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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]

The article discusses the therapeutic promise of the anti-infective surface coatings against device-associated infections. Topics discussed include the delivery of antibiotics for the prevention of the pathogenic adhesion on medical devices, the growing concern on the resistance developed by infectious agents, and the preparation of the tethered drug surfaces through the formation of a chemical bond between the drug target and functional groups.

Highlights: [•] The most common optical biosensors are waveguides and surface-plasmon resonance. [•] The output signal depends on local concentration and distance from the surface. [•] Waveguide and surface-plasmon resonance are comparable but there are nuances. [•] Optical biosensors can be applied to detect microorganisms and in cell-based assays. [•] Long-range structures overcome the shallow probe distance and can be more sensitive. [Copyright &y& Elsevier]

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has been used for over a decade for the determination of purity and accurate molecular masses of macromolecular analytes, such as proteins, in solution. In the last few years the technique has been adapted to become a new surface analysis method with unique capabilities that complement established biomaterial surface analysis methods such as XPS and ToF-SSIMS. These new MALDI variant methods, which we shall collectively summarize as Surface-MALDI-MS, are capable of desorbing adsorbed macromolecules from biomaterial surfaces and detecting their molecular ions with high mass resolution and at levels much below monolayer coverage. Thus, Surface-MALDI-MS offers unique means of addressing biomaterial surface analysis needs, such as identification of the proteins and lipids that adsorb from multicomponent biological solutions in vitro and in vivo, the study of interactions between biomaterial surfaces and biomolecules, and identification of surface-enriched additives and contaminants. Surface-MALDI-MS is rapid, experimentally convenient, overcomes limitations in mass resolution and sensitivity of established biochemical techniques such as SDS-PAGE, and can in some circumstances be used for the quantitative analysis of adsorbed protein amounts. At this early stage of development, however, limitations exist: in some cases proteins are not detectable, which appears to be related to tight surface binding. This review summarizes ways in which Surface-MALDI-MS methods have been applied to the study of a range of issues in biomaterials surfaces research. [Copyright &y& Elsevier]

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]

Ethnopharmacological relevance For traditional medicinal purposes Aboriginal Australians have utilised numerous plant species, Eremophila alternifolia is among the most prominent. Traditionally, fresh leaves, leaf-infusions and handmade leaf-pastes have been used as both external and internal preparations to provide relief from a variety of conditions. Preparations of the species have been used to treat various infections of skin, eyes and throat including the treatment of septic wounds. These usages suggest that the plant contains antibacterial compounds; however, to date they have not been isolated and identified. Aim of the study The present study aimed to identify antibacterial compounds from this important traditionally recorded medicinal species. Materials and methods Bioassay-guided fractionation was used to isolate compounds from the crude leaf-extract. Antibacterial activity of pure compounds was assessed through broth microdilution method by determining both minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). Structure elucidation was performed using spectroscopic techniques such as 1D and 2D nuclear magnetic resonance spectroscopy and high resolution mass spectrometry. Results Four compounds have been isolated from the leaf-extract; they include previously known flavanones [pinobanksin ( 1 ), pinobanksin-3-acetate ( 2 ) and pinobanksin-3-cinnamate ( 3 )] and a serrulatane diterpene, 8-hydroxyserrulat-14-en-19-oic acid (4). While compound 4 had been found in other Eremophilas , flavanones 2 and 3 are identified for the first time from the genus Eremophila . The flavanone 3 is the most promising antibacterial compound with significant activity (10−20 µM) against strains of the Gram-positive bacterium Staphylococcus aureus including methicillin resistant and biofilm forming strains. No activity was observed for any isolated compounds against the Gram-negative bacterium Escherichia coli . Conclusion The antibacterial activity of the crude extract of E. alternifolia and of the isolated compounds against Gram-positive bacteria provides a Western scientific explanation of the therapeutic modality of this plant species in traditional Aboriginal medicinal practice. [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]

Long-range surface plasmon resonance (LRSPR) is a powerful biosensing technology due to a substantially larger probing depth into the medium and sensitivity, compared with conventional SPR. We demonstrate here that LRSPR can provide sensitive noninvasive measurement of the dynamic fluctuation of adherent cells, often referred to as the cellular micromotion. Proof of concept was achieved using confluent layers of 3T3 fibroblast cells and MDA-MB-231 cancer cells. The slope of the power spectral density (PSD) of the optical fluctuations was calculated to determine the micromotion index, and significant differences were measured between live and fixed cell layers. Furthermore, the performances of LRSPR and conventional surface plasmon resonance (cSPR) were compared with respect to micromotion monitoring. Our study showed that the micromotion index of cells measured by LRSPR sensors was higher than when measured with cSPR, suggesting a higher sensitivity of LRSPR to the micromotion of cells. To investigate further this finding, simulations were conducted to establish the relative sensitivities of LRSPR and cSPR to membrane fluctuations. Increased signal intensity was predicted for LRSPR in comparison to cSPR, suggesting that membrane fluctuations play a significant role in the optical micromotion measured in LRSPR. Analogous to cellular micromotion measured using impedance techniques, LRSPR micromotion has the potential to provide important biological information on the metabolic activity and viability of adherent cells. [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]

