Microencapsulated preparations for bedbugs: effectiveness, application, results. Are microencapsulated preparations for bedbugs effective Microcapsules preparations
![Microencapsulated preparations for bedbugs: effectiveness, application, results. Are microencapsulated preparations for bedbugs effective Microcapsules preparations](https://i0.wp.com/klopexpert.ru/wp-content/uploads/mikrokapsulirovannye-preparaty-ot-klopov-2.jpg)
The article provides an overview of the prospects for the use of microencapsulation in modern pharmaceutical practice. The examples show a range of technological and pharmacological problems that can be solved using microencapsulation: a decrease in the reactivity of medicinal substances, an increase in shelf life, a decrease in the toxicity of medicinal substances, imparting new physical properties to a substance, masking organoleptic properties. Some technological aspects of the issue of microencapsulation are reflected, in particular, approaches to the formation of the shell, a list of auxiliary substances used in the process of microencapsulation. Information is presented on the main directions of the use of microcapsules in modern pharmaceutical and medical practice: drugs (long-acting forms of nitroglycerin, enzymes, antitumor agents) and dietary supplements based on probiotics, as well as diagnostic tools. The prospect of using microencapsulation of anti-tuberculosis drugs is noted.
microcapsules
medications
study
composition of microcapsules
membrane
anti-tuberculosis drugs
1. Avtina N.V. Development of a children's dosage form based on metronidazole microcapsules // Scientific Bulletin of the Belgorod State University. Medicine. Pharmacy. - 2011. - No. 4 (99). - Issue. 13. - S. 170-176.
2. Avtina N.V. Development of the composition and technology of microcapsules with late bird cherry extract // Modern problems of science and education. - 2012. - No. 4. - Access mode: www..04.2014).
3. Assortment. The site of the Art Life company [Electronic resource] - Access mode: http://www.shop-artlife.ru/ (date of access: 04/21/2014).
4. Bykovskaya E.E., Krolevets A.A. Method for obtaining microcapsules / Patent No. 2012110715/15, 03/20/2012.
5. Bykovskaya E.E., Krolevets A.A. A method for obtaining microcapsules of drugs from the cephalosporin group // RF Patent No. 2012109496/15, 13.03.2012.
6. Vilesov A.D. Dosage form of long-acting disulfiram and method for its preparation // Patent RF No. 2011118789/15, 10.05.2011.
7. Ganina V.I., Anan'eva N.V., Kalinina L.V. Microencapsulation as a way to protect probiotic cultures from adverse conditions // 2nd Intern. scientific-practical. conf. "Prospects for the production of food products of a new generation": Sat. Art. - Omsk: FGOU VPO OmGAU, 2005. - P.100-102.
8. Study of the parameters of microencapsulation when obtaining a prolonged form of naltrexone / E.A. Petrova et al. // Khim.-farmats. and. - 2014. - 31. - S. 50-53.
9. Coin Bob Microcapsules // RF Patent No. 2359662, 06/27/2009.
10. Krikova A.V., Stepanova E.F. Technology for the preparation of tablets with microcapsules of diosmin // Bulletin of new medical technologies. - 2006. - T. XIII, No. 2. - S. 144-145.
11. Marconi M., Kalanchi M., Gentilini L. Method for obtaining a microencapsulated composition / Pat. 2059409, 05/10/1996.
12. Diagnostic methods for Helicobacter pylori (HP) [Electronic resource] - Access mode: http://vmede.org/ (date of access: 25.05.2014).
13. Michel Schneider, Philippe Boussat Microcapsules, manufacturing method and their application // RF Patent No. 96117128/14, 1995.11.21.
14. Muravyov I.A., Andreeva I.N. Influence of microencapsulation on the release rate of theophylline from tablets // Pharmacy. - 1987. - No. 2. - S. 19-21.
15. OST 91500.05.001-00. Pharmaceutical quality standards. Basic provisions. – M.: MZ RF, 2000. – 38 p.
16. Polkovnikova Yu.A., Stepanova E.F. Choice of excipients for microencapsulation of afobazole // 2nd Intern. scientific-practical. conf. "Young scientists in solving urgent problems of science": Sat. scientific tr. - Vladikavkaz, 2011. - Part 1. – P.289–291.
17. Obtaining microcapsules based on apple pectin and β-lactoglobulin containing rifampicin / Z.K. Mukhidinov et al., Khim.-Pharmac. and. - T. 46, No. 5. - 2012. - S. 46-49.
18. Postrash Ya.V., Khishova O.M. Microencapsulation in pharmacy - current state and prospects // Bulletin of Pharmacy. - 2010. - No. 2 (48). - P. 1-7.
