Water-Stable Plasma-Polymerized N,N-Dimethylacrylamide Coatings to Control Cellular Adhesion

Abstract

The plasma polymerization of amide-based precursors is a nearly unexplored research area, which is in contrast with the abundance of reports focusing on amidebased surface modification using wet chemistry. Therefore, this study aims to profoundly investigate the near-atmospheric pressure plasma polymerization of N,N-dimethylacrylamide (DMAM) to obtain stable coatings. In contrast to the unstable coatings obtained at lower discharge powers, the stable coatings that were obtained at higher powers showed a lower hydrophilicity as assessed by water contact angle (WCA). This decrease in hydrophilicity with increasing plasma power was found to be related to a reduced preservation of the monomer structure, as observed by Fourier transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and XPS C 60 depth profiling, a rarely used but effective combination of techniques. Furthermore, the chemical composition of the coating was found to be in good agreement with the plasma active species observed by optical emission spectroscopy. Additionally, XPS C 60 depth profiling indicated a difference between the top layer and bulk of the plasma polymer due to spontaneous oxidation and/or postplasma coating deposition. Finally, the stable coatings were also found to have cell-interactive behavior toward MC3T3 as studied by in vitro live/dead fluorescence imaging and (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assays. With the latter technique, a cell viability of up to 89% as compared with tissue culture plates after 1 day of cell culture was observed, indicating the potential of these coatings for tissue engineering purposes.

Evaluation of cross-linking and degradation processes occurring at polymer surfaces upon plasma activation via size-exclusion chromatography

“…For PEtOx, C1s high-resolution spectra were calibrated at 285.35 eV (the average energy of C-C and C-N bonds which are equally present in PEtOx). As such, the peak of the O1s and N1s spectra can respectively be found at 531 and 399.7 eV, which is in agreement with previous measurements of other amide-containing polymers [2] . For a qualitative comparison of the high-resolution spectra in between the different plasma treatments, the bond energies were obtained from literature and PMMA/PEtOx control measurements and the used energies are summarized in Table 1 [ 2 , 43-45 ].…”

“…The thickness of the coatings was assessed by making a scratch in the polymer film and measuring the step height between unscratched and scratched areas making use of an atomic force microscope (AFM), as also described in a previous work [2] . All measurements were performed by means of an XE-70 AFM (Park Systems), used in the noncontact mode with a silicon cantilever (Nanosensors TM PPP-NCHR).…”

Chemical characterization of plasma-activated polymeric surfaces via XPS analyses: A review

“…The use of Fourier-transform infrared spectroscopy (FTIR) has also faced the restriction of its analysis depth going way beyond a few nanometers to reach several hundreds of nanometers. This technique was therefore mainly utilized to qualitatively determine functional groups on relatively thick coatings deposited upon plasma polymerization processes that fall outside the scope of this review paper [39]. As such, the XPS technique, being distinguished by an analysis depth approximately equaling the region depth affected by the plasma activation (a few nanometers), is an excellent alternative determining the surface chemical composition and functionalities [20,[25][26][27][28][29].…”

“…Besides determining the surface elemental composition on defined points, XPS offers some more advanced measurement capabilities. For instance, XPS mapping discerns the distribution of elements across a surface [15], high resolution spectral measurement enables the recognition of surface chemical bonds through peak deconvolution [19,29,44,45], XPS combined with specialized sputtering guns such as a the Buckminster fullerene (C 60 ) ion gun and Ar-ion gun is able to provide advanced chemical depth profiling [25,39,46] and angle resolved XPS can also acquire chemical information as a function of depth in a less destructive manner but with a more limited depth range [45]. These techniques with some of their corresponding applications involving plasma activation of polymers will be discussed elaborately later on after a brief description of the XPS principle.…”

Composite yarns with antibacterial nanofibrous sheaths produced by collectorless alternating‐current electrospinning for suture applications

“…The most prominent contributions of the secondary amide can be observed at 3298 cm À1 (N H stretching), 1640 cm À1 (C═O stretching, amide I band) and 1544 cm À1 (N H bending and C N stretching, amide II band), 1261 cm À1 (C N stretching, amide III bands). 36,40 The aliphatic chain results in the main contribution at 2931 and 2859 cm À1 (asymmetric and symmetric C H stretching, respectively) and smaller peaks at 1462 and 1416 cm À1 (C H bending vibrations). The additional peak that appeared at 1728 cm À1 could be attributed to the absorption of C═O from the by-products of the acid-catalyzed amide hydrolytic degradation which was initiated by formic, acetic, and sulfuric acid.…”