Acrylic Acid Plasma Research Articles

Osteosarcoma growth on trabecular bone mimicking structures manufactured via laser direct write

 This paper describes the direct laser write of a photocurable acrylate-based PolyHIPE (High Internal Phase Emulsion) to produce scaffolds with both macro- and microporosity, and the use of these scaffolds in osteosarcoma-based 3D cell culture. The macroporosity was introduced via the application of stereolithography to produce a classical “woodpile” structure with struts having an approximate diameter of 200 μm and pores were typically around 500 μm in diameter. The PolyHIPE retained its microporosity after stereolithographic manufacture, with a range of pore sizes typically between 10 and 60 μm (with most pores between 20 and 30 μm). The resulting scaffolds were suitable substrates for further modification using acrylic acid plasma polymerisation. This scaffold was used as a structural mimic of the trabecular bone and in vitro determination of biocompatibility using cultured bone cells (MG63) demonstrated that cells were able to colonise all materials tested, with evidence that acrylic acid plasma polymerisation improved biocompatibility in the long term. The osteosarcoma cell culture on the 3D printed scaffold exhibits different growth behaviour than observed on tissue culture plastic or a flat disk of the porous material; tumour spheroids are observed on parts of the scaffolds. The growth of these spheroids indicates that the osteosarcoma behave more akin to in vivo in this 3D mimic of trabecular bone. It was concluded that PolyHIPEs represent versatile biomaterial systems with considerable potential for the manufacture of complex devices or scaffolds for regenerative medicine. In particular, the possibility to readily mimic the hierarchical structure of native tissue enables opportunities to build in vitro models closely resembling tumour tissue.

Acrylic acid plasma polymerization and post-plasma ethylene diamine grafting for enhanced bone marrow mesenchymal stem cell behaviour on polycaprolactone nanofibers

Electrospun polycaprolactone (PCL) nanofibers (NFs) have been extensively researched for tissue engineering purposes, despite their hydrophobic surface properties which compromise their cell interactivity. To enhance this interactivity, within this study, the surface of PCL NFs was first modified by acrylic acid plasma polymerization. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed that the plasma process did not damage the NFs. Water contact angle (WCA) and zeta potential measurements showed a significant wettability increase and surface charge decrease, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the NFs were coated with a plasma polymer containing O-based functional groups, which could be related to the aforementioned changes in surface wettability and charge. Additionally, a post-plasma grafting step of ethylene diamine on the surface carboxylic acid groups was performed to investigate the influence of COOH-groups on bone marrow mesenchymal stem cell (BMST) adhesion and proliferation. WCA, zeta potential and XPS measurements confirmed the successful conversion of carboxylic acid into primary amine groups, while SEM indicated that the NF morphology did not change upon the reaction. PCL NFs subjected to this post-plasma grafting evoked the best BMST behaviour, indicating that minor changes in the surface chemistry can have a significant effect on cell-biomaterial interactions.

Mitigation of membrane fouling by nano/microplastics via surface chemistry control

Nano/microplastic materials fouling across filtration membranes can impact the performance of filtration systems, which constitutes a critical challenge for water facilities operation. In this study, plasma surface modifications aiming at reducing nano/microplastic materials adsorption on ultrafiltration membranes were investigated. Hydrophilic acrylic acid and cyclopropylamine plasma coatings caused a water flux decline of less than 8% after 6 h of crossflow filtration. Both hydrophilic coatings reduced the percentage of nano/microplastics adsorbed on the membranes by more than 60%. On the contrary, the hydrophobic hexamethyldisiloxane layer had no impact on the cumulative percentage of adsorbed nano/microplastics compared to that of the pristine poly(sulfone) membranes, which culminated at 40%, resulting in a water flux decline of 40% upon filtration for both membranes. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was then applied to the system particle-membrane, which identified polar forces as the predominant intermolecular interactions contributing to membrane fouling. Tuning the hydrophilicity of the membranes was, therefore, a more efficient strategy to reduce nano/microplastic materials adsorption during filtration than tailoring the surface charge of the membranes, showing potential for complex water matrices remediation.

