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Refereed/Peer-reviewed The demand for medical implants globally has increased significantly due to an aging population amongst other reasons. Despite the overall increase in the survivorship of Ti6Al4V implants, implant infection rates are increasing due to factors such as diabetes, obesity, and bacterial resistance to antibiotics. Two commonly found bacteria implicated in implant infections are Staphylococcus aureus and Pseudomonas aeruginosa. Based on prior work that showed nanostructured surfaces might have potential in passively killing these bacterial species, we developed a hierarchical, hydrothermally etched, nanostructured titanium surface. To evaluate the antibacterial efficacy of this surface, etched and as-received surfaces were inoculated with S. aureus or P. aeruginosa at concentrations ranging from 10(2) to 10(9) colony-forming units per disc. Live/dead staining revealed there was a 60% decrease in viability for S. aureus and greater than a 98% decrease for P. aeruginosa on etched surfaces at the lowest inoculum of 10(2) CFU/disc, when compared to the control surface. Bactericidal efficiency decreased with increasing bacterial concentrations in a stepwise manner, with decreases in bacterial viability noted for S. aureus above 10(5) CFU/disc and above 10(6) CFU/disc for P. aeruginosa. Surprisingly, biofilm depth analysis revealed a decrease in bacterial viability in the 2 mu m layer furthest from the nanostructured surface. The nanostructured Ti6Al4V surface developed here holds the potential to reduce the rate of implant infections.

Dye sensitized solar cells (DSSC) are an attractive third-generation photovoltaic technology particularly promising for operation under diffuse and lower light conditions. However, high costs of the precious metals used for sensitizing dyes and low charge generation capability parameters limit the utility of DSSCs in comparison to conventional silicon solar cells. In this study, tin oxide (SnO2) photoelectrodes are treated with non-thermal atmospheric pressure plasmas to enhance photovoltaic performance. The effects of nitrogen and argon plasma surface treatment of photoanodes on the efficiency enhancement of DSSCs are systematically investigated by fabricating solar cells using pristine SnO2 and plasma-treated photoanodes. Solar cells made with Eosin Y sensitized pristine SnO2 photoanode exhibited a short circuit current density (JSC) of 1.03 mA cm−2 and an overall power conversion efficiency (PCE) of 0.30% whereas solar cells made with nitrogen plasma treated photoanode exhibited a JSC of 6.20 mA cm−2 and an overall PCE of 1.53% (4 times enhancement) under the same illumination of 100 mW cm−2 (AM 1.5). The efficiency of the solar cells fabricated with Ar plasma treated SnO2 photoanodes also showed an enhanced power conversion efficiency. Further characterizations revealed that the surface plasma treatments increased the surface roughness of the photoanodes. Plasma treatment led to the incorporation of nitrogen species and removal of surface impurities resulting in an increase in dye adsorption in the photoanode and hence the enhancement in the efficiency of the DSSC. This study demonstrated a one-pot treatment method for efficiency enhancement which could be used in various applications such as photovoltaic, catalytic and energy generation applications including DSSCs, thin-film solar cells, perovskite solar cells, gas sensing, bio-sensing, supercapacitors, Li-ion batteries and others. Refereed/Peer-reviewed

The metal ion release characteristics and biocompatibility of meta-based materials are key factors that influence their use in orthodontics. Although stainless steel-based alloys have gained much interest and use due to their mechanical properties and cost, they are prone to localised attack after prolonged exposure to the hostile oral environment. Metal ions may induce cellular toxicity at high dosages. To circumvent these issues, orthodontic brackets were coated with a functional nano-thin layer of plasma polymer and further immobilised with enantiomers of tryptophan. Analysis of the physicochemical properties confirmed the presence of functional coatings on the surface of the brackets. The quantification of metal ion release using mass spectrometry proved that plasma functionalisation could minimise metal ion release from orthodontic brackets. Furthermore, the biocmpatibility of the brackets has been improved after functionalisation. These findings demon-strate that plasma polymer facilitated surface functionalisation of orthodontic brackets is a promising approach to reducing metal toxicity without impacting their bulk properties. Refereed/Peer-reviewed

