Biocompatibility of Cyclopropylamine-Based Plasma Polymers Deposited at Sub-Atmospheric Pressure on Poly (ε-caprolactone) Nanofiber Meshes.

In this work, cyclopropylamine (CPA) monomer was plasma-polymerized on poly (ε-caprolactone) nanofiber meshes using various deposition durations to obtain amine-rich surfaces in an effort to improve the cellular response of the meshes. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the surface morphology and surface chemical composition of the PCL samples, respectively. The measured coating thickness was found to linearly increase with deposition duration at a deposition rate of 0.465 nm/s. XPS analysis revealed that plasma exposure time had a considerable effect on the surface N/C and O/C ratio as well as on amino grafting efficiency and amino selectivity. In addition, cell studies showed that cell adhesion and proliferation significantly improved for all coated samples.

Plasma Functionalization of Polycaprolactone Nanofibers Changes Protein Interactions with Cells, Resulting in Increased Cell Viability.

The surface properties of electrospun scaffolds can greatly influence protein adsorption and, thus, strongly dictate cell-material interactions. In this study, we aim to investigate possible correlations between the surface properties of argon, nitrogen, and ammonia and helium plasma-functionalized polycaprolactone (PCL) nanofibers (NFs) and their cellular interactions by examining the protein corona patterns of the plasma-treated NFs as well as the cell membrane proteins involved in cell proliferation. As a result of the performed plasma treatments, PCL NFs morphology was preserved, while wettability was improved profoundly after all treatments because of the incorporation of polar surface groups. Depending on the discharge gas, different types of groups are incorporated, which influenced the resultant cell-material interactions. Argon plasma-functionalized PCL NFs, only enriched by oxygen-containing functional groups, were found to show the best cell-material interactions, followed by N2 and He/NH3 plasma-treated samples. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and liquid chromatography-mass spectrometry clearly indicated an increased protein retention compared with non-treated PCL NFs. The nine proteins retained best on plasma-treated NF are important mediators of extracellular matrix interaction, illustrating the importance thereof for cell proliferation and the viability of cells. Finally, 92 proteins that can be used to differentiate how the different plasma treatments are clustered and subjected to a gene ontology study, illustrating the importance of keratinization and extracellular matrix organization.

Effects of a dielectric barrier discharge (DBD) treatment on chitosan/polyethylene oxide nanofibers and their cellular interactions.

In this study, chitosan (CS)/polyethylene oxide (PEO) nanofibrous mats (Ø: 166 ± 43 nm) were fabricated by electrospinning and subsequently surface-modified by a dielectric barrier discharge (DBD) sustained in argon, ammonia/helium or nitrogen. The surface properties of the CS/PEO nanofibers (NFs) before and after plasma treatment were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Additionally, the mechanical properties and PEO leaching in aqueous conditions of the different NFs under study were examined by tensile tests and nuclear magnetic resonance (1H NMR) spectroscopy respectively. Finally, cell behavior and cell morphology of human foreskin fibroblasts (HFFs) on the CS/PEO NFs were evaluated via live/dead fluorescence microscopy, MTT assays and SEM. The obtained results revealed that the surface free energy of the CS/PEO NFs was significantly increased after plasma modification, which was correlated to an enrichment in surface oxygen (Ar, N2, NH3/He) and nitrogen (N2, NH3/He) functional groups. All performed plasma treatments also led to an increase in ultimate tensile strength, most likely due to an increased fiber-to-fiber friction. Additionally, it was also observed that N2 plasma treatment resulted in a decrease in PEO release, which could be attributed to more pronounced surface cross-linking. Cellular interactions on the CS/PEO NFs also significantly increased due to the performed plasma treatments. The best cellular response was noted for the Ar plasma modification although the surface hydrophilicity was the lowest in this case. These observations thus suggest that not only the wettability characteristics but also the presence of distinct functional groups on plasma-treated CS/PEO NFs have a significant influence on the observed enhanced cellular interactions.

Fabrication of PEOT/PBT Nanofibers by Atmospheric Pressure Plasma Jet Treatment of Electrospinning Solutions for Tissue Engineering.

This study focuses on the enhanced electrospinning of 300-Polyethylene oxide-polyethylene oxide terephthalate/polybutylene terephthalate (PEOT/PBT). An atmospheric pressure plasma jet for liquid treatment is applied to a solution with 9 w/v% PEOT/PBT dissolved in either chloroform (CHCl3 ), CHCl3  + N,N-dimethylformamide (DMF), CHCl3  + methanol (MeOH), or CHCl3  + hexafluoroisopropanol (HFIP). For all conditions, the plasma-treated samples present better-quality fibers: less or no-beads and uniform fiber diameter distribution. Except for CHCl3  + DMF, no significant changes to the material bulk are detected, as shown with size exclusion chromatography (SEC). X-ray photoelectron spectroscopy (XPS) spectra performed on nanofibers record an increase in C-C bonds for the CHCl3  + DMF combination upon plasma modification, while a shift and slight increase in oxygen-containing bonds is found for the CHCl3  + HFIP and CHCl3  + MeOH mixtures. MTT assay shows no-cytotoxic effects for CHCl3  + DMF, while a better cellular adhesion is found on nanofibers from CHCl3  + MeOH and CHCl3  + HFIP. Among the examined additives, MeOH is preferable as it produces beadless electrospun nanofibers with an average diameter of 290 ± 100 nm without causing significant changes to the final nanofiber surface properties.

Atmospheric Pressure Plasma Jet Treatment of Poly-ε-caprolactone Polymer Solutions To Improve Electrospinning.

An atmospheric pressure plasma jet (APPJ) specifically designed for liquid treatment has been used in this work to improve the electrospinnability of a 5 w/v % solution of poly-ε-caprolactone (PCL) in a mixture of chloroform and N,N-dimethylformamide. Untreated PCL solutions were found to result in nonuniform fibers containing a large number of beads, whereas plasma-treated solutions (exposure time of 2-5 min) enabled the generation of beadless, uniform nanofibers with an average diameter of 450 nm. This enhanced electrospinnability was found to be mainly due to the highly increased conductivity of the plasma-modified PCL solutions. Consequently, more stretching of the polymer jet occurred during electrospinning, leading to the generation of bead-free fibers. Plasma treatment also results in an increased viscosity and decreased pH values. To explain these observed changes, optical emission spectroscopy (OES) has been used to examine the excited species present in the APPJ in contact with the PCL solution. This study revealed that the peaks attributed to H, CH, CH2, and C2 species could be responsible for the degradation of solvent molecules and/or PCL structures during the plasma treatment. Size exclusion chromatography and X-ray photoelectron spectroscopy results showed that the molecular weight and the chemical composition of PCL were not significantly affected by the APPJ treatment. Plasma exposure mainly results in the degradation of the solvent molecules instead of modifying the PCL macromolecules, preserving the original polymer as much as possible. A hypothesis for the observed macroscopic changes in viscosity and pH values could be the generation of new chemical species such as HCl and/or HNO3. These species are characterized by their high conductivity, low pH values, and strong polarity and could enhance the solvent quality for PCL, leading to the expansion of the polymer coil, which could in turn explain the observed enhanced viscosity after plasma modification.