Characterization of functionalized coatings prepared from pulsed plasma polymerization

Material assembly based on elastomer part and metallic substrate has been widely used in many industrial sectors. However, the adhesion between the two materials requests specific processes and adhesives. Plasma technology is an interesting way to prepare the assembly since the plasma polymer layers used for the adhesive joint can bear different reactive chemical functions toward the elastomer. Three different plasma coatings are synthesized from acetylene, acrylic acid, and maleic anhydride plasma because of their respective chemical functions able to open the carbon-carbon double bond of the elastomer (rubber, fluoroelastomer). For such a purpose, fine-tuning of plasma parameters was essential to preserve the precursor chemistry and to avoid any degradation. Pulsed plasma discharge was selected, plasma parameters defined thanks to the design of experiment. The different plasma polymers were characterized by FTIR, XPS and NEXAFS spectroscopies and surface energy measurement.

Atmospheric pressure cold plasma anti-biofilm coatings for 3D printed food tools

Increasing adoption of 3D printing in the daily life and, specifically, the food field (kitchen tools and food contact containers) is associated with potential health risks when printed tools are made by specialized centers and designed for disabled patients, who cannot re-print them with the necessary periodicity. The characteristic pattern of 3D printing promotes bacterial adhesion and biofilm formation. In this work acrylic acid (AcAc) and tetraethyl orthosilicate (TEOS) coatings applied by plasma-polymerization have been developed to reduce biofilm formation by Pseudomonas aeruginosa, Escherichia coli and Listeria monocytogenes on 3D printed PLA materials. Chemical (generation of a hydration layer) and morphological (a decrease in distance between peaks) modifications provoked by plasma-polymerized treatments could explain the reduction in bacterial attachment and biofilm formation. AcAc coatings were more effective than TEOS coatings, and showed up to a 47.7% (L. monocytogenes), 50.4% (P. aeruginosa) and 64.1% (E. coli) relative biofilm production, when compared with untreated samples. Industrial relevance textNowadays, products manufactured by 3D printing technologies are constantly growing; resulting in a greater flexibility and customization in the designs and a reduction of production costs. One of the main applications of 3D printed tools is the food industry, specifically, kitchen tools and containers for disabled people. There are great difficulties when it comes to disinfecting these types of parts. So, the health risks associated with the use of 3D printed tools for food contact applications should be attended. Our study demonstrated that acrylic acid plasma coatings are suitable for decreasing the amount of biofilm generated by different bacteria over 3D printed poly-lactic acid (PLA) substrates. Plasma coatings make it possible to address food-related health issues through the generation of safe tools manufactured by 3D printing. The mitigation of those issues will allow the food industry to safely employ a technology as versatile as 3D printing.

A green approach to modify surface properties of polyamide thin film composite membrane for improved antifouling resistance

A green approach based on plasma enhanced chemical vapour deposition (PECVD) method was adopted in this work to modify surface properties of thin film composite (TFC) membranes for improved antifouling resistance during desalination process. Two types of hydrophilic monomers, i.e., acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) was respectively deposited onto the surface of commercial TFC membranes (XLE and NF270) and the effect of plasma deposition time (15 s, 1 min and 5 min) on the membrane physiochemical properties was investigated using different analytical instruments. The deposition of AA and HEMA was able to improve the membrane hydrophilicity owing to the presence of hydroxyl and carboxyl functional groups. However, prolonged plasma polymerization period was not encouraged as it led to the formation of thicker skin layer that significantly reduced water permeability. With 15-s plasma deposition time, AA and HEMA-modified XLE and NF270 membranes could achieve higher NaCl and Na2SO4 rejections as well as demonstrate 100% flux recovery rate. The improved antifouling resistance of modified TFC membranes is mainly due to the improved surface hydrophilicity coupled with greater surface charge properties. This work demonstrated a rapid solvent-free surface modification method that can be employed to enhance TFC membrane properties for desalination process.

Low-pressure plasma activation enables enhanced adipose-derived stem cell adhesion.

Human adipose-derived stem cells (hASCs) have become an important cell source for the use in tissue engineering and other medical applications. Not every biomaterial is suitable for human cell culture and requires surface modifications to enable cell adhesion and proliferation. Our hypothesis is that chemical surface modifications introduced by low-discharge plasma enhance the adhesion and proliferation of hASCs. Polystyrene (PS) surfaces were modified either by ammonia (NH3 ), carbon dioxide (CO2 ) or acrylic acid (AAc) plasma. The results show that the initial cell adhesion is significantly higher on all modified surfaces than on unmodified material as evaluated by bright field microscopy, live/dead staining, total DNA amount and scanning electron microscopy. The formation of focal adhesions was well pronounced on the Tissue Culture PS, NH3 -, and CO2 -plasma modified samples. The number of matured fibrillar adhesions was significantly higher on NH3 -plasma modified surfaces than on all other surfaces. Our study validates the suitability of chemical plasma activation and represents a method to enhance hASCs adhesion and improved cell expansion. All chemical modification promoted hASCs adhesion and can therefore be used for the modification of different scaffold materials whereby NH3 -plasma modified surfaces resulted in the best outcome concerning hASCs adhesion and proliferation.

