Suture, polymers

Artificial Soft Biologies. In addition to sutures, polymers are used for a number of biomedical applications, as illustrated in Figure 5.128. Polymers used for hard structural applications such as dentures and bones are presented in this figure, but will be described in the next section. In this section, we will concentrate on polymers for soft biological material applications and will limit the description to mechanical properties as much as possible. 

Hu W, Huang ZM (2010) Biocompatibility of braided poly(L-lactic acid) nanofiber wires applied as tissue sutures. Polym Int 59(1 ) 92—99... 

Tomihata K, Suzuki M, OkaT and Ikada Y (1998a), A new resorbable monofilament suture, Polymer Degrad Stabil, 59,13-18. 

The chemical structures of the most common suture polymers are given in Figs 13.9-13.16. The suture biomaterials shown in Table 13.1 have previously been reported by our laboratory to have successfully formed barbed sutures (Dattilo,2002 Ingle,2003). It has been shown that different polymer... 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

The concept of using biodegradable materials for implants which serve a temporary function is a relatively new one. This concept has gained acceptance as it has been realized that an implanted material does not have to be inert, but can be degraded and/or metabolized in vivo once its function has been accompHshed (12). Resorbable polymers have been utilized successfully in the manufacture of sutures, small bone fixation devices (13), and dmg dehvery systems (qv) (14). 

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. 

Copolymers of S-caprolactone and L-lactide are elastomeric when prepared from 25% S-caprolactone and 75% L-lactide, and rigid when prepared from 10% S-caprolactone and 90% L-lactide (47). Blends of poly-DL-lactide and polycaprolactone polymers are another way to achieve unique elastomeric properties. Copolymers of S-caprolactone and glycoHde have been evaluated in fiber form as potential absorbable sutures. Strong, flexible monofilaments have been produced which maintain 11—37% of initial tensile strength after two weeks in vivo (48). 

Braided Synthetic Absorbable Sutures. Suture manufacturers have searched for many years to find a synthetic alternative to surgical gut. The first successful attempt to make a synthetic absorbable suture was the invention of polylactic acid [26023-30-3] suture (15). The polymer was made by the ring-opening polymerization of L-lactide [95-96-5] (1), the cycUc dimer of L-lactic acid. 

Monofilament Synthetic Absorbable Sutures. Ethicon iatroduced the first monofilament synthetic absorbable suture ia 1984 when it marketed PDS polydioxanone (4) sutures. The polymer is produced by the bulk polymerisation of 2,5- -dioxanone. The suture is distributed under the trade name PDS 11. It is claimed to retain approximately 50% of its strength four weeks after implantation, 25% at six weeks, and to be absorbed within six months. 

Poliglecaprone-25 is a copolymer of 75% glycoHde and 25% caprolactone. The molecular weight and the percentages of glycoHde and caprolactone are not the same as the coating polymer on Dexon II, but the stmcture (3) is as shown for that polymer. The suture is distributed under the trade name Monocryl. It is claimed to retain approximately 20 to 30% of its strength two weeks after implantation and to be absorbed ia 91 to 119 days. 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

There has been recent interest in lactic acid polymers and copolymers. These materials are environmentally attractive in that renewal and cheap source materials such as potato waste and cheese whey may be used. Such materials have been used for some time in degradable and resorbable surgical sutures but recent efforts have been directed at food packaging applications. There is... 

Despite the universal use of sutures for wound closure, there is a need to utilize adhesives instead, because of their ease of use and the reduced risk of infection. Alkyl cyanoacrylate adhesives have been studied extensively for this use, and a significant amount of research has been performed to evaluate their interaction with living tissue [40,41 J. They have been approved for external use only, because of concerns with the fact that the polymers do not readily biodegrade and can cause inflammation around the area to which it was applied. However, these concerns are reduced for -butyl cyanoacrylate, as compared to the ethyl cyanoacrylate. There is even some evidence that their use as liquid sutures actually reduces the rate of infection around the healing wound or surgical incision [42J. 

Polymers are a fundamental part of the modem world, showing up in everything from coffee cups to cars to clothing. In medicine, too, their importance is growing for purposes as diverse as cardiac pacemakers, artificial heart valves, and biodegradable sutures. 

Sei f-Tfst 19.4A (a) Write the formula for the monomer of the polymer sold as Teflon, — (CF2CF2),—. (b) The polymer of lactic acid (16) is a biodegradable polymer made from renewable resources. It is used in surgical sutures that dissolve in the body. Write the formula for a repeating unit of this polymer. 

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