Why is radiation sterilization necessary? Radiation sterilization. Sterilization of medical devices made of polymeric 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 of 3 to 10 million electron volts (MeV) with a beam power in the range of 1 to 10 kW is sufficient to penetrate the product, hermetically packed in ready-to-ship containers.

The electrons, scanning the product, pass through many secondary particles, including ions and free radicals. Secondary particles break the DNA chains of microorganisms and inner surface packaging, and inside the product, thus blocking their further reproduction. Pathogenic microbes are destroyed, and as a result, products are sterilized.

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

The effectiveness of radiation sterilization depends on the total radiation dose and does not depend on time. The mean lethal dose for microorganisms is always the same, whether irradiation is carried out at low intensity for a long period of time or briefly at 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: high degree inactivation of microorganisms, the possibility of sterilizing large batches of materials, process automation, the possibility of sterilizing materials in any sealed package (except radioopaque). An important circumstance is that the temperature of the sterilized products does not increase during sterilization.

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

The short duration of exposure to accelerated electrons reduces the potential effects of oxidation, minimizing disruption to the structure of both the product and the packaging material. With time and in-depth development of technology, the cost of EL sterilization has dropped to a quite acceptable level, causing interest from the food and packaging industries. The cost of sterilization by ionizing radiation is 4-5 times lower than the cost of sterilization by thermal or gas methods.

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

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

In recent years, there has been an increase in demand for sterile single-use medical products. At present, disposable medical clothing, underwear and disposable medical devices personal protective equipment are increasingly being used in medical and preventive institutions of the Russian Federation. The range of medical products subjected to radiation sterilization is more than 254 types of products.

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

  • Single-use medical products that come into contact with blood and lymph (single-use injection syringes, single-use injection needles, etc.);
  • Medical devices in constant or prolonged contact with internal environment body (implanted catheters, sensors, contraceptives, orthopedic endoprostheses);
  • Medical products in contact with the wound surface (dressing, anti-burn, drainage, absorbent materials, suture surgical 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 decontaminate objects in need of conservation and intended for medical use is called radiation sterilization. With radiation sterilization, sterilization is achieved without high temperature, therefore radiation or radiation sterilization is also called cold sterilization.

The radiosterilization 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 treated objects.

With the help of ionizing radiation, dressings and suture materials, 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 products made from plastics, such as blood service systems and syringes. The single use of these syringes eliminates the risk of infection with 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 polymer materials like 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 pay off within the first few years.

Sterilization of medical devices made of polymeric 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 through repeated or repeated use of the device, even if it is sterilized after use.

2) limiting repeated use of the product, depends on the degree of radiation resistance of the polymer material, which changes its structure, deforms, loses elasticity, strength and transparency, can begin to release substances that have a toxic effect on the body. Syringes are the most widely used. A variety of sizes and designs, with and without needles, for hypodermic injections, disposable syringes are produced in millions of pieces per year and are subjected to radiation sterilization.

Plastic syringes are manufactured and sterilized by radiation 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 packaging, which to a greater extent guarantees that microorganisms do not get on the product from external environment. However, for the most part, several individually wrapped syringes are placed in a common second pack.

Several small batches of double-wrapped syringes are boxed 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 of radiation for syringes. There are two points of view. In the USA and England, a dose of 25 kGy has been adopted for sterilization of syringes, and in the Scandinavian countries, the minimum sterilizing dose is 32 kGy (for sterilization at gamma units) -35 kGy (for sterilization at accelerators). The dose of 25 kGy was chosen in the USA based on Van Winkle's work in the 1950s, which showed that the most resistant micro-organisms that seeded products manufactured in the USA could die at 19 kGy, even if they were present at concentrations higher than at normal contamination.Depending on a series of factors ("safety factor", change in density), the dose guaranteeing sterility ranged from 23 to 26 kGy. These values ​​determined the choice of a dose of 25 kGy for disposable medical products made of plastic. Somewhat later in Denmark in connection with the start of industrial production of radiation-sterilized disposable syringes by E. Christensen were carried out fundamental research showing that in the air industrial premises and the products themselves may contain highly radio-reactive microorganisms. To achieve a bactericidal effect upon seeding with these highly radioactive bacteria, a dose significantly exceeding 25 kGy was required. An increase in the radiation dose for reliable sterilization was required not only by a high degree of radioresistance of the detected bacteria, but also by the number of bacteria per unit of sterilized products before irradiation - the initial contamination of products.