Acrylic acid plasma coatings for enhanced cell migration in PCL 3D additive manufactured scaffolds

This study describes the additive manufacturing of 3D polycaprolactone (PCL) scaffolds and their subsequent surface modification using non-thermal plasma technology (NTP) for musculoskeletal applications. 100% interporous scaffolds with porosities ranging from 37 to 66% were manufactured and characterized using scanning electron microscopy (SEM). 2 NTP-based modification strategies were employed: 1) He activation and 2) Acrylic acid NTP polymerization. Gas flow, system pressure and scaffold porosity were systematically varied and their influence on functional group incorporation efficiency and distribution were studied using X-ray Photoelectron Spectroscopy (XPS). The NTP-coated samples with optimal operational parameters were conducted to a series of in-vitro experiments involving MC3T3-E1 osteoblasts and adipose derived mesenchymal stem cells (ADSCs) and the influence on cell adhesion, proliferation and migration was analyzed and compared to untreated and plasma-activated samples. The NTP-based acrylic acid coating was found to effectively stimulate cell migration throughout the porous PCL scaffolds for the MC3T3 cells and was also responsible for better ADSC cell adhesion and migration, making them promising structures for musculoskeletal applications.

Acrylic Acid Plasma Coated 3D Scaffolds for Cartilage tissue engineering applications

The current generation of tissue engineered additive manufactured scaffolds for cartilage repair shows high potential for growing adult cartilage tissue. This study proposes two surface modification strategies based on non-thermal plasma technology for the modification of poly(ethylene oxide terephthalate/poly(butylene terephthalate) additive manufactured scaffolds to enhance their cell-material interactions. The first, plasma activation in a helium discharge, introduced non-specific polar functionalities. In the second approach, a carboxylic acid plasma polymer coating, using acrylic acid as precursor, was deposited throughout the scaffolds. Both surface modifications were characterized by significant changes in wettability, linked to the incorporation of new oxygen-containing functional groups. Their capacity for chondrogenesis was studied using ATDC5 chondroblasts as a model cell-line. The results demonstrate that the carboxylic acid-rich plasma coating had a positive effect on the generation of the glucoaminoglycans (GAG) matrix and stimulated the migration of cells throughout the scaffold. He plasma activation stimulated the formation of GAGs but did not stimulate the migration of chondroblasts throughout the scaffolds. Both plasma treatments spurred chondrogenesis by favoring GAG deposition. This leads to the overall conclusion that acrylic acid based plasma coatings exhibit potential as a surface modification technique for cartilage tissue engineering applications.

Properties, ageing behavior and stability of bipolar films containing nano-layers of allylamine and acrylic acid plasma polymers

In this work, a dielectric barrier discharge (DBD) has been used for the deposition of bipolar films containing alternating nano-layers of plasma polymerized allylamine (PPAam) and acrylic acid (PPAac). Various films were obtained by varying the single-layer thickness of each plasma polymer while maintaining a constant total film thickness and two kinds of films were fabricated via different depositing sequences (PPAam/Aac and PPAac/Aam). Films properties, ageing in air and stability in water over a 7 days period were investigated. Results showed that, COO− and NH3+ polar entities, generated from the interaction of PPAam and PPAac, are present in the bipolar films. Concerning the films stability, the different reaction mechanisms involved in the formation of each kind of films resulted in a higher amount of polar groups in the PPAam/Aac films; this conferred these films a higher stability than PPAac/Aam. Concerning the films ageing behavior, all prepared samples underwent some kind of ageing which was found to be dependent on the deposition sequence. Results also showed that bipolar coatings exhibited better cell-material interactions compared to PPAam and PPAac films; with a better cell viability observed on PPAam/Aac coatings after 1 and 7 days culture.

Oxygen and Acrylic Acid Plasma Treatment on Titanium Mesh for Improving the Hydroxyapatite Formation.

