Search

Plasma polymers from glycidol vapors are of interest for direct covalent grafting of molecules bearing amine or thiol groups. The question of whether pulsed plasma operation might lead to a higher surface density of epoxide groups and a higher density of grafted molecules is studied using the antifungal drug caspofungin. X‐ray photoelectron spectroscopy and Time of flight‐secondary ions mass spectrometry analysis followed by caspofungin grafting revealed that both continuous wave and pulsed plasmas led to surface epoxides but with higher densities upon pulsing. Investigations into stability suggested that glycidol plasma polymer coatings were still able to immobilize caspofungin after 2 years of storage, making them suitable for applications where grafting of molecules needs to be done immediately before usage of a device. [ABSTRACT FROM AUTHOR]

Plasma polymers have long been of interest as thin film coatings on biomedical devices and products, to generate desirable surface properties for favorable bio‐interfacial interactions. Plasma polymers have also been used as platforms for the covalent immobilization of bioactive molecules. More recently, additional aspects have been investigated, such as selective prevention of adhesion of microbial pathogens, either via plasma polymers per se or including antimicrobial drugs. Plasma polymers have also been investigated for the release of silver ions and small organic molecules. Complementing low‐pressure plasma approaches, processes at atmospheric pressure have attracted interest recently, including for nano/biocomposite coatings. This contribution reviews the use of plasma polymers for intended biomedical applications, with a focus on more recent topic areas. [ABSTRACT FROM AUTHOR]

Improved retention of desirable chemical structures during plasma polymerization requires rational tailoring of plasma‐phase conditions. Using ethyl trimethylacetate, we studied the effects of pressure and power on the contribution of intact molecular ions to deposition and retention of ester groups. The abundance of protonated molecular ions in plasmas varies with pressure and power, but the functionality of plasma polymers, assessed by X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry, is not correlated. Together with high ion flux, the ion energy distribution was found to be a key parameter and needs to be tailored to enable the soft landing of ions on the surface after traversing the sheath. The compromise between the abundance of ions and their energy distribution is optimal near the transition between the α and γ plasma phases. [ABSTRACT FROM AUTHOR]

Even without an additional layer of pulsed wave glycidol plasma polymer. B Outside Front Cover b : Continuous wave plasma polymerization of glycidol can directly immobilize amine containing anti-fungal biomolecules on substrates such as biomedical devices. This is facilitated by the abundance of epoxide groups on such plasma polymers to undergo ring-opening reaction. [Extracted from the article]

Abstract: Atom transfer radical polymerization (ATRP) of methacrylic acid (MAA) is challenging. Herein is reported a study of conditions for facile surface‐initiated ATRP by activator regenerated electron transfer (SI‐ARGET‐ATRP) growth of poly‐methacrylic acid (PMAA) chains from a plasma polymer surface bearing surface‐immobilized α‐bromoisobutyryl bromide, with no deoxygenation required. Factors that affect PMAA polymer growth off the surface under ARGET‐ATRP conditions are systematically investigated, such as monomer/catalyst ratio, solvent, and, most importantly, addition of salts and change of pH. While the concentrations of the copper catalyst and acid affect grafting, the most pronounced effect arises from the concentration of chloride ions. Adding 0.1 m NaCl and acidifying the reaction solution to pH 3 offers the best trade‐off between reaction rate and reproducibility; yielding ≈60 nm thick PMAA graft polymers in 1 h under ambient conditions. Using this easily scalable recipe and surface analysis, the grafted polymers are verified to be pure PMAA and the graft coatings to be homogenous across a substrate of 100 mm diameter. [ABSTRACT FROM AUTHOR]

The paper by Garakani et al. SP [ sp 3 SP ] sp describes the effects of different LP/AP plasma processes on electrospun scaffolds for developing a three-dimensional (3D) bone tumor interface model for customized chemotherapeutic drug-testing screening. Since then, many other surface modification plasma processes have been investigated and scaled up to products, with the joint interdisciplinary efforts of plasma scientists, biologists, engineers, veterinarians, and medical doctors. Hegemann et al. SP [ sp 4 SP ] sp describe plasma-deposited AgO SB I x i sb -doped TiO SB I x i sb coatings characterized by rapid antibacterial activity based on the generation of reactive oxygen species (ROS). [Extracted from the article]

In comparison with other chemistries, little has been reported on sulfur-containing plasma polymers; reasons include low volatility or high toxicity of monomers. Here, we report on plasma polymerization of dimethyl sulfoxide, by itself and its co-polymerization with 1,7-octadiene to generate S-containing plasma polymers. Results show dominance of SS, SH, and SC with small percentages of SO and SO2. Upon storage in air there were no observable changes to the oxidation states of the S atoms in these plasma polymers, whereas the hydrocarbon component underwent oxidative changes. Methods were studied to oxidize the initial sulfur-containing surface groups, but approaches such as H2O2 treatment post-deposition and electrical biasing during deposition did not affect the oxidation states of the incorporated S. [ABSTRACT FROM AUTHOR]

