New plasma-assisted polymerization/activation route leading to a high density primary amine silanization of PCL/PLGA nanofibers for biomedical applications

Abstract

Surface modification of hydrophobic nanofibers (NFs) to introduce cell-interactive chemical functionalities remains a challenge in biomedical applications. This study presents a novel three-step plasma-based method for synthesizing coatings with improved chemical selectivity compared to conventional plasma polymers. The process involved hexamethyldisiloxane (HMDSO) plasma polymerization followed by helium plasma activation, both performed in a medium-pressure dielectric barrier discharge. Scanning electron microscopy analysis demonstrated that the plasma-based steps did not cause damage to the NFs. X-ray photoelectron spectroscopy (XPS) and water contact angle measurements revealed the formation of a hydrophilic silanol-rich layer after HMDSO plasma polymerization and helium plasma activation. In the third step, (3-aminopropyl)triethoxysilane (APTES) was grafted onto the plasma polymer to introduce primary amine groups onto the surface, as confirmed by XPS. Although the APTES-based layer exhibited partial removal when exposed to aqueous environments, a stable aminated layer remained on the NF surface, which significantly enhanced Schwann cell responses compared to untreated and HMDSO-based coated NFs. This enhancement was confirmed through fluorescent imaging using live-dead staining, immunostaining, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. These coatings with a high selectivity in their chemical functionality (amines, or other functionalities via silanization agent selection), offer a promising surface functionalization approach for tissue engineering scaffolds.