title: Synthesis, degradability, and drug releasing properties of methyl esters of fungal poly(beta,L-malic acid).
abstract: Methyl esters of microbial poly(beta,L-malic acid) for conversion degrees of 25, 50, 75, and 100% were prepared by treatment of the polyacid with diazomethane. Esterification proceeded with retention of the molecular weight of the parent polyacid and the copolymers displayed a blocky microstructure consisting of short segments of malic and methyl malate sequences. The thermal stability of the copolyesters was lower than those of the parent homopolymers and all of them were fairly crystalline with melting temperatures within the range of 170-175 degrees C. They were degraded rapidly by water, the hydrolysis rate being highly dependent on the methylation degree. Microspheres with mean-average diameters in the range of 1-20 microm were prepared from the 100% methylated product by the emulsion-evaporation solvent method. Encapsulation of erythromycin was efficiently performed in these microparticles and its releasing upon incubation in simulated physiological medium was evaluated for different drug loads. Drug delivery was observed to occur by a releasing mechanism largely determined by the hydrodegradation of the host polymer and independent of the amount of loaded drug.
authors.affiliation: Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647, 08028 Barcelona, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Portilla-Arias
authors.forename: Montserrat
authors.initials: M
authors.lastname: García-Alvarez
authors.forename: Antxon Martínez
authors.initials: AM
authors.lastname: de Ilarduya
authors.forename: Eggerhard
authors.initials: E
authors.lastname: Holler
authors.forename: Juan A
authors.initials: JA
authors.lastname: Galbis
authors.forename: Sebastián
authors.initials: S
authors.lastname: Muñoz-Guerra
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D004337:Drug Carriers; D004917:Erythromycin / Q000737:chemistry* / Q000493:pharmacokinetics; D004951:Esterification; D004952:Esters; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008049:Lipase / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008293:Malates / Q000138:chemical synthesis* / Q000737:chemistry*; D008745:Methylation; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D015394:Molecular Structure; D008970:Molecular Weight; D010316:Particle Size; D016839:Physarum polycephalum / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D012995:Solubility; D013818:Thermogravimetry; D044366:Transition Temperature; D014961:X-Ray Diffraction
chemical_list: D004337:Drug Carriers; D004952:Esters; D008293:Malates; D011108:Polymers; C121060:poly(malic acid); D004917:Erythromycin; D008049:Lipase