Host-defense antimicrobial peptides (AMPs) are a promising lead in the search for novel antibiotics. Many of these peptides exhibit broad-spectrum antibacterial ability, low toxicity toward human cells, and little susceptibility to induction of bacterial resistance. Our research focuses on the development of synthetic polymers that are able to mimic the amphiphilic and cation-rich characteristics of AMPs. This derives bioactive polymers that retain the activity profile of AMPs while utilizing a construct that is less expensive and easier to produce and manipulate chemically. This review details structure-activity relationships (SARs) of a new class of arginine-rich, synthetic AMP mimicking polymers (SAMPs), the guanylated polymethacrylates. These are contrasted with those of amine-based polymers that are mimics of lysine-rich AMPs. The ideal composition for candidates for practical applications was identified as those containing guanidines as a cation source, having a low molecular weight and a low level of lipophilicity. This gave polymers with high potency against Gram-positive strains of bacteria (e.g., Staphylococcus epidermidis MIC = 10 μg/mL) and low toxicity towards human red blood cells (<4% hemolysis at given MIC). This work emphasizes the need to rationalize observed biological activities based not purely on the global lipophilic and cationic character of polymers but rather to consider the profound effect that specific pendant functional groups may have on the potency, selectivity, and mechanisms behind the action of antimicrobial polymers. [ABSTRACT FROM AUTHOR]

Abstract: We report the total synthesis of leubethanol (1), a serrulatane compound that has recently been reported as having considerable antibacterial activity against multidrug-resistant bacteria, such as Staphylococcus aureus, and is of interest for applications in the control of bacterial biofilms in human medicine. Our synthetic route begins with (−)-isopulegol (4) and key steps include substrate directed hydroboration to generate the C1′ stereocentre and formation of the aromatic ring via the α-oxoketene-S,S-acetal intermediate 3. Overall the conversion of (−)-isopulegol (4) to leubethanol was achieved in 13 steps and an overall yield of 7%. Comparison of our spectroscopic data with those reported for leubethanol (1), isolated from Leucophyllum frutescens, verified the structure of the natural product. [Copyright &y& Elsevier]

Abstract: Addition of ionized terminal groups to PEG graft layers may cause additional interfacial forces to modulate the net interfacial interactions between PEG graft layers and proteins. In this study we investigated the effect of terminal sulfonate groups, characterizing PEG-aldehyde (PEG-CHO) and sulfonated PEG (PEG-SO3) graft layers by XPS and colloid probe AFM interaction force measurements as a function of ionic strength, in order to determine surface forces relevant to protein resistance and models of bio-interfacial interaction of such graft coatings. On the PEG-CHO surface the measured interaction force does not alter with ionic strength, typical of a repulsive steric barrier coating. An analogous repulsive interaction force of steric origin was also observed on the PEG-SO3 graft coating; however, the net interaction force changed with ionic strength. Interaction forces were modelled by steric and electrical double layer interaction theories, with fitting to a scaling theory model enabling determination of the spacing and stretching of the grafted chains. Albumin, fibrinogen, and lysozyme did not adsorb on the PEG-CHO coating, whereas the PEG graft with terminal sulfonate groups showed substantial adsorption of albumin but not fibrinogen or lysozyme from 0.15M salt solutions. Under lower ionic strength conditions albumin adsorption was again minimized as a result of the increased electrical double-layer interaction observed with the PEG-SO3 modified surface. This unique and unexpected adsorption behaviour of albumin provides an alternative explanation to the “negative cilia” model used by others to rationalize observed thromboresistance on PEG-sulfonate coatings. [Copyright &y& Elsevier]

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]

Abstract: In this work we report a detailed X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) study of poly(ethylene glycol) PEG-like chemical gradients deposited via plasma enhanced chemical vapour deposition (PECVD) at two different load powers using diethylene glycol dimethyl ether (DG) as a monomer. Principal component analysis (PCA) was applied to the ToF-SIMS data both before and after protein adsorption on the plasma polymer thin films. Results of the PCA loadings indicated a higher content of hydrocarbon fragments across the higher load power gradient, which adsorbed higher amounts of proteins. Gradients deposited at a lower load power retained a higher degree of monomer like functionality as did the central region directly underneath the knife edge electrode. Analysis of the adsorption of serum proteins (human serum albumin and fetal bovine serum) was monitored across the gradient films and increased with decreasing ether (PEG-like) film chemistries. The effect of protein incubation time on the levels adsorbed fetal bovine serum on the plasma polymer films was critical, with significantly more protein adsorbing after 24hour incubation times on both gradient films. The attachment of HeLa cells on the gradients appeared to be dictated not only by the surface chemistry, but also by the adsorption of serum proteins. XPS analysis revealed that at surface ether concentrations of less than 70% in the gradient films, significant increases in protein and cell attachment were observed. [Copyright &y& Elsevier]

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]

