Synthetic polymers Tissue

Key words synthetic polymers, tissue engineering, bone scaffold, hydrogels, drug delivery. 

Biomaterials for Cardiovascular Devices. Perhaps the most advanced field of biomaterials is that for cardiovascular devices. For several decades bodily parts have been replaced or repaired by direct substitution using natural tissue or selected synthetic materials. The development of implantable-grade synthetic polymers, such as siHcones and polyurethanes, has made possible the development of advanced cardiac assist devices (see... 

The first synthetic polyglycoHc acid suture was introduced in 1970 with great success (21). This is because synthetic polymers are preferable to natural polymers since greater control over uniformity and mechanical properties are obtainable. The foreign body response to synthetic polymer absorption generally is quite predictable whereas catgut absorption is variable and usually produces a more intense inflammatory reaction (22). This greater tissue compatibihty is cmcial when the implant must serve as an inert, mechanical device prior to bioresorption. 

Acrylic Resins. The first synthetic polymer denture material, used throughout much of the 20th century, was based on the discovery of vulcanised mbber in 1839. Other polymers explored for denture and other dental uses have included ceUuloid, phenolformaldehyde resins, and vinyl chloride copolymers. Polystyrene, polycarbonates, polyurethanes, and acryHc resins have also been used for dental polymers. Because of the unique combination of properties, eg, aesthetics and ease of fabrication, acryHc resins based on methyl methacrylate and its polymer and/or copolymers have received the most attention since their introduction in 1937. However, deficiencies include excessive polymerization shrinkage and poor abrasion resistance. Polymers used in dental appHcation should have minimal dimensional changes during and subsequent to polymerization exceUent chemical, physical, and color stabiHty processabiHty and biocompatibiHty and the abiHty to blend with contiguous tissues. 

The term "bioenertness" is a relative one since few if any synthetic polymers are totally biocompatible with living tissues. The terra is used here on the basis of preUminary in vitro and in vivo tests, together with chemical evaluations based on analogies with other well-tested systems. Two different types of polyphosphazenes are of interest as bioinert materials those with strongly hydrophobic surface characteristics and those with hydrophilic surfaces. These will be considered in turn. 

In macromolecular dmg delivery systems, dmgs are attached to polymeric compounds, such as synthetic polymers [60], dendrimers [61], and antibodies [62], in order to enhance the delivery of the active substance to the diseased tissue and to reduce the toxicity to healthy tissue. The use of macromolecular delivery systems provides several advantages extension of the half-life of the dmg, the ability to introduce targeting moieties into the carrier, the possibility of triggered dmg release, and the aforementioned reduced cytotoxicity. 

Abstract Synthetic polymers and biopolymers are extensively used within the field of tissue engineering. Some common examples of these materials include polylactic acid, polyglycolic acid, collagen, elastin, and various forms of polysaccharides. In terms of application, these materials are primarily used in the construction of scaffolds that aid in the local delivery of cells and growth factors, and in many cases fulfill a mechanical role in supporting physiologic loads that would otherwise be supported by a healthy tissue. In this review we will examine the development of scaffolds derived from biopolymers and their use with various cell types in the context of tissue engineering the nucleus pulposus of the intervertebral disc. 

P A Gunatillake, P.A., and Adhikari. R., Biodegradable Synthetic Polymers for tissue engineering, European Cells and Materials Vol. 5. 2003 (pages 1-16). 

Table 1. Adhesion of synthetic polymers to connective tissue under the effect of benzoyl chloride...

The use of synthetic polymers in medicine and biotechnology is a subject of wide interest. Polymers are used in replacement blood vessels, heart valves, blood pumps, dialysis membranes, intraocular lenses, tissue regeneration platforms, surgical sutures, and in a variety of targeted, controlled drug delivery devices. Poly(organosiloxanes) have been used for many years as inert prostheses and heart valves. Biomedical materials based on polyphosphazenes are being considered for nearly all the uses mentioned above. 

Watanabe S, Kato H, Shimizu Y et al. (1981) Antibacterial biomaterials by immobilization of hen egg-white lysozyme onto collagen-synthetic polymer composites - histological-findings of immobilized lysozyme in the tissue of a different species. Artif Organs 5 309-309... 

Polyglycolide was one of the first synthetic polymers used as a degradable surgical suture [122]. Fig. 8 shows the glycolide monomer and polymer structures. This aliphatic polyester is biodegradable and exhibits negligible toxicity when implanted in tissue. It is also possible to fabricate a strong fiber of this polyester with satisfactory mechanical properties. 

The aliphatic poly(ether lactonejs are a group of synthetic polymers with high elasticity and high tissue absorptivity [293]. The ether function in the polymer backbone adds flexibility to the ester chain. Ring-opening polymerization of l,4-dioxan-2-one yields an elastic polymer, polydioxanone, with a tensile strength similar to that of human tissue [294]. Polydioxanone has been successfully used to prepare monofilament sutures, with a flexibility superior to that of PGA sutures [294]. Recently, the lipase-catalyzed polymerization of polydioxanone was demonstrated [295]. 

Other polymers are partly from a natural origin the chain molecule has grown in a living tissue, but has been chemically modified into a half-synthetic polymer . 

Both natural polymers such as polysaccharides and synthetic polymers such as polylysine, polyglutamic acid, polyphosphazenes, copolymers of vinylpyrrolidone, copolymers of 2-hydroxypropylmeth-acrylamide, and etc. have been used as drug carriers. The structure of these polymers can be modified by the incorporation of hydro-phobic units, sugar residues, or sulfonyl groups to achieve a specific tissue affinity. 

Cardiovascular-functional polymers cover almost all categories of synthetic polymers and large numbers of biopolymers. They are used to build the device bulk, act as surface-modifying additives [SMA], and also formulate tissue adhesives [11-17]. 

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