Halloysite nanotubes (HNTs) are highly stable aluminosilicate with hollow tubular structure. It features a unique architectural effect from both interior and exterior surface. These special characteristics make HNT an interesting nano-object in many areas such as a vehicle for drug delivery or as a template for chemical reactions. In this work, HNT was used as a versatile template for the fabrication of a novel composite material. Specifically, thiolate ligand protected ultra-small gold nanoclusters (AuNCs; diameter less than 3 nm), which exhibits molecular like properties such as HOMO-LUMO transition and photoluminescence were synthesized selectively within the interior and on the exterior surface of HNT (referred as AuNCs@HNT-In and AuNCs@HNT-Out, respectively). Such spatially selective localization of NCs was achieved by loading the intermediate Au(I)-thiolate complexes (formed during the synthesis of AuNCs) through electrostatic interaction, followed by their in-situ mild reduction at moderate temperature. All these composite materials are highly stable at ambient conditions and luminescent under UV light. Finally, the catalytic efficiency of the composite materials was evaluated by the reduction reaction of 4-nitrophenol. At similar experimental condition, AuNCs@HNT-Out showed the highest catalytic activity when compared with individual AuNCs and AuNCs@HNT-In, mainly due to the higher exposure of the active sites of NCs while being supported on the outermost surface of HNT. This clay-NC synergy may make these composites suited not only for catalysis but also for sensing, drug delivery and environmental applications Refereed/Peer-reviewed

Water vapor is one of the crucial impurities in biogas which have to be removed for optimal performance.Utilization of natural zeolites as water vapor adsorbents is one of the proposed solutions. However, the small specific surface area of natural zeolite needs to be improved to increase the material adsorption capacity, one ofthe methods being physicochemical treatment. The consequences of the increased specific surface area by physicochemical treatment are the Si/Al ratio and hydrophobicity enhancement which counterbalance the benefits of the increased specific surface area. In this work, plasma activation treatment was applied successfully to increase the water adsorption capacity of natural zeolites after dealumination. The transformations of the chemical and physical properties of the material after plasma treatment are discussed. Our results point that the certain intrinsic properties on the zeolites in terms of Si/Al ratio and specific surface area are prerequisite to benefit from plasma activation. This work offers a new perspective on improving porous silica-based materials water adsorption characteristics which could lead to improved adsorbents in the future. Refereed/Peer-reviewed

To combat infections on biomedical devices, antimicrobial coatings have attracted considerable attention, including coatings comprising naturally occurring antimicrobial peptides (AMPs). In this study the aim was to explore performance upon extended challenge by bacteria growing in media above samples. The AMPs LL37, Magainin 2, and Parasin 1 were selected on the basis of well-known membrane disruption activity in solution and were covalently grafted onto a plasma polymer platform, which enables application of this multilayer coating strategy to a wide range of biomaterials. Detailed surface analyses were performed to verify the intended outcomes of the coating sequence. Samples were challenged by incubation in bacterial growth media for 5 and 20 h. Compared with the control plasma polymer surface, all three grafted AMP coatings showed considerable reductions in bacterial colonization even at the high bacterial challenge of initial seeding at 1 &times, 107 CFU, but there were increasing numbers of dead bacteria attached to the surface. All three grafted AMP coatings were found to be non-toxic to primary fibroblasts. These coatings thus could be useful to produce antibacterial surface coatings for biomaterials, though possible consequences arising from the presence of dead bacteria need to be studied further, and compared to non-fouling coatings that avoid attachment of dead bacteria.

Refereed/Peer-reviewed 3D printing provides numerous opportunities for designing tissue engineering constructs with intricate porosity, geometry and favourable mechanical properties and has the potential to revolutionize medical treatments. However, an often-encountered restriction is the selection of materials suitable for utilization in 3D printing, not all of which have appropriate biocompatibility properties. In this work, fused deposition modeling was employed to fabricate 3D PCL constructs without the use of any solvent. Plasma deposition was used to modify the surface of the scaffolds, followed by immobilization of silver nanoparticles. The physico-chemical and mechanical analyses demonstrated that the scaffolds retained their porosity and mechanical integrity. The mechanical properties evaluated by the nanoindentation technique demonstrated an increase in reduced modulus to 1.87 ± 0.012 GPa for PCL scaffolds functionalized with silver nanoparticles for 24 hours. We also showed complete prevention of colonization by medically relevant pathogens. The modified scaffolds had good biocompatibility. The immune response studies in the culture of macrophages confirmed a reduction in the level of expression of pro-inflammatory cytokines which is a key requirement for successful wound healing. The in vivo studies on Sprague Dawley rats indicated enhanced angiogenesis and the absence of foreign body reaction for scaffolds functionalized with silver nanoparticles for 6 hours. The 3D printing approach presented in this study provides new sustainable opportunities that can be adopted for designing biomaterial constructs with enhanced biological properties.