Customized titanium (Ti) meshes were treated with O2 plasma and acrylic acid plasmapolymerization (PPAAc). The optimum conditions for PPAAc were as follows: 20 W, 15 mTorr, and 5 min. Hydroxyapatite formation increased in Ti meshes treated with O2 and PPAAc compared with that in untreated Ti meshes. Moreover, MC3T3-E1 cells exhibited improved cell spreading, attachment, proliferation in PPAAc treated Ti mesh than in untreated Ti mesh. This result revealed that O2 and PPAAc surface treatment on Ti mesh was potential tool for improving the bone formation on the Ti mesh clinically application.

Duty cycle dependent chemical structure and wettability of RF pulsed plasma copolymers of acrylic acid and octafluorocyclobutane

Octafluorocyclobutane and acrylic acid (C4F8-co-AA) plasma copolymer coatings are deposited using a pulsed wave (PW) radio frequency (RF) plasma on low density polyethylene (LDPE). The influence of duty cycle in pulsed process with the monomer feed rate on the surface chemistry and wettability of C4F8-co-AA plasma polymer coatings is studied. The concentration of the carboxylic acid (hydrophilic) groups increase, and that of fluorocarbon (hydrophobic) groups decrease by lowering the duty cycle. The combined effect of surface chemistry and surface morphology of the RF pulsed plasma copolymer coatings causes tunable surface wettability and surface adhesion. The gradual emergence of hydrophilic contents leads to surface heterogeneity by lowering duty cycle causing an increased surface adhesion in hydrophobic coatings. The C4F8-co-AA plasma polymer coatings on the nanotextured surfaces are tuned from repulsive superhydrophobicity to adhesive superhydrophobicity, and further to superhydrophilicity by adjusting the duty cycles with the monomer feed rates.

Acrylic acid plasma polymerized poly(3-hydroxybutyrate) membranes for methanol/MTBE separation by pervaporation

Plasma polymerized acrylic acid (AA) thin films on poly(3-hydroxybutyrate) (PHB) membranes were evaluated as composite membranes for methanol/methyl tert-butyl ether (MTBE) separation by pervaporation (PV). Composite membranes were prepared in an inductively coupled radiofrequency plasma reactor. Experiments were performed at different powers (7.2 to 29.2W) and pressures, using pure AA monomer, as well as AA/air and AA/argon mixtures. Depositions chemical characteristics were determined through FTIR spectroscopy, hydrophilic character through contact angle measurements, and SEM images were also taken to analyze surface morphology. In PV measurements, membranes were methanol selective; the separation factor exceeded that of pure PHB membranes in all cases. Fluxes were lower than the original membrane but the performance separation index (PSI) was always higher. Results presented in terms of permeability were between 660 and 4045barrer for methanol, while for MTBE they were markedly lower, between 10.5 and 57.7barrer. These large differences in permeabilities caused high selectivities which ranged from 24 to 79.

Colloidal crystal based plasma polymer patterning to control Pseudomonas aeruginosa attachment to surfaces

