Influence of water/O2 plasma treatment on cellular responses of PCL and PET surfaces.

In this study, low pressure water/O2 plasma treatment was performed in order to obtain COOH functionalities on the surface of poly-ε-caprolactone (PCL) membranes as well as non-woven polyester fabric (NWPF) discs. The plasma treatments were performed in a cylindrical, capacitively coupled RF-plasma-reactor and then following steps were performed: in situ (oxalyl chloride vapors) gas/solid reaction to convert -OH functionalities into -COCl groups; and hydrolysis under open laboratory conditions using air moisture for final-COOH functionalities. COOH and OH functionalities on modified surfaces were detected quantitatively by using fluorescent labeling technique and an UVX 300G sensor. Electron spectroscopy for chemical analysis (ESCA) was used to evaluate the relative surface atomic compositions and the carbon and oxygen linkages located in non-equivalent atomic positions of untreated and modified surfaces. Atomic force microscope (AFM) analysis showed that nanoscale features of the PCL surfaces are dramatically changed during the surface treatments. Scanning electron microscopy (SEM) results indicated the changes in the relatively smooth appearance of the untreated NWPF discs after the plasma treatment. Periodontal ligament (PDL) fibroblasts were used in cell culture studies. Cell culture results showed that plasma treated PCL membranes and NWPF discs were favorable for the PDL cell spreading, growth and viability due to the presence of functional groups and/or nanotopographies on their surfaces.

RF hydrazine plasma modification of chitosan for antibacterial activity and nanofiber applications.

Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66Pa) with 13.56MHz frequency at a power of 100W for 30min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436cm(-1) that confirmed increasing functional groups based on H-bonding. The number of NH(2) groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.

Water/O2-plasma-assisted treatment of PCL membranes for biosignal immobilization.

The main purpose of this study was to obtain COOH functionalities on the surface of poly-epsilon-caprolactone (PCL) membranes using low-pressure water/O(2)-plasma-assisted treatment. PCL membranes were prepared using the solvent-casting technique. Then, low-pressure water/O(2) plasma treatments were performed in a cylindrical, capacitively coupled RF-plasma-reactor in three steps: H(2)O/O(2)-plasma treatment; in situ (oxalyl chloride vapors) gas/solid reaction to convert -OH functionalities into -COCl groups; and hydrolysis for final -COOH functionalities. Optimization of plasma modification processes was done using the DoE software program. COOH and OH functionalities on modified surfaces were detected quantitatively using the fluorescent labeling technique and an UVX 300G sensor. Chemical structural information of untreated, plasma treated and oxalyl chloride functionalized PCL membranes were acquired using pyrolysis GC/MS and ESCA analysis. High-resolution AFM images revealed that nanopatterns were more affected than micropatterns by plasma treatments. AFM images recorded with amino-functionalized tips presented increased size of the features on the surface that suggests higher density of the carboxyls on the nanotopographical elements. Low-pressure water/O(2)-plasma-treated and oxalyl chloride functionalized samples were biologically activated with insulin and/or heparin biosignal molecules using a PEO (polyoxyethylene bis amine) spacer. The success of the immobilization process was checked qualitatively by ESCA analysis. In addition, fluorescent labeling techniques were used for the quantitative determination of immobilized biomolecules. Cell-culture experiments indicated that biomolecule immobilization onto PCL scaffolds was effective on L929 cell adhesion and proliferation, especially in the presence of heparin.

Plasma-mediated grafting of poly(ethylene glycol) on polyamide and polyester surfaces and evaluation of antifouling ability of modified substrates.