This work deals with Ni catalysts supported on both mono and binary oxide prepared by a conventional wet impregnation method. The catalytic properties of the material were investigated in oxy-steam reforming of methane (OSRM) process. The physicochemical properties of the catalysts were extensively studied using techniques such as Temperature Programmed Reduction (TPR-H2), Temperature Programmed Desorption of Ammonia (TPD-NH3), Brunauer Emmett Teller Method (BET), X-ray Diffraction studies (XRD), Thermal Analysis coupled with Mass Spectrometry (TG-DTA-MS), Time of Flight Secondary Ion Mass Spectrometer (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscope with EDX detector (SEM-EDX). The catalytic activity results showed that the Ni/CeO2∙La2O3 (2:1) catalyst exhibited superior activity and high selectivity towards hydrogen formation in the studied process due to the high content of Ni species present on the catalyst surface. The low activity of the Ni catalysts supported on La2O3 or binary oxide with high content of lanthanum oxide is related to the strong interaction of NiO with support. Refereed/Peer-reviewed

The fast degradation and consequent loss of mechanical integrity is a major problem of biodegradable Mg alloy, which limits its clinical viability. This paper presents the influence of a synergistic approach combining burnishing and hydroxyapatite (HA) coating on biomechanical integrity, degradation and immune response of Mg alloy (AZ31B). The burnishing resulted in smooth surface topography, increased hardness from 0.87 to 1.45 GPa and induced microstructural disturbances with deformation twins/twin bands, which enabled formation of a dense and compact platelet-like crystals HA coating of 110 μm thickness. Compared to the untreated and burnished specimens, the burnished + HA coated surface provided remarkably higher corrosion resistance as indicated by lower corrosion current density and smaller mass loss. HA coating and surface integrity enhancement by burnishing were predominantly responsible for improved corrosion resistance. HA coating on the burnished surface exhibited hydrophilic properties and adequate bonding strength. While the modified surfaces promoted cell growth, the burnished + HA surface outperformed in exhibiting less pro-inflammatory and high anti-inflammatory cytokines, demonstrating that the treated surfaces were not posing any threat to immune cells. The findings indicate that the synergistic surface treatment can be a viable means to enhance corrosion resistance and immune response of Mg alloys implants. Refereed/Peer-reviewed

The stable nitroxide radical TEMPO [(2,2,6,6-Tetramethylpiperidin-1-yl)oxyl] has a multitude of applications in fields ranging from energy storage to biomedical applications and many more. However, to date, the processes of incorporating nitroxide radicals into thin-film coatings are laborious and not cost-effective, which hinders their wider use in many applications. In contrast, the authors have recently demonstrated the facile method of plasma polymerization of TEMPO into thin-film coatings that retain the stable nitroxide radicals. In this work, we are using three types of mass spectroscopic methods (plasma-mass spectrometry, time of flight secondary ion mass spectrometry, and high-performance liquid chromatography-mass spectrometry) and electron spin resonance to track the fate of the TEMPO molecule from monomer flask through the plasma and inside the resulting coatings. The results of this study demonstrate that TEMPO is a versatile monomer that can be used across different plasma reactors and reliably retain the stable nitroxide radical in the resulting thin-film coatings if certain process conditions are observed, namely, higher process pressures and lower powers.

In this study, the antibacterial efficacy of NO-releasing porous silicon nanoparticles (pSiNPs) is reported. NO-releasing pSiNPs were produced via the conjugation of S-nitrosothiol (SNO) and S-nitrosoglutathione (GSNO) donors to the nanoparticle surfaces. The release of the conjugated NO caused by the decomposition of the conjugated SNO and GSNO was boosted in the presence of ascorbic acid. The released NO was bactericidal to Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), and eliminated bacterial growth within 2 h of incubation without compromising the viability of mammalian cells. These results demonstrate the advantages of NO-releasing pSiNPs for antibacterial applications, for example, in chronic wound treatment. Refereed/Peer-reviewed

Controlled synthesis of hollow polymeric nanocapsules has attracted significant attention in a wide range of applications. This paper reports a facile method for the synthesis of hybrid starch nanocapsules decorated with silver nanoparticles using the inverse miniemulsion polyaddition technique. Silver nanoparticles are formed and embedded in the shell of the nanocapsules during the polyaddition process without using any additional reducing agents. We found that silver also acts as a lipophobe that builds up osmotic pressure in the droplets facilitating the formation of stable round shaped nanocapsules. The nanocapsules' shell thickness could be tuned from 13 to 29 nm by varying the amount of cross-linker. We investigated the minimum inhibitory concentration (MIC) of the nanocapsules against Staphylococcus epidermidis ATCC 35984 and Escherichia coli ATCC 25922 which are two bacteria of medical relevance. The silver nanoparticle decorated nanocapsules showed antibacterial properties against both bacteria at the MIC of 2.315 mu g mL(-1) while control nanocapsules without silver had no antibacterial activity. Refereed/Peer-reviewed

