What is radiation sterilization for? Radiation sterilization. Sterilization of medical devices made of polymer materials

In recent years, new safe sterilization technologies have appeared - electron beam and gamma radiation sterilization.

The electron beam method uses a high level of electron energy as a means of sterilization. Electrons are accelerated to the speed of light using a linear accelerator. Electron energy in the range from 3 to 10 million electron volts (MeV) with a beam power in the range from 1 to 10 kW is sufficient to penetrate into the product, hermetically packed in a container ready for shipment.

When electrons scan a product, they pass through a variety of secondary particles, including ions and free radicals. Secondary particles break the DNA chains of microorganisms both on the inner surface of the package and inside the product, thus blocking their further multiplication. Pathogenic microbes are destroyed, and as a result, the product is sterilized.

The sterilizing agent for radiation sterilization can also be penetrating gamma or beta radiation. The most widely used is the gamma-emitting isotope of cobalt-60, less often the isotope of cesium-137 due to its low energy and radiation levels. Beta-emitting isotopes are rarely used in general, since beta-radiation has much less penetrating power.

The effectiveness of radiation sterilization depends on the total radiation dose and does not depend on time. The average lethal dose for microorganisms is always the same, whether irradiation is carried out at a low intensity for a long period of time or for a short time at a high radiation intensity. A dose of 25 kGy (2.5 Mrad) reliably guarantees the destruction of highly resistant spore forms of microorganisms.

Radiation sterilization has a number of technological advantages: a high degree of inactivation of microorganisms, the ability to sterilize large batches of materials, process automation, the ability to sterilize materials in any hermetically sealed packaging (except radio nontransparent). An important circumstance is that the temperature of the sterilized products does not increase during sterilization.

Note that electron-beam (EL) radiation does not imply deep penetration into the product, as gamma radiation does. Depending on the density of the product, EL radiation penetrates the product to a depth of 40 cm from the surface. The effect of EL radiation is limited to a few seconds, as opposed to many hours of exposure to gamma radiation.

The short duration of exposure to accelerated electrons reduces the possible effects of oxidation, minimizing disruption to the structure of both the product and the packaging material. With time and advanced technology development, the cost of EL sterilization has dropped to an acceptable level, generating interest from the food and packaging industry. The cost of sterilization by ionizing radiation is 4-5 times lower than the cost of sterilization by thermal or gas method.

Radiation sterilization of medical devices is one of the most advanced radiation-technological processes introduced in our country and in many countries.

Due to its high penetrating power, it is possible to sterilize medical products in a packaged and ready-to-release form, which gives additional advantages to the method of radiation sterilization compared to traditional methods.

In recent years, there has been an increase in demand for sterile medical devices for single use. Currently, disposable medical clothing, underwear and disposable medical supplies personal protection are increasingly used in medical institutions of the Russian Federation. The range of medical devices subjected to radiation sterilization comprises more than 254 types of products.

The technology of radiation sterilization of the following medical devices is practically used:

  • Single-use medical devices in contact with blood and lymph (single-use injection syringes, single-use injection needles, etc.);
  • Medical devices in constant or long-term contact with internal environment organism (implantable catheters, sensors, contraceptives, orthopedic endoprostheses);
  • Medical devices in contact with the wound surface (dressings, anti-burn, drainage, absorbent materials, surgical suture material, etc.);
  • Products that are in contact with mucous membranes and skin for a long time (gynecological, urological, dental instruments);
  • Medical clothing, underwear and disposable medical personal protective equipment.

The use of radiation to supply objects in need of conservation and intended for medical use is called radiation sterilization. With radiation sterilization, dehumidification is achieved without high temperature, therefore radiation or radiation sterilization is also called cold.

The radio sterilization method must meet two requirements:

Irradiation should have a bactericidal effect on microorganisms with different radiosensitivity;

Radio sterilization should not change the qualities and properties of the processed objects.

With the help of ionizing radiation, dressings and sutures, some drugs, including antibiotics and hormones, biological tissues, etc. are sterilized.