19. Register of medicines of Russia [Electronic version]. – Access mode: http://www.rlsnet.ru/ (date of access: 03/25/2014).
20. Sardushkin M.V. Synthesis and main colloid-chemical characteristics of rifampicin microcapsules obtained by simple coacervation: Ph.D. dis. … cand. tech. Sciences. - M., 2013. - 18s.
21. VIDAL Handbook. Medicines in Russia. – M.: Astra Pharm Service, 2011. – 1488 p.
22. Tiraspolskaya S.G. Development of technology and methods for the analysis of phencarol microcapsules // Development, research and marketing of pharmaceutical products: Sat. scientific tr. - Pyatigorsk, 2005. - Issue. 60. - S. 290-291.
23. Federal register of permitted dietary supplements: website "On dietary supplements.ru" [Electronic resource]. – Access mode: http://obad.ru/. (Date of access: 04/27/2014).
24. How to replace probiotics [Electronic resource]. – Access mode: http://subtilis.ru (date of access: 05/19/2014).
25. Chueshov V.I., Chernov N.E. Industrial technology of medicines: in 2 volumes. - Kharkov: Osnova, 1999. - T. 2. - 704 p.
26. Present Status of Nanoparticle Research for Treatment of Tuberculosis / ShegokarRanjita, Al ShaalLoaye, Mitri Khalil // J. Pharm. pharmaceuticals. sci. - 2011. - No. 14(1). - R. 100-116.
27. Shah, N.P. Microencapsulation of probiotic bacteria and their survival in frozen fermented dairy desserts / N.P. Shah // Aust. J. Dairy Technol. - 2000. - Vol. 55. – P. 139-144.
The term "microencapsulation" appeared in the technological literature in the early 60s. Since then, there has been a growing interest in the production of microcapsules of medicinal substances. This is evidenced by numerous publications on this issue, both here and abroad.
Microcapsules- capsules consisting of a thin shell made of a polymer or other material, spherical or irregular in shape, ranging in size from 1 to 2000 microns, containing solid or liquid active ingredients with or without the addition of excipients (OST 91500.05.001-00). Most often, microcapsules with a size of 100 to 500 microns are used. Particle size< 1 мкм называют нанокапсулами .
Microcapsules are currently used in various industries. In agriculture and in everyday life, microencapsulated insecticides are widely used. Microcapsules with vitamins, essential and fatty oils are part of various cosmetic products (creams, gels, serums). Microencapsulated probiotics are used in feed and feed additives in veterinary medicine.
However, in the pharmaceutical industry, microcapsules do not find such a wide practical application, although there is an obvious prospect of their use. With the help of microencapsulation, the following problems can be solved: reduce the reactivity of medicinal substances, lengthen the shelf life of labile and rapidly perishable medicinal substances, reduce the toxicity of the substance, give the substance new physical properties - reduce volatility, change density, mask color, taste, smell. Microcapsules make it possible to ensure the prolongation of the action of drugs.
An important field of application of microencapsulation in pharmacy is the combination in a total dosage of medicinal substances that are incompatible when mixed in free form. Microencapsulation is used to separate drug substances that react with each other, combined in one dosage form.
Microencapsulation stabilizes unstable drugs (vitamins, antibiotics, vaccines, sera, enzymes). Thus, patents are known in the field of microencapsulation of cephalosporins in konjac gum, beta-lactam antibiotics - kanamycin in sodium alginate, as well as kanamycin, ampicillin, benzylpenicillin in sodium carboxymethylcellulose.
An example of the use of microencapsulation to increase the stability of drugs is the encapsulation of extracts of medicinal plant materials.
One of the main objectives of microencapsulation is to achieve a prolonged action upon oral administration with a simultaneous decrease in the maximum level of concentration in the body. In this way, it is possible to reduce the number of doses of the drug, eliminate the irritating effect on tissues associated with the adhesion of tablets to the walls of the stomach.
An example of the use of microcapsules to reduce toxicity is the microencapsulation of novocainamide, acetylsalicylic acid and other drugs. Italian scientists have carried out microencapsulation of ketoprofen, a poorly soluble analgesic that is well absorbed from the gastrointestinal tract, but causes irritation, and this has reduced the negative effect of the drug on the body.
And further: in the treatment of chronic alcoholism, a long-term intake of traditional tablets "Teturam" inside is necessary, which is not convenient for patients and is sometimes difficult to implement. The injection method is also not optimal due to the use of an organic solvent. A method has been developed for obtaining an agent for the correction of disorders in alcoholism in the form of a long-acting dosage form of disulfiram containing microcapsules of a medicinal substance coated with a two-layer shell of polysaccharides. This achieves a stable kinetics of drug release into tissues and a long-term prolongation effect, which makes it possible to facilitate course treatment.
