Synergistic enhancement of endothelial cell function via aligned fibers, thiol plasma polymerization, and gelatin...

Bioengineered vascular grafts have emerged as a promising alternative to autografts for replacing diseased blood vessels. However, their success critically depends on the ability to support the formation of a confluent monolayer of junctional endothelial cells (ECs) aligned along the vessel's longitudinal axis. To address this, a multifaceted approach combining exclusive topographical and biochemical cues was employed to design a vascular scaffold. Poly(ε-caprolactone) (PCL) nanofibers (NFs) were first electrospun in both random and aligned orientations and subsequently coated with a thiol-rich layer, leveraging the dual functionality of thiol groups in promoting direct cell adhesion and enabling biomolecule immobilization. This thiolation was achieved via plasma polymerization using a dielectric barrier discharge system at medium pressure with 1-propanethiol as the precursor, followed by gelatin adsorption. Morphological and chemical analyses were conducted using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Results confirmed the successful deposition of a thiol-rich coating, with total sulfur content exceeding 10% and CS bond content surpassing 17%, while maintaining fiber orientation and inter-fiber porosity. The coatings exhibited good aqueous stability, with minimal physical or chemical degradation over 40 days. Plasma-induced thiolation significantly enhanced gelatin adsorption as evidenced by increased nitrogen content on thiolated NFs, likely through electrostatic interactions between protonated gelatin side chains (NH₃⁺) and surface thiolate groups (S^-). Mechanical testing demonstrated that plasma coatings generally increased NF stiffness and strength, highlighting the need for fine-tuning scaffold properties to meet vascular tissue engineering (TE) demands. To evaluate endothelialization, primary human umbilical cord vein cells (HUVECs) were seeded on various NF configurations. Across both NF orientations, thiol-rich coatings improved cell adhesion, viability, and proliferation, with further enhancement upon gelatin adsorption. The cells exhibited cobblestone morphology on random NFs and oriented cell arrangements on aligned NFs, closely mimicking the native endothelium. Collectively, this study highlights the synergistic benefits of combining fiber alignment, thiol functionalization, and gelatin adsorption to create a biomimetic scaffold effectively supporting endothelialization and offering strong potential for vascular TE applications.