B Outside Front Cover b : Plasma polymers have long been of interest as thin film coatings on biomedical devices and products, to generate desirable surface properties for favourable bio-interfacial interactions. The cover image symbolically depicts plasma's versatility in its ability to modify biomedical surfaces for various purposes. Further details can be found in the article by Bryan R. Coad, Pietro Favia, Krasimir Vasilev, and Hans J. Griesser (e2200121) (© Image provided by Bryan Coad) GLO:B3XB/01nov22:ppap202270030-gra-0001.jpg PHOTO (COLOR): . gl. [Extracted from the article]

In this work, we aimed to understand the key properties that confer antibacterial activity to chlorinated plasma polymers, by investigating plasma polymers deposited from a series of chlorinated precursor molecules and also investigating the effect of plasma conditions. Results revealed that only precursors with a Cl/C ratio ≥1.5 generate effective antibacterial coatings, whereas the coating thickness is irrelevant. Furthermore there is a 'sweet spot' in process conditions to generate coatings with optimal antimicrobial activity. Lastly, we investigated the release of chlorinated fragments and attenuation of the surface-active antibacterial properties of the chlorinated plasma polymers by overcoating them with a perfluorinated plasma polymer. [ABSTRACT FROM AUTHOR]

Coatings deposited by microwave plasma enhanced CVD have potential for applications as protective coatings against mechanical and environmental damage. The properties of plasma polymer coatings can, however, vary markedly with deposition conditions, and we report here that this is also the case for coatings deposited from mixtures of tetramethyldisiloxane (TMDSO) and oxygen. Hardness, modulus, stress, mass, and surface chemical compositions all varied considerably with the TMDSO/O2 ratio. Post-plasma reactions led to changes in the physical properties of coatings, which were found to be dependent on the oxygen concentration at the time of deposition. Coatings deposited at low oxygen concentration lost mass, became more rigid, became less tensile in stress, and underwent a large increase in hardness and modulus. These coatings were found to craze over periods of up to six months. Coatings deposited at high oxygen concentrations were observed to gain mass, became less rigid, and showed reduced compressive stress. They were more stable but their mechanical mismatch with polymer substrates affects their performance as protective coatings. [ABSTRACT FROM AUTHOR]

We here report two reactor designs for the efficient and uniform plasma treatment of particles: 1) retrofitting an existing plasma reactor with a loudspeaker for agitation (LPR) and 2) adapting a rotary evaporator by adding custom electrodes (RPR). Both designs offer versatility, low building cost, convenience of use, flexibility, facile vacuum sealing and achieve effective agitation and coating of particles. The latter was exemplified by plasma polymerizing perfluorooctane (PFO) onto micron-sized polystyrene particles. The coated particles were evaluated by XPS, ToF-SIMS and water contact angle measurement to compare and contrast the resulting PFO plasma coatings (PFOpp) between the two reactor designs. The highest fluorine to carbon ratio (1.85, Teflon = 2) was achieved at a pressure of 100 mTorr in the RPR. [ABSTRACT FROM AUTHOR]

This review surveys low-pressure plasma-based methods for producing hydrophilic and hydrogel-like bio-interface coatings without reactive functional groups in aqueous media. The main focus of the review is one-step plasma polymerization; other plasma-based methods such as plasma with grafting are also discussed within the context of monomers used, process development, ageing properties, and interaction of these coatings with proteins and cells. Coatings containing polyethylene glycol (PEG) or polyethylene oxide (PEO), acrylamides such as N-isopropylacrylamide (NIPAM), and sulfonate (SO3) or sulfate (SO4) moieties are reviewed here. [ABSTRACT FROM AUTHOR]

Phosphate groups are part of biological molecules involved in bio-interfacial phenomena but monomers containing these groups are not volatile enough to be plasma polymerized (pp). Hence monomers with lower oxidation states of P are needed which then does not enable prediction of the oxidation state(s) of P in the pps, nor of possible aging effects. XPS and FTIR analyses of pps from triisopropyl phosphite (TIP) and diethyl phosphite (DEP) reveal the presence of phosphate and polyphosphate groups, while phosphonate and phosphate are found in pps of co-polymerized 1,7-octadiene and TIP. Post-plasma aging and electrical biasing have negligible effects on the oxidation state of P in TIP pps. [ABSTRACT FROM AUTHOR]