Examples can be found in the literature of correcting bad taste with microencapsulation. So, when developing a children's syrup, it was proposed to include metronidazole in microcapsules to mask an unpleasant bitter taste, as well as to prolong the pharmacological action. There is evidence of the development of microcapsules with ibuprofen and paracetamol for the correction of bitter taste.
The problem of prolonging, reducing the irritating effect of drugs, ensuring stability using microencapsulation can be solved by choosing the appropriate film formers, thickness and size of microcapsules.
The size of microcapsules varies from fractions of a micrometer to several millimeters. The content of the encapsulated substance is usually 70-85% by weight of the capsule (sometimes up to 95-99%). The shell of microcapsules can be single or multilayer, and depending on the properties of the substance that forms it, elastic or rigid.
Medicinal substances in the process of microencapsulation can be included in the membrane or in the core. Lipophilic substances are suitable for inclusion in a lipid or lipid/polymeric membrane material. Thus, the possibility of microencapsulation of vitamin E, prednisolone, chloramphenicol and salbutamol into the membrane shell has been shown. Microcapsules can also contain several pharmacologically active substances of different nature at the same time: a capsule can contain one substance in the membrane, and the second substance in the core.
The requirements for the permeability of the shell are determined by the purpose of the microcapsules - if the medicinal substance needs to be protected from the environment, then the shell must be low-permeable. In this case, the contents of the microcapsules are protected by a shell that is impermeable to it and is released only after it is dissolved. The choice of the shell is also determined by the physicochemical properties of the encapsulated content - hydrophilic substances in dissolved form suggest being enclosed in a hydrophobic shell.
If, as an option for microcapsules, a liquid dosage form with an aqueous medium (solution, suspension, syrup) is assumed, then to prevent the gradual dissolution of microcapsules and their uniform distribution, the shell of microcapsules must also be hydrophobic.
If the shell is permeable to the contents of the core, for example, it is constructed from ethylcellulose, then the release rate is determined by diffusion and depends on the thickness of the shell, the size of the microcapsules, the presence of pores and the solubility of the substance in the external environment. The use of diffusion-permeable membranes is justified for microencapsulation of water-soluble substances that irritate the mucous membrane - acetylsalicylic acid, iron sulfate. The shells, which are impermeable to the internal phase and the environment, ensure the strength and tightness of the packaging of the microcapsule core. They are used to isolate substances from each other in the event of their interaction, as well as to impart flow properties to liquid and viscous compositions.
The contents of the microcapsules may also be gaseous. So, for diagnostic purposes, microcapsules with an air-filled or gas-filled core and a lipid membrane are used in combination with a biodegradable polymer.
The substances used to form hydrophilic shells are high-molecular compounds of animal and vegetable origin - proteins (gelatin, albumin, casein), dextrans, pectins, alginates, chitosan, agar, cellulose derivatives, natural resins (gums, shellac), synthetic polymers - polyolefins, polyvinyl alcohol, polyvinyl acetate, polyamides, polylactides, polyglycolides, etc.
The hydrophobic shell may include solid vegetable oils (coconut, palm), hydrogenated vegetable oils (cotton, corn, peanut), hydrogenated fatty acids, monoglycerides and diglycerides of fatty acids, monoglycerides and diglycerides of esterified fatty acids, waxes (bees, carnauba, candelilla), paraffin, ozocerite.
Microcapsule technology can use surfactants, typically where the particle size of the final product is critical, such as injectables. If microcapsules are used in the manufacture of an oral formulation, then a surfactant need not be present, as the final particle size is generally not critical. Polyvinyl alcohol, phospholipids, sorbitan ethers and esters, ethoxylated saturated glycerides or polyglycerides of fatty acids are used as surfactants to stabilize the emulsion in the preparation of microcapsules.
On the basis of microcapsules, it is possible to produce such dosage forms as tablets, suspensions, subcutaneous implants, capsules. There are studies on the development of syrups with microcapsules. By suspending the microcapsules in a physiological solvent, sonographic contrast agents are obtained.
Many studies have been devoted to research in the field of microencapsulation of pharmaceuticals, but only a limited group is used in practice.
Thus, microencapsulation is currently finding practical application as a technology for the immobilization of microorganisms - an alternative to inclusion in a gel. The advantage of this method is a higher cell load, which is one of the necessary criteria for ensuring the effectiveness of oral probiotic drugs.
Microencapsulation also makes it possible to increase the resistance of probiotics to aggressive factors of the gastrointestinal tract - the low pH of the stomach, the action of enzymes and bile. The company "Art Life" offers dietary supplements for food "Probinorm", which is a capsule with microencapsulated lacto- and bifidobacteria. Microencapsulation as a method of enzyme immobilization has also found practical application in pharmacy. The semi-finished product "Pancrelipase" containing microencapsulated pancreatin for filling capsules has been introduced into the radar station.