Hydrophilically substituted diterpenes of the structural class of serrulatanes have attracted attention as novel antibacterial compounds that are effective even against multidrug-resistant Staphylococcus aureus, a key bacterium involved in human infections. The mechanism of action has, however, not been established yet. Available data on structure-activity relationships suggest that the aromatic hydroxy group is essential for activity, and the strongest activity has been found for naphthyl compounds. In this context, it is reported that two highly active serrulatanes isolated from leaf resin of the Australian plant species Eremophila duttonii showed instability upon separation. Acetylation of hydroxy groups generated stable compounds that could be isolated and identified by NMR spectroscopy. The acetylated compounds showed little antibacterial activity, but such activity, as well as oxidative instability, was restored after hydrolysis of the acetate groups. Thus, phenolic hydroxy groups are essential for the mechanism of action of these compounds. The reaction products were not purifiable in sufficient quantities, but indications point to oxidation to quinones. Such oxidation may be a key aspect of the antibacterial activity of this class of compounds. [ABSTRACT FROM AUTHOR]

Covalently grafted poly(ethylene oxide) coatings have been widely studied for use in biomedical applications, particularly for the reduction of protein and other biomolecule adsorption. However, many of these studies have not characterized the hydrated structure of the coatings. This new study uses a combination of silica colloid probe interaction force measurements using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) in order to determine the grafting density and hydrated layer structure of monomethoxy poly(ethylene oxide) aldehyde layers, covalently grafted onto amine plasma polymer surfaces, and their interactions with silica surfaces. For high grafting densities, purely repulsive interactions were measured as expected for densely grafted polymer brushes. These interactions could be described by theoretical expectations for compression of one polymer brush layer. However, at lower grafting densities, attractive interactions were observed at larger separation distances, originating from bridging interactions due to adsorption of the PEO chains on the surface of the silica colloid probe. This is a new finding indicating that the coupled PEO molecules have sufficient conformational freedom to interact strongly with an adjacent surface or, for example, protein molecules for which there is an affinity. The attractive interactions could be removed by grafting an additional PEO layer onto the silica colloid probe. Protein adsorption measurements confirmed that at high grafting densities, the amount of adsorbed protein on the PEO grafted surfaces was greatly reduced, to the order of the detection limit for the XPS technique. [ABSTRACT FROM AUTHOR]

Abstract: We report a search for antimicrobial compounds in the Australian plant Eremophila serrulata. Bioassay directed fractionation of a diethyl ether extract prepared from the leaves of E. serrulata led to the isolation of two compounds, an ο-naphthoquinone, 9-methyl-3-(4-methyl-3-pentenyl)-2,3-dihydronaphtho[1,8-bc]pyran-7,8-dione (2), and a serrulatane diterpenoid, 20-acetoxy-8-hydroxyserrulat-14-en-19-oic acid (3). Two other known serrulatane-type diterpenoids, 8,20-dihydroxyserrulat-14-en-19-oic acid (4) and 8,20-diacetoxyserrulat-14-en-19-oic acid (5) were also isolated. None of these compounds had previously been tested for antimicrobial activity. Compounds 2–5 showed antimicrobial activity against Staphylococcus aureus (ATCC 29213) with minimum inhibitory concentrations (MICs) ranging from 15.6 to 250μg/mL. Compound 2 was the most active with an MIC of 15.6μg/mL and a minimum bactericidal concentration (MBC) of 125μg/mL. This compound also showed antimicrobial activity against other Gram-positive bacteria including Streptococcus pyogenes, and Streptococcus pneumoniae. No activity was observed for this compound against all Gram-negative bacteria tested. [Copyright &y& Elsevier]

Abstract: Brominated furanones have attracted recent interest as antibacterial compounds. To utilize them as protective coatings in biomedical device applications, they must be covalently immobilized onto solid surfaces; however, interfacial coupling protocols developed for other biomolecules are not applicable to furanones. An azide reaction scheme has enabled covalent immobilization onto fluorinated ethylene propylene copolymer but its chemistry is less predictable, requiring detailed characterization by XPS and tapping mode AFM after each step of the immobilization sequence. XPS curve fitting resolved components in the C1s, N1s and Br3d regions. Angle dependent XPS was used to assess the depth distributions and layer thicknesses. The results indicated successful covalent immobilization of furanones; however, side reactions occurred. In addition to the expected Ctribution from bromine ion (Br−) was detected, indicating that photo-degradation of furanones took place during UV illumination, and this reaction was found to increase with illumination time. The Br− was removed by washing with water, whereas the C from immobilized furanone remained. Spectroscopic characterization will assist in elucidating the structure of furanone coatings, understanding their mode of action when covalently immobilized on surfaces, and rationally designing and optimizing an effective antibacterial coating for biomedical applications. [Copyright &y& Elsevier]

