Lactic acid oligomers

Lactic acid oligomer microspheres containing aclarubicin have been studied for selective lymphatic delivery. Low (less than 10,000 molecular weight oligomers were used to produce microspheres designed to release drug over a 30-day period (99). Additives have been used to alter the release rate of aclarubicin-loaded poly(lactide) microspheres (100). Mitomycin C was incorporated into poly(lactic... 

H., and Muranishi, S., Lactic acid oligomer microspheres containing an anticancer agent for selective lymphatic delivery. 

Figure 8 General structure of polyorthoesters. The functional group R can be varied to impart different properties to the polymer. Presence of lactic acid oligomer segments at R catalyzes degradation of the polymer.

L-Lactic acid oligomer microsphere Aclarubicin, cisplatin Incorporation... 

Renewable materials can be used in the preparation of polyurethanes. Glycosides of polytetrahydrofuran have been used with diisocyanates.164 Castor oil (which contains about 2.7 OH per molecule) has also been used.165 Polyols derived from epoxidized soybean oil have been used to make polyurethanes.166 Lactic acid oligomers can be used.167 Wheat Board is made from wheat straw and isocyanates.168 It is said to be lighter and as strong as and more resistant to moisture than conventional particle board. No formaldehyde is needed for this building material. 

Figure 6 The concept of the stereocomplex hydrogel system. The hydrogel is simply obtained after mixing aqueous solutions of dex-(L)-lactate (L-lactic acid oligomer grafted to dextran) and dex-(D)-lactate.

De Jong SJ, De Smedt SC, Wahls MWC, Demeester J, Kettenes-van den Bosch JJ, Hennink WE. Novel self-assembled hydrogels by stereocomplex formation in aqueous solution of enantiomeric lactic acid oligomers grafted to dextran. Macromolecules 2000 33 3680-3686. 

Wada R, Hyon S-H, Ikada Y, Nakao Y, Yoshikawa H, Muranishi S. Lactic acid oligomer microspheres containing an anticancer agent for selective lymphatic delivery I. in vitro studies. Journal of Bioactive and Compatible Polymers. 1988 3 126-136. 

Yoshikawa H, Nakao Y, Takada K, Muranishi S, Wada R, Tabata Y et al. Targeted and sustained delivery of aclarubicin to lymphatics by lactic acid-oligomer microsphere in rat. Chemical and Pharmaceutical Bulletin. March 1989 37(3) 802-804. PubMed PMID 2752497. 

A crude lactide stream produced in the lactide synthesis reactors contains lactic acid, lactic acid oligomers, water, meso-lactide, and further impurities. Two main separation methods, distillation and crystallization, are currently employed for lactide purification. Crystallization may be carried out either by solvent crystallization or melt crystallization. The most used method for production of ultra-pure lactide in laboratory is by repeated recrystallization of a saturated lactide solution in mixtures of toluene and ethyl acetate [15, 23, 24]. Lactide purification using C4-12 ethers [25], and an organic solvent that is immiscible with water to extract the solution with water [26] are also reported. Melt crystallization is more practical in industry for lactide purification. Several types of equipment are described in the literature for melt crystallization [17, 27-30]. This method uses the differences in the melting points of L-, D-, and meso-lactide for separating the different lactides from each other. In a distillation process, the crude lactide is first distilled to remove the acids and water, and then meso-lactide is separated from lactide [11, 31]. Different methods are reported in the literature for distillation purification of lactide [32, 33]. In... 

Ren et al. studied the effect of different diisocyanates as chain-extenders on chain extending of lactic acid oligomers. The results showed that the diisocyanate could be used as chain extenders to get high-molecular-weight chain-linked LA polymers. 1,6-hexamethylene diisocyanate [HDI] as chain-extender was better than methylenediphenyl diisocyanate [MDI] and isophorone diisocyanate (IPDI) [14]. 

Kylma, J., Tuominen, J., Helminen, A, and Seppala, J. (2001). Chain extending of lactic acid oligomers. Effect of 2,2 -bis(2-oxazoline) on 1,6-hexamethylene diisoiyanate linking reaction. 

Dozens of environmental microbes have been reported to degrade PLLA or PDLLA [189]. The PLLA and PDLLA in the environment are assumed to initially undergo chemical hydrolytic degradation followed by the bioassimilation of degraded low molecular weight lactic acid oligomers and monomers [288]. The mineralization of PLLA by microbes to form CO2 occurs in soils [289] and compost [290]. The microbes in compost induce degradation... 

Noda, M. and Okuyama, H. (1999) Thermal catalytic depolymerization of poly(L-lactic acid) oligomer into LL-lactide Effects of Al, H, Zn and Zr compounds as cattilysts. Chemical Pharmaceutical Bulletin, 47, 467- 71. 

Mauduit, J., Bukh, N. and Vert, M., Gentamycin/poly-(lactic acid) blends aimed at sustained release local antibiotic therapy administered per-operatively. I. The case of gentamycin base and gentamycin sulfate in poly (DL-lactic acid) oligomers, J. Controlled Release, 23, 209-220 (1993). 

Suitable 2-hydroxy carboxylic acid derivatives are the cyclic dimers glycolide, L-lactide, D-lactide and meso-lactide, as well as lactic acid esters and lactic acid oligomers (37). 

L-lactic acid oligomer D-lactic acid oligomer Stereocomplex... 

L-lactic acid oligomers esterified with N-(2-hydro g ropyl) methacrylate and showed that the hydrolytic degradation of hydro g -terminated L-lactic acid oligomers seemed to proceed via a hack-hiting cleavage, which resulted in dimer formation, whereas that of acetylated L-lactic acid oligomers took place via random chain cleavage. 

Yan S, Yin J, Yang Y, Dai Z, Ma J, Choi X (2007) Stffface-grafted silica linked with L-lactic acid oligomer a novel nanofiller to improve the performance of biodegradable poly(L-lactide). Polymer 48(6) 1688—1694... 

Tabata, Y., Takebayashi, Y., Ueda, T., and Ikada, Y., 1993a, A formulation method using D,L-lactic acid oligomer for protein release with reduced initial burst, J. Controlled Release 23 55-64. 

The chirality of lactic acid often results in confusion regarding nomenclature. A number of different names are used in the literature. This confusion is the result of mixing the molecular structure and a physical property (optical rotation). (5 )-Lactic acid (or L-lactic acid) has a slightly positive specific optical rotation and is frequently named L-( -h )-lactic acid [14]. However, a concentrated solution of (5 )-lactic acid at equilibrium contains lactic acid oligomers, which results in an overall negative optical rotation. Therefore, it is advised to use the structural RIS notation or the older notation of l and d and avoid the -h and — of the optical rotation (Table 1.1). 

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