Comparative Study of the Surface Properties and Cytocompatibility of Plasma-Treated Poly-ε-Caprolactone Nanofibers Subjected to Different Sterilization Methods

Abstract

A major challenge in the design of tissue-engineered scaffolds is mimicking the architectural and functional properties of the extracellular matrix (ECM) and preserving these properties after sterilization. Therefore, the first part of this study is dedicated to the electrospinning of poly-epsilon-caprolactone (PCL) nanofibers, the second part focuses on a nm-thick surface chemical modification via a medium pressure non-thermal plasma treatment and the third part investigates the sterilization effects on the surface of the plasma-treated nanofibers. The surface physico-chemical properties are characterized by 3 techniques: scanning electron microscopy (SEM), water contact angle (WCA) goniometry and X-ray photoelectron spectroscopy (XPS). In addition, the cellular performance is evaluated by studying the adhesion and proliferation of adipose-derived stem cells on the samples. The results reveal that argon and air plasmas enhance nanofiber wettability by grafting oxygen-containing functionalities onto the surface. At extended treatment times, argon plasma causes mild morphological alterations, while air plasma provokes pronounced damage, even in short treatment times. In the next step, undamaged plasma-modified fibers are subjected to ethylene oxide (EtO), H2O2 plasma (HP) and UV sterilization techniques. Regardless of the sterilization method, better cytocompatibility is detected on plasma-treated nanofibers compared to untreated nanofibers. EtO increases the WCA and changes the morphology of the plasma-treated samples; these changes are mainly due to the reactions between EtO molecules and the grafted functional groups. HP provokes a total loss of the fibrillary architecture because of the complex thermo-oxidative reactions that occur during the process. UV does not affect the physico-chemical properties of the plasma-modified nanofibers, and UV-sterilized samples show a significantly higher cellular proliferation rate compared to EtO- and HP-sterilized samples. Overall, it can be concluded that plasma-treated nanofibers should be sterilized by UV to maintain their beneficial surface properties induced by non-thermal plasma.