Acrylic acid plasma polymerization and post-plasma ethylene diamine grafting for enhanced bone marrow mesenchymal stem cell behaviour on polycaprolactone nanofibers

Abstract

Electrospun polycaprolactone (PCL) nanofibers (NFs) have been extensively researched for tissue engineering purposes, despite their hydrophobic surface properties which compromise their cell interactivity. To enhance this interactivity, within this study, the surface of PCL NFs was first modified by acrylic acid plasma polymerization. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed that the plasma process did not damage the NFs. Water contact angle (WCA) and zeta potential measurements showed a significant wettability increase and surface charge decrease, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the NFs were coated with a plasma polymer containing O-based functional groups, which could be related to the aforementioned changes in surface wettability and charge. Additionally, a post-plasma grafting step of ethylene diamine on the surface carboxylic acid groups was performed to investigate the influence of COOH-groups on bone marrow mesenchymal stem cell (BMST) adhesion and proliferation. WCA, zeta potential and XPS measurements confirmed the successful conversion of carboxylic acid into primary amine groups, while SEM indicated that the NF morphology did not change upon the reaction. PCL NFs subjected to this post-plasma grafting evoked the best BMST behaviour, indicating that minor changes in the surface chemistry can have a significant effect on cell-biomaterial interactions.