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Biodegradable Polymers: Production...”, Technologica Acta, Vol CORE Metadata, citation and similar papers at core.ac.uk A. Cipurković, E. Horozić, N. Đonlagić, S. Marić, M. Saletović, Z. Ademović, “Biodegradable polymers: production...”, Technologica Acta, vol. 11, no. 1, pp. 25–35, 2018. 25 BIODEGRADABLE POLYMERS: PRODUCTION, PROPERTIES AND APPLICATION IN MEDICINE SCIENTIFIC REVIEW PAPER Amira Cipurković1, Emir Horozić2, Nusreta Đonlagić1, Snježana Marić1, Mirzeta Saletović1, Zahida Ademović2 RECEIVED ACCEPTED 1Faculty of Natural Science and Mathematics, University of Tuzla, Bosnia and Herzegovina 2018-01-22 2018-05-18 2Faculty of Technology, University of Tuzla, Bosnia and Herzegovina * [email protected] ABSTRACT: Biodegradable polymers (biopolymers) represent materials of new generation with application in different areas of human activity. Their production has recently reached a commercial level. They can be divided according to the origin (natural and synthetic), according to the chemical composition, methods of obtaining, ap- plication etc. The use of biopolymers in medicine depends on their biocompatibility, mechanical resistance, and sorptive characteristics. Today, they are the most commonly used as implants in vascular and orthopedic surgery, for the production of materials such as catheters, products for gynaecology and haemodialysis, tooth reconstruc- tion, etc. In pharmacy, they are used as a medicine matrix-carrier to allow controlled release of drug within the body. Within this review paper, the properties and methods of production of certain biopolymers such as polygly- colic acid (PGA), polylactide acid (PLA), poly-ε-coprolactone (PCL) and polybutylene succinate (PBS) will be de- scribed in detail, as well as their application in medicine and pharmacy. KEYWORDS: polyglycolic acid (PGA), polylactide acid (PLA), poly-ε-coprolactone (PCL), polybutylene succi- nate (PBS) INTRODUCTION amide, or ether chemical bonds. In general, biode- gradable polymers can be grouped into two large A biomaterial is defined as any natural or syn- groups on basis of their structure and synthesis. One thetic substance engineered to interact with biological of these groups is agro-polymers, i.e. those derived systems to direct medical treatment. from biomass. The other consists of bio polyesters, Biomaterials must be biocompatible meaning that which are those derived from microorganisms or syn- they perform their function with an appropriate host thetically made from either naturally or synthetic response [1]. Biodegradable polymers comprise ester, monomers [2]. Figure 1. Classification of the main biodegradable polymers [3] ISSN 1840-0426 (P); ISSN 2232-7588 (E) http://tf.untz.ba/technologica-acta 26 A. Cipurković, E. Horozić, N. Đonlagić, S. Marić, M. Saletović, Z. Ademović, “Biodegradable polymers: production...”, Technologica Acta, vol. 11, no. 1, pp. 25–35, 2018. Biodegradable polymers represent a growing garded as suitable compounds to make bioresorbable field. A vast number of biodegradable polymers (e.g. therapeutic devices [5]. Biodegradable polymers that cellulose, chitin, starch, polyhydroxyalkanoates, are often used as biomaterials are shown in Figure 2. polylactide, polycaprolactone, collagen and other polypeptides) have been synthesized or are formed in a natural environment during the growth cycles of organisms. Some microorganisms and enzymes ca- pable of degrading such polymers have been identi- fied. There are different classifications of biodegrad- able polymers, hereby is presented the classification according to the synthesis process, which is shown in Figure 1. Polyesters are among the most used biodegrad- able plastics, given their hydrolysable ester bonds; therefore they represent a valid solution for biomedi- cal applications. The properties of these materials strictly depend on the monomers used for their syn- thesis. The aliphatic polyesters are almost the only high Figure 2. Biodegradable polymers used as biomaterials in hu- molecular weight biodegradable compounds and thus man organism [7] have been extensively investigated. Their hydroly- sable ester bonds make them biodegradable. Ali- To be used as biomaterials, biodegradable poly- phatic polyesters can be classified into two types ac- mers should have three important properties: bio- cording to the bonding of the constituent monomers. compatibility, bioabsorbility and mechanical resis- The first class consists of the polyhydroxy- tance. The use of enzymatically degradable natural alkanoates. These are polymers synthesized from hy- polymers, as proteins or polysaccharides, in biomedi- droxyacids, HO-R-COOH. cal applications began thousands of years ago, Examples are poly(glycolic acid) or poly(lactic whereas the application of synthetic biodegradable acid). Poly(alkene