Near-Surface Structure of Plasma Polymer Films Affects Surface Behavior in Water and its Interaction with Proteins

Abstract

Using low pressure plasma polymerization, nano-scaled oxygen-rich plasma polymer films (CO) were deposited onto pristine silicon wafers as well as on nitrogencontaining plasma polymer (CN) model surfaces. We investigate the influence of the nature of the substrate as well as a potential sub-surface effect emerging from the buried CO/CN interface, just nanometers below the surface. X-ray Photoelectron Spectroscopy and Timeof-Flight Secondary Ion Mass Spectrometry revealed two important phenomena that occurred during the deposition of the terminal CO layer: (1) a strong degree of oxidation, already for 1 nm nominal thickness, and (2) a gradual transition in chemical composition between the two layers, clearly indicating that effectively a vertical chemical gradient results, even when a two-step coating process was applied. Such terminal gradient film structures were used to study film stability in aqueous environments. Molecular rearrangements were scrutinized in the top-surface in contact with water and we found that the top-surface chemistry and wetting properties of the oxygen-rich termination layer matched those of thick CO reference coatings. Nevertheless, the adsorption of green fluorescent protein (GFP) was observed to be sensitive to the CO terminal layer thickness. Namely, an enhanced protein adsorption was observed for 1-2 nm thick CO layers on CN, whereas a significantly reduced protein adsorption was seen on C 3 nm thick CO terminal layers. We

Plasma Treatment of Composite Piezoelectric Thin Films for Good Adhesion of Printed Conductive Ink

“…Even better wettability was noticed in the case of the plasma polymerized C 2 H 4 film with O-rich functional groups, resulting from the use of CO 2 as a heteroatom source (Figure c). The presence of these two gases in the glow discharge leads to the formation of ionic groups such as −COOH and −CHO that are responsible for increasing the wettability by lowering the WCA from 108 to 27° right after the treatment. The low-pressure argon plasma treatment is mainly an etching/ablative plasma that introduces new chemical groups present under the surface layer .…”

Extending the Range of Controlling Protein Adsorption via Subsurface Architecture

“…Recent reports have described unexpected long-range effects that change surface properties while originating nanometers below the surface. , A physically and chemically stable vertical gradient architecture can be designed, comprising a hydrophilic to hydrophobic transition in the subsurface. Plasma enhanced chemical vapor deposition (PECVD) is a technique that is well suited to form such vertical gradient structures by variation of the deposition conditions in an in situ multistep process. ,, Plasma polymerization is based on the plasma activation of organic compounds, the monomer, in the gas phase yielding a “plasma polymer” deposit. One can vary the properties of such films during growth over nanometers; for example, chemical composition, thickness, hydrophilicity, density, or cross-linking.…”

“…Plasma enhanced chemical vapor deposition (PECVD) is a technique that is well suited to form such vertical gradient structures by variation of the deposition conditions in an in situ multistep process. 5,7,8 Plasma polymerization is based on the plasma activation of organic compounds, the monomer, in the gas phase yielding a "plasma polymer" deposit. One can vary the properties of such films during growth over nanometers; for example, chemical composition, thickness, hydrophilicity, density, or cross- linking.…”

pH-Responsive Chitosan/Alginate Polyelectrolyte Complexes on Electrospun PLGA Nanofibers for Controlled Drug Release

“…Therefore, statistical significance was assessed by a Kruskal–Wallis test for the groups followed by pairwise comparison with the Dunn test (Bonferroni corrections), and results were accepted as significantly different for p < 0.05. All the tests were performed in R, and the p -values mentioned in the text are the adjusted values [ 46 ].…”