At present, the value of initial contamination plays a decisive role in choosing the dose of radiation and for hygiene requirements in production, so even in countries where for sterilization plastic products a dose of 25 kGy is accepted, a mandatory study of the initial contamination of products is carried out. In recent years, due to the growing public health demand for disposable syringes, some countries have purchased syringes. Thus, they use products sterilized at doses well above 25 kGy. The Scandinavian countries, which widely use radiation sterilization of single-use plastic medical products, when choosing the radiation dose, must take into account the initial contamination of syringes and proceed from the fact that the more microorganisms inoculate the product, the more likely it is that among them there may be microorganisms with high radioresistance. In this case, the dose of 25 kGy does not guarantee the sterility of all products.

The method of radiation sterilization is also widely used for decontamination of blood service products (blood transfusion and collection systems, blood storage bags). For these products, as well as for various plastic tubes and catheters that are introduced into the body during operations and research, there are increased requirements for the reliability of sterilization. The special demands on the sterility of these products are understandable. It is related to the fact that blood service systems (blood collection and transfusion, blood bags or reservoirs) are used in medical practice to transfuse blood to sick people with weakened resistance to infection. Therefore, even a few microorganisms entering 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 these parts are made of various polymeric materials and metal. When parts of the system are manually assembled, they are contaminated and therefore the initial contamination of blood service systems is much greater compared to the initial contamination of syringes or catheters that do not require manual assembly. The complexity of products and the presence of solid parts that have an angular shape often leads 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 (internal, directly adjacent to the product, and external, into which an already hermetically sealed inner bag with the product is placed), or several systems (5-10 pieces, each in individual packaging) are enclosed in a common outer bag . The relatively large initial contamination of blood service systems and their use for an organism with reduced resistance to infection, for a weakened organism, require a particularly careful approach to the choice of a sterilizing radiation dose. In this case, for greater assurance, it is preferred to irradiate at doses approaching 40 kGy or even more than 42-45 kGy.

The question of the sterilizing radiation dose in the radiation sterilization method is the main, if not decisive, in the entire 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 polymeric materials for 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 materials from which the products are made and in which they are packed, and the tightness of the packaging. When sterilizing other single-use plastic medical devices, the same requirements 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 must be observed.

In still big guarantees sterility, stricter sanitary and hygienic conditions during manufacture and possibly less initial contamination require artificial blood vessels, artificial heart valves, and plastic tubes used in tracheotomy, which are now widely used in surgery and made from polymeric materials. The range and quantity of plastic medical products are constantly growing, 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 in demand for disposable plastic medical products from year to year, as well as the use of the method of radiation sterilization of laboratory glassware made of polymeric materials, forces the development of the radiation technology industry, which creates large industrial-type stationary irradiation installations. These installations, which require significant capital investments, increase the cost of radiation sterilization compared to the cost of thermal or gas sterilization. However, the longer such an installation works, the less the sterilization of medical devices costs every year of its operation. It should also be borne in mind that modern medicine cannot do without the use of such products, materials and drugs that require radiation sterilization. Therefore, despite the fact that the cost of radiation sterilization will remain higher for a long time compared to the cost of other sterilization methods, it is impossible to abandon this method of provision 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 temperature. 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 shells are inactivated at 160-170°C.

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

Sterilization by dry heat is carried out in air sterilizers (the former name is “dry ovens” or “Pasteur ovens”). The air sterilizer is a tightly closed metal cabinet heated by electricity 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°C - 30 min, 180°C - 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 sterilized items do not withstand such treatment, and therefore they are decontaminated in steam sterilizers.

Processing with steam under pressure in steam sterilizers (old name - "autoclaves") is the most versatile method of sterilization.

Steam sterilizer (there are many of its modifications) - a metal cylinder with strong walls, hermetically sealed, consisting of a water-steam and sterilizing chambers. The apparatus is equipped with a pressure gauge, thermometer and other instrumentation. An increased pressure is created in the autoclave, which leads to an increase in the boiling point.

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

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

Sterilization over an open fire. Photo: musicalwds

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

Currently, another 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.

Sterilization with gases 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.

Before chemical sterilization, all products to be processed must be dried.

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, objects made of non-heat-resistant polymers, nutrient 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, such as endoscopes, neutralization with the help of chemical solutions has begun to be used. 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 in sterile gloves. Store these products for no more than 3 days.

Radiation sterilization is 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 industrial settings and is also used in cases where the objects 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 uneconomical.