Polyoxazolines arise as a promising new class of polymers for biomedical applications, but creating oxzoline-based coatings via conventional methods is challenging. Herein, nanoscale polyoxazoline coatings were generated via a single step plasma deposition process. The effects of plasma deposition conditions on the film stability, structure and chemical group density were investigated. Detailed examination of the physical and chemical properties of plasma deposited polyoxazoline via XPS, FTIR, contact angle and ellipsometry unravels the complex functionality of the films. Partial retention of the oxazoline ring facilitates a covalent reaction with the carboxylic acid groups present on nanoparticles and biomolecules. Surface bound proteins effectively retain their bioactivity, therefore a vast range of potential applications unlocks for plasma deposited polyoxazoline coatings in the field of biosensing, medical arrays and diagnosis. Refereed/Peer-reviewed

Ultrasmall silver nanoparticles (AgNPs; size < 3 nm) have attracted a great deal of interest as an alternative to commercially available antibiotics due to their ability to eliminate a wide range of microbial pathogens. However, most of these ultrasmall AgNPs are highly reactive and unstable, as well as susceptible to fast oxidation. Therefore, both the stability and toxicity remain major shortcomings for their clinical application and uptake. To circumvent these problems, we present a novel strategy to impregnate ultrasmall AgNPs into a biocompatible thermosensitive hydrogel that enables controlled release of silver alongside long-term storage stability and highly potent antibacterial activity. The advantage of this strategy lies in the combination of a homogenous dispersion of AgNPs in a hydrogel network, which serves as a sustained-release reservoir, and the unique feature of ultrasmall AgNP size, which provides an improved biofilm eradication capacity. The superior biofilm dispersion properties of the AgNP hydrogel is demonstrated in both single-species and multispecies biofilms, eradicating ∼80% of established biofilms compared to untreated controls. Notably, the effective antibacterial concentration of the formulation shows minimal toxicity to human fibroblasts and keratinocytes. These findings present a promising novel strategy for the development of AgNP hydrogels as an efficient antibacterial platform to combat resistant bacterial biofilms associated with wound infections. Refereed/Peer-reviewed

This forward looking concise review describes recent advances in the field of nanoengineered plasma polymer films. These types of coatings are relevant in many fields of application and have gained substantial research and technological interestover the last decade. The review starts with an introduction of plasma polymerization as a technique for preparation for nanometer thin polymer-like coatings. This is followed by the examples of the use of nanoengineered plasma polymer coatings in applications relevant to biomedical devices. Applications in antibacterial coatings and drug delivery vehicles are discussed. Significant section of this paper is dedicated to cell guidance surfaces which have an extensive range of applications ranging from coatings for medical devices to research tools that can help unraveling complex biological questions and vehicles for the growing field of cell therapies. The vision of the authors about the future directions of the field have also been presented, including a section on novel oxazoline based coatings that carry great promise for advances in the biomaterial and biomedical fields. Refereed/Peer-reviewed

Refereed/Peer-reviewed The growing demand for titanium-based implants and the subsequent rise in implant-associated infections necessitate novel developments in anti-infective technologies. Recent research has drawn inspiration from nature to solve this problem. The nanoscale topography observed on cicada and dragonfly wings serves as a blueprint for synthetic analogs which seek to kill bacteria on contact through mechanical forces. This type of interaction has been dubbed the mechano-bactericidal effect. Various techniques have been utilized to mimic and improve upon these natural bactericidal surfaces. Alkaline hydrothermal etching is a simple and cost-effective technique to fabricate nanoscale protrusions on titanium and its alloys. This review aims to consolidate the current knowledge surrounding how fabrication parameters lead to varying surface topographies on titanium substrates, and subsequently, how surface topography and bacterial characteristics affect bactericidal activity. The bactericidal mechanism of hydrothermally etched titanium is inferred from comparisons with similar mechano-bactericidal biomaterials. The hostility of hydrothermally etched titanium toward bacteria is discussed in contrast to the observed host cell compatibility. Last, suggestions are made for the standardization of terminology in this emerging field.

This work presents, for the first time, the comparative physicochemical and reactivity studies of a range of bimetallic Pt-Ni, Pd-Ni, Ru-Ni, and Ag-Ni catalysts in the oxy-steam reforming (OSR) of liquefied natural gas (LNG) reaction towards hydrogen generation. In order to achieve the intended purpose of this work, a binary oxide CeO2·ZrO2 (1:2) support was prepared via a co-precipitation method. The catalysts’ physicochemical properties were studied using X-ray diffraction (XRD), BET, TPR-H2, TPD-NH3, SEM-EDS and XPS methods. The highest activity in the studied process was exhibited by the 1%Pt-5%Ni catalyst supported on CeO2·ZrO2 (1:2) system. The highest activity of this system is explained by the specific interactions occurring between the components of the active phase and between the components of the active phase and the carrier itself. The activity results showed that this catalytic system exhibited above 71% of the methane conversion at 600 °C and 60% yield of hydrogen formation. The results of this work demonstrate that the Pt-Ni and Ru-Ni catalytic systems hold promise to be applied in the production of hydrogen to power solid oxide fuel cells.