In modern pharmaceutical practice, prolonged dosage forms of nitroglycerin have been used in chronic forms of coronary heart disease, to prevent angina attacks, and in heart failure. Tablets or capsules containing nitroglycerin in microcapsules are intended for oral administration. The therapeutic effect develops gradually and usually lasts for several hours. Such tablet forms of long-acting nitroglycerin are used, such as "Sustak", "Nitro-mac retard".
The use of microcapsules for the introduction of antibacterial antiblastoma compounds is promising. The advantage of microcapsules is that they can be implanted in the right place, for example, in the immediate vicinity of the tumor, and provide a gradual release of the active substance, avoiding systemic toxic effects on the body. Polymeric nanocapsules with sorption of medicinal substances in the particle mass ensure the delivery of highly toxic medicinal substances into cells with a minimum manifestation of the overall toxic effect. This property is also used in the development of nanocapsules with highly toxic antitumor drugs. On the pharmaceutical market there is the drug "Decapeptyl Depot" - an injectable form of decapeptyl of prolonged action with microcapsules - a drug used in hormone-dependent prostate cancer.
With the use of microcapsules, new types of diagnostic products are created (encapsulated unstable reagents for blood and urine tests, thermal recording films, as well as coal and ion-exchange resins).
The use of microencapsulation to create anti-tuberculosis drugs is promising. Development on the basis of controlled release systems will create a rapid therapeutic effect, achieve a constant concentration of the drug in the blood, reduce the course dose and reduce the frequency of side effects. Research on microencapsulation of rifampicin has already been carried out in the Republic of Kazakhstan, in the pharmaceutical company "Romat".
Russian scientists have developed a technique for microencapsulation of rifampicin for inclusion in inhaled dosage forms. A decrease in long-term systemic exposure and delivery of an antibacterial agent directly to the target organ - the lungs, can be achieved with the inhalation method of introducing microencapsulated forms of rifampicin capable of controlled and selective release of the antibiotic through the capsule shell, providing its prolonged action. Prospects for the use of nanoencapsulated forms of rifampicin, isoniazid, pyrazinamide are shown in pharmacological studies by foreign scientists.
Thus, microencapsulation is a promising method for creating innovative dosage forms with prolonged action, which allows expanding the range of drugs and changing approaches to the treatment of certain socially significant diseases - tuberculosis, cancer, substance abuse, requiring long-term therapy with fairly toxic substances.
Reviewers:
Efimenko N.V., Doctor of Medical Sciences, Professor, Professor of the Pyatigorsk State Research Institute of Balneology, FMBA, Pyatigorsk.
Andreeva I.N., Doctor of Pharmaceutical Sciences, Professor, Professor of the Department of Tourism, KMVIS, Pyatigorsk.
Bibliographic link
Stepanova E.F., Kim M.E., Murzagulova K.B., Evseeva S.B. MICROCAPSULES: PERSPECTIVES OF USE IN MODERN PHARMACEUTICAL PRACTICE // Modern problems of science and education. - 2014. - No. 5.;URL: http://science-education.ru/ru/article/view?id=14927 (date of access: 11/27/2019). We bring to your attention the journals published by the publishing house "Academy of Natural History"
Microencapsulated preparations were developed specifically for the persecution of domestic pests in a closed living space, in close proximity to a person. Poison components are enclosed in a polymer or gelatin microcapsule with a diameter of 30 microns. The protective shell protects a person from getting harmful chemicals into the air and inhaling them. The capsule protects the drug contained inside it from the effects of external factors. This ensures a prolonged action of the insecticide, it retains its activity for up to a year after application.
Substances enclosed in the membrane do not harm a person when treating a room. The shell is destroyed only upon contact with an insect.
The chemical does not act on the bug immediately during disinfestation, but upon direct contact with the insect.
Modern microencapsulated insecticides may contain one or more active ingredients. Depending on the active poisonous substance, micropreparations from bed bugs are divided into:
- organophosphorus;
- organochlorine;
- synthetic pyrethroids.
Advantages and disadvantages of microcapsules
Like any insecticide, modern microgranules have their advantages and disadvantages. Knowing them, you can easily choose drugs that are suitable for each case individually. The main advantages of microcapsules are:
But the use of insecticides in capsules has its drawbacks:
- high price;
- active action against bedbugs does not begin immediately after application, but immediately after contact of the capsule with an insect;
- the product is not recommended for the treatment of heavily contaminated premises;
- storage difficulties - the drug does not tolerate low temperatures.
