Polyglycolide-lactide

Occasionally in the synthesis of the copolymers, insoluble material is produced. This results from polymer containing blocks of polyglycolide rather than the desired random structure. Obviously, such compositions would have considerable effect on the performance of controlled release formulations utilizing those polymers. This problem is particularly evident when one is seeking to utilize the 50 50 glycolide/lactide copolymer as a biodegradable excipient. However, with carefully controlled polymerization conditions, useful 50 50 polymer is readily produced. 

Various studies have been made on the effects of radiation on lactide/glycolide polymers (24,38,58). Gilding and Reed (24) reported the effect of y rays on Dexon sutures. Those results confirmed that deterioration of the sutures occurs but that random chain scission is not the primary mechanism. Number average-molecular weight Mn showed a dramatic decrease at doses above 1.0 Mrad. Thus, unzipping of the polymer chain appeared to be the more dominant process, at least in the case of polyglycolide. 

The use of polylactides for delivery of insect hormone analogs and other veterinary compounds (115,116) has been studied. Microspheres, pellets, and reservoir devices based on polyglycolide, poly-(DL-Iactide), poly(L-lactide), and various copolymers have been used to deliver methoprene and a number of juvenile hormone analogs. ... 

Meanwhile Ethicon (and others) developed alternative absorbable surgical sutures, based, for example, on copolymers of polyglycolide with poly-L-lactide or poly(trimethylene carbonate), and on polydioxanone, and on poly(e-oxycaproate), and also on copolymers of these with polyglycolide or with each other. These different structures made it possible to provide fibres with different rates of absorption, with different degrees of stiffness or flexibility, and for use in monofilaments, braided multifilaments, and other yam structures, as required for different surgical operations. 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization of Lactides and Glycolides Preparation of Poly lactides, Polyglycolide, and Poly(lactide-co-glycolide)... 

Other types of synthetic biopolymers that have been in use for medical applications for a number of years are polyglycolide, polydioxanone and poly(lactide-co-glycolide). 

A scientific breakthrough in order to design USCAs on demand can be seen in the third generation (Myomap, Quantison, BiSphere and Sonavist). Compared to the more or less free bubbles of the first and second generations, the novel type of USCAs consist of encapsulated microbubbles with a shell formed by a biopolymer (like human albumin) and/or a biocompatible synthetic polymer (like copolymers of poly-lactide and polyglycolide or derivatives of polycyanoacrylate). In addition to the prolongation of the lifetime in the blood stream, these polymer-stabilized microbubbles can be manufactured to fulfill certain needs, and to interact with diagnostic ultrasound in a defined and optimal manner. 

Poly (e-caprolactone), poly lactides, and polyglycolides have quite unusual properties of biodegradability and biocompatibility. The majority of polymers used in the biomedical field to develop implants, sutures, and controlled drug-delivery systems are the aforesaid resorbable polyesters produced by ring-opening polymerization of cyclic (di)esters. 

Tensile and in vitro and breaking strength retention data of typical monofilament sutures made of the polymers described in Section 8.3.2 are summarized in Table 8.6. The data in Table 8.6 indicate that the polymers described in Table 8.5 can be converted to monofilament sutures with competitive strength retention and breaking strength profiles as the commercially available braided sutures made of polyglycolide or 90/10 poly(glycolide-co-/-lactide). 

FIGURE 42.2 The effect of poly(L-lactide) composition in polyglycolide on the time required for 50% mass loss implanted under the dorsal skin of rat. (From Miller, R.A., Brady, J.M., and Outright, D.E., 1977. /. Biomed. Mater. 

It is always possible to copolymerize two monomers in order to get a new polymer composition with desired properties. For example, PLGA is copolymerized from polyglycolide with either L-lactide or o-lactide (Figure 21.8). The copolymer has been used in medical devices and drug applications. 

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