Carbon quantum dots (CQDs, C-dots or CDs) are an emerging type of nanomaterial which has received immense attention due to their numerous applications. However, most of the reported CQDs in literature typically emit single emission peak under an excitation. Multipeak emissions without any complicated techniques will be ideal for various applications in the fields of ratiometric sensing, optoelectronics, and multifunctional bio-imaging systems. Here, a fast, effective, and single-step method is developed for the bulk synthesis of CQDs using atmospheric pressure air plasmas. Structural, morphological, and chemical properties are characterized by advanced analytical techniques. The CQDs have an average diameter of about 3 nm with a narrow size distribution. Emission wavelengths of 470 nm for blue emissive CQDs and 515 nm for green emissive CQDs are observed. Concentration dependency of the CQDs suggests that the switchable mechanism is due to the formation of PTSA excimers. Dual-emissive CQDs have the potential to be used in bi-channel ratiometric determination for metal ions, pH sensing, tumor diagnosis and detection, and solid-state lighting materials. The proof-of-principle demonstration of the use of dual-emissive CQDs (DCQDs) as a fluorescent sensor of Cu2+ ions is also presented to highlight the possible applications Refereed/Peer-reviewed

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems with detrimental implications for ecosystem recovery. Here we critically review the pros and cons of functionalised nanoclays and provide new perspectives on the synthesis of environmentally friendly varieties. Particular focus is given to finding alternatives to conventional surfactants used in modified nanoclay products, and to exploring strategies in synthesising nanoclay-supported metal and metal oxide nanoparticles. A large number of promising nanoclay-based sorbents are yet to satisfy environmental biocompatibility in situ but opportunities are there to tailor them to produce ‘‘biocompatible’’ or regenerative/reusable materials. Refereed/Peer-reviewed

The nature of the protein corona forming on biomaterial surfaces can affect the performance of implanted devices. This study investigated the role of surface chemistry and wettability on human serum-derived protein corona formation on biomaterial surfaces and the subsequent effects on the cellular innate immune response. Plasma polymerization, a substrate-independent technique, was employed to create nanothin coatings with four specific chemical functionalities and a spectrum of surface charges and wettability. The amount and type of protein adsorbed was strongly influenced by surface chemistry and wettability but did not show any dependence on surface charge. An enhanced adsorption of the dysopsonin albumin was observed on hydrophilic carboxyl surfaces while high opsonin IgG2 adsorption was seen on hydrophobic hydrocarbon surfaces. This in turn led to a distinct immune response from macrophages; hydrophilic surfaces drove greater expression of anti-inflammatory cytokines by macrophages, whilst surface hydrophobicity caused increased production of proinflammatory signaling molecules. These findings map out a unique relationship between surface chemistry, hydrophobicity, protein corona formation, and subsequent cellular innate immune responses; the potential outcomes of these studies may be employed to tailor biomaterial surface modifications, to modulate serum protein adsorption and to achieve the desirable innate immune response to implanted biomaterials and devices. usc Refereed/Peer-reviewed

Plasma coatings deposited from oxazoline precursors have recently emerged as a valuable utility in many biotechnology application, however, their wider utilization by researchers and industry rely on their long term performance, and more specifically on the retention of their reactivity. Yet, plasma polymers are known to be susceptible to post-fabrication oxidation processes and intrinsic restructuration. Here,the aging of coatings deposited from oxazoline precursors was studied over12 months via XPS, ToF-SIMS,and sessile drop contact angle analysis for samples stored under various conditions. The extent of the damages caused by light and oxygen are identified and explained. Storage away from ambient light and undervacuum proved to retain highreactivity toward COOH-bearingligand and biomolecules even 12 months post deposition. Refereed/Peer-reviewed

One of the biggest challenges associated with exposed core glass optical fiber-based sensing is the availability of techniques that can be used to generate reproducible, homogeneous and stable surface coating. We report a one step, solvent free method for surface functionalization of exposed core glass optical fiber that allows achieving binding of fluorophore of choice for metal ion sensing. The plasma polymerization-based method yielded a homogeneous, reproducible and stable coating, enabling high sensitivity aluminium ion sensing. The sensing platform reported in this manuscript is versatile and can be used to bind different sensing molecules opening new avenues for optical fiber-based sensing. Refereed/Peer-reviewed