The effects of pinning density, chain length, and ‘cloud point’ (CP) versus non-CP grafting conditions have been studied on the ability of polyethylene glycol (PEG) layers to minimize adsorption from a multicomponent (lysozyme, human serum albumin (HSA), IgG and lactoferrin) protein solution. Methoxy-terminated aldehyde-PEG (M-PEG, MW 5000) and dialdehyde-PEG (PEG(ald)2, MW 3400) were grafted by reductive amination onto two surfaces of different amine group density, generated by radio-frequency glow discharge (r.f.g.d.) deposition of n-heptylamine (HA) (low density) or allylamine (AlA) (high density) r.f.g.d. polymer layers. The PEG graft density was varied also by increasing the temperature and salt (K2SO4) content of the grafting solution; it reached a maximum at the CP of the PEGs. The CP reaction conditions were critical for producing PEG layers capable of minimizing protein adsorption. X-ray photoelectron spectroscopy (XPS) showed that under these conditions, PEG(ald)2 produced a thick linear PEG layer, most likely by aldol condensation. Protein adsorption was assessed using XPS and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) in the surface mode (Surface-MALDI-MS). Coatings grafted at non-CP conditions showed some protein adsorption, as did the HA/M-PEG layer grafted at the CP. On the other hand, no protein adsorption was detected on the HA/PEG(ald)2, AlA/M-PEG, and AlA/PEG(ald)2 surfaces when grafted at the CP. Thus, the effects of pinning density and chain length are interrelated, but the key factor is optimization of PEG chain density by use of the CP conditions, provided that a sufficient density of pinning sites exists. [Copyright &y& Elsevier]

Purpose. This study investigated whether a glycoprotein coating that will be used to enhance corneal epithelialization affects in situ nutritional passage through a permeable membrane. Methods. Sixteen adult cats were equally divided into two groups. Polycarbonate membranes with pore size of 0.1æm and total pore area (porosity) of 3.1% were used as implant materials. The membranes for Group 1 were coated with a thin layer of Collagen I, while the membranes for Group 2 were uncoated. Each membrane with 8-mm diameter was implanted into an interlamellar pocket of the cornea. The eyes were observed for approximately 35 days to monitor clinical signs of nutritional deficiency of the cornea, and then 7 membranes were removed from the eyes. The permeability of the explanted membranes to glucose, inulin and albumin was used to predict the in situ difference between the coated and uncoated groups in regard to nutritional passage through the membranes. To investigate the long-term effect of the surface coating on corneal health, two animals from Group 1 were followed for up to two years and then both eyes of each animal underwent histological examination. Results. Clinically, no post-surgical complications associated with nutritional deficiency were observed in any of the eyes. Nutritional permeability tests showed no significant differences between the coated and uncoated membranes. Histologically, the long-term animals showed no abnormal morphology associated with nutritional deficiency in the cornea anterior or posterior to the membranes. Conclusions. A thin glycoprotein coating on a permeable membrane does not appear to affect the nutritional supply of the anterior cornea and therefore can be used to enhance epithelialization of synthetic corneal onlays in vivo. [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]

Thin polymeric coatings are commonly used for altering surface properties and modulating the interfacial performance of materials. Possible contributions from the substrate to the interfacial forces and effects are, however, usually ignored and are not well understood, nor is it established how the coating thickness modulates and eventually eliminates contributions from substrates to the van der Waals (vdW) interfacial force. In this study we quantified, by colloid-probe atomic force microscope (AFM) and by theoretical calculations, the interfacial vdW contributions from substrates acting through ethanol plasma polymer (EtOHpp) coatings of a range of thicknesses on Au and Si bulk materials. In approach force curves against EtOHpp-coated Au substrates the magnitude of the vdW force decreased as the EtOHpp coating thickness increased to 18 nm and then plateaued with further increases in coating thickness, providing direct evidence for a contribution to the total interfacial vdW force from the Au substrate acting through thin coatings. The experimental observations accord with theoretical calculations of the thickness dependence of Hamaker coefficients derived from rigorous simulation using the Lifshitz theory. In addition, the measured forces agree well with theoretical predictions including correction for finite roughness. Thus, our experimental and theoretical results establish how the thickness of polymer thin film coatings modulates the total interfacial vdW force and how this can be used to tune the net vdW force so as to either contain a large substrate contribution or arise predominantly from the polymeric overlayer. Our findings enable rational design of coating thickness to tailor interfacial interactions and material performance. [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]