Ionizing radiation is also used to produce vaccines and sterilize toxins. Particularly promising is the method of radiation sterilization of various disposable plastic products, for example, blood service systems and syringes. A single use of these syringes eliminates the risk of contracting infectious hepatitis, which is observed when sterilizing syringes in the usual way. Radiation sterilization is widely introduced into the production of such medical devices from polymeric materialslike syringes, blood service systems, and drugs and biological tissues.

At the same time, the introduction of radiation sterilization into practice encounters some difficulties associated with the need for significant costs for the construction of special radiation installations and the purchase of radioactive sources, the cost of which remains very high everywhere. However, as shown by economic calculations made by foreign firms, the costs are paid off within the first few years.

Sterilization of medical devices made of polymer materials

This group includes products that are used once. Single use is determined by two conditions:

1) The most important is the need to exclude the possibility of transmission of infection with repeated or repeated use of the product, even if it is sterilized after use.

2) limiting multiple use of the product, depends on the degree of radiation resistance of the polymer material, which changes its structure, deforms, loses its elasticity, strength and transparency, may begin to release substances that have a toxic effect on the body. The most widespread are syringes. Disposable syringes are produced in millions of pieces per year and are subjected to radiation sterilization of various sizes and designs, with or without needles, for hypodermic injection.

Plastic syringes are produced and sterilized by the radiation method in the USA, England, Sweden, Denmark, Norway, Finland, France, Canada, Italy, Germany and other countries. Typically, each syringe (with or without a needle) is individually packaged to ensure the sterility of the product after radiation treatment for long term (1-2 years). Sometimes some companies produce syringes in double packs, which to a greater extent guarantees against the ingress of microorganisms on the product from the external environment. However, for the most part, several individually wrapped syringes are placed in a common second package.

Several small batches of double-packed syringes are stacked in boxes and sterilized in large batches. For sterilization, two types of radiation installations are used:

1.isotopic, in which Co 60 is used as a source of gamma radiation;

2. electron accelerators.

Controversy flares up when choosing a sterilizing dose for syringes. There are two points of view. In the United States and England, a dose of 25 kGy is accepted for sterilizing syringes, and in the Scandinavian countries the minimum sterilizing dose is 32 kGy (when sterilized on gamma devices) -35 kGy (when sterilized on accelerators). The dose of 25 kGy was chosen in the USA based on the work of Van Winkle, carried out in the 50s, and showed that the most resistant microorganisms that seeded products manufactured in the USA "can die at 19 kGy, even if they are present in concentrations higher than at Depending on a number of factors ("safety factor", density change), the dose guaranteeing sterility ranged from 23 to 26 kGy. These values \u200b\u200bdetermined the choice of a dose of 25 kGy for single-use medical devices made of plastic. Somewhat later in Denmark, in In connection with the beginning of the industrial production of radiation-sterilized disposable syringes, E. Christensen basic researchshowing that in the air industrial premises and the products themselves may contain highly radioactive microorganisms. To achieve a bactericidal effect when seeding with these highly radioactive bacteria, a dose significantly exceeding 25 kGy was required. An increase in the radiation dose for reliable sterilization required not only a high degree of radioresistance of the identified bacteria, but also the number of bacteria per unit of sterilized products before irradiation - the initial contamination of the product.

At present, the magnitude of the initial contamination plays a decisive role in the choice of the radiation dose and for hygiene requirements in production, therefore, even in those countries where a dose of 25 kGy is used for sterilizing plastic products, a mandatory study of the initial contamination of products is carried out. In recent years, due to the increasing demand from healthcare for disposable syringes, some countries have purchased syringes. Thus, they use products that have been sterilized at doses significantly higher than 25 kGy. The Scandinavian countries, which widely use radiation sterilization of single-use plastic medical devices, must take into account the amount of initial contamination of syringes when choosing a radiation dose and proceed from the fact that the more microorganisms seeding the product, the more chances that microorganisms with high radio resistance. In this case, a dose of 25 kGy does not guarantee the sterility of all products.

