Challenges in the Characterization of Plasma-Processed Three-Dimensional Polymeric Scaffolds for Biomedical Applications

Abstract

Low-temperature plasmas offer a versatile method for delivering tailored functionality to a range of materials. Despite the vast array of choices offered by plasma processing techniques, there remain a significant number of hurdles that must be overcome to allow this methodology to realize its full potential in the area of biocompatible materials. Challenges include issues associated with analytical characterization, material structure, plasma processing, and uniform composition following treatment. Specific examples and solutions are presented utilizing results from analyses of three-dimensional (3D) poly(ε-caprolactone) scaffolds treated with different plasma surface modification strategies that illustrate these challenges well. Notably, many of these strategies result in 3D scaffolds that are extremely hydrophilic and that enhance human Saos-2 osteoblast cell growth and proliferation, which are promising results for applications including tissue engineering and advanced biomedical devices.

N2/H2o Plasma Assisted Functionalization of Poly(ε‐caprolactone) Porous Scaffolds: Acidic/Basic Character versus Cell Behavior

“…We believe that our cross-section WCA measurements are heavily affected by the fact that when the samples are cut, untreated, hydrophobic PCL becomes exposed, and that these surfaces dominate the interaction with the water drop, resulting in limited wetting and adsorption. [38] We thus conclude that all N 2 /H 2 O treatments, in our conditions, allow scaffolds to absorb water with respect to untreated materials. This should allow better performances as cell-culture substrates both in vitro and in vivo.…”

“…As our cross‐section XPS data show that the surfaces of the inner pores are efficiently modified by our treatments (Figure ), we expected good water adsorption levels also in the core of the scaffolds. We believe that our cross‐section WCA measurements are heavily affected by the fact that when the samples are cut, untreated, hydrophobic PCL becomes exposed, and that these surfaces dominate the interaction with the water drop, resulting in limited wetting and adsorption . We thus conclude that all N 2 /H 2 O treatments, in our conditions, allow scaffolds to absorb water with respect to untreated materials.…”

“…We note that, except for 100 N 2 samples, no significant differences are observed along the depth of the scaffolds in terms of both O/C and N/C ratios. These results are affected, to some extent, by the presence of untreated PCL in the area of analysis due to the cutting of the scaffold by the scalpel . For this reason, the results obtained on the external surface of the material (top) cannot be compared to that of the internal surface.…”

Thin Film Deposition on Open‐Cell Foams by Atmospheric Pressure Dielectric Barrier Discharges

“…[2][3][4][5][6][7] Moreover, among various gas phase techniques, [1,[8][9][10][11][12] over the last decade, the low pressure plasma-enhanced chemical vapor deposition (PECVD) has demonstrated to be a viable approach for surface modification of porous materials, as for instance widely reported in the case of polymer scaffolds for tissue engineering applications. [1,[11][12] Deposition inside porous scaffolds is driven by the non-line-of-sight ability of low pressure plasmas for surface modification of objects with complex 3D geometries. Specifically, diffusion of reactive depositing species into the scaffold interior is thought to control thin film deposition in low pressure PECVD processes.…”

“…[1,13] Several studies reported, in fact, that limited penetration of thin film precursors within porous 3D structures can result in gradients of both coating thickness and surface chemical composition moving from the exterior to the interior of the plasma-treated substrate. [1,[11][12] Treatment uniformity throughout the entire porous structure could be improved if the discharge could ignite inside the substrate pores and, therefore, with atmospheric pressure operation. In fact, to achieve plasma ignition, pores dimension must be consistently greater than the Debye length, and for substrates having sub-millimeter pore sizes this is unlikely to occur under low pressure plasma conditions.…”