Objectives: Fungal biofilms caused by Candida spp. are a major contributor to infections originating from infected biomaterial implants. Since echinocandin-class molecules interfere with the integrity of the fungal cell wall, it was hypothesized that surface-immobilized anidulafungin and micafungin could play a role in preventing fungal adhesion and biofilm formation on surfaces.Methods: Anidulafungin and micafungin were covalently coupled to biomaterial surfaces and washed. Surface-sensitive instrumental analysis quantitatively and qualitatively confirmed their presence. Analysis after washing experiments provided evidence of their covalent immobilization. The in vitro antifungal properties of surfaces were confirmed using static biofilm assays and fluorescence microscopy kinetic studies.Results: Antifungal surface coatings eliminated 106 cfu/cm2 inoculations of Candida albicans and prevented biofilm formation and hyphal development on coated surfaces. Surfaces were successively exposed to fresh inoculum and were effective for at least five challenges in eliminating adherent yeasts.Conclusions: We have observed antifungal and anti-biofilm activity of surfaces bearing conjugated echinocandins, which operate through surface contact. The analytical and biological evidence suggests an antifungal mechanism for echinocandins that does not rely upon freely diffusing molecules. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SO 3 and PO 3 groups produced by Michael addition on heptylamine plasma polymer. • XPS analysis shows that protein adsorption saturated between 1 and 2 h. • QCM-D shows that passivation with HSA leads to reversible adsorption of lysozyme. • For fibrinogen, partial displacement occurs, regardless of surface chemistry. • Protein adsorption onto SO 3 or PO 3 surfaces is not dominated by electrostatics. Abstract As some proteins are known to interact with sulfated and phosphated biomolecules such as specific glycosaminoglycans, this study derives from the hypothesis that sulfonate and phosphonate groups on solid polymer surfaces might cause specific interfacial interactions. Such surfaces were prepared by plasma polymerization of heptylamine (HA) and subsequent grafting of sulfonate or phosphonate groups via Michael-type addition of vinylic compounds. Adsorption of the proteins fibrinogen, albumin (HSA) and lysozyme on these functionalised plasma polymer surfaces was studied by XPS and quartz crystal microbalance with dissipation (QCM-D). It was also studied whether pre-adsorption with HSA would lead to a passivated surface against further adsorption of other proteins. XPS confirmed grafting of vinyl sulfonate and vinyl phosphonate onto the amine surface and showed that the proteins adsorbed to saturation at between 1 and 2 h. QCM-D showed rapid and irreversible adsorption of albumin on all three surfaces, while lysozyme could be desorbed with PBS to substantial extents from the sulfonated and phosphonated surfaces but not from the amine surface. Fibrinogen showed rapid initial adsorption followed by slower additional mass gain over hours. Passivation with albumin led to small and largely reversible subsequent adsorption of lysozyme, whereas with fibrinogen partial displacement yielded a mixed layer, regardless of the surface chemistry. Thus, protein adsorption onto these sulfonated and phosphonated surfaces is complex, and not dominated by electrostatic charge effects. [ABSTRACT FROM AUTHOR]

Objectives Fungal biofilms caused by Candida spp. are a major contributor to infections originating from infected biomaterial implants. Since echinocandin-class molecules interfere with the integrity of the fungal cell wall, it was hypothesized that surface-immobilized anidulafungin and micafungin could play a role in preventing fungal adhesion and biofilm formation on surfaces. Methods Anidulafungin and micafungin were covalently coupled to biomaterial surfaces and washed. Surface-sensitive instrumental analysis quantitatively and qualitatively confirmed their presence. Analysis after washing experiments provided evidence of their covalent immobilization. The in vitro antifungal properties of surfaces were confirmed using static biofilm assays and fluorescence microscopy kinetic studies. Results Antifungal surface coatings eliminated 106 cfu/cm2 inoculations of Candida albicans and prevented biofilm formation and hyphal development on coated surfaces. Surfaces were successively exposed to fresh inoculum and were effective for at least five challenges in eliminating adherent yeasts. Conclusions We have observed antifungal and anti-biofilm activity of surfaces bearing conjugated echinocandins, which operate through surface contact. The analytical and biological evidence suggests an antifungal mechanism for echinocandins that does not rely upon freely diffusing molecules. [ABSTRACT FROM AUTHOR]

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]

In recent years, increasing evidence has been collated on the contributions of fungal species, particularly Candida , to medical device infections. Fungal species can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. Thus, there is a clear need for effective preventative measures, such as thin coatings that can be applied onto medical devices to stop the attachment, proliferation, and formation of device-associated biofilms. However, fungi being eukaryotes, the challenge is greater than for bacterial infections because antifungal agents are often toxic towards eukaryotic host cells. Whilst there is extensive literature on antibacterial coatings, a far lesser body of literature exists on surfaces or coatings that prevent attachment and biofilm formation on medical devices by fungal pathogens. Here we review strategies for the design and fabrication of medical devices with antifungal surfaces. We also survey the microbiology literature on fundamental mechanisms by which fungi attach and spread on natural and synthetic surfaces. Research in this field requires close collaboration between biomaterials scientists, microbiologists and clinicians; we consider progress in the molecular understanding of fungal recognition of, and attachment to, suitable surfaces, and of ensuing metabolic changes, to be essential for designing rational approaches towards effective antifungal coatings, rather than empirical trial of coatings. [ABSTRACT FROM AUTHOR]

One of the most significant hurdles to the affordable, accessible delivery of cell therapy is the cost and difficulty of expanding cells to clinically relevant numbers. Immunotherapy to prevent autoimmune disease, tolerate organ transplants or target cancer critically relies on the expansion of specialized T cell populations. We have designed 3D-printed cell culture lattices with highly organized micron-scale architectures, functionalized via plasma polymerization to bind monoclonal antibodies that trigger cell proliferation. This 3D technology platform facilitate the expansion of therapeutic human T cell subsets, including regulatory, effector, and cytotoxic T cells while maintaining the correct phenotype. Lentiviral gene delivery to T cells is enhanced in the presence of the lattices. Incorporation of the lattice format into existing cell culture vessels such as the G-Rex system is feasible. This cell expansion platform is user-friendly and expedites cell recovery and scale-up, making it ideal for translating T cell therapies from bench to bedside. [ABSTRACT FROM AUTHOR]

