USING THE STATE-OF THE ART TECHNIQUES OF TEACHING BY CLASSIFICATION REPAIRING AND RECOVERING PROCESS OF SKIN BY BIOPOLYMERS IN MEDICAL AND ENGINEERING EDUCATION

ABSTRACT

In the last years, biopolymers are becoming one of the vital factors for processes of recovering and repairing of skin and of course tissue engineering. Generally, skin tissue that has been somewhat harmed or cuts can regenerate in a relatively brief time, whereas serious injuries may require implantation or artificial skin. To achieve these goals, skin regeneration is essential. As we know, the materials that we can use them in implantation are important involved in skin regeneration  at the same time, the environment produced with polymer hydrogel  scaffolding should be similar to the real environment and safe for skin cell growth. Our conclusions were focused on biopolymers that regenerate the skin from natural and synthetic polymers. Moreover, we tried to analysis the behaviors of those polymers and their applications in tissue engineering, and their ability to drugs delivery. We hope this knowledge will be of use to researchers, teachers and students with little or no previous experience in in this field who have identified a potential application for 3D printing in a medical context, or those with a more general interest in the techniques.

АННОТАЦИЯ

В последние годы биополимеры становятся одним из важнейших факторов восстановления и восстановления кожи и, конечно, тканевой инженерии. Как правило, кожная ткань, которая была несколько повреждена или порезана, может регенерироваться за относительно короткое время, тогда как серьезные травмы могут потребовать имплантации или искусственной кожи. Для достижения этих целей необходима регенерация кожи. Как мы знаем, материалы, которые мы можем использовать для имплантации, важны для регенерации кожи, в то же время среда, созданная с помощью каркасов из полимерного гидрогеля, должна быть похожа на реальную среду и безопасна для роста клеток кожи. Наши выводы были сосредоточены на биополимерах, которые регенерируют кожу из натуральных и синтетических полимеров. Более того, мы попытались проанализировать поведение этих полимеров и их применение в тканевой инженерии, а также их способность доставлять лекарства. Мы надеемся, что эти знания будут полезны исследователям, преподавателям и студентам с небольшим опытом или без опыта в этой области, которые определили потенциальное применение 3D-печати в медицинском контексте, или тем, кто интересуется этими методами в более общем плане.

Keywords: Polymers: Biopolymers: Regeneration: Skin: Tissue Engineering: Education: Teaching

Ключевые слова: Полимеры: Биополимеры: Регенерация: Кожа: Тканевая инженерия: Образование: Обучение

1. Introduction

The skin is important as a protector of human body, and given its significance, we always consider it as a most needed organ in our body due to its different and complex capacities. The skin defends us from external influences such as changes in temperature and others by sending signals to the brain. We think that the skin is a powerful defender, unfortunately it is not powerful as we know. It is hindered by some external influences, such as heat, cold, and rays, under those affects, the skin loses some of it's vital functions. For example, first and second-degree burns are treated leaving scars. As for burns of the third degree, the body often can not self-treat it because it has caused great damage to the skin. Hence, the patients need immediate skin transplantation to save them from bacterial infections and may lead to fulfillment if you do not find adequate care. This transplant process in the past periods found a very fast development by researchers, especially in the field of regenerative tissue engineering for the skin, given that this tissue can be called alien, and it needs critical factors that must be taken into account such as biocompatibility, biological decomposition and non-toxicity. The materials which is containing from hydrophilic particles are considered the most suitable materials  in tissue engineering and  regeneration. Polymers have a importance  in the field of the regenerative skin engineering due to their puzzling properties in this regard by attracting and retaining water molecules just like what happens in the natural body. Tissue engineering and its regeneration is the biomedical field of research and application where members are built in the laboratory for treatment. Either by surgical or implanted using stem cells taken from the same patient, he became one of the driving science in the fields of medicine and engineering in general.

2. Classification of polymers.

2.1. Based on sources.

2.1.1.Natural polymers: These are substances that are naturally obtained in life, such as living organisms such as pigs and chickens. Even our bodies contain many natural polymers, such as proteins and nucleic acids. Alternatively, it is obtained through the polymerization process such as polyethylene, polyacrylates and methacrylate[1] [2].

2.1.2.Synthetic polymers: These polymers are compounds are obtained laboratory by chemical reactions by binding the monomers together. It is intended for use in various applications that are incompatible with natural polymers such as poly (L-lactic glycolic acid)[2].

2.1.3.Semi-synthetic polymers: This type of materials are materials in which the original polymer is manufactured in a chemical-treated but the origin of this substance is a natural polymer. Like cellulose, it is a natural polymer and after treatment, it contains nitrocellulose. Samples  include nylon, polyester and Teflon[2].

