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New macromolecular micelles based on degradable amphiphilic block copolymers of malic acid and malic acid ester
Author(s) -
CammasMarion Sandrine,
Béar MarieMaud,
Harada Atsushi,
Guérin Philippe,
Kataoka Kazunori
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(20000201)201:3<355::aid-macp355>3.0.co;2-9
Subject(s) - micelle , copolymer , amphiphile , chemistry , polymer chemistry , polymerization , prepolymer , malic acid , macromolecule , critical micelle concentration , organic chemistry , polymer , aqueous solution , citric acid , biochemistry , polyurethane
To study the behaviour of polymeric materials under in‐vivo conditions, degradable macromolecular micelles based on amphiphilic block copolymers of poly( β ‐malic acid) as hydrophilic units and poly( β ‐malic acid alkyl esters) as hydrophobic blocks are studied. First three β ‐substituted β ‐lactones, benzyl malolactonate, butyl malolactonate, and butyl 3‐methylmalolactonate were prepared, starting from aspartic acid. A prepolymer based on benzyl malate units was synthesized by anionic ring‐opening polymerization of benzyl malolactonate. Then the carboxylic end groups of this prepolymer were used as initiator for the polymerization of the second lactone, e. g. butyl malolactonate or butyl 3‐methylmalolactonate. The prepolymer and block copolymers have been characterized by 1 H NMR and size exclusion chromatography (SEC). Degradable macromolecular micelles were prepared from the block copolymers by two different methods and characterized by dynamic light scattering and fluorescence measurements using pyrene as a fluorescence probe. It was shown that these amphiphilic degradable copolymers form stable micelles under physiological conditions (10 –2 M phosphate buffered solution, PBS, pH 7.4 with 0.15 M NaCl). Moreover, it was displayed that the characteristics of these macromolecular micelles, especially the critical micellar concentration (cmc), are depending on the chain length of both blocks and on the chemical structure of the hydrophobic block. A very important conclusion of this study is, that micelle formation is dependent on the pH of the medium. Therefore, besides the fact that such micelles are potentially degradable into non‐toxic low molecular weight molecules, their properties and stability were proven to be pH‐dependent. This property can lead development of an “intelligent” drug carrier able to release the entrapped biologically active molecule depending on the pH values.