The propensity of glycosaminoglycans to mediate cell–cell and cell–matrix interactions opens the door to capture cells, including circulating blood cells, onto biomaterial substrates. Chondroitin sulfate (CS)-B is of particular interest, since it interacts with the receptor (EGF)-like module-containing mucin-like hormone receptor-like 2 precursor (EMR2) displayed on the surface of leukocytes and endothelial progenitor cells. Herein, CS-B and its isomer CS-A were covalently immobilized onto heptylamine plasma polymer films via three different binding chemistries to develop platform technology for the capture of EMR2 expressing cells onto solid carriers. Surface characterization verified the successful immobilization of both glycosaminoglycans. The EMR2 expressing human myeloid cell line U937 preferentially bound onto CS-B-modified substrates, and U937 cells preincubated with CS-B in solution exhibited reduced affinity for the substrate. The direct capture of hematopoietic and blood-circulating endothelial cell types via a glycosaminoglycan-binding surface receptor opens an unexplored route for the development of biomaterials targeted at these cell types. [ABSTRACT FROM AUTHOR]

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]

Large numbers of Mesenchymal stem/stromal cells (MSCs) are required for clinical relevant doses to treat a number of diseases. To economically manufacture these MSCs, an automated bioreactor system will be required. Herein we describe the development of a scalable closed-system, packed bed bioreactor suitable for large-scale MSCs expansion. The packed bed was formed from fused polystyrene pellets that were air plasma treated to endow them with a surface chemistry similar to traditional tissue culture plastic. The packed bed was encased within a gas permeable shell to decouple the medium nutrient supply and gas exchange. This enabled a significant reduction in medium flow rates, thus reducing shear and even facilitating single pass medium exchange. The system was optimised in a small-scale bioreactor format (160 cm2) with murine-derived green fluorescent protein-expressing MSCs, and then scaled-up to a 2800 cm2 format. We demonstrated that placental derived MSCs could be isolated directly within the bioreactor and subsequently expanded. Our results demonstrate that the closed system large-scale packed bed bioreactor is an effective and scalable tool for large-scale isolation and expansion of MSCs. [ABSTRACT FROM AUTHOR]

While plasma polymerization is used extensively to fabricate functionalized surfaces, the processes leading to plasma polymer growth are not yet completely understood. Thus, reproducing processes in different reactors has remained problematic, which hinders industrial uptake and research progress. Here we examine the crucial role pressure plays in the physical and chemical processes in the plasma phase, in interactions at surfaces in contact with the plasma phase, and how this affects the chemistry of the resulting plasma polymer films using ethanol as the gas precursor. Visual inspection of the plasma reveals a change from intense homogeneous plasma at low pressure to lower intensity bulk plasma at high pressure, but with increased intensity near the walls of the chamber. It is demonstrated that this occurs at the transition from a collision-less to a collisional plasma sheath, which in turn increases ion and energy flux to surfaces at constant RF power. Surface analysis of the resulting plasma polymer films show that increasing the pressure results in increased incorporation of oxygen and lower cross-linking, parameters which are critical to film performance. These results and insights help to explain the considerable differences in plasma polymer properties observed by different research groups using nominally similar processes. [ABSTRACT FROM AUTHOR]

Here, we report on the development of advanced biopolymer-coated drug-releasing implants based on titanium (Ti) featuring titania nanotubes (TNTs) on its surface. These TNT arrays were fabricated on the Ti surface by electrochemical anodization, followed by the loading and release of a model antibiotic drug, gentamicin. The osteoblastic adhesion and antibacterial properties of these TNT–Ti samples are significantly improved by loading antibacterial payloads inside the nanotubes and modifying their surface with two biopolymer coatings (PLGA and chitosan). The improved osteoblast adhesion and antibacterial properties of these drug-releasing TNT–Ti samples are confirmed by the adhesion and proliferation studies of osteoblasts and model Gram-positive bacteria ( Staphylococcus epidermidis ). The adhesion of these cells on TNT–Ti samples is monitored by fluorescence and scanning electron microscopies. Results reveal the ability of these biopolymer-coated drug-releasing TNT–Ti substrates to promote osteoblast adhesion and proliferation, while effectively preventing bacterial colonization by impeding their proliferation and biofilm formation. The proposed approach could overcome inherent problems associated with bacterial infections on Ti-based implants, simultaneously enabling the development of orthopedic implants with enhanced and synergistic antibacterial functionalities and bone cell promotion. [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]

