Fundamental Biomaterials: Polymers

Sabu Thomas, Preetha Balakrishnan, M.S. Sreekala, Sreekala Meyyarappallil Sadasivan

• Publisher: Woodhead Publishing
• Year: 2018
• Print ISBN: 9780081021941
• eBook ISBN: 9780081021958
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Fundamental Biomaterials: Polymers provides current information on findings and developments of biopolymers and their conversion from base materials to medical devices. Chapters analyze the types of polymers and discuss a range of biomedical applications. It is the first title in a three volume set, with each reviewing the most important and commonly used classes of biomaterials and providing comprehensive information on classification, materials properties, behavior, biocompatibility and applications. The book concludes with essential information on wear, lifetime prediction and cytotoxicity of biomaterials. This title will be of use to researchers and professionals in development stages, but will also help medical researchers understand and effectively communicate the requirements of a biomaterial for a specific application. Further, with the recent introduction of a number of interdisciplinary bio-related undergraduate and graduate programs, this book will be an appropriate reference volume for large number of students at undergraduate and post graduate levels. - Provides current information on findings and developments of biopolymers and their conversion from base materials to medical devices - Includes analyses of the types of polymers and a discussion of a range of biomedical applications - Presents essential information on wear, lifetime prediction and cytotoxicity of biomaterials - Explores both theoretical and practical aspects of polymers in biomaterials

1

Polymeric biomaterials: State-of-the-art and new challenges

Preetha Balakrishnan*; V.G. Geethamma*; Meyyapallil Sadasivan Sreekala^†; Sabu Thomas* ^* Mahatma Gandhi University, Kottayam, India
^† Sree Sankara College Kalady, Ernakulam, India

Abstract

The previous two decades have made noteworthy advances in the improvement of biodegradable polymeric materials for biomedical applications. Biodegradable materials as a substitute for creating helpful devices, medicate discharge, and so forth are utilized broadly. Each of these applications requests materials with particular physical, substance, organic, biomechanical, and corruption properties to give proficient treatment. The biomedical area is a specific space of enthusiasm for polymer researchers since it asks for an ever-increasing number of complex structures in their endeavors to satisfy the prerequisites of a large number of various applications. To be sure, in this area, the objectives are gone for abusing mixes with properties that can be considered as under control as far as material designing and properties are concerned. Conversely, the methodologies need to consider complex organic frameworks and procedures that are a long way from being comprehended and along these lines aced, in light of their whole control by nature.

Keywords

Polymer; Biomaterials; Biodegradable

Acknowledgment

The authors are grateful to the Department of Science and Technology (DST) for awarding INSPIRE fellowship to Preetha Balakrishnan.

1.1 Introduction

Biomaterials are naturally available materials set inside a patient on a long haul or changeless premise. Until early this century, plants and creature sources were the main materials utilized as a part of the act of wound dressing and dental repair. From that point forward, science and prescription have gained significant ground. For more than 50 years, significant advances have occurred in medicinal gadgets that entail contact with living tissues. Advances in designing and a more prominent accessibility of manufactured materials set off the improvement of built polymers for use in biomaterials and restorative in light of the fact that antimicrobials and different medications have decreased the danger of contamination and dismissal, and research on the structure and capacity of biomaterials has taken a core interest. Today, new materials last more and perform better. Among them, polymer-based biomaterial increase merits significantly more consideration because of an assortment of reasons. They tended to a few issues in restorative field which incorporates dental, neurological, cardiovascular, and embed gadgets to drag out the life of patients.

