title: Enzymatic degradation of monolayer for poly(lactide) revealed by real-time atomic force microscopy: effects of stereochemical structure, molecular weight, and molecular branches on hydrolysis rates.
abstract: The influences of the stereochemical structure, the molecular weight, and the number of molecular branches for poly(lactide) (PLA) on enzymatic hydrolysis rates of PLA monolayers were studied by atomic force microscopy (AFM) and the Langmuir-Blodgett (LB) technique. Monolayers of six kinds of PLA with different molecular weights, stereochemical structure, and numbers of molecular branches were prepared by LB techniques and then characterized by AFM in air. The PLA molecules covered homogeneously with a silicon substrate and did not form lamellar crystals in the monolayer. We determined the initial hydrolysis rate of PLA monolayers in presence of proteinase K by volumetric analysis from the continuous AFM height images. The presence of D-lactyl unit reduced the hydrolysis rate of the monolayer. The hydrolysis rate for the linear PLLA samples increased with a decrease in the molecular weight. In contrast, the rates of erosion for branched PLLA monolayers were independent of the molecular weight of samples. The erosion rate of branched PLLA monolayers was found to be dependent on the average molecular weight of PLLA segment in branched molecules, not on the overall molecular weight of samples. From these results, furthermore, the hydrolysis mode of PLAs by proteinase K is discussed.
authors.affiliation: Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Numata
authors.forename: Anna
authors.initials: A
authors.lastname: Finne-Wistrand
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Albertsson
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Doi
authors.forename: Hideki
authors.initials: H
authors.lastname: Abe
mesh_terms: D000327:Adsorption; D001672:Biocompatible Materials / Q000737:chemistry; D002384:Catalysis; D019286:Endopeptidase K / Q000737:chemistry; D006868:Hydrolysis; D018625:Microscopy, Atomic Force / Q000379:methods*; D008968:Molecular Conformation; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012825:Silicon; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D013499:Surface Properties; D013696:Temperature
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; D011108:Polymers; C033616:poly(lactide); D019286:Endopeptidase K; D012825:Silicon