Porous materials have been applied for various applications, mainly as adsorbent and catalyst. One of them is zeolite, particularly in a synthetic form which has excellent performance but has some drawbacks of high cost, complex processing, and waste production. Meanwhile, natural zeolite is available in abundant amount and has low-cost provisioning, so it has prospective room for developed. Some of the common types of natural zeolites are mordenite and clinoptilolite; one of the availabilities is located in Gunungkidul, Yogyakarta, Indonesia. The typical modification of zeolite is dealumination which was also applied to the natural zeolite. Dealumination was carried out to improve the natural zeolite properties, particularly Si/Al ratio. The various types of dealumination process were conducted in variable of acid concentration (0 to 12 N HCl), volume ratio (1:1, 1:2, 1:4), soaking time studies (1, 2, 4, 24 hours), agitation (stirring and no stirring), and multi-stage dealumination (1 to 10 stages). XPS analysis determined the Si/Al ratio, then supported by XRD and BET to explore the other characteristics transformation of crystal structure and specific surface area. In the single stage dealumination, the highest Si/Al ratio of 16.2 was produced at 12 N HCl, 1:4 volume ratio, 24 hours soaking time and stirring action. Meanwhile, the multi-stage dealumination has the evidence to improve the Si/Al ratio sequentially than others variable in single stage dealumination; the highest Si/Al ratio attained over than 120 at the most upper stage of dealumination. Moreover, dealumination treatment also increases the specific surface area over than 220m 2 /g, but the multi-stage variable was not affected much. The multi-stage dealumination effect provides prospective application of mordenite-clinoptilolite natural zeolite, particularly in the high Si/Al ratio, as hydrophobic surface porous adsorbent or catalyst. Refereed/Peer-reviewed

Plasma polymers are unconventional organic thin films which only partially share the properties traditionally attributed to polymeric materials. For instance, they do not consist of repeating monomer units but rather present a highly cross linked structure resembling the chemistry of the precursor used for deposition. Due to the complex nature of the deposition process, plasma polymers have historically been produced with little control over the chemistry of the plasma phase which is still poorly understood. Yet, plasma polymer research is thriving, in par with the commercialisation of innumerable products using this technology, in fields ranging from biomedicalto green energy industries. Here, we briefly summarise the principles at the basis of plasma deposition and highlight recent progress made in understanding the unique chemistry and reactivity of these films. We then demonstrate how carefully designed plasma polymer films can serve the purpose of fundamental research and biomedical applications. We finish the review with a focus on a relatively new class of plasma polymers which are derived from oxazoline-based precursors. This type of coating has attracted significant attention recently due to its unique properties. Refereed/Peer-reviewed

The development of suitable biomaterials is key to the progress of biomedical engineering. Plasma deposition is a versatile and waste free technique that can be used to produce surfaces with well denied chemical and physical properties. In this mini-review we show how well-char-acterised plasma deposited organic films have been used to screen and identify optimum substrate properties for several different biomedical applications. By providing as an example the plasma deposited poly oxazolines, we demonstrate the generation of advances biomaterial surfaces capable of limiting biofilm formation, guiding stem cell differentiation and even sensing cancer cells in urine. Refereed/Peer-reviewed

Refereed/Peer-reviewed Tissue engineered constructs having desired biomimetic and mechanical properties emerged due to the complexities involved in conventional skin grafting. They facilitate tissue regeneration without compromising mechanical properties. Herein, we report the fabrication of polycaprolactone (PCL) scaffold by fused deposition modeling and immobilization of gold nanoparticles onto the polymer surface after modifying the PCL surface using plasma polymerization. 3D printed PCL scaffolds inlaid with gold nanoparticles (Au-PCL) were characterized for their structural and mechanical properties using FESEM, and nano-indentation. The surface chemistry was analyzed using X-ray photon electron spectroscopy (XPS), wettability was determined using water contact angle studies and surface topography was imaged by atomic force microscopy (AFM). The surface modification of 3D printed scaffolds significantly improved their hydrophilicity suggesting that hydrophobicity which restricts the use of PCL in biological applications could be overcome by plasma modification. Nanoindentation studies showed that Au-PCL scaffolds exhibited remarkable enhancement in mechanical properties with reduced Young’s modulus of 1.81 GPa. Biocompatibility was assessed by measuring cell viability, cell attachment and immune response. In vitro biocompatibility studies indicated good attachment of viable cells onto the gold nanoparticles incorporated 3D printed network. Immune response studies indicated that scaffolds did not enhance the production of pro-inflammatory cytokines such as TNF-α, IL-8 and IL-β. Collectively, plasma modification and surface immobilization of gold nanoparticles onto the 3D printed PCL scaffold is a simple and cost-effective technique to enhance the mechanical properties and biocompatibility of hydrophobic scaffolds like PCL, thereby making this technique a very promising tool for futuristic applications of scaffolds.

