Polylactic acids applications

Polylactic acid (PLA) has been produced for many years as a high-value material for use in medical applications such as dissolvable stitches and controlled release devices, because of the high production costs. The very low toxicity and biodegradability within the body made PLA the polymer of choice for such applications. In theory PLA should be relatively simple to produce by simple condensation polymerization of lactic acid. Unfortunately, in practice, a competing depolymerization process takes place to produce the cyclic lactide (Scheme 6.10). As the degree of polymerization increases the rate slows down until the rates of depolymerization and polymerization are the same. This equilibrium is achieved before commercially useful molecular weights of PLA have been formed. 

In addition to solvent uses, esters of lactic acid can be used to recover pure lactic acid via hydrolysis, which in-tum is used to make optically active dilactide and subsequently polylactic acid used for drag delivery system.5 This method of recovery for certain lactic acid applications is critical in synthesis of medicinal grade polymer because only optically active polymers with low Tg are useful for drug delivery systems. Lactic acid esters themselves can also be directly converted into polymers, (Figure 1), although the commercial route proceeds via ring-opening polymerization of dilactide. 

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. 

Silva et al. (2006) studied starch-based microparticles as a novel strategy for tissue engineering applications. They developed starch-based microparticles, and evaluated them for bioactivity, cytotoxicity, ability to serve as substrates for cell adhesion, as well as their potential to be used as delivery systems either for anti-inflammatory agents or growth factors. Two starch-based materials were used for the development of starch-based particulate systems (1) a blend of starch and polylactic acid (SPLA) (50 50 w/w) and (2) a chemically modifled potato starch, Paselli II (Pa). Both materials enabled the synthesis of particulate systems, both polymer and composite (with BG 45S5). A simple solvent extraction method was employed for the synthesis of SPLA and SPLA/BG microparticles, while for Pa and Pa/BG... 

Polylactic acid has been studied extensively for controlled release applications ranging from the oral delivery of simple drugs such as indomethacin9 to the parental administration of complex proteins such as insulin.10 Polylactic acid of different molecular weights has been studied as matrix material for parenteral administration. Seki et al.11 used polylactic acid 6000 and Smith and Hunneyball8 used polylactic acid 100,000 for the controlled delivery of drugs by the parenteral route. Several polylactic acid systems have been studied for the controlled... 

CGP 57813 is a peptidomimetic inhibitor of human HIV-1 protease. This lipophilic compound has been successfully entrapped in polylactic acid (PLA) and into pH-sensitive methacrylic acid copolymer particles (EUDRAGIT L 1 GO-55) [69], After the application of a film-coating, the plasma concentration was acceptable and reached similar levels as with injections of drug-loaded PLA carriers. To hinder the proteolytic degradation of a drug, two types of enteric-coated pellets were applied simultaneously. One contained the protease inhibitor coated... 

Lactic acid is an important chemical that has wide applications in food, pharmaceutical, cosmetic, and chemical industries. There are increasing interests in production of lactate esters and biodegradable polylactic acid (PLA) from lactic acid. Lactate esters are a relatively new family of solvents with specific properties. They are considered safe and are biodegradable (1). In many situations they can replace toxic solvents. Their functions vary from that of intermediates in chemical reactions to solvents in ink formulations and cleaning applications (2). PLA has been widely used in medical implants, sutures, and drug-delivery systems because of its capacity to dissolve over time (3-5). PLA also can be used in products such as plant pots, disposable diapers, and textile fabrics. 

Biobased polymers from renewable materials have received increased attention recently. Lactate is a building block for bio-based polymers. In the United States, production of lactic acid is greater than 50,000 metric tons/yr and projected to increase exponentially to replace petroleum-based polymers. Domestic lactate is currently manufactured from corn starch using the filamentous fungus Rhizopus oryzae and selected species of lactic acid bacteria. The produced lactic acid can then be polymerized into polylactic acid (PLA) which has many applications (Hatti-Kaul et al., 2007). However, so far, no facility is built to use biomass derived sugars for lactic acid production. More research needs to be done to develop microbes using biomass derived sugars for lactate production. 

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beet, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications. 

Polylactic acid has many potential uses, including many applications in the textile and medical industries as well as the packaging industry. 

Polylactic acid based fibres have various attributes that make them attractive for many traditional applications. PLA polymers are more hydrophilic than PET, have a lower density, and have excellent crimp and crimp retention. Shrinkage of PLA materials and thermal bonding temperatures are easily controllable. These polymers tend to be stable to ultraviolet light resulting in fabrics that show little fading. They also offer low flammability and smoke generation characteristics. 

The major classes of biopolymer, starch and starch blends, polylactic acid (PLA) and aliphatic-aromatic co-polyesters, are now being used in a wide variety of niche applications, particularly for manufacture of rigid and flexible packaging, bags and sacks and foodservice products. However, market volumes for biopolymers remain extremely low compared with standard petrochemical-based plastics. For example, biopolymer consumption accounted for just 0.14% of total thermoplastics consumption in Western Europe for 2005. 

Polylactic acid was first discovered in the 1930s when a DuPont scientist, Wallace Caruthers, produced a low molecular weight PLA product. In 1954, DuPont patented Carothers process. Initially the focus was on the manufacture of medical grade applications due to the high cost of the polymer, but advances in fermentation of glucose, which forms lactic acid, has dramatically lowered the cost of producing lactic acid and significantly increased interest in the polymer. 

Hunt, J. Large-scale production, properties and commercial applications of polylactic acid polymers. Polym. Degrad. Stab. 1998, 59 (1-3), 145-152. 

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