Despite their drawbacks, microencapsulated preparations are very effective and safe in the fight against bed bugs. Due to the prolonged action of such products, repeated pest control is not required for prevention purposes.
- around the bed and under it;
- on the bed frame
- behind and under furniture;
- under the mattress
- in bed crevices and gaps;
- on ventilation grilles;
- near baseboards;
- in the cracks on the floor and in the walls;
- on the reverse side of paintings, carpets, posters.
After the end of the procedure for distributing the remedy for bedbugs, it is better to wash your hands with soap and water, and the best option is to work with rubber gloves.
To enhance the effect of microcapsules with prolonged and delayed action, it is recommended to combine with instant insecticides: liquids and aerosols. The liquid agent infects bedbugs instantly, but does not affect clutches with eggs. And microcapsules allow you to exterminate surviving bugs and young larvae after hatching. In heavily contaminated rooms, it is recommended to use multi-component capsules.
Relatively recently, the range of means for the extermination of domestic bugs was supplemented by microencapsulated preparations. This is the name of a special form of release of insecticides, in which the active substance is in microscopic capsules made of natural (gelatin, starch, etc.) and synthetic (polyvinyl acetate, polyacrylamide, etc.) materials.
Operating principle
Microencapsulated preparations are characterized by prolonged action. The principle of operation of this agent is based on the ability of the active substance to gradually penetrate through the shell to the surface of the capsules.
In addition, the shells of the capsules can collapse under the weight of the bugs. That is, if an insect passes over the surface on which the drug is applied, then it can crush several microcapsules, as a result of which the poisonous substance will fall on the paws and body of the individual.
Pros of using
Modern microencapsulated preparations have many useful qualities. Here are the most notable benefits:
There are some negative points in the use of microencapsulated products:
- drugs do not begin to act immediately after application, but after the active substance comes to the surface of the capsules. The process of penetration of the active substance to the surface can take up to 10 days;
- high price and short shelf life;
- exactingness to storage temperatures, products do not tolerate high temperatures and freezing.
Advice! A significant disadvantage is the fact that bedbugs eventually develop resistance (immunity) to the active substances of microencapsulated preparations. That is, it does not make sense to carry out repeated processing by the same means.
Descriptions of some tools
On sale you can find a fairly wide range of microencapsulated drugs. Most often used:
- Get (Get);
- Xulat C25;
- Minap-22;
- Effective Ultra.
Minap-22
An effective remedy for bedbugs is Minap-22, which is a microencapsulated suspension. The active ingredient in the product is chlorpyrifos, which is contained in a concentration of 9.3%. This is a fairly low concentration, so the drug does not pose a threat to humans.
In addition, the product practically does not smell, which is quite unusual for insecticides. The activity of the drug begins to appear on the 3-4th day and persists for several months.
Advice! Minap-22 is the only microencapsulated agent that is undemanding to storage temperature. After freezing and thawing Minap-22 retains its effectiveness.
geth
Get is a microencapsulated agent, the active substance of which is chlorpyrifos. It is highly effective against bedbugs, but it is odorless and almost completely safe for people.
Xulat C25
The microencapsulated suspension Xulat C25 looks like a white viscous liquid. As part of the drug:
- chlorpyrifos (active substance concentration 25%);
- emulsifiers and preservatives;
- capsule formers;
- dispersion substances;
- fragrances.
Water is used as a solvent in this product. Xulat has activity against most insects that settle in human habitation. After application, it remains active for several months.
Effective Ultra
The microencapsulated drug Effective Ultra is produced in the Netherlands. Differs in the use of two active substances at once:
- propoxur carbamate (concentration 17.2%);
- tetramethrin is a substance from the group of pyrethroids (concentration (0.86%).
In addition, synergistic substances are included in Effective Ultra, they enhance the effect of the main substance. The following are used as synergists in Effective Ultra:
- piperonyl butoxide (concentration 1.66%);
- MGK-264 (concentration 4.96%).
Water was used to dissolve the main substances. Effective Ultra can be used against any insects that settle in human habitation. The activity of the product after application lasts up to 3 months.
Microencapsulated drugs are available in concentrated form packaged in small vials. Before use, the product is diluted with water in the proportions indicated on the package. You can apply the product with a brush or with a spray bottle.
Since the products have a prolonged and delayed action, they are often used in combination with concentrated emulsions. That is, first, pest control is performed using a liquid agent, while most of the bugs die. Then a microencapsulated agent is applied to exterminate insects that survived during the first treatment, as well as a new generation of bug larvae emerging from eggs that were not damaged during pest control.
Microencapsulated preparations are effective and almost completely safe for humans. However, they are expensive and have a delayed effect.