Wound infections arising from bacterial contamination and colonisation are of substantial burden to healthcare. Currently, bandages are used to merely provide wounds with physical barriers to bacteria, however they quickly become saturated and ineffective. Silver containing wound dressings have gained commercial and scientific attention as a potential solution to the problem of wound infections. In this work, we compare the antibacterial efficacy of recently patented silver nanoparticle loaded plasma polymer film technology and a commercially available GranuFoam Silver® silver-coated wound dressings. The silver nanoparticle loaded foams contained lower amount of elemental silver than the commercially available wound dressings but both silver-loaded foams had comparable antibacterial capacity. Furthermore, the silver nanoparticle loaded foams had greater hydrophilicity which may be beneficial in applications. Collectively, the results demonstrate that the nanoparticle loaded plasma polymer coating can be used on medical devices such as wound dressings with similar efficacy to existing products. Refereed/Peer-reviewed

Infections caused by the bacterial colonization of medical devices are a substantial problem to patients and healthcare. Biopassive polyoxazoline coatings are attracting attention in the biomedical field as one of the potential solutions to this problem. Here, we present an original and swift way to produce plasma-deposited oxazoline-based films for antifouling applications. The films developed via the plasma deposition of 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline have tunable thickness and surface properties. Diverse film chemistries were achieved by tuning and optimizing the deposition conditions. Human-derived fibroblasts were used to confirm the biocompatibility of oxazoline derived coatings. The capacity of the coatings to resist biofilm attachment was studied as a function of deposition power and mode (i.e., continuous wave or pulsed) and precursor flow rates for both 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline. After careful tuning of the deposition parameters films having the capacity to resist biofilm formation by more than 90% were achieved. The substrate-independent and customizable properties of the new generation of plasma deposited oxazoline thin films developed in this work make them attractive candidates for the coating of medical devices and other applications where bacteria surface colonization and biofilm formation is an issue. Refereed/Peer-reviewed

Controlling the release kinetics from a drug carrier is crucial to maintain a drug's therapeutic window. We report the use of biodegradable porous silicon microparticles (pSi MPs) loaded with the anticancer drug camphothecin, followed by a plasma polymer overcoating using a loudspeaker plasma reactor. Homogenous "Teflon-like" coatings were achieved by tumbling the particles by playing AC/DC's song "Thunderstruck". The overcoating resulted in a markedly slower release of the cytotoxic drug, and this effect correlated positively with the plasma polymer coating times, ranging from 2-fold up to more than 100-fold. Ultimately, upon characterizing and verifying pSi MP production, loading, and coating with analytical methods such as time-of flight secondary ion mass spectrometry, scanning electron microscopy, thermal gravimetry, water contact angle measurements, and fluorescence microscopy, human neuroblastoma cells were challenged with pSi MPs in an in-vitro assay, revealing a significant time delay in cell death onset. Refereed/Peer-reviewed

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.

Copper and gold doped copper catalysts supported on multi-walled carbon nanotubes were prepared by wet impregnation and deposition–precipitation methods, respectively. The catalysts were tested in the oxy-steam reforming of methanol (OSRM) and characterized by XRD, SEM-EDS, TOF-SIMS, thermo-gravimetric analysis and temperature-programmed desorption of ammonia. The reactivity results showed the promotion effect of gold on the activity and selectivity of the copper catalysts in the OSRM. The formed Cu–Au alloy as an active phase was responsible for the activity and selectivity improvement of the bimetallic catalysts in the oxy-steam reforming of methanol. The formation of an Au–Cu alloy was confirmed by the XRD, TOF-SIMS and SEM-EDS techniques. The reducibility and acidity of the tested catalysts are important factors, which influence the activity of the copper and gold–copper catalysts.

