No abstract

Three-dimensional (3D) scaffolds with optimum physicochemical properties are able to elicit specific cellular behaviors and guide tissue formation. However, cell–material interactions are limited in scaffolds fabricated by melt extrusion additive manufacturing (ME-AM) of synthetic polymers, and plasma treatment can be used to render the surface of the scaffolds more cell adhesive. In this study, a hybrid AM technology, which combines a ME-AM technique with an atmospheric pressure plasma jet, was employed to fabricate and plasma treat scaffolds in a single process. The organosilane monomer (3-aminopropyl)trimethoxysilane (APTMS) and a mixture of maleic anhydride and vinyltrimethoxysilane (MA-VTMOS) were used for the first time to plasma treat 3D scaffolds. APTMS treatment deposited plasma-polymerized films containing positively charged amine functional groups, while MA-VTMOS introduced negatively charged carboxyl groups on the 3D scaffolds’ surface. Argon plasma activation was used as a control. All plasma treatments increased the surface wettability and protein adsorption to the surface of the scaffolds and improved cell distribution and proliferation. Notably, APTMS-treated scaffolds also allowed cell attachment by electrostatic interactions in the absence of serum. Interestingly, cell attachment and proliferation were not significantly affected by plasma treatment-induced aging. Also, while no significant differences were observed between plasma treatments in terms of gene expression, human mesenchymal stromal cells (hMSCs) could undergo osteogenic differentiation on aged scaffolds. This is probably because osteogenic differentiation is rather dependent on initial cell confluency and surface chemistry might play a secondary role.

Various new plasma‐based surface technological processes are made feasible by localizing atmospheric‐pressure discharges to predefined volumes with sub‐millimeter linear dimensions. So‐called Plasma Printing processes use cold discharges in microcavities formed temporarily by contacting a substrate with a suitably designed kind of plasma stamp. Aside from dielectric barrier discharges driven by mid‐frequency (MF) AC voltages, cold microplasmas can also be sustained in arrangements without a dielectric barrier, if RF excitation is used. The modification or coating of internal surfaces in already sealed microfluidic systems promises the achievement of a wide range of physico‐chemical surface properties which are difficult to attain by wet‐chemical or low‐pressure plasma processes. Using a proper electrode arrangement, the coating or modification can be localized to a selected segment of a microfluidic system.magnified image

The interest in applications of atmospheric‐pressure plasmas to solve surface‐technological tasks was originally motivated primarily by the expectation that major cost savings could be achieved if plasma‐based processes, conventionally run below 1 mbar, could now be performed at ambient pressure. However, it was soon recognized that, working at 1 bar, also completely new techniques are made feasible by the utilization of microdischarges, thanks to strongly reduced mean free paths of plasma constituents. The present contribution gives an overview of a number of possibilities, studied in the recent years, to apply atmospheric‐pressure microplasmas for the patterned coating or surface modification of two‐ and three‐dimensional substrates.

Quantitative determination of primary amino group densities using chemical derivatization (CD) ATR FT‐IR spectroscopy was applied to study the amination rate in N2 + NH3 and Ar + NH3 dielectric barrier discharge afterglows. Compared to N2 + H2 mixtures and pure N2, the initial plasma‐amination rate is reduced, presumably due to a smaller concentration of reactive species that are consumed by reactions with NH3. The aging behavior of LDPE samples plasma treated in the afterglow of N2, N2 + H2, and N2 + NH3 discharges was also studied using CD XPS and CD ATR FT‐IR measurements over a period of 6 weeks after the treatment. Using gas mixtures of N2 + H2, the highest amount of primary amino groups was obtained. It has been ascertained that the primary amino groups are not stable during the storage under ambient conditions due to the oxidation of the surface and migration processes.