The method of radiation sterilization is also widely used for the provision of blood service products (transfusion and blood collection systems, blood storage bags). For these products, as well as for various plastic tubes and catheters that are inserted into the body during operations and research, increased requirements are imposed on the reliability of sterilization. The special requirement for sterility of these products is understandable. It is connected with the fact that blood service systems (blood collection and transfusion, bags or reservoirs for storing blood) are used in medical practice for blood transfusion to sick people with weakened resistance to infection. Therefore, the ingress of even units of microorganisms into such a weakened organism can lead to serious complications, for example, to blood poisoning.

Blood service systems consist of various components: tubes, droppers, filters, needles, clamps. All of these parts are made of various polymeric materials and metal. When parts of the system are manually assembled, they become contaminated and therefore the initial contamination of the blood service systems is much greater than the initial contamination of syringes or catheters that do not require manual assembly. The complexity of products and the presence of solid parts with an angular shape often lead to a violation of the sealing of individual packaging, both during sterilization and during storage of systems. Therefore, double packaging is used everywhere; either each product is enclosed in two bags (the inner one, directly adjacent to the product, and the outer one, into which the already sealed hermetically sealed inner bag with the product is inserted), or several systems (5-10 pieces, each individually wrapped) are enclosed in a common outer bag ... The relatively large initial contamination of the blood service systems and their use for an organism with a reduced resistance to infection, for a weakened organism, requires a particularly careful approach to the choice of a sterilizing dose of radiation. In this case, for greater assurance, they prefer to irradiate in doses approaching 40 kGy or even more than 42-45 kGy.

The question of the sterilizing dose of radiation in the radiation sterilization method is the main, if not decisive, in the whole problem of radiation sterilization, since the radiation dose determines the feasibility and cost of the process. The expediency of using the method of radiation sterilization is limited, in turn, by the radiation resistance of polymer materials of products and packaging. All this taken together has a great influence on the sanitary and hygienic requirements for factories - manufacturers of products subject to radiation sterilization, and for the packaging of these products: the very materials from which the products are made and in which they are packed, and to the tightness of the packaging. When sterilizing other medical devices made of plastics that are used once, the same requirements should be observed regarding the radiation dose, initial contamination and sanitary and hygienic conditions at work, the radiation resistance of the materials from which the device is made, and regarding packaging.

In still big guarantees The artificial blood vessels, artificial heart valves, plastic tubes used in tracheotomy, which are now widely used in surgery, are in need of sterility, in stricter sanitary and hygienic conditions during manufacture and the lowest possible initial contamination. The range and number of plastic medical products is growing all the time, and products subject to radiation sterilization reach tens and hundreds of millions of pieces annually - even for such small countries as Denmark, Holland, Belgium and Sweden. The constant increase from year to year in the demand for medical devices made of disposable plastics, as well as the use of the method of radiation sterilization of laboratory glassware made of polymer materials, is forcing the development of the branch of radiation technology, which creates large stationary irradiation installations of industrial type. These installations, which require significant capital investment, add to the cost of radiation sterilization compared to heat or gas sterilization. However, the longer this installation is in operation, the less sterilization of medical devices costs every year. It should be borne in mind that modern medicine cannot do without the use of such products, materials and drugs that require radiation sterilization. Therefore, in spite of the fact that the cost of radiation sterilization will remain higher for a long time in comparison with the cost of other sterilization methods, it is impossible to refuse this method for economic reasons.


Sterilization involves the complete inactivation of microbes in the objects being processed.

There are three main methods of sterilization: thermal, radiation, chemical.

Heat sterilization based on the sensitivity of microbes to high temperatures. At 60 ° C and the presence of water, protein denaturation, degradation of nucleic acids and lipids occurs, as a result of which the vegetative forms of microbes die. Spores containing a very large amount of water in a bound state and having dense membranes are inactivated at 160-170 ° C.

For heat sterilization, mainly dry heat and pressurized steam are used.

Dry heat sterilization is carried out in air sterilizers (formerly known as "dry heat ovens" or "Pasteur ovens"). An air sterilizer is a metal, tight-fitting cabinet, electrically heated and equipped with a thermometer. Disinfection of the material in it is carried out, as a rule, at 160 ° C for 120 minutes. However, other modes are also possible: 200 ° С - 30 min, 180 ° С - 40 min.