Surface modification has been identified as an important technique that could improve the response of the body to implanted medical devices. Collagen production by fibroblasts is known to play a vital role in wound healing and device fibrous encapsulation. However, how surface chemistry affects collagen I and III deposition by these cells has not been systematically studied. Here, we report how surface chemistry influences the deposition of collagen I and III by primary human dermal fibroblasts. Amine (NH3), carboxyl acid (COOH), and hydrocarbon (CH3) surfaces were generated by plasma deposition. This is a practically relevant tool to deposit a functional coating on any type of substrate material. We show that fibroblasts adhere better and proliferate faster on amine-rich surfaces. In addition, the initial collagen I and III production is greater on this type of coating. These data indicates that surface modification can be a promising route for modulating the rate and level of fibrous encapsulation and may be useful in informing the design of implantable biomedical devices to produce more predictable clinical outcomes. Refereed/Peer-reviewed

Plasma polymers derived from oxazoline precursors present a range of versatile properties that is fueling their use as biomaterials. However, coatings deposited from commonly used methyl and ethyl oxazoline precursors can be sensitive to the plasma deposition conditions. In this work, we used various spectroscopic methods (ellipsometry, x-ray photoelectron spectroscopy, and time of flight secondary ion mass spectrometry) and cell viability assays to evaluate the transferability of deposition conditions from the original plasma reactor developed by Griesser to a new wider, reactor designed for upscaled biosensors applications. The physicochemical properties, reactivity, and biocompatibility of films deposited from 2-isopropenyl-2-oxazoline were investigated. Thanks to the availability of an unsaturated pendant group, the coatings obtained from this oxazoline precursor are more stable and reproducible over a range of deposition conditions while retaining reactivity toward ligands and biomolecules. This study identified films deposited at 20 W and 0.012 mbar working pressure as being the best suited for biosensor applications. Refereed/Peer-reviewed

Silver nanoparticles have applications in plasmonics, medicine, catalysis and electronics. We report a simple, cost-effective, facile and reproducible technique to synthesise silver nanoparticles via plasma-induced non-equilibrium liquid chemistry with the absence of a chemical reducing agent. Silver nanoparticles with tuneable sizes from 5.4 to 17.8 nm are synthesised and characterised using Transmission Electron Microscopy (TEM) and other analytic techniques. A mechanism for silver nanoparticle formation is also proposed. The antibacterial activity of the silver nanoparticles was investigated with gram-positive and gram-negative bacteria. The inhibition of both bacteria types was observed. This is a promising alternative method for the instant synthesis of silver nanoparticles, instead of the conventional chemical reduction route, for numerous applications. Refereed/Peer-reviewed

Herein, we report about the monometallic Ni and bimetallic Pd-Ni catalysts supported on CeO2-Al2O3 binary oxide, which were investigated in oxy-steam reforming of methanol (OSRM). Monometallic and bimetallic supported catalysts were prepared by wet aqueous impregnation and subsequent impregnation method, respectively. The physicochemical properties of the catalytic systems were investigated using various methods such as: BET, XRD, TPR-H2, TPD-NH3, XPS and SEM-EDS techniques. It has been proven that the addition of palladium to the nickel catalyst facilitates its reduction. The activity tests performed for all catalysts confirmed the promotion effect of palladium on catalytic activity of nickel catalyst and selectivity towards hydrogen production. Both nickel and bimetallic palladium-nickel supported catalysts showed excellent stability during the reaction. Such catalytic systems are valuable for the advance of the field of fuel cell technology.

This feature article begins by outlining the problem of infection and its implication on healthcare. The initial introductory section is followed by a description of the four distinct classes of antibacterial coatings and materials, i.e., bacteria repealing, contact killing, releasing and responsive, that were developed over the years by our team and others. Specific examples of each individual class of antibacterial materials and a discussion on the pros and cons of each strategy are provided. The article contains a dedicated section focused on silver nanoparticle based coatings and materials, which have attracted tremendous interest from the scientific and medical communities. The article concludes with the author’s view regarding the future of the field.

The importance of nanostructured surfaces in a range of technological and biological processes is well documented within literature, yet often ill-understood. Simple and reliable methods for the preparation of nanotextured surfaces are required to advance both fundamental understandings of nanoscale phenomena and our capacity to design nano-engineered materials for specific applications. Nano engineered surfaces are, for instance, needed to shed light on the effect of nanostructures' size and density on immune cells cytokine production. In applied bioengineering, nanostructured artificial surfaces could be specifically tailored to enhance the osteo-integration of implants. This study presents a versatile, plasma polymer enabled method for the generation of surfaces with well-defined nanotopography and tailored outermost surface chemistry. This was achieved by finely controlling the covalent bonding of gold nanoparticles of desired size to plasma-deposited poly(methyloxazoline) interlayer deposited on the material substrate. An additional 5 nm thin polymer was deposited over the nanostructures providing a uniformly tailored outermost surface chemistry while preserving the topography. This rapid, versatile, substrate independent, and scalable strategy for the preparation of a well-defined nanotopography surface has promising prospects in many fields relying on surface engineering, including food and membrane technologies, biomaterial and environmental engineering, sensing, marine sciences, and even pollution control. Refereed/