Microencapsulation is the process of encapsulating microscopic particles of solid, liquid or gaseous medicinal substances. The size of particles enclosed in a microcapsule can vary widely: from 1 to 6500 microns, i.e., up to the size of small granules or capsules (6.5 mm). The most widely used in medicine are microcapsules ranging in size from 100 to 500 microns. Modern technology makes it possible to coat particles smaller than 1 µm. Such particles with shells are called nanocapsules, and the process of their production is called nanoencapsulation.
Capsules with liquid and gaseous substances have a spherical shape, with solid particles - usually irregular, since the film is thin and fixes all the irregularities of the particles. The content of medicinal substances can vary from 15 to 99% of the mass of microcapsules.
Microencapsulation has been used in pharmaceutical technology With late 50s - early 60s of the current century, in the chemical, printing, cosmetic and other industries - a little earlier.
Microcapeulation achieves:
a) protection of unstable drugs from environmental influences (vitamins, antibiotics, enzymes, vaccines, sera, etc.);
b) masking the taste of bitter and nauseating drugs;
c) release of medicinal substances in the desired area of the gastrointestinal tract (enteric-soluble microcapsules);
d) prolongation of action. A mixture of microcapsules differing in size, thickness and nature of the shell, placed in an operculated capsule in combination With a granular or powdered substance that ensures the maintenance of a certain level of the drug in the body and an effective therapeutic effect for a long time;
e) combining in one container incompatible with each other in pure form (use of separating coatings);
c) "transformation" of liquids and gases into a pseudo-solid state, i.e. into a loose mass consisting of microcapsules with a hard shell filled with liquid or gaseous medicinal substances.
Microencapsulation technology
Existing methods of microencapsulation are divided into three main groups: physical, physico-chemical and chemical.
Physical Methods
Physical methods for microencapsulation are numerous. These include drageeing, spraying, spraying in a fluidized bed, dispersion in immiscible liquids, extrusion methods, electrostatic method, etc. The essence of all these methods is the mechanical coating of solid or liquid particles of medicinal substances.
The use of one or another method depends on whether the “core” (the contents of the microcapsule) is a solid or liquid substance.
Coating method. Applicable for microencapsulation of solid medicinal substances. The latter in the form of a homogeneous crystalline mass (with the required particle size) in a rotating coating pan is sprayed from the nozzle with a solution of the film former. The resulting films dry out in a current of heated air supplied to the boiler. The thickness of the shell. microcapsules depends on the temperature, concentration and speed of spraying the film-forming solution. Microcapsules with a hard core obtained by drageeing are also called micropellets.
spray method. It is usually used for microencapsulation of solids, which must first be transferred to the state of thin suspensions. Upon receipt of such microcapsules, usually having a fatty shell, the cores are suspended in a solution or melt of fatty substances (wax, cegyl alcohol, glycerol mono- or dishearate, etc.), followed by spraying and drying the suspension in a spray dryer. The resulting dry microcapsules have a size of 30-50 microns.
Dispersion methods in immiscible liquids. Applicable for the encapsulation of liquid substances. In particular, the drip method (see p. 583), used to obtain soft capsules, can also be used for microcapsules. To do this, the flow rate of the water jet in the outer tube must be so high (for example, 4.73 l / min) compared to the speed of movement of the liquid medicinal substance and the molten film former (for example, 30 ml / min) that the water flow breaks off droplets of the required size .
Usually this method is technologically carried out as follows. The heated emulsion of the oily drug solution stabilized with gelatin (O/B type emulsion) is dispersed in the cooled liquid paraffin using a stirrer. As a result of cooling, the smallest droplets are covered with a rapidly gelatinous shell. The frozen balls are separated by a mouth of liquid paraffin, washed with an organic solvent and dried. The size of the microcapsules obtained in this way usually ranges from 100-150 microns.
Method of "spraying" in a fluidized bed. This method is used in devices, the basic design of which is similar to the SP-30 and SG-30 used in tablet production or granulation.
The simplest deposition process occurs when microencapsulation of solid drugs substances. Solid cores are liquefied with a stream of air or another gas and a solution (or melt) of a film-forming substance is “sprayed” onto them using a nozzle. Solidification of liquid shells occurs as a result of evaporation of the solvent or cooling, or both at the same time,
In the case of microencapsulation of liquid medicinal substances, the latter are emulsified (if they are insoluble in water) or dissolved (if they are water-soluble) by heating in an aqueous solution of a film former (eg gelatins). The heated emulsion (solution) is sprayed with a broken nozzle into a fluidized system With hydrophobized starch. Droplets, which are liquid microcapsules, getting into this system, are covered with the smallest particles of starch that stick to the gelatin shell and dry quickly.