Ethnopharmacological relevance Australian Aboriginal people used crushed leaves of Geijera parviflora Lindl. both internally and externally for pain relief, including for toothache ( Cribb and Cribb, 1981 ). This study tested the hypothesis that this traditional use might be at least in part explained by the presence of compounds with anti-inflammatory activity. Materials and methods A crude extract (95% EtOH) was prepared from powdered dried leaves. From the CH 3 Cl fraction of this extract compounds were isolated by bioassay-guided fractionation and tested for: (1) cytotoxicity in RAW 264.7 murine leukemic monocyte–macrophages, (2) prostaglandin E 2 (PGE 2 ) inhibitory activity in 3T3 Swiss albino mouse embryonic fibroblast cells, as well as (3) nitric oxide (NO) and (4) tumour necrosis factor alpha (TNFα) inhibitory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Isolated compounds were also tested for (5) antibacterial activity against a panel of Gram-positive ( Staphylococcus aureus ATCC 29213 and ATCC 25923, Staphylococcu s epidermidis ATCC 35984, biofilm-forming) and Gram-negative ( Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) strains by broth microdilution. Results Eleven compounds were isolated, including one new flavone and one new natural product, with a further four compounds reported from this species for the first time. Some of the compounds showed good anti-inflammatory activity in vitro . In particular, flindersine ( 1 ) and N-(acetoxymethyl) flindersine ( 3 ) inhibited PGE 2 release with IC 50 values of 5.0 μM and 4.9 μM, respectively, without any significant cytotoxicity. Several other compounds showed moderate inhibition of NO ( 5 , 6 , 7 ) and TNF-α ( 6) , with IC 50 in the low micromolar range; however much of this apparent activity could be accounted for by the cytotoxicity of these compounds. None of the compounds showed anti-bacterial activity. Conclusions The inhibition of PGE 2 , an important mediator of inflammation and pain, by flindersine and a derivative thereof, along with the moderate anti-inflammatory activity shown by several other compounds isolated from Geijera parviflora leaf extract, support the traditional use of this plant for pain relief by Australian Aboriginal people. [ABSTRACT FROM AUTHOR]

Microwave PECVD with vapours of tetramethyldisiloxane and oxygen was used to deposit transparent organosilicone coatings on PMMA. The ratio of tetramethyldisiloxane to oxygen within the plasma has a large influence on the chemical and physical properties of the deposited coatings. The oxygen flow rate was varied during deposition so as to deposit a chemically graded coating. Grading offers the ability to change the chemical and mechanical properties of a coating from the substrate to the surface. Coatings with constant oxygen flow rate were compared to those with oxygen varied in an exponential-like increase, a linear increase and a logarithmic-like increase during deposition. Additionally, a linear increase in power level during deposition was also explored. The coatings were characterised via their stress levels, refractive index and adhesion to PMMA. Abrasion and durability performance were also determined, via the steelwool test, salt water boil test and stress to craze test. It was found that the rate of grading significantly influenced the stress and performance of the coating. For enhanced coating performance, in all tests, an exponential-like increase of oxygen was shown to be best. Industrially, these coatings are relevant to the aviation and automotive industries as protective coatings on plastic windows or lenses. [ABSTRACT FROM AUTHOR]

Abstract: Five anthranilic acid derivatives, a mixture I of three new compounds 11′-hexadecenoylanthranilic acid (1), 9′-hexadecenoylanthranilic acid (2), and 7′-hexadecenoylanthranilic acid (3), as well as a new compound 9,12,15-octadecatrienoylanthranilic acid (4) together with a new natural product, hexadecanoylanthranilic acid (5), were isolated from Geijera parviflora Lindl. (Rutaceae). Their structures were elucidated by extensive spectroscopic measurements, and the positions of the double bonds in compounds 1–3 of the mixture I were determined by tandem mass spectrometry employing ozone-induced dissociation. The mixture I and compound 5 showed good antibacterial activity against several Gram-positive strains. [Copyright &y& Elsevier]

Abstract: Microbial attachment onto biomedical devices and implants leads to biofilm formation and infection; such biofilms can be bacterial, fungal, or mixed. In the past 15years, there has been an increasing research effort into antimicrobial surfaces but the great majority of these publications present research on bacteria, with some reports also testing resistance to fungi. Very few studies have focused exclusively on antifungal surfaces. However, with increasing recognition of the importance of fungal infections to human health, particularly related to infections at biomaterials, it would seem that the interest in antifungal surfaces is disproportionately low. In studies of both bacteria and fungi, fungi tend to be the minor focus with hypothesized antibacterial mechanisms of action often generalized to also explain the antifungal effect. Yet bacteria and fungi represent two Distinct biological Domains and possess substantially different cellular physiology and structure. Thus it is questionable whether these generalizations are valid. Here we review the scientific literature focusing on surface coatings prepared with antifungal agents covalently attached to the biomaterial surface. We present a critical analysis of generalizations and their evidence. This review should be of interest to researchers of “antimicrobial” surfaces by addressing specific issues that are key to designing and understanding antifungal biomaterials surfaces and their putative mechanisms of action. [Copyright &y& Elsevier]

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]

