Biopolymers lactide

More than a dozen biocompatible and biodegradable polymers have been described and studied for their potential use as carriers for therapeutic proteins (Table 13.5). However, some of the monomer building blocks such as acrylamide and its derivatives are neurotoxic. Incomplete polymerization or breakdown of the polymer may result in toxic monomer. Among the biopolymers, poly-lactide cofabricated with glycolide (PLG) is one of the most well studied and has been demonstrated to be both biocompatible and biodegradable [12]. PLG polymers are hydrolyzed in vivo and revert to the monomeric forms of glycolic and lactic acids, which are intermediates in the citric acid metabolic pathway. 

Lactic acid 1,2-Propanediol 2,3-Pentanedione, acrylic acid, acrylate polymers, cyclic lactide (dilactide), propylene glycol Acidulant biopolymers, flavourings, pH buffers, preservatives, resins, solvent Polymers Hofvendahl et al., 1999 Hofvendahl and Hahn-Hagerdal, 2000 Datta and Henry, 2006 Bennett and San, 2001... 

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). 

One of the most highly developed biopolymers is poly (lactic acid) (PLA). In the USA, PLA is manufactured by NatureWorks at a plant in Nebraska using lactic acid derived from corn. (Lactic acid can also be obtained from other natural sources such as wheat or potatoes.) Poly (lactic acid) is produced by ring opening polymerization of the lactide, as shown in Figure 8.12. 

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. 

Keywords Polydactic acid), poly(lactide), biopolymer, PLA synthesis, degradation, crystallization, mechanical properties, barrier properties, process, applications, automotive, packaging... 

GRO 10] Groot W., Boren T., Lifecycle assessment of the manufacture of lactide and PLA biopolymers from sugarcane in Thailand , International Journal of LifeCycle Assessment, vol. 15, p. 970, 2010. 

Wanamaker, C.L., Tolman, W.B. and Htilmyer, M.A. (2009) 2-Biopolymers poly(D-lactide)-poly(menthide)-poly(D-lactide) triblock copolymers as crystal nucleating agents for poly(L-lactide). Macromolecular Symposia, 283-284,130-138. 

Chitosan is a water-insoluble, nontoxic, edible, biodegradable polymer (polysaccharide) that is obtained commercially from chitin by alkaline deacetylation [103]. Chitosan is the second most abundant biopolymer in nature after cellulose. Since chitosan is a polycationic polymer, its high sensitivity to moisture limits its applications. One way to overcome this drawback is to blend the material with humidity resistant polymers such has PLA. Suyatma et al. [104] combined hydrophilic chitosan with hydrophobic PLA (92% L-lactide and 8% mesolactide, Mw = 49,000 Da) by solution and film mixing, resulting in improved water barrier properties and decreased water sensitivity of the chitosan films. However, testing of mechanical and thermal properties revealed that chitosan and PLA blends are incompatible. 

The aim of the present study is to develop new methods for the fabrication of nanoporous biopolymer materials by combining recent advances in the field of elaboration of nanostructured inorganic materials and biodegradable polymer. For this purpose we synthesized poly(DL-lactide) (PDLLA) copolymerized with poly(ethylene oxide) (PEO). 

One biopolymer that is already used as a matrix for composite production is poly(lactic acid) (PLA). The PLA is a thermoplastic biopolymer with lactic acid which is derived from starch by a fermentation process as its basic monomer. High molecular weight PLA is polymerized by the lactide ring opening polymerization to PLA (Garlotta, 2001 Gupta et al., 2007 Lim et al., 2008). 

Biopolymers have also been used to wrap CNTs in efforts to functionalize them for aqueous dispersion. Chitosan, poly(L-lactide) [93], and cellulose [94] are some of the polymers that are commonly employed. Chitosan in particular has been the subject of considerable research because of the ease with which it is functionalized. For instance, enzyme attachment has been used to produce robust chemical sensors for glucose [95,96]. Layered arrangement of chitosan/CNT composite produced a low-power requirement electrochemical actuator with superior mechanical properties and repeatability [97]. 

Groot, W.J., Boren, T., 2010. Life cycle assessment of the manufacture of lactide and PEA biopolymers from sugarcane in Thailand. Int. J. Life Cycle Assess. 15, 970—984. 

Most polymer systems used in physical encapsulation systems are based on biopolymers such as chitosan, dextran, polylactides, or copolymers of lactide and glycolic acid. These are often prepared with PEG chains to enhance circulation and avoid rapid protein deposition. These polymers have good biodegradation properties, they are hiocompatible and biodegradable, and produce well-tolerated degradation... 

Dias et al., [119] developed dressings by impregnation of the antiinflammatory quercetin and anesthetic thymol by supercritical fluid in biopolymers Chen et al., [120] obtained micronized polymer composites loaded with lysozyme by the process of solution-enhanced dispersion by supercritical CO2 from a solution containing lysozyme / poly (L-lactide) / poly (ethylene glycol). Morgado et al., [121] successfully used supercritical CO2 for... 

Vert M (2002), Polyglycolide and copolyesters with lactide , in Doi Y and Steinbuchel A, Biopolymers 4, Polyesters III, Weinheim, WUey-VCH, 179-202. 

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