toxicity of chemical sterilants. Information about the radiolysis products of natural and synthetic polymers used in the medical industry is required for the evaluation of the safety of the process. 

The field of carbohydrate radiation chemistry was reviewed by Phil-lips12,13 in 1961 and in 1971. Since then, knowledge has increased so rapidly that it is useful to review it anew. Those readers interested in food sterilization by radiation, and in related studies on carbohydrates, are referred to the review by Dauphin and Saint-Lebe,14 wherein references not given in the present article may be found. 

Food and instruments can also be sterilized by radiation treatment with no overall harmful effects. 

Heat-sensitive materials may be sterilized by radiation, providing the product and its container are not radiation sensitive. It is particularly used with plastics, and more widely used with containers than with products. An alternative is ethylene oxide gas. This presents problems in that the gas must be brought into contact with the cell walls of contaminating bacteria. Ethylene oxide is highly reactive and can only be used when it can be proved not to react with the product. 

This property of radiation processing was used early on for polymer modification. Nowadays, the modification of polymers covers radiation cross-linking, radiation induced polymerization (graft polymerization and curing) and the degradation of polymers. Likewise, medical products to be sterilized by radiation are often made from polymeric materials, which must be resistant to the administered dose. 

Ionizing radiation has been used to control harmful insects. Captured males are sterilized by radiation and released to mate, thereby reducing the number of offspring. This method has been used to control the Mediterranean fruit fly in California and disease-causing insects, such as the tsetse fly and malarial mosquito, in other parts of the world. 

Sterilization by radiation must be carried out by exposure to radiation which ensures sterilization according to defined parameters this type of sterilization must be compatible with the nature of the product or material the packaging and the distribution of the load in the packing. 

Medical applications of PP such as disposable syringes, hospital trays, and labware are contingent on sterilizability, either autoclaving or radiation. Disposable syringes that are sterilized by radiation require special formulations to prevent discoloration (yellowing) or brittleness as a consequence of degradation and cross-linking. 

When a = 1, Af, = 2 M . G of CM-chitosan in solid state calculated by the Charlesby-Pinner equation is 0.49, which means that CM-chitosan has good stability even when the absorbed dose reaches the sterilization dose (25kGy). Therefore, it can be sterilized by radiation that is promising for biomedical application. 

After implantation as dural substitute, collagen gradually degrades and cells synthesize their own dura mater. The non-degradable PET mesh remains in organism as unnecessary ballast. It is very important that collagen biomaterials can be effectively cross-linked and simultaneously sterilized by radiation technique, which does not produce toxic by-products detrimental to wound healing. 

Commercial polymer films can be easily microstructured using Laser Interference Patterning. In that way, the scope of the technique is increased since materials having well-known bulk and surface properties can be microstructured, allowing direct application, for example, in biomedical devices poly(etheretherketone) resists sterilization by radiation or heat treatment and it has been used to produce kidney dialysis machine components poly(etherimide) is used in harmonic scalpels polycarbonate (PC) is used in electrophysiology cathethers and poly(imide) (PI) is used in off pump coronary artery bypass devices.Moreover, the surface of already fabricated systems could be modified using this technique since it can be applied in air without altering the shape of the samples. 

Radiation-induced changes in plastics can be reduced or increased by certain measures. Stabilization is desired for plastics used, e.g., in nuclear reactor construction, or intended to be sterilized by radiation. Here, irradiation doses can reach levels of several kGy at which plastic properties would already begin to change. Sensibilization, on the other hand, is desired for radiation-chemical processes to reduce the doses required for crosslinking or for other reactions, i.e., to lower the cost of irradiation. Stabilization and sensibilization thus can affect various parallel reactions either uniformly or selectively [710]. 

Because of the health and environmental issues with ethylene oxide sterilization, numerous manufacturers of medical products prefer sterilization by radiation. This method is clean, leaves no residue, and enables sterilization of packaged parts. Due to the complex safety technology and high capital investment, sterilization and shipping are often outsourced to specialized companies. 

Paper/foil and paper/film laminations are used for many appHcations including candy wrappers, microwave packaging, ice cream carton lids, and reflective building insulation. Flexible laminations are multilayered composites, with each each component providing special properties. Examples include snack food bags, aseptic containers sterilized by radiation or heat, meat packages, solar screen laminations, and flexible air ducts. 

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