Dynamic wettability study on the functionalized PEGylated layer on a polylactide surface constructed by the coating of aldehyde–ended poly(ethylene glycol) (PEG)/polylactide (PLA) block copolymer

Abstract

A block copolymer of α-acetal-poly(ethylene glycol) and polylactide(PEG/PLA) was prepared and utilized as a surface modifier to construct a functionalized PEG layer on a PLA substrate by simple coating. An active functional group, aldehyde, was readily prepared by the derivatization of an α-acetal group at the tethered PEG-chain end and can be further utilized to link bioactive functionality molecules such as sugars and proteins. The PEGylated surface thus prepared was characterized by the method of dynamic wetting using the Wilhelmy plate technique and by the surface/interfacial free energy calculation. The results of the dynamic wetting study suggested that the interactions of PEG on the surface with water induce the reorientation of the hydrophilic PEG component to accommodate itself optimally with the water phase, resulting in a significant reduction in the interfacial free energy. By employing the extended Fowkes' equation, the polar interactions are accurately estimated in the free energy calculation of PEGylated surface; the polar components in surface free energy may be divided into two contributions with distinctive characteristics; one is the γsh component reflecting water-interactive Lewis sites and the other is the γsp component reflecting the dipole moment on the surface. The γsp component, related to the PEG conformation via the dipole moment on the substrate, was suggested to be a determinant factor in the protein adsorption. Because these surfaces have both non-fouling and ligand-binding properties, they might support the selective binding and the growth of particular cell populations, and eventually, they are expected to have a high utility in biomedical fields including the field of tissue engineering.