Sterilized by dry heat laboratory glassware and other glass products, tools, silicone rubber, i.e. objects that do not lose their qualities at high temperatures.

Most of the items to be sterilized cannot withstand this kind of treatment, and therefore are disinfected in steam sterilizers.

Steam treatment under pressure in steam sterilizers (formerly called "autoclaves") is the most versatile sterilization method.

A steam sterilizer (there are many modifications) is a metal cylinder with strong walls, hermetically sealed, consisting of a steam and sterilizing chambers. The device is equipped with a manometer, thermometer and other instrumentation. The autoclave is pressurized, which increases the boiling point.

Since, in addition to the high temperature, microbes are also affected by steam, the spores die already at 120 ° C. The most common operating mode for a steam sterilizer is 2 atm. - 121 ° C - 15-20 min. The sterilization time decreases with increasing atmospheric pressure and, consequently, the boiling point (136 ° C - 5 min). Microbes die in a few seconds, but the material is processed for a longer time, since, firstly, there must be a high temperature inside the material to be sterilized and, secondly, there is a so-called safety field (designed for a small malfunction of the autoclave).

Most of the items are sterilized in an autoclave: dressings, linen, corrosion-resistant metal instruments, culture media, solutions, infectious material, etc.

Sterilization over an open fire. Photo: musicalwds

One of the types of heat sterilization is fractional sterilization, which is used to process materials that cannot withstand temperatures above 100 ° C, for example, to sterilize culture media with carbohydrates, gelatin. They are heated in a water bath at 80 ° C for 30-60 minutes.

Currently, one more method of heat sterilization is used, designed specifically for milk - ultra high temperature (UHT): milk is processed for several seconds at 130-150 ° C.

Chemical sterilization involves the use of toxic gases: ethylene oxide, a mixture of OB (a mixture of ethylene oxide and methyl bromide in a weight ratio of 1: 2.5) and formaldehyde. These substances are alkylating agents, their ability in the presence of water to inactivate active groups in enzymes, other proteins, DNA and RNA leads to the death of microorganisms.

Gas sterilization is carried out in the presence of steam at a temperature of 18 to 80 ° C in special chambers. In hospitals, formaldehyde is used, in industrial conditions - ethylene oxide and a mixture of OB.

All products to be processed must be dried prior to chemical sterilization.

This type of sterilization is unsafe for personnel, for environment and for patients using sterilized items (most sterilizing agents remain on the items).

However, there are objects that can be damaged by heat, such as optical instruments, radio and electronics, items made of non-heat-resistant polymers, culture media with protein, etc., for which only chemical sterilization is suitable. For example, spaceships and satellites equipped with precision equipment are decontaminated with a gas mixture (ethylene oxide and methyl bromide) for their decontamination.

Recently, in connection with the widespread use in medical practice of products made of thermolabile materials equipped with optical devices, for example, endoscopes, they began to use neutralization using chemical solutions. After cleaning and disinfection, the device is placed for a certain time (from 45 to 60 minutes) in a sterilizing solution, then the device must be washed with sterile water. For sterilization and washing use sterile containers with lids. The product sterilized and washed from the sterilizing solution is dried with sterile wipes and placed in a sterile container. All manipulations are carried out under aseptic conditions and with sterile gloves. These products are stored for no more than 3 days.

Radiation sterilization carried out either with the help of gamma radiation or with the help of accelerated electrons.

Radiation sterilization is an alternative to gas sterilization in an industrial setting, and it is also used in cases where the items to be sterilized cannot withstand high temperatures. Radiation sterilization allows you to process a large number of items at once (for example, disposable syringes, blood transfusion systems). Due to the possibility of large-scale sterilization, the use of this method is quite justified, despite its environmental hazard and uneconomic efficiency.

