For most tissue engineering applications, surface modification and sterilization of polymers are critical aspects determining the implant success. The first part of this study is thus dedicated to modifying polycaprolactone (PCL) surfaces via plasma treatment using a medium pressure dielectric barrier discharge, while the second part focuses on the sterilization of plasma-modified PCL. Chemical and physical surface changes are examined making use of water contact angle goniometry (WCA), x-ray photoelectron spectroscopy and atomic force microscopy. Bioresponsive properties are evaluated by performing cell culture tests. The results show that air and argon plasmas decrease the WCA significantly due to the incorporation of oxygen-containing functionalities onto the PCL surface, without modifying its morphology. Extended treatment times lead to PCL degradation, especially in the case of air plasma. In addition to surface modification, the plasma potential to sterilize PCL is studied with appropriate treatment times, but sterility has not been achieved so far. Therefore, plasma-modified films are subjected to UV, H ₂ O ₂ plasma (HP) and ethylene oxide (EtO) sterilizations. UV exposure of 3 h does not alter the PCL physico-chemical properties. A decreased wettability is observed after EtO sterilization, attributable to the modification of PCL chain ends reacting with EtO molecules. HP sterilization increases the WCA of the plasma-treated samples, presumably due to the scission of the hydrophilic bonds generated during the prior plasma treatments. Moreover, HP modifies the PCL surface morphology. For all the sterilizations, an improved cell adhesion and proliferation is observed on plasma-treated films compared to untreated ones. EtO shows the lowest proliferation rate compared to HP and UV. Overall, of the three sterilizations, UV is the most effective, since the physical alterations provoked by HP might interfere with the structural integrity when it comes to 3D scaffolds, and the chemical modifications caused by EtO, in addition to its toxicity, interfere with PCL bioactivity.

Nowadays, the high incidence of peripheral nerve injuries and the low success ratio of surgical treatments are driving research to the generation of novel alternatives to repair critical nerve defects. In this sense, tissue engineering has emerged as a possible alternative with special attention to decellularization techniques. Tissue decellularization offers the possibility to obtain a cell-free, natural extracellular matrix (ECM), characterized by an adequate 3D organization and proper molecular composition to repair different tissues or organs, including peripheral nerves. One major problem, however, is that there are no standard quality control methods to evaluate decellularized tissues. Therefore, in this review, a brief description of current strategies for peripheral nerve repair is given, followed by an overview of different decellularization methods used for peripheral nerves. Furthermore, we extensively discuss the available and currently used methods to demonstrate the success of tissue decellularization in terms of the cell removal, preservation of essential ECM molecules and maintenance or modification of biomechanical properties. Finally, orientative guidelines for the evaluation of decellularized peripheral nerve allografts are proposed.

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-ε-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.