ABSTRACT
High molecular weight aliphatic polyesters of the poly(2-hydroxy acid) type were synthesized for the first time more than 40 years ago when the ring-opening polymerization of l,4-dioxane-2,6-dione (glycolide = GA) and 3,5-dimethyl-l,4dioxane-2,6-dione (lactide = LA) was discovered [1, 2]. For many years these polymers, which form the PLA/GA family, were regarded as useless compounds because of their sensitivity to heat and water which precluded thermal processings based on extrusion or injection molding. This situation ended in the 1960s when advantage was taken of their sensitivity to water to make artificial degradable sutures of the poly(glycolic acid) type, PGA, aimed at replacing denatured collagen known as Catgut [3, 4], In 1966, Kulkarni et al. [5] showed that high molecular weight poly(L-lactic acid) and poly(DL-lactic acid) were also degradable in vivo and
VERT, SCHWARCH, AND COUDANE
thus of interest for biomedical applications. Since then, poly(2-hydroxy acids) have been studied extensively with respect to potential applications as temporary thera peutic aids in surgery and in pharmacology [6]. PLA/GA devices for bone fracture internal fixation (Biofix from Finland, Phusilines from France) and antitumoral drug delivery systems (Zoladex from UK, Decapeptyl from France, Enanthone from Japan) are now commercially available. Because of their biocompatibility, their degradability, the mineralization or metabolization of their degradation by products, and the fact that a large range of properties can be covered by taking advantage of copolymerization and stereocopolymerization, PLA/GA polymers are presently considered as the most attractive compounds for temporary therapeutic applications in the biomedical field [6].