Another sterilization method is filtration. Filtration using various filters (ceramic, asbestos, glass), and especially membrane ultrafilters from colloidal solutions of nitrocellulose or other substances, allows you to free liquids (blood serum, drugs) from bacteria, fungi, protozoa and even viruses. To accelerate the filtration process, an increased pressure is usually created in the container with the filtered liquid or a reduced pressure in the container with the filtrate.

At present, modern methods of sterilization, created on the basis of new technologies, using plasma and ozone are finding more and more widespread use.



The beginning of the development of radiation sterilization was laid about 15 years ago. Scientists found that the methods of disinfecting and preserving food products existing at that time worsen the state of the planet's ozone layer. A new method was developed - processing with gamma rays and accelerated electrons.

This method proved to be much more effective - food remained usable longer. For a long time, their appearance and taste properties. The technique was approved by representatives The World Organization health care. Now radiation sterilization is carried out in about seventy countries of the world.

According to statistics compiled by members of the International Radiation Association, European countries send over 200,000 tons of irradiated food to the market every year. An optimal gamma ray treatment mode has been developed for most products. A study of their harmlessness and suitability for use was carried out.

The use of radiation sterilization in medicine

Gamma radiation is becoming more and more widespread as a method for disinfecting dressings, medicines, and surgical instruments. It is also used for pharmaceutical serums, food products, etc. This method is referred to as cold sterilization, since the temperature of the irradiated object rises slightly.

In such industrial sector special installations are used, the operation of which is carried out in strict accordance with the instructions. When sterilization is required on a solid scale, conveyors are created. Materials are processed in packaged form.

The enterprises are installing electron accelerators and gamma installations. During the passage of electrons through matter, a large proportion of their energy is spent on ionization. As a result, the destruction of microorganisms is carried out. The level of viruses and disease-causing bacteria is reduced in proportion to the amount of used electron energy.

The advantages of radiation sterilization over gas

The goods are processed by being placed in sealed packages. Thanks to this, their shelf life is increased. You can start using the products immediately after irradiation.

In the field of operation of the irradiation facility, no associated harmful substances are generated. Products sterilized by gamma rays remain dry and free from carcinogenic components.

Radiation sterilization of medical devices, pharmaceuticals, packaging, cosmetics and raw materials of plant and animal origin

Ionizing radiation applications
Ionizing radiation is widely used in various industries:
1. Modification and improvement of material properties
Stitching of polymers (cables and wires, pipes)
Manufacture of heat-shrinkable products
Stitching of electrical products
Modification of tire components
2. Food processing
Decontamination and shelf life extension
Disinsection of agricultural products
Phytosanitary control of products
3. Sterilization of medical devices
Sterilization of disposable medical products
Sterilization of pharmaceutical products
Sterilization of raw materials of plant origin
4. Environmental applications radiation
Cleaning of associated gases
Cleaning wastewater
Disinfection of hazardous organic and medical waste

Applied equipment
The company "Accentr" plans to place on the territory Ivanovo region an enterprise for radiation processing of products at contract basis
-
Center for radiation sterilization.
The main task of the projected enterprise is "Sterilization of medical products"
The Radiation Sterilization Center includes:

Installation based on an electron accelerator with a capacity of up to 15000 kg / h

Warehouse complex for 5000 m2 for storing processed and unprocessed products

Microbiological and radiation control laboratories to ensure quality control of the processing process
Radiation processing facility based on high-energy linear electron accelerator, 10 MeV, 20 kW


Radiation Sterilization Center.

Comprehensive solution.

The center provides everything the necessary conditions to ensure a high-quality and efficient sterilization process
Radiation
sterilization
Laboratory
radiation monitoring
Laboratory
microbiological
control
Optimal geographic location allowing to reduce the manufacturer's costs for product logistics -\u003e to reduce the cost.
High production capacity.
The possibility of a significant increase in the volume of sterile products - sterilization is no longer a limiting factor.
Certification according to international standards ISO 13485, ISO 11137, ISO 9000
Quality control: the ability to export products of medical devices manufacturers to the EU, USA.
Consulting on the sterilization process.
 Development of sterilization technology, selection of packaging, selection of materials to ensure high quality and economical.

