Facile immobilization of vascular endothelial growth factor on a tannic acid-functionalized plasma-polymerized allylamine coating rich in quinone groups†
Biomolecules with thiol or amine groups can easily be covalently immobilized onto a substrate equipped with quinone groups in a mild alkali buffer solution based on Schiff base or Michael addition reactions. In this study, we reported a simple two-step approach to creating a functional coating with abundant quinone groups for facile immobilization of vascular endothelial growth factor (VEGF) in mild phosphate buffered saline (PBS, pH 7.4). This approach initially involved the deposition of an amine-bearing plasma-polymerized allylamine (PPAam) coating. Tannic acid (TA) was subsequently used for introducing phenolic hydroxylic hydroxyl/quinone groups. The results of water contact angles (WCAs), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis (XPS) revealed the effective conjugation of TA to PPAam, as well as the immobilization of VEGF to TA-functionalized PPAam (TA-PPAam). The result of a quartz crystal microbalance with dissipation (QCM-D) showed that 158 ± 13 ng cm−2 of VEGF was successfully immobilized onto the TA-PPAam surface. TA-PPAam bound with VEGF significantly enhanced human umbilical vein endothelial cell (HUVEC) proliferation, indicating the good retention of the bioactivity of VEGF. The TA-PPAam functional coating provided a novel, facile strategy for the covalent immobilization of biomolecules, especially growth factors, under mild reaction conditions.