A simple cold plasma technique was developed to functionalize the surfaces of polyamide (PA) and polyester (PET) for the grafting of polyethylene glycol (PEG) with the aim of reducing biofilm formation. The surfaces of PA and PET were treated with silicon tetrachloride (SiCl4) plasma, and PEG was grafted onto plasma-functionalized substrates (PA-PEG, PET-PEG). Different molecular weights of PEG and grafting times were tested to obtain optimal surface coverage by PEG as monitored by electron spectroscopy for chemical analysis (ESCA). The presence of a predominant C-O peak on the PEG-modified substrates indicated that the grafting was successful. Data from hydroxyl group derivatization and water contact angle measurement also indicated the presence of PEG after grafting. The PEG-grafted PA and PET under optimal conditions had similar chemical composition and hydrophilicity; however, different morphology changes were observed after grafting. Both PA-PEG and PET-PEG surfaces developed under optimal plasma conditions showed about 96% reduction in biofilm formation by Listeria monocytogenes compared with that of the corresponding unmodified substrates. This plasma functionalization method provided an efficient way to graft PEG onto PA and PET surfaces. Because of the high reactivity of Si-Cl species, this method could potentially be applied to other polymeric materials.

Plasma-enhanced modification of xanthan gum and its effect on rheological properties.

The structure and rheological properties of xanthan gum (XG) modified in a cold plasma environment were investigated. XG was functionalized in a capacitively coupled 13.56-MHz radio frequency dichlorosilane (DS)-plasma conditions and, consecutively, in situ aminated by ethylenediamine. The surface structure of modified XG was evaluated on the basis of survey and high-resolution ESCA, FTIR, and fluorescence labeling techniques. The types of species generated in DS-plasma were reported using residual gas analysis (RGA). The aqueous solutions of modified XG were cross-linked and cured at room temperature to form stable gels. The dynamic rheological characteristics of virgin XG and functionalized and cross-linked XG were compared. It was found that parameters such as plasma treatment time and concentration of solutions can be optimized to form stable gels of XG. Thus, cold plasma technology is a novel, efficient, and nonenzymatic route to modify XG.

Plasma synthesis of carbon magnetic nanoparticles and immobilization of doxorubicin for targeted drug delivery.

Using dense medium plasma technology, carbon magnetic nanoparticles (CMNP) were synthesized at room temperature and atmospheric pressure. Based on results from X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy, we conclude that these nanoparticles are composed of spherical particles, 40-50 nm in diameter, with iron/iron oxide particles dispersed in a carbon-based host-structure. Thermal gravimetry/differential thermal gravimetry analysis shows these nanoparticles are stable to temperatures as high as 600 degrees C. The synthesized CMNP were treated by argon-plasma, aminated with ethylene diamine and subsequently activated by generating aldehyde groups on them. Free doxorubicin (DOX) molecules were then immobilized onto the surfaces of activated CMNP particles to form CMNP-DOX conjugates. The corresponding loading efficiency was determined. The in vitro antiproliferative activity of immobilized doxorubicin in the conjugates was demonstrated in tumor cell cytotoxicity assays. It is suggested that this CMNP-DOX system can be used for targeted drug-delivery systems.

Treatment of methyl tert-butyl ether contaminated water using a dense medium plasma reactor: a mechanistic and kinetic investigation.

Plasma treatment of contaminated water appears to be a promising alternative for the oxidation of aqueous organic pollutants. This study examines the kinetic and oxidation mechanisms of methyl tert-butyl ether (MTBE) in a dense medium plasma (DMP) reactor utilizing gas chromatography-mass spectrometry and gas chromatography-thermal conductivity techniques. A rate law is developed for the removal of MTBE from an aqueous solution in the DMP reactor. Rate constants are also derived for three reactor configurations and two pin array spin rates. The oxidation products from the treatment of MTBE-contaminated water in the DMP reactor were found to be predominately carbon dioxide, with smaller amounts of acetone, tert-butyl formate, and formaldehyde. The lack of stable intermediate products suggests that the MTBE is, to some extent, oxidized directly to carbon dioxide, making the DMP reactor a promising tool in the future remediation of water. Chemical and physical mechanisms together with carbon balances are used to describe the formation of the oxidation products and the important aspects of the plasma discharge.