Radiation Sterilization Center

The main services of the Center for Radiation
processing:

Radiation sterilization of medical devices
Radiation sterilization of pharmaceuticals
 Sterilization of raw materials of plant and animal origin
 Sterilization / disinfection of packaging materials
Sterilization of cosmetic and perfumery products
The center also offers a number of services for
quality assurance of processing
products:
Development technological process sterilization of all products
Developing requirements for product packaging to ensure cost-effective and quality sterilization
Conducting periodic validations of the sterilization process
Conducting routine daily monitoring
Microbiological control of bioburden of non-sterile products
Control of dose absorption

Benefits of radiation sterilization



Simplicity and reliability of the sterilization process.
To achieve stable sterilization results, it is necessary to control only 3 parameters (beam energy, electron beam current, conveyor speed). The sterilization process is automatically controlled automated system control, all parameters are recorded and monitored to ensure reliability and stability of the result, which guarantees a sterility level of products 10
-6.

High productivity and processing time
The production capacity of the plant allows processing up to 150,000 cubic meters of products per year. Sterilization of one package of products occurs in a matter of seconds.
The products are ready for use immediately after the completion of the sterilization process; it does not take a long time to aerate the products.

Processing of products in final packaging
Ionizing radiation has a high penetrating ability, which makes it possible to process products in transport packaging.

Does not require specialized packaging.
Suitable for all types of packaging materials. No specialized gas-permeable or vapor-permeable materials are required.

Process suitable for heat sensitive products

Clean process. There is no chemical contamination of products.

Sterilization technologies.





Parameter / Technology



Thermal
Chemical
Radiation
Steam-treatment with saturated steam under pressure
Air-treatment with dry hot air
Glasperlen - the environment of incandescent glass balls
Ethylene oxide gas vapor
(ethylene oxide sterilization), formalins, etc.
Antiseptic solutions (formaldehyde, glutaraldehyde, ethyl alcohol, hydrogen peroxide, chlorhexidine, etc.)
Effect of electron beam radiation
The action of gamma radiation (source -
cobalt60, less often cesium).
Performance
Sterility degree
Duration of product processing
Initial investment volume
Packaging requirements
Legend
The best indicator for this parameter among the technologies under consideration
Average indicator for this parameter among the technologies under consideration
The worst indicator for this parameter among the technologies under consideration

Sterilization technologies.

№
Product group of medical
products / Method
Radiation
Gas


Steam


1.
Single-use syringes
±***
±***
-
2.
Dressings and Wound Care
+
±**
±*
3.
Disposable nonwovens for patient and medical staff protection
+
±**
-
4.
Sterile surgical materials for tissue joining
+
+
±*
5.
Catheters, medical tubes
+
+
±*
6.
Sterile medical gloves
+
+
-
7.
Medical instruments
+
+
±*
8.
Blood transfusion systems
+
+
±*
* Steam sterilization method is only suitable for heat-resistant materials. Most modern medical devices are not resistant to high temperatures (they are destroyed, lose their properties).
** Absorption of toxic gases by nonwoven fabrics is possible for some types of fibers.
*** Application of radiation sterilization methods is possible if the syringe is made of radiation-resistant polypropylene.
**** In some syringe designs, EtO will not penetrate the space between the stem and barrel.

Factors in which only radiation sterilization is possible

For some types of products, only radiation sterilization is applicable:
Closed packaged products
-Many products are made of highly durable and non-breathable materials that cannot be sterilized by methods that require steam or gas penetration and pressure changes. These products range from medical products to raw materials and consumer products such as peat, teats and teething rings for children, and all hermetically sealed products.
Densely packed products
- a large amount of raw materials packed in boxes and barrels cannot be sterilized with gas or steam due to their limited penetration into the product. In this case, steam and gas can lead to the formation of lumps or other types of product deterioration. Spices, talc, raw materials of plant and animal origin, powders and other similar materials are processed precisely by the radiation method.
 Unwanted chemical residues in products
- some types of products absorb / adsorb chemical reagents or products of their reactions during gas sterilization. Radiation sterilization is a "clean" process as no chemical agents are used, only reading energy.

 

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