Another method of sterilization 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 fluids (blood serum, drugs) from bacteria, fungi, protozoa and even viruses. To speed up the filtration process, it is common to create an increased pressure in the container with the filtered liquid or a reduced pressure in the container with the filtrate.

Currently, modern methods of sterilization, created on the basis of new technologies, using plasma and ozone, are increasingly being used.



The development of radiation sterilization began about 15 years ago. Scientists have found that the methods of disinfection and preservation of food that existed 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 turned out to be much more effective - food remained fit for consumption longer. For a long time it remained the same appearance and taste properties. The methodology was approved by representatives World Organization healthcare. 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 more than 200 thousand tons of irradiated food to the market every year. For most goods, an optimal mode of processing with gamma rays has been developed. 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 of disinfecting dressings, medicines, and surgical instruments. It is also used for pharmaceutical serums, food products, etc. This method belongs to the number of cold sterilizations, 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 needed on a solid scale, conveyors are created. Materials are processed in packaged form.

Electron accelerators and gamma units are installed at the enterprises. During the passage of electrons through matter, a large proportion of their energy is spent on ionization. As a result, microorganisms are destroyed. The level of viruses and pathogenic bacteria is reduced in proportion to the amount of electron energy used.

Advantages of radiation sterilization over gas

Goods are processed while being placed in sealed packages. This increases their shelf life. You can start using the product immediately after irradiation.

In the field of operation of the irradiation plant, no associated harmful substances are created. Products sterilized by gamma rays remain dry and do not contain carcinogenic components.

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

Applications of ionizing radiation
Ionizing radiation is widely used in various industries:
1. Modification and improvement of material properties
Crosslinking of polymers (cables and wires, pipes)
Production of heat-shrinkable products
Crosslinking of electrical products
Tire component modification
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
Associated gas cleaning
cleaning Wastewater
Disinfection of hazardous organic and medical waste

Applied equipment
The company "Accentre" plans to place on the territory Ivanovo region 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 15,000 kg/h

Warehouse complex for 5000 m2 for storage of processed and unprocessed products

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


Radiation sterilization center.

Complex solution.

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

Center for Radiation Sterilization

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/decontamination of packaging materials
Sterilization of cosmetics and perfumes
The center also offers a range of services for
processing quality assurance
products:
Development technological process sterilization of all products
Develop product packaging requirements to ensure cost-effective and quality sterilization
 Periodic validation of the sterilization process
 Carrying out routine daily control
Microbiological control of bioburden of non-sterile products
Dose absorption control

Benefits of Radiation Sterilization



Simplicity and reliability of the sterilization process.
Only 3 parameters (beam energy, electron beam current, conveyor speed) need to be controlled to achieve stable sterilization results. The sterilization process is automatically controlled automated system control, all parameters are recorded and monitored to ensure the reliability and stability of the result, guaranteeing the level of sterility 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, no long time is required for product aeration.

Processing of products in final packaging
Ionizing radiation has a high penetrating power, 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.

The process is suitable for heat-labile products

Clean process. There is no chemical contamination of products.

Sterilization technologies.





Parameter/Technology



Thermal
Chemical
radiation
Steam treatment with pressurized saturated steam
Air-treatment with dry hot air
Glasperlenic – medium of hot glass beads
Gas–oxyethylene vapor
(ethylene oxide sterilization), formalins, etc.
Antiseptic solutions (formaldehyde, glutaraldehyde, ethyl alcohol, hydrogen peroxide, chlorhexidine, etc.)
The action of electron beam radiation
The action of gamma radiation (source -
cobalt60, rarely cesium).
Performance
Degree of sterility
Product processing time
The amount of initial investment
Packing Requirements
Conventions
The best indicator for this parameter among the considered technologies
Average for this parameter among the considered technologies
The worst indicator for this parameter among the considered technologies

Sterilization technologies.

№
Product group of medical
products/Method
Radiation
Gas


Steam


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

Factors under which only radiation sterilization is possible

For some products, only radiation sterilization is applicable:
Closed packaged products
Many products are made from highly durable and non-breathable materials that cannot be sterilized by methods that require steam or gas penetration and pressure changes. The list of such products is wide from medical devices to raw materials and consumer products such as peat, nipples and teething rings for children, as well as all hermetically sealed products.
Densely packed products
- a large amount of raw materials packed in boxes and drums cannot be sterilized with gas or steam due to their limited penetration into the product. At the same time, steam and gas can lead to the formation of lumps or other types of product damage. 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 since no chemical agents are used, only reading energy.

 

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