Packaging and sterilization

Because medical textile materials are used in a medical environment, quite often in direct contact with the human body, it is important to ensure that these materials are sterile prior to application, that is, they are free of bacterial contamination. Sterility of the finished product is achieved in two stages first, medical textile materials are packed in appropriate packaging and second, they are sterilized with an appropriate method. 

Because of the wide variety of products in the medical textiles industry, packaging requirements differ from product to product, and a wide range of materials can be used to pack medical textile products. For the production of wound dressings, individual products are first packed in pouches before being packed into cartons and boxes. The pouches are often made from a combination of paper, polymer film, and aluminum 

Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents such as fungi, bacteria, viruses, spore, etc., which are present on a surface or contained in a fluid or a compound such as a medical textile material. Sterilization can be achieved by applying heat, chemicals, irradiation, high pressure, or filtration. In the medical textile industry, the main methods used to sterilize products are heat, ethylene oxide, gamma irradiation, and electron radiation. 

A typical sterilization process with EtO consists of a preconditioning phase, the actual sterilization run, and a period of poststerilization aeration to remove toxic residues, such as EtO, ethylene glycol (formed out of EtO and ambient humidity), and ethylene chlorohydrme (formed out of EtO and materials containing chlorine, such as PVC). In the medical device industry EtO is the most common sterilization method, used for over 70% of total sterilizations and 50% of all disposable medical devices. 

Radiation sterilization involves the exposure of medical textile products to radiations such as electron beams. X-rays, gamma rays, or subatomic particles. Gamma rays are very penetrating and are commonly used for the sterilization of disposable medical 

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Sanitization is a cleaning procedure that reduces microbial contaminants on certain surfaces to safe or relatively safe levels, as defined by the EPA or pubHc health authorities. The article is usually cleaned with hot water and various germicidal detergents. Sanitization can be safe for a product in contact with intact skin or for food utensils, but it is not considered safe for articles to be inserted in the human body. Effective sanitization is a requirement in the processing of reusable medical suppHes before packaging and sterilization. It is also a requirement in the maintenance of utensils and containers used for food preparation. 

Jerusalem artichoke hydrolyzate, preparation of a osmanthus flower extract, and blending, packaging, and sterilizing. 

The formulation, analytical chemistry, packaging and sterilization/microbiological work needed and... 

The purpose of this chapter is to review historical and contemporary packaging and sterilization methods for UHMWPE. Obviously, all of the sterilization methods currently employed by the orthopedic community fulfill their intended purpose, namely the eradication of bacterial agents, which may result in sepsis and premature revision. The diverse sterilization methods in current use reflect the lack of scientific consensus as to which of the currently favored sterilization methods provides the most advantageous long-term UHMWPE product for the ultimate user, namely the patient. 

In the Longevity process, the UHMWPE bars are warmed, placed in a carrier on a conveyor, and are exposed to electron beam radiation, with a total dose of 100 kGy. The UHMWPE does not heat above the melt transition during the crosslinking. After irradiation, the UHMWPE is heated above the melt temperature (>135°C) for stabilization of free radicals. Components are then machined from the Longevity material, enclosed in gas-permeable packaging, and sterilized by gas plasma. 

The Prolong process is similar to the previously described DURASUL except that an electron beam irradiation dose of 65 kGy is used for Prolong and continuous compression-molded bars are processed as with Longevity. Components are machined from processed Prolong maferial, enclosed in gas-permeable packaging, and sterilized by gas plasma (Figure 15.6). 

Sterilization by various methods (conventional steam autoclaving, dry heat sterilization in air at 160-180°C, and packaging and sterilization in sealed glass ampoules) originates films with the composition Ti02- Their thickness is 2-6 nm, depending on the method of sterilization. Heat sterilization increased the thickness of the original oxide by a factor of ca. 2 (Lausmaa and Kasemo, 1990). 

Once a deiice is formulated, processed, stablized, packaged and sterilized, it is important to chemically and physically characterize the product to insure that the final device is safe and remains die same from lot to lot. These tests include biocompatibility assessment, mechanical stablity, biodegradation rate and in vivo function in an end-use application. 

The distortion of components by the heat treatments can occur but this problem can be solved by controlling the uniformity of heating. Another undesirable effect of the heat treatment is the formation of surface oxide scales which have to be removed either chemically (acid) or mechanically (sand-blasting). After the scales are removed the surface of the component is polished to a mirror or mat finish. The surface is then cleaned, degreased, and passivated in nitric acid (ASTM Standard F86). The component is washed and cleaned again before packaging and sterilizing. 

In order to possess the right characteristics to meet end-use requirement, fibers, yams, and textile fabrics are often treated in a number of chemical, physical, and biological processes, such as bleaching to remove impurities and dyeing to give the material appropriate color and appearance. In addition to these traditional processes, textile materials used for medical applications need to be packaged and sterilized before they can meet the functional and safety requirements of a medical product. 

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