2.2. Based on structure.

2.2.1.Linear polymers: It is a long continuous chain of carbon that binds to hydrogen bonds between carbon and carbon and takes its name from the polymer structural repeat unit. It is dissolved with ion exchange groups in water. In addition, bound together by ion cross-linking agents. It has high melting points, such as poly (vinyl chloride)[2].

2.2.2.Branched polymers: This kind of polymers that contain secondary polymer chains that link to the primary spine. This bond is polymeric or H-shaped, having low tensile strength, low density, low boiling and melting points compared to its predecessor. It differs from linearity because it is less solid and dense, also fragile because the linear polymer contains a large number of relatively short branches. Examples include starch and glycogen[2].

2.2.3.Cross-linked or network polymers: Here the monomers are bound together to form a three-dimensional network, the monomers are bound together with strong covalent bonds, because it consists of bi-function and tri-function in nature between the various polymer chains, which can be either linear or non-linear[2, 3].

2.3. Based on molecular forces.

2.3.1.Elastomers: These materials are materials that combine the plasticity and elastic properties. It is processed on traditional plastic equipment, for example BUNA-S AND BUNA-N.[2]

2.3.2.Thermoplastic polymers: Plastic polymers that change their shape by heat and return to their solid state at normal temperature. It is filled with Polyethylene and polypropylene, which is used in catheters and others[2].

2.3.3.Thermosetting: Also, polymers affected by heat change from shape to liquid, and when the temperature decreases, it returns to normal. The main physical difference between it and thermoplastics is that thermoplastics can be melted in a liquid, but they are always solid and do not return to the liquid state. Examples include polyurethane, silicone and phenolic[2].

2.3.4.Fibers: This class of polymers appears as strings and is easily woven, linked with a hydrogen bond or bipolar reaction. It has strong bonds between its molecules giving it a less elastic trait and high tensile strength, for example nylon-66[2].

2.4. Based on mode of polymerization.

2.4.1.Addition polymers: These polymers that is the result of binding monomers such as alkene to one another or in addition to cationic root media. Such as polystyrene, polyethylene and polyacrylates[2].

2.4.2.Condensation polymers: Condensation polymerization is a reaction that joins two functional groups, such as the alcohol group and the mostly carboxyl group, resulting in a portion of water. Such as polyester, polyamide, polysiloxane[2].

2.5. Susceptibility of backbone. (not given in figure. 1)

2.5.1.Degradable polymers: This type of polymers that dissolve external influences, such as microorganisms, acids, or strong bases, leaving behind by-products that are soluble in water so that these wastes do either not because any dangerous effects, and finally they metabolize or are excreted outside the body. Such as poly (L-lactic acid), poly(glycolic acid)[2].

2.5.2.Non- degradable polymers: These substances meant to not degrade by biological agents. It does not degrade to an environmentally safe natural condition over time. It consists of long chains of carbon and hydrogen atoms, most of which are plastic materials that are difficult for enzymes and organisms to break their bonds and digest. Among its peculiarities is that it is cheap, varied and durable. Such as polyhydroxy butyrate (PHB), polycaprolactone (PCL)[2].

Figure. Classification of polymers

3. Polymers used for skin tissue engineering.

3.1. Natural polymers.

3.1.1. Cellulose: It is frequently used in wound dressings but not natural, but rather modified to active molecules such as antimicrobial agents, enzymes, antioxidants, and growth factors. It is hydrophilic and biocompatible with the hydroxyl group. Bacterial cellulose: is an innovative natural polymeric raw material with a nanostructured structure. It also used in wound dressings, has high mechanical strength and has swelling properties. Carboxymethylcellulose (CMC) is widely used in cellulose wound dressing with the carboxymethyl group. It is a loving, soluble and swollen polymer in water[4]. [5]

3.1.2. Dextran: carboxymethyl benzyl amide sulfonate dextran (CMBDS) is widely used in wound healing and various biomedical applications and its properties are heparin-like and soluble. Glycosaminoglycan stimulates wound healing in various parts of the body. It has antimicrobial properties, especially in the proliferation of Staphylococcus aureus. It also has a specific effect on the proliferation of tumor cells. Aqueous cyclodextrins used to control odors in modern dressings[5].