Microencapsulation method using centrifugation. Under the influence of centrifugal force, the particles of encapsulated medicinal substances (solid or liquid) pass through the film of the film-forming solution, are covered by it, forming a microcapsule. Film formers use substances whose solutions have sufficient surface tension (gelatin, sodium alginate, polyvinyl alcohol, and some others) and optimal viscosity. The size and shape of the microcapsules will depend on these parameters.
Electrostatic microencapsulation method. One of the new and original methods developed in the USA. A number of devices have been proposed. The size of the obtained microcapsules is from 5 to 20 microns.
Physical and chemical methods
The main physicochemical method is microencapsulation using the phenomenon of coacervation.
At present, the process of coacervation of macromolecular compounds is considered as the formation of a two-phase system as a result of separation. One phase is a solution of a macromolecular substance in a solvent, the second is a solution of a solvent in a macromolecular substance. A solution richer in a macromolecular substance is often released in the form of droplets of coacervate. With further dehydration, the coacervates pass into the sediment. Subsequently, the shells of the drops are subjected to hardening to increase the mechanical strength of the microcapsules, which is carried out in various ways (cooling, evaporation of the solvent And etc.).
It is necessary to distinguish between simple and complex coacervation. The first takes place during the interaction of a solution of one polymer and a drug (low molecular weight) substance. Coacervation in the interaction of two polymers is called complex or complex.
Simple coacervation method. The process of formation of micro-capsules of simple coacervation proceeds as follows (Fig. 206).
The substance to be encapsulated (oil, oil solutions of vitamins, hormones and other drugs) is emulsified into a solution
re gelatin at 50°C. It turns out an O / W emulsion with a possible degree of dispersion of 2-5 microns (Fig. 206, a).
A 20% aqueous solution of sodium sulfate is added to the film-forming solution (the latter in this system is the external environment) with constant stirring. The dehydrating properties of sodium sulfate cause coacervation of gelatin. A heterogeneous liquid system is formed with a non-uniform distribution of the dissolved substance in it (Fig. 206.6), consisting of two phases - enriched and depleted in solute molecules (gelatin). For example, in a 3% gelatin solution, two phases are formed with different gelatin content: in the coacervate layer, 2.02%, and in the rest, in the equilibrium liquid, 0.98%.
Microdrops of coacervate with decreasing temperature begin to concentrate around drops of oil, initially forming a "necklace" of microdroplets of coacervate (Fig. 206, c). Then the microdroplets merge, covering the drop of oil with a solid thin layer, until a microcapsule is formed with a liquid film of gelatin (Fig. 206, d).
To gel the shells of microcapsules, the mixture is quickly poured into a container with a cold solution of sodium sulfate (18-20°C).
The microcapsules are filtered off and washed with water to remove the sodium sulfate solution. This operation can be carried out on suction filters, frame filter presses or using centrifuges. The shells of microcapsules contain 70-80% water. Drying of microcapsules can be thermal (shelf convective dryers, vibrofluidized bed dryers) or it can be carried out using adsorbents (silica gel dryers), treatment with dewatering liquids (strong ethanol) and other methods.
The method of simple coacervation can also microencapsulate solid, water-insoluble medicinal substances (sulfonamides, antibiotics, luminal, etc.).
Complex coacervation method. Complex coacervation is accompanied by an interaction between the positive and negative charges of the two polymers and is usually caused by a change in pH. Complex co-acervates can be one-, two- and three-component. In one-component coacervates, both polymers belong to the same group of chemical compounds and the particles of both are amphions (have an equal number of positive and negative charges, amphoteric particles). In these systems, the positive charges of one amphion are attracted to the negative charges of another amphion and vice versa. In two-component coacervates, both polymers are different compounds and carry opposite charges: positive macroions - macrocations or negative - macroanions.
In these systems, the interaction occurs between the microcation+macroanion compounds. Three-component coacervates are formed by mixing an amphion, a macroion (macrocation or macroanion) and salt additives containing microions (cations and anions).
Using the example of coacervates consisting of gelatin and gum arabic, i.e., using the example of two-component coacervation, let us analyze the process of formation of microcapsules with medicinal substances by the complex coacervation method.
Prepare a 10% gelatin solution (pH 8.0). In an 11% solution of gum arabic, an oil or an oily solution of a medicinal substance is emulsified. Both liquids are mixed with a stirrer (mixture temperature 50°C to avoid gelation). A sodium hydroxide solution is added until the pH of the mixture is 6.5, at which the electric charges of both polymers become opposite. The mixture is diluted with water and 10% acetic acid solution, the pH is reduced to approximately 4.5. At this pH value, gelatin macrocations are attracted to gum arabic macroanions, coacervate droplets envelop the oil droplets and form shells. For tanning shells of microcapsules add 37% formaldehyde solution. After the shells have hardened, the temperature of the mixture is lowered to 10° C. and the pH is increased to 9.0 for even greater shell strength. After that, the microcapsules are dried and subjected to sieving to isolate the fraction of the required size.