Event Abstract Back to Event Colloidal crystal based plasma polymer patterning to control Pseudomonas aeruginosa attachment to surfaces Hitesh Pingle1, Peng-Yuan Wang1, 2, Helmut Thissen2, Sally Mcarthur1 and Peter Kingshott1 1 Swinburne University Of Technology,Hawthorn, Department of Chemistry and Biotechnology, Australia 2 CSIRO Manufacturing Flagship, Bay view Avenue, Clayton,, Australia Introduction: Infections from biofilm formation on medical devices is a global problem with risks to human health and huge costs to health care worldwide[1],[2]. Bacteria have unique capabilities to generate resistance against antimicrobial agents. Recent studies have shown that extra-cellular DNA is a key molecule that helps biofilms form[3],[4], but the precise mechanisms of how bacteria and DNA interact at surfaces remains unknown. It has been shown that micro- and nanotopography and chemistry on surfaces can influence initial biomolecule adsorption, and subsequent bacterial adhesion[5]-[7]. However, there are fewer reports using such approaches for selectively grafting of DNA to understand the mechanisms of initial bacterial attachment responsible for biofilm formation. Material and Methods: Colloidal self-assembly was used to pattern surfaces with colloidal crystals to use as masks against allylamine plasma polymer (AAMpp) and acrylic acid plasma (AACpp) deposition to generate highly ordered patterns from the micro- to the nanoscale. PEG-aldehyde was grafted to the plasma regions via ‘cloud point’ grafting to prevent the attachment of bacteria on the plasma patterned surface regions, thereby controlling the adhesive sites by choice of the colloidal crystal morphology. Salmon sperm DNA was physically or covalently attached on both patterned and flat surfaces. P. aeruginosa was chosen to study the bacterial interactions with these chemically patterned surfaces. Scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Epi-fluorescence microscopy were used for pattern characterization, surface chemical analysis, and imaging of attached bacteria. Results: The AAMpp, AACpp, PEG and eDNA patterns were developed using the colloidal lithography approach. XPS results confirm the successful grafting of PEG and eDNA on the plasma coated surfaces. The AAMpp surface showed increased bacterial attachment compared to control while PEG and eDNA coated surface showed reductions in bacterial attachment as highlighted in Figures 1 and 2. FIG. 1. Epifluorescence images of DAPI stained P. aeruginosa attachment to (a) a 5 µm AAMpp pattern (b) a 5 µm AAMpp-DNA pattern (c) a 5 µm AAMpp_PEG pattern (d) a 5 µm AAMpp-PEG_DNA pattern. All scale bars: 50µm. FIG. 2. SEM images of P. aeruginosa attachment onto (a) a 5 µm AAMpp pattern (b) a 5 µm AAMpp-DNA pattern (c) a 5 µm AAMpp-PEG pattern (d) a 5 µm AAMpp-PEG-DNA pattern All scale bars: 10µm. Discussion: The bacterial attachment increase on the AAMpp surface is most likely due to the amine groups displaying a positive charge that attract the negatively charged extra-cellular polysaccharides on the bacterial cell surfaces. AACpp and DNA both contain negatively charged groups thus repulsion of bacteria is the most likely cause for the reduced bacterial attachment. Micron sized plasma patterns were able to trap bacteria due to the different chemistries presented. Different sized plasma patterns were generated through the use of different sized colloidal particles used as masks for plasma deposition. Conclusion: Surface charge plays an essential role in initial attachment of bacteria. Different chemical patterns made from colloidal crystal masking are easy to fabricate and could be useful in further applications in biomaterials research. The results showed that PEG and DNA patterns can be easily fabricated with exquisite control of pattern size and spacing and this is a useful tool to help understand how bacterial attach to surfaces. The Australian Research Council is acknowledged for funding a PhD scholarship for Hitesh Pingle through the Discovery.; The Scientific Industrial Endowment Fund (SIEF) is acknowledged for providing a John Stocker Postdoctoral Research Fellowship for Peng Yuan Wang.; This work was supported in part at both the Bio-interface Engineering Hub at Swinburne and the Melbourne Centre for Nanofabrication as part of the Victorian Node of the Australian National Fabrication Facility, a company established under the National Collaborative Research Infrastructure Strategy to provide nano and micro-fabrication facilities for Australia’s researchers.

Glow-discharge radio frequency plasma polyether and fluoropolyether coated substrates prevent IgG protein adsorption

Event Abstract Back to Event Glow-discharge radio frequency plasma polyether and fluoropolyether coated substrates prevent IgG protein adsorption Marvin M. Mecwan1* and Buddy Ratner1* 1 University of Washington, Bioengineering, United States Introduction: Protein-based pharmaceuticals present unique challenges in processing, packaging and delivery. All proteins rapidly adsorb to solid surfaces, essentially irreversible, and frequently leads to denaturation or aggregation of the protein. Also, there are concerns with substances from the packaging leaching out and affecting proteins. This study examines fundamental aspects of protein interactions with surfaces, particularly using glow discharge plasma-treated surfaces which can be readily applied to delivery devices, packaging and processing equipment [1],[2] and may lead to a new generation of surfaces effective for protein manufacture, storage and delivery. This research particularly focuses on plasma tetraglyme (TG), acrylic acid (AA), perfluoropropylene (C3F6), and perfluoromethyl vinyl ether (C3F6O) plasma treated glass, stainless steel, and cyclic olefin polymer (COP) substrates and their interaction with IgG. Methods: Glass and COP (8mm φ discs), and 316L stainless steel (7 x 7 mm2) substrates were sequentially cleaned with DCM, acetone, and methanol in a sonication bath for 10 mins x 2. RF-Plasma deposition and delamination: Substrates were loaded into the reactor, and argon etched (40W for 5 min). Using a mass flow controller, the monomer of choice was introduced into the chamber and were plasma deposited. Plasma-treated samples (n=3/group) were washed using DI water x 3 over 24 hours to assess whether coatings would delaminate. ESCA analyses were done using an S-Probe ESCA (with monochromatic Al K-alpha X-rays focused to 800µm spot size) using survey and detailed C1s scans. Data was analyzed using ESCA analysis software. IgG adsorption studies: Bovine IgG was tagged using an ICl method. Plasma-treated samples (n=3/treatment group) were immersed in 0.1mg/mL I-125 tagged bovine IgG solution in 1x cPBS with sodium iodide (cPBSI) for 1 hr. Samples were rinsed with cPBS x 3 and counted for 10 mins using a gamma counter. Cytotoxicity studies: Plasma-coated samples were eluted in complete growth medium for 24 hrs (370C, 5% CO2­ incubator). ~80% confluent NIH-3T3 fibroblasts were exposed to eluates from the plasma coated substrates, and observed over 48 hrs using an inverted microscope. ISO 10993-5 guidelines were used for cytotoxic evaluation. Results and Discussion: ESCA scans of plasma-treated substrates showed absence of substrate associated peaks (such as Fe or Si), suggesting that coatings did not delaminate; also implies that plasma coatings on substrates are at least 10 nm thick (ESCA resolution is 100Å). Furthermore, experimental and theoretical elemental compositions of the surfaces align well. Protein adsorption studies show that tetraglyme and acrylic acid plasma coatings are essentially non-fouling (<2 ng/cm2) as compared to C3F6 and C3F6O plasma coatings which adsorbed proteins in the range of 10-14 ng/cm2. Furthermore, all plasma treated substrates show reduced protein adsorption compared to untreated controls. Moreover, fibroblasts exposed to all plasma coating eluates remained viable after 48 hours. Conclusions: The data demonstrate that plasma-treated polyether and fluoropolyether substrates can create a new generation of surfaces that can be used for contact with protein therapeutic agents.Future studies will be aimed at investigating the strength of bonding of IgG to these surfaces, as well as protein aggregation studies. Winston Ciridon; Xia Dong, PhD

Reaction of CO2Gas with (radicals in) Plasma-Polymerized Acrylic Acid (and Formation of COOH-Rich Polymer Layers)

In contrast to most of the existing literature on plasma polymerization of acrylic acid (AA), not only the chemical structure and film thickness of the deposits were studied, but also a new way to obtain COOH-rich surfaces were studied. This is an important aspect when applying the obtained coatings for biomedical and electronics applications. Therefore, acrylic acid/CO2 polymer films with a thickness of ca. 150 nm were deposited in the pulsed plasma regime onto polyethylene and aluminum. Their structure–property relationships were studied in dependence on the mixture ratio of acrylic acid monomer and CO2 gas. The influence of the CO2 gas on the regularity and functionality of plasma-deposited poly(acrylic acid) (PAA) was studied in detail using bulk-sensitive (FTIR) as well as surface-sensitive methods, such as X-ray photoelectron spectroscopy. Results obtained show, in presence of a small amount of CO2 gas within the acrylic acid plasma, a structure of PAA with high concentration of COOH groups was estimated. A polymer network is obtained with an increasing abundance of branched groups for AA/CO2 with increasing CO2 gas in the mixture.

Assembly of graphene oxide on nonconductive nonwovens by the synergistic effect of interception and electrophoresis

Electrophoretic deposition has always been an attractive method to deposit nanoparticles on conductive materials, while most fiber-based materials have poor conductivity which limits the application of electrophoretic deposition in assembling nanoparticles onto fiber-based materials. A new approach to assemble graphene oxide (GO) nanosheets on nonconductive nonwovens via the synergistic effect of electrophoresis and fiber interception was reported in this study. To improve surface wettability, polypropylene (PP) nonwovens were modified by acrylic acid and subsequent N2 plasma treatment. Then GO nanosheets were anchored onto modified nonwovens by electrophoresis process and nonwoven interception. The results of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) manifested that etching and grafting simultaneously occurred on the surface of modified PP nonwovens, resulting in a great improvement of nonwoven hydrophily, which corresponded to the results of water contact angle. Furthermore, the results of X-ray diffraction, energy dispersive X-ray, SEM, and FTIR indicated that different amounts of GO nanosheets were successfully assembled onto modified PP nonwovens. This method provides a new avenue for incorporating carbon nanoparticles with nonconductive fiber-based materials, and modified PP nonwovens assembled with GO nanosheets show good air filtration performance for sodium chloride aerosol with a filtration efficiency of 87.9 % and a pressure drop of 36.4 mmH2O, and the reduced GO/PP composite nonwovens exhibit enhanced conductivity.

Screening rat mesenchymal stem cell attachment and differentiation on surface chemistries using plasma polymer gradients

It is well known that the surface chemistry of biomaterials is important for both initial cell attachment and the downstream cell response. Surface chemistry gradients are a new format that allows the screening of the subtleties of cell–surface interactions in high throughput. In this study, two surface chemical gradients were fabricated using diffusion control during plasma polymerization via a tilted mask. Acrylic acid (AA) plasma polymer gradients were coated on a uniform 1,7-octadiene (OD) plasma polymer layer to generate OD–AA plasma polymer gradients, whilst diethylene glycol dimethyl ether (DG) plasma polymer gradients were coated on a uniform AA plasma polymer layer to generate AA–DG plasma polymer gradients. Gradient surfaces were characterized by X-ray photoelectron spectroscopy, infrared microscopy mapping, profilometry, water contact angle (WCA) goniometry and atomic force microscopy. Cell attachment density and differentiation into osteo- and adipo-lineages of rat-bone-marrow mesenchymal stem cells (rBMSCs) was studied on gradients. Cell adhesion after 24h culture was sensitive to the chemical gradients, resulting in a cell density gradient along the substrate. The slope of the cell density gradient changed between 24 and 6days due to cell migration and growth. Induction of rBMSCs into osteoblast- and adipocyte-like cells on the two plasma polymer gradients suggested that osteogenic differentiation was sensitive to local cell density, but adipogenic differentiation was not. Using mixed induction medium (50% osteogenic and 50% adipogenic medium), thick AA plasma polymer coating (>40nm thickness with ∼11% COOH component and 35° WCA) robustly supported osteogenic differentiation as determined by colony formation and calcium deposition. This study establishes a simple but powerful approach to the formation of plasma polymer based gradients, and demonstrates that MSC behavior can be influenced by small changes in surface chemistry.

Protein adsorption and cell adhesion on three-dimensional polycaprolactone scaffolds with respect to plasma modification by etching and deposition techniques

In this work, protein adsorption and cell adhesion on three-dimensional (3D) polycaprolactone (PCL) scaffolds treated by plasma etching and deposition were performed. The 3D PCL scaffold used as a substrate of a bone tissue was fabricated by recent rapid prototype techniques. To increase surface properties, such as hydrophilicity, roughness, and surface chemistry, through good protein adhesion on scaffolds, oxygen (O2) plasma etching and acrylic acid or allyamine plasma deposition were performed on the 3D PCL scaffolds. The O2 plasma etching induced the formation of random nanoporous structures on the roughened surfaces of the 3D PCL scaffolds. The plasma deposition with acrylic acid and allyamine induced the chemical modification for introducing a functional group. The protein adsorption increased on the O2 plasma-etched surface compared with an untreated 3D PCL scaffold. MC3T3-E1 cells adhered bioactively on the etched and deposited surface compared with the untreated surface. The present plasma modification might be sought as an effective technique for enhancing protein adsorption and cell adhesion.

Effects of gas atmospheres on poly(lactic acid) film in acrylic acid plasma treatment

Plasma polymerized acrylic acid (AA) coatings were deposited on poly(lactic acid) (PLA) films in various gas atmospheres during the pre-treatment of PLA and the deposition of AA, respectively. Therefore, this work was twofold: the argon pretreated PLA films followed by a deposition in argon were investigated against the mixture of argon and oxygen pretreated ones under the same deposition conditions; the plasma deposition of AA operating in different atmospheres (argon, oxygen and nitrogen) was employed to modify the pretreated PLA in oxygen. Chemical and physical changes on the plasma-treated surfaces were examined using contact angle, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and attenuated total reflection infrared (ATR-FTIR) analysis. The results showed that the discharge gas can have a significant influence on the chemical composition of the PLA surfaces: oxygen plasmas introduced oxygen-containing groups in company with surface etching in pretreatment and deposition, while argon discharges was able to achieve much better hydrophilic behavior and high retention ratio of poly(acrylic acid) (PAA) coating before and after washing in water.