3.1.3. Collagen: It is a protein, found outside the cell, and is often composed of proline, hydroxyl-proline glycine, and arginine. It is made of fibroblasts, and it enters the scaffolds of some tissue engineering, such as bone, cartilage, and tendons, for their biocompatibility, and their biodegradability, and provides[4] strength to various body structures. It also enters in all stages of wound healing due to the decrease of its antigenic properties and the adhesion of cells directly to it[6]. It protects the body from diseases by preventing absorption and dispersion. Pathogenic substances such as UV rays, microorganisms and cancer cells. It obtained from the hides of cows, pigs and chickens, as well as from ocean animals such as octopus.[4, 6, 7].

3.1.4. Gelatin: derived from collagen, and obtained through the hydrolysis of animal tissues such as the skin of cows and pigs. It is biologically compatible and biodegradable and not attacked by the immune system. It divided into gelatin A, which  derived from acidic treated materials and contains the isoelectric point (positive charge at the neutral pH) [5]. In addition, gelatin B is derived from alkali-treated materials and contains the isoelectric point (negative charge at the neutral pH). It used as a scaffold for tissue engineering, also in the delivery of the drug, as many of the capsules that are delivered orally are gelatin; gelatin and some other natural polymers have been studied in the laboratory and in the body that can deliver the pulmonary drug[4].[7]

3.1.5.Chitosan: Cationic polymer derived from chitin (polysaccharide). It contains a common polymer of β-glucosamine and N-acetyl-D-glucosamine. It is the second most abundant natural polymer after cellulose.[4] Chitosan is suitable for binding with red blood cells that allow them to rapidly coagulate blood، modify the function of inflammatory cells and act as a semi-permeable biological dressing، maintains sterile، regenerated and biologically compatible wound secretions، and not attacked by the immune system and nontoxic system[5, 6]. It also induces fibroblasts to secrete the interleukins and the latter works in the migration and spread of cells. The(2) most important characteristics that make chitosan important in healing[5, 7].

3.1.6. Alginates: It is a non-branched linear polysaccharide. Used in wound dressings and burns based on genes[6]. Obtained from treated algae such as calcium, sodium and collagen genes are absorbent bandages of natural fibers. Among its properties, it can absorb large quantities of body fluids 20 times the size. Other materials such as zinc genes and silver genes have been obtained that have antimicrobial, wound and burn properties[4] [8].

3.1.7. Agar: It is a natural biological material obtained from continuous fibers in the ethanol coagulation bath using a mixture of dimethyl sulfoxide as a suitable solvent. Among its properties is that it is swollen by 400 - 50% and a tensile strength of 30 - 50 MPa[8].

3.1.8.Glycosaminoglycan: Hyaluronic acid from ECM is known to be a non-immunomodulatory linear glycemic, obtained from N-acetyl-d-glucosamine and glucuronic acid and has an effect on wound healing[4]. 

3.2. Synthetic polymers

Synthetic polymers are complex nanomaterials with small pores and very high surface area, manufactured with different technologies. Used to heal wounds and burns, most of them by electrical fixation, in order to produce nanofibers. Its characteristics: it has excellent mechanical properties, suitable hydrolysis also, thermal stability.

3.2.1. Polyurethane: Polyurethane was first used to produce fibrous nanoparticles as an alternative to the skin in 2003. It found excellent properties such as good oxygen permeability, fluid discharge capacity, and the ability to classify water vapor transmission, as an antimicrobial. The obligation is to reduce the polyurethane polymer and it can be overcome by coating it with collagen or collagen-based peptides, which greatly increases the adhesion and biocompatibility properties[2, 6].

3.2.2.Poly(L-lactic glycolic acid: The polylactic and polglycolic acid that resulted in nanofibers was subsequently used to transplant them to a surface with the fibrous cells of the skin. The results were that the cells were able to spread and form multiple layers after 28 days. In other studies, the nature of water-repellent synthetic polymers and the absence of peptide infiltration affects cell adhesion [2, 8, 9].

4. Conclusion.

Polymers used in tissue regeneration, whether natural or synthetic, must have several properties, including being biologically renewable, biodegradable, biocompatible, non-antigenic, non-toxic, blood compatible, and biological functions. Because of these desirable properties, natural and synthetic materials have been widely proposed as scaffolding in tissue engineering applications and as a vector for various drug delivery systems.

Acknowledgements

We would like to express my deep gratitude to Professor İdris Kabalci  and Professor Ziyodulla Yusupov, for their patient guidance, enthusiastic encouragement of this work. My grateful thanks are also extended to Mr. Youssouf Abakar Adam who is master student of the department of Biomedical engineering of Karabuk university for his help in finding materials, referances and doing the data analysis.

Conflicts and interest.

If you will face to any conflicts during the read this work you should know they are  only my mistakes which come from my inexperience. I will be happy if you share about your interests on the topic by this contact,dilmurod.juraev.92@gmail.com .

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