The possibility of biomaterials was exhibited not long after World War II, and polymers were rapidly part of the researched biomedical materials. Nowadays, employments of polymers are fundamental to surgeries, for prosthetic systems, and in pharmacology, for sedate definition and controlled pharmaceutical transport. In this way, the division of biomaterials is basic from the socio-effective point of view. Various polymeric blends with known names are found in the extent of biomaterials. They match basically balanced biopolymers or with inorganic biomaterials (metals, amalgams, ceramic creation, and so forth.). Polymers are commonly arranged in three gatherings: thermoplastics, rubbers, and thermosets. Thermoplastics, which are regularly alluded to as “plastics,” are direct or stretched polymers that can be softened upon the application of heat; they can be formed and remolded from previous forms. At present, plastics are the most broadly utilized polymers. Rubbers are materials that show elastomeric properties (i.e., they can be extended effortlessly to high augmentations and will spring back quickly when the anxiety is discharged) and are depicted as crosslinkable linear polymers. Common rubbers incorporate silicone rubbers and acrylonitrile/butadiene copolymers. Thermosets are intensely cross- connected polymers that are ordinarily unbending and immovable. They comprise a thick, three-dimensional (3D) subatomic system and, similar to rubbers, corrupt as opposed to liquefy after warming. Regular thermosetting polymers incorporate phenol-formaldehyde or urea-formaldehyde saps and superior cements, for example, epoxy pitches. Despite the fact that the biomedical utilizations of enzymatically degradable characteristic polymers, for example, collagen goes back a huge number of years, the use of engineered biodegradable polymers began just in the latter half of the 1960s [1]. The moderate advancement in the improvement of biodegradable biomaterials can be credited to a few novel difficulties in creating resorbable clinical materials contrasted with creating item polymers. A biomaterial can be characterized as a material planned to interface with natural frameworks to assess, treat, increase, or supplant any tissue, organ, or capacity of the body [2,3]. The material ought not to bring out a managed fiery or harmful reaction upon implantation in the body. The materials should have the following essential properties:

• ● It should have an acceptable shelf life.
• ● The degradation time of the material should match the healing or the regeneration process.
• ● The material should have appropriate mechanical properties for the indicated application and the variation in mechanical properties with degradation should be compatible with the healing or regeneration process.
• ● The degradation products should be nontoxic, and should be able to get metabolized and cleared from the body. The material should have appropriate permeability and processability for the intended application.

The current endeavors in biodegradable polymer union have been centered around hand crafting and integrating polymers with custom-fitted properties for particular applications by: (1) creating novel engineered polymers with one-of-a-kind sciences to expand the assorted qualities of a polymer structure, (2) creating biosynthetic procedures to frame biomimetic polymer structures, and (3) receiving combinatorial and computational methodologies in biomaterial configuration to quicken the disclosure of novel, resorbable polymers. A portion of the current biomedical uses of biodegradable polymeric materials include: (1) vast inserts, for example, bone screws, bone plates, and preventative supplies; (2) little embeds, for example, staples, sutures. and nano- or small-scale measured medication conveyance vehicles; (3) plain films for guided tissue recovery; and (4) multifilament networks or permeable structures for tissue building [4]. A tissue designing methodology utilizes a biodegradable build to amass cells in three measurements to form into working tissues eventually. Polymeric materials with an extensive variety of mechanical and corruption properties are required to emulate the properties of different tissues. In controlled medication conveyance, bioactive specialists are entangled inside a biodegradable polymer framework from which they are discharged in a disintegration or dissemination controlled form or a blend of both. The discharge qualities of the bioactive operators can be successfully regulated by appropriately designing the network parameters.

Table 1.1 shows some of the commonly used polymers for bioapplications. Some polymers are currently used clinically and some for biomedical applications.

Table 1.1

Commonly used polymers for biomedical applications

Polymer	Biomedical applications
Poly(methyl methacrylate)	Rigid contact lenses, intraocular lens
Polymeric compounds based on methyl methacrylate	Acrylic cements for orthopedy and odontology, facial prostheses, joint surgeries, filling of bone cavities, and porous bony tissues
Poly(2-hydroxyethyl methacrylate)	Flexible contact lenses, plastic surgery, hemocompatibility of surfaces
Nylon-type polyamides	Sutures
Poly(vinyl chloride)	Blood pushes, catheters
Poly(ethylene terephtalate)	Vascular protheses, cardiac valves
Polytetrafluoroethylene	Orthopedy, vascular clips polyurethanes catheters, cardiac pumps silicones plastic surgery, tubes, oxygenators

