Surface structural analysis of Polylactic acid at Biointerface

Polylactic acid (PLA) is a naturally produced biomaterial. As PLA grows in popularity, understanding its structural responsiveness to different types of biological entities becomes significant. In this study, we investigated the roles of crystal structure and degree of crystallinity of PLA at biointerfaces. To examine the biological activities at the PLA surface, we selected fibrinogen as a model protein and E. coli as a model bacterium. We prepared thick films (thickness > 100 nm) and thin films (thickness < 20 nm) of PLA on Silicon film with different crystallinity by controlling the annealing temperature. The surfaces were characterized by atomic force microscopy, differential scanning calorimetry, and wide-angle X-ray scattering. Protein adsorption was quantified by photon-counting spectrofluorometry using Alexa Fluor 488-labeled fibrinogen, and bacteria attachment was analyzed by confocal microscopy using Hoechst 33342 (a cell-permeable dye) and propidium iodide (a membrane-impermeant dye) to visualize live and dead bacteria, respectively. The attachment of both fibrinogen and E. coli increases with decreasing crystallinity. Moreover, greater adhesion of fibrinogen was measured on the thicker films whereas increased adhesion of E. coli was present on thinner films. The details will be discussed at the poster presentation.