In the case of microencapsulation of water-soluble medicinal substances, the isolation of a new phase in an organic solvent medium is used, and cellulose ethers, siloxane polymers, polyvinyl chloride and some other polymers are used as the shell material.
Let us take microencapsulation of vitamins C and B as an example. Finely divided preparations are dispersed in a film-forming solution: ascorbic acid in a solution of ethylcellulose in methyl etiketone or acetylcellulose in acetone, thiamine chloride in a solution of cellulose acetate phthalate in a mixture of acetone and hexane. With the slow addition of a high-molecular precipitant (polysiloxane liquid) to these systems, a new dispersed phase is released, which is localized in the form of microdroplets around ascorbic acid crystals, then merging into a continuous shell. The subsequent operations are common: curing the microcapsule shells, separating the microcapsules from the dispersion medium, washing and drying.
Chemical Methods
The production of microcapsules by the chemical method is based on the reaction of polymerization and polycondensation at the water-oil interface. To obtain microcapsules by this method, a drug substance, a monomer (eg, methyl methacrylate), and a polymerization reaction catalyst (eg, benzoyl peroxide) are dissolved in oil. The resulting solution is heated for 15-20 minutes at a temperature of 55°C and poured into an aqueous solution of the emulsifier. An M/W type emulsion is formed which is held for 4 hours to complete the polymerization. The resulting polymethyl methacrylate, insoluble in oil, forms a dense shell around the droplets of the latter. The formed microcapsules are separated from the medium, washed and dried.
Application of microcapsules
Currently, a number of medicinal substances are produced in the form of microcapsules: vitamins, antibiotics, anti-inflammatory, diuretic, cardiovascular, anti-asthmatic, antitussive, sleeping pills, anti-tuberculosis, etc. In addition, microcapsules can be used in the form of spansuls, as well as in the form tablets, suspensions and rectal capsules. Currently, the possibility of using microcapsules in injections, eye drops, and implantable tablets is being investigated. Of great interest will be adhesive tapes coated with the thinnest layer of microencapsulated medicinal substances.
Microencapsulation opens up interesting possibilities with a number of drugs that cannot be realized in conventional dosage forms. An illustration of the possibilities of encapsulation is the use of nitroglycerin in microcapsules. Conventional nitroglycerin in sublingual tablets or drops (on a piece of sugar) has a short period of action. Microencapsulated nitroglycerin has the ability to be released in the body for a long time. Especially effective is the combination of conventional (fast-absorbing) nitroglycerin together with microencapsulated.
![](https://i0.wp.com/1klop.com/wp-content/auploads/117291/sredstvo-ot-postelnyh-klopov.jpg)
Bullet - a proven and reliable insecticide against bedbugs
- the contents of the ampoule dissolve in 0.5 liters of water;
- hard surfaces are abundantly wiped with a cloth or cotton swab moistened with a solution;
- the solution is sprayed onto soft surfaces.
The instructions indicate that the contents of the ampoule must be dissolved in one and a half liters of water. But for greater effectiveness of the drug, it is best to use a solution of higher concentration. During treatment with Bullet's solution, dishes and food must be removed.
Lethal Weapon Lambda Zone
This is a modern super remedy against blood-sucking insects. Designed and manufactured in South Korea. To prepare it, using special equipment, lambda-cyhalothrin is placed in a nanotube with a concentration of 2.5%. Microencapsulated suspension Lambda Zone has many advantages over other insecticides:
Regent for cockroaches
To use the drug Lambda Zone, you must:
- dilute 10 ml of the product in one liter of water;
- pour the solution into a spray bottle;
- put on gloves, a respirator and a gown;
- apply to furniture, bed, floor, baseboards and other surfaces where bugs can live;
- you need to process each corner, so the product will have to be diluted several times:
- keep the room with the windows closed for half an hour;
- well ventilate the apartment.
Do not treat clothes, children's toys, bedding with a solution.
For use, a solution is used, which is prepared according to the table of concentrations that is attached to the drug. When spraying the solution, it is imperative to use personal protective equipment.
Dust is a powerful and effective tool
The composition of the powder includes various insecticides, which makes it not only a powerful drug, but also long acting agent. The effectiveness of Dust does not weaken even with temperature changes. However, increased humidity in the room can reduce the effect of the powder.
To help home masters: Combat from cockroaches