1.2 Biodegradable polymers for biomedical applications

Engineered and naturally occurring polymers were broadly utilized as biodegradable materials for medicinal applications. Generally, biodegradation of this sort of materials includes hydrolytic and enzymatic cleavage of delicate bonds in polymers, which later prompts polymer disintegration [5]. Contingent upon the method of cleavage, these polymers are additionally grouped into hydrolytically degradable polymers and enzymatically degradable polymers. Hydrolytically degradable polymers will be polymers that have hydrolytically labile concoction bonds in their spine. The practical gatherings helpless to hydrolysis incorporate esters, orthoesters, anhydrides, carbonates, amides, urethanes, ureas, and so forth. Characteristic polymers can be considered as the principal biodegradable biomaterials utilized clinically. The rate of in vivo corruption of enzymatically degradable polymers, in any case, fluctuates fundamentally with the site of implantation relying upon the accessibility and centralization of the compounds. Synthetic change of these polymers additionally can essentially influence their rate of debasement. Regular polymers have a few inborn points of interest, for example, bioactivity, the capacity to introduce receptor-restricting ligands to cells, helplessness to cell-activated proteolytic debasement, and normal rebuilding. The characteristic bioactivity of these normal polymers has its own drawbacks. These incorporate a solid immunogenic reaction related with the greater part of the polymers, the complexities related with their cleansing, and the likelihood of infection transmission [6].

1.2.1 Polyglycolide

Polyglycolide can be considered as one of the primary manufactured biodegradable polymers researched for biomedical applications. Polyglycolide is an exceptionally crystalline polymer (45%–55% crystallinity) and in this way displays a high tractable modulus with low dissolvability in natural solvents. The glass transition temperature of the polymer ranges from 35°C to 40°C and the liquefying point is more prominent than 200°C. Notwithstanding its low solvency, this polymer has been created into an assortment of structures. Expulsion, infusion, and pressure forming, as well as particulate draining and dissolvable throwing are some of the procedures used to create polyglycolide-based structures for biomedical applications [7]. Because of its superb fiber-shaping capacity, polyglycolide was at first examined for creating resorbable sutures. The principal biodegradable engineered suture called DEXON that was affirmed by the United States (US) Food and Drug Administration in 1969 depended on polyglycolide. Nonwoven polyglycolide textures have been widely utilized as framework lattices for tissue recovery because of its phenomenal degradability, great mechanical properties, and cell suitability on networks. A polyglycolide nonwoven texture fibrin stick composite framework is as of now experiencing clinical trials. It is being explored as a biocompatible dural substitute because of its superb skin-shutting capacity without requiring sutures and its capacity to help recover organic tissues [8].

1.2.2 Poly(α-esters)

These are thermoplastic polymers with labile aliphatic linkages in their spine that are powerless for cleavage. Albeit all polyesters are hypothetically degradable as esterification is an artificially reversible process, just aliphatic polyesters with sensibly short aliphatic chains between ester bonds can debase over the time allotted, required for a large portion of the biomedical applications. Poly(α-esters) involve the soonest and most broadly examined class of biode...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• 1: Polymeric biomaterials: State-of-the-art and new challenges
• 2: Polymeric membranes: Classification, preparation, structure physiochemical, and transport mechanisms
• 3: Polysaccharides as biomaterials
• 4: Natural rubber and silicone rubber-based biomaterials
• 5: Hydrogels, DNA, and RNA polypeptides for the preparation of biomaterials
• 6: 3D bioprinting of polysaccharides and their derivatives: From characterization to application
• 7: Xyloglucan for drug delivery applications
• 8: Plasma polymerization and plasma modification of surface for biomaterials applications
• 9: Textile-based biomaterials for surgical applications
• 10: In vivo biocompatiblity studies: Perspectives on evaluation of biomedical polymer biocompatibility
• 11: Polymeric materials for targeted delivery of bioactive agents and drugs
• 12: Medical grade biodegradable polymers: A perspective from gram-positive bacteria
• 13: Investigation of wear characteristics of dental composites filled with nanohydroxyapatite and mineral trioxide aggregate
• 14: Biodegradable superabsorbents: Methods of preparation and application—A review
• 15: Life cycle analysis and wear and fatigue behavior of polymeric biomaterials
• Index