Wehave synthesized a series of copolymers containing both positivelycharged (amine, guanidine) and hydrophobic side chains (amphiphilicantimicrobial peptide mimics). To investigate the structure–activityrelationships of these polymers, low polydispersity polymethacrylatesof varying but uniform molecular weight and composition were synthesized,using a reversible addition–fragmentation chain transfer (RAFT)approach. In a facile second reaction, pendant amine groups were convertedto guanidines, allowing for direct comparison of cation structureon activity and toxicity. The guanidine copolymers were much moreactive against Staphylococcus epidermidisand Candida albicanscompared tothe amine analogues. Activity against Staphylococcusepidermidisin the presence of fetal bovine serumwas only maintained for guanidine copolymers. Selectivity for bacterialover mammalian cells was assessed using hemolytic and hemagglutinationtoxicity assays. Guanidine copolymers of low to moderate molecularweight and hydrophobicity had high antimicrobial activity with lowtoxicity. Optimum properties appear to be a balance between chargedensity, hydrophobic character, and polymer chain length. In conclusion,a suite of guanidine copolymers has been identified that representa new class of antimicrobial polymers with high potency and low toxicity. [ABSTRACT FROM AUTHOR]

Abstract: Coated layers of biologically active molecules on synthetic biomaterials and biomedical devices can promote a variety of desirable biological reactions by the host body or the biological medium, such as cell and tissue attachment or deterring bacterial biofilm formation. Such coated layers should be immobilised covalently in order to avoid competitive displacement phenomena, and the use of surface-activating plasmas or plasma polymer interlayers with suitable chemical surface groups has proved to be very convenient means of grafting bioactive molecules onto solid materials surfaces. We review selected work on the covalent immobilisation of proteins and peptides onto solid biomaterial surfaces and describe efforts towards plasma methods that allow biomolecules to be covalently captured in a single step. After reviewing a number of approaches, we discuss in more detail the use of plasma polymer interlayers that possess aldehyde or epoxide surface groups; these groups react readily with amine groups on proteins and peptides without undesirable side reactions, and avoid other issues such as crosslinking. We also emphasise the importance of detailed surface analysis to verify that covalent grafting has indeed taken place, and to assess the surface density of grafted molecules. With suitably chosen peptides or proteins, such covalently grafted layers can support the surface attachment of delicate cells, or combat bacterial biofilm formation. [Copyright &y& Elsevier]

Poly(ethylene glycol)(PEG) is one of the most extensively studiedantifouling coatings due to its ability to reduce protein adsorptionand improve biocompatibility. Although the use of PEG for antifoulingcoatings is well established, the stability and density of PEG layersare often inadequate to provide optimum antifouling properties. Toimprove on these shortcomings, we employed the stepwise constructionof PEG layers onto a silicon surface. Acetylene-terminated alkyl monolayerswere attached to nonoxidized crystalline silicon surfaces via a one-stephydrosilylation procedure with 1,8-nonadiyne. The acetylene-terminatedsurfaces were functionalized via a copper-catalyzed azide–alkynecycloaddition (CuAAC) reaction of the surface-bound alkynes with anazide to produce an amine terminated layer. The amine terminated layerwas then further conjugated with PEG to produce an antifouling surface.The antifouling surface properties were investigated by testing adsorptionof human serum albumin (HSA) and lysozyme (Lys) onto PEG layers fromphosphate buffer solutions. Detailed characterization of protein foulingwas carried out with X-ray photoelectron spectroscopy (XPS) and time-of-flightsecondary ion mass spectrometry (ToF-SIMS) combined with principalcomponent analysis (PCA). The results revealed no fouling of albuminonto PEG coatings whereas the smaller protein lysozyme adsorbed toa very low extent. [ABSTRACT FROM AUTHOR]

Abstract: Pilidiostigmin, a novel dimeric acylphloroglucinol derivative, was isolated from the leaves of the Australian plant species Pilidiostigma glabrum (Myrtaceae). Pilidiostigmin exists in the plant in the form of a sodium salt, which is rare in natural products. The elucidation of the structure and relative configuration was achieved by spectroscopic measurements with special emphasis on 1D and 2D NMR techniques. Pilidiostigmin was found to display biological activity; it significantly and dose-dependently inhibited the synthesis of nitric oxide in LPS-stimulated RAW 264.7 macrophages at low micromolar concentrations. [Copyright &y& Elsevier]

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]

Surface density gradients of streptavidin (SAV) werecreated onsolid surfaces and demonstrated functionality as a bioconjugationplatform. The surface density of immobilized streptavidin steadilyincreased in one dimension from 0 to 235 ng cm–2over a distance of 10 mm. The density of coupled protein was controlledby its immobilization onto a polymer surface bearing a gradient ofaldehyde group density, onto which SAV was covalently linked usingspontaneous imine bond formation between surface aldehyde functionalgroups and primary amine groups on the protein. As a control, humanserum albumin was immobilized in the same manner. The gradient densityof aldehyde groups was created using a method of simultaneous plasmacopolymerization of ethanol and propionaldehyde. Control over thesurface density of aldehyde groups was achieved by manipulating theflow rates of these vapors while moving a mask across substrates duringplasma discharge. Immobilized SAV was able to bind biotinylated probes,indicating that the protein retained its functionality after beingimmobilized. This plasma polymerization technique conveniently allowsvirtually any substrate to be equipped with tunable protein gradientsand provides a widely applicable method for bioconjugation to studyeffects arising from controllable surface densities of proteins. [ABSTRACT FROM AUTHOR]