dicarboxylate)s represent the sec- polymers dates back some fifty years. Current appli- ond class. They are prepared by polycondensation of cations of biodegradable polymers include surgical diols and dicarboxylic acids. Examples are implants in vascular or orthopaedic surgery and plain poly(butylene succinate) and poly(ethylene succi- membranes. Biodegradable polyesters are widely nate) [4]. Application of biomaterials in therapy are employed as a porous structure in tissue engineering various and some of these applications are aimed at because they typically have good strength and an ad- replacing a lost function or an organ and request a justable degradation speed [4]. Biodegradable poly- therapeutic device made of biomaterials (prosthesis) mers are also used as implantable matrices for the for the rest of the patient's lifetime. Many other bio- controlled release of drugs inside the body or as ab- medical applications require a therapeutic aid for a sorbable sutures [6]. limited period of time. Accordingly, it is desirable that the temporary therapeutic aid disappear from the SYNTHESIS, PROPERTIES AND APPLICATION OF body after healing in order to avoid the storage of any SOME BIODEGRADABLE POLYMERS foreign materials. Whereas permanent aids require biostable bioma- Properties and methods of production of most com- terials, temporary aids should be preferably made of mon biopolymers polyglycolic acid (PGA), polylac- degradable or biodegradable compounds that can be tide acid (PLA), poly-ε-coprolactone (PCL) and eliminated from the body or to be bioassimilated after polybutylene succinate (PBS) are described, as well use. as their application in medicine and pharmacy. Historically, biopolymers, i.e. polymers of natu- ral origin such as polysaccharides and proteins, were POLYGLYCOLIC ACID (PGA) primarily used as sources of wound dressings and Polyglycolide or polyglycolic acid (PGA) is a suture threads either under their natural forms or after biodegradable, thermoplastic polymer and the sim- some chemical treatments. Because macromolecular plest linear, aliphatic polyester (Figure 3). PGA has compounds are usually biodegradable, i.e. degraded been known since 1954 as a tough fiber-forming via biological processes, biopolymers are often re- polymer [8]. Polyglycolide has a glass transition ISSN 1840-0426 (P); ISSN 2232-7588 (E) http://tf.untz.ba/technologica-acta A. Cipurković, E. Horozić, N. Đonlagić, S. Marić, M. Saletović, Z. Ademović, “Biodegradable polymers: production...”, Technologica Acta, vol. 11, no. 1, pp. 25–35, 2018. 27 temperature between 35-40°C and its melting point is reported to be in the range of 225-230°C. PGA also Synthesis. Poly(glycolic acid) can be obtained by exhibits an elevated degree of crystallinity, around a number of processes starting with different reac- 45-55%, thus resulting in insolubility in water. The tants, and products so obtained have different phys- solubility of this polyester is somewhat unique, in icochemical properties. In fact, for the different ap- that its high molecular weight form is insoluble in plication areas, basic materials are of prime impor- almost all common organic solvents (acetone, di- tance, together with the technology to form implants chloromethane, chloroform, ethyl acetate, tetrahydro- or other forms. For instance, in the orthopaedic field, furan), while low molecular weight oligomers suffi- mechanical properties and design of the end product ciently differ in their physical properties to be more will be essential; to a lesser extent this will be the soluble. However, polyglycolide is soluble in highly case in the pharmaceutical field, and so less attention fluorinated solvents like hexafluoroisopropanol needs to be paid to these aspects [10]. PGA can be (HFIP) and hexafluoroacetone sesquihydrate that can obtained through several different processes starting be used to prepare solutions of the high molecular with different materials: polycondensation of glycolic weight polymer for melt spinning and film prepara- acid, ring-opening polymerization of glycolide and tion. Fibers of PGA exhibit high strength and solid-state polycondensation of halogenoacetates. modulus (7 GPa) and are particularly stiff [9]. Polycondensation of glycolic acid is the simplest process available to prepare PGA, but it is not the O most efficient because it yields a low molecular weight product. The most common synthesis used to O produce a high molecular weight form of the polymer H OH is ring-opening polymerization of "glycolide", the n cyclic diester of glycolic acid (Figure 4). Figure 3. PGA structure O C O O O catalyst heat O CH2 C O CH2 C O C n O polyglycolide Glycolide Figure 4. Ring-opening polymerization of glycolidIn spite of its low solubility, this polymer has been fabricated into a variety
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