Poly /polylactide biomedical applications

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., poly(ethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

Polycondensation of aUgrl/atyl phosphoric dichlorides with hydro -telechelic oligomers [poly(glycolic acid), polylactide, and copolymers] has been used for the preparation of various PPEs with biomedical applications such as nerve guidance conduits and microspheres for drug delivery systems. ... 

PUs have been developed and thoroughly investigated for various industrial and biomedical applications [1-3], By alternately connecting soft and hard segments together through urethane bonds, assorted PUs, such as poly(E-caprolactone) (PCL) containing block PUs [21], polylactide (PLA)-based PUs [22], and poly(E-caprolactone-co-lactide acid) (PCLA)-based PUs [23], were prepared with useful shape-memory properties. 

Aliphatic polyesters are biocompatible and biodegradable polymers that are widely used in biomedical applications. Within these, polylactides and poly(s-caprolactone) are two of the most studied ones (Fig. 2). These polyesters can be synthesized via ring-opening polymerization of the corresponding cyclic esters (s-caprolactone and lactide) and via polycondensation of lactic acid. In material science, both pure aliphatic polyesters and natural polysaccharides have limitations in some specific applications. These limitations can be overcome by the introduction of hydrophilic groups (carbohydrate compounds) into the aliphatic polyesters and modifications of natural polysaccharides with hydrophobic polyesters. 

Over the past several decades, polylactide - i.e. poly(lactic acid) (PLA) - and its copolymers have attracted significant attention in environmental, biomedical, and pharmaceutical applications as well as alternatives to petro-based polymers [1-18], Plant-derived carbohydrates such as glucose, which is derived from corn, are most frequently used as raw materials of PLA. Among their applications as alternatives to petro-based polymers, packaging applications are the primary ones. Poly(lactic acid)s can be synthesized either by direct polycondensation of lactic acid (lUPAC name 2-hydroxypropanoic acid) or by ring-opening polymerization (ROP) of lactide (LA) (lUPAC name 3,6-dimethyl-l,4-dioxane-2,5-dione). Lactic acid is optically active and has two enantiomeric forms, that is, L- and D- (S- and R-). Lactide is a cyclic dimer of lactic acid that has three possible stereoisomers (i) L-lactide (LLA), which is composed of two L-lactic acids, (ii) D-lactide (DLA), which is composed of two D-lactic acids, and (iii) meso-lactide (MLA), which is composed of an L-lactic acid and a D-lactic acid. Due to the two enantiomeric forms of lactic acids, their homopolymers are stereoisomeric and their crystallizability, physical properties, and processability depend on their tacticity, optical purity, and molecular weight the latter two are dominant factors. 

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