This paper investigated the impacts of two deposition times (30 s, 60 s) and discharge powers (20 W, 50 W) on the resultant chemical and physical properties of plasma polymers (pp) formed using heptylamine (HA) or propionaldehyde (PA) monomers. Pinhole-free pp films were formed on all surfaces at deposition rates that varied according to both the time and power employed. XPS and ToF-SIMS analysis showed that power has a more of an effect than time on the chemical properties of the pp, which may be attributed to differences in monomer fragmentation and cross-linking. Mesenchymal stem cell (MSC) adhesion did not vary on the four different HApp surfaces, whereas a negative correlation between cell attachment and increasing plasma energy was observed on PApp surfaces. This suggests that the presence of oxygenated groups, particularly aldehyde and carboxylic groups, may have a dominant impact on MSC adhesion to these functional polymer substrates. [ABSTRACT FROM AUTHOR]

Favourable properties of polycarbonate have led to it replacing glass in many applications; however it does require a protective coating. Plasma deposited protective coatings of amorphous SiO xC yH z have, however, shown marginal adhesion to polycarbonate. This study has shown that plasma pre-treatments using vapours from the alcohol family improved the coating adhesion on two types of polycarbonate. It is suggested that these plasmas both etch the polycarbonate and deposit a thin plasma polymer layer. It was previously reported that a similar adhesion improvement was obtained on PMMA, however under shorter treatment times. The variation has been linked to the difference in etch rates of the two polymers. This has led to an improved understanding of the etching mechanism of both polymers when exposed to radicals. [ABSTRACT FROM AUTHOR]

Surface modification of materials with microscale features through plasma treatment or deposition is of high value, and is considered one of the great challenges in plasma-based materials processing. This article reports a versatile method for the fabrication of microcavity plasma array devices. A 7 × 7 microcavity plasma array device (each cavity was 250 µm in diameter and separated by 500 µm) was used in this study to demonstrate the capability of these devices for localised, non-contact surface treatment/polymer deposition. The device can be reused multiple times for plasma treatment and polymerisation. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging and region of interest (ROI) analysis, in addition to surface hydration, were employed to characterise the micropatterns on microplasma-treated PS. The results showed that microplasma treatment/deposition could be spatially confined to regions exposed to the individual ignited microcavities. However, the results also demonstrated that the size of the treated spots tended to increase with increasing treatment time until they eventually overlapped resulting in a homogeneous surface treatment confined to the size of the array. Similarly, the concentration of oxygen quantified on the treated spots reached saturation after 75 s of treatment. The versatility of the device was demonstrated by depositing an array of octadiene plasma polymer (ODpp) onto a silicon substrate as confirmed by XPS imaging and ROI analysis. A key advantage of these microcavity array devices is that they can be easily integrated into manufacturing and do not require contact with the substrate surface to impart well-defined chemical modifications on materials surfaces. [ABSTRACT FROM AUTHOR]

The well-characterized small heat-shock protein, αB-crystallin, acts as a molecular chaperone by interacting with unfolding proteins to prevent their aggregation and precipitation. Structural perturbation (e.g., partial unfolding) enhances the in vitro chaperone activity of αB-crystallin. Proteins often undergo structural perturbations at the surface of a synthetic material, which may alter their biological activity. This study investigated the activity of αB-crystallin when covalently bound to a support surface; αB-crystallin was immobilized onto a range of solid material surfaces, and its characteristics and chaperone activity were assessed. Immobilization was achieved via a plasma-deposited thin polymeric interlayer containing aldehyde surface groups and reductive amination, leading to the covalent binding of αB-crystallin lysine residues to the surface aldehyde groups via Schiff-base linkages. Immobilized αB-crystallin was characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and quartz crystal microgravimetry, which showed that ∼300 ng cm−2 (dry mass) of oligomeric αB-crystallin was bound to the surface. Immobilized αB-crystallin exhibited a significant enhancement (up to 5000-fold, when compared with the equivalent activity of αB-crystallin in solution) of its chaperone activity against various proteins undergoing both amorphous and amyloid fibril forms of aggregation. The enhanced molecular chaperone activity of immobilized αB-crystallin has potential applications in preventing protein misfolding, including against amyloid disease processes, such as dialysis-related amyloidosis, and for biodiagnostic detection of misfolded proteins. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 376-389, 2011 [ABSTRACT FROM AUTHOR]

Purpose: In this study we investigated the relationship between surface topography and initial epithelialization of synthetic lenticules in vivo. Methods: Millipore ultrafiltration membranes of three different pore sizes were used as model lenticule materials. The nominal membrane pore sizes were 0.1 μm, 0.45 μm, and 3 μm; the surface roughness increased in the same order. The membranes were coated with a thin layer of collagen I and implanted in a circular pocket of the anterior cornea of adult cats, and were clinically evaluated for the extent of epithelialization and the persistence of epithelial attachment. Results/Conclusions: It was demonstrated that a smooth surface appears more attractive for initial epithelialization than a rough surface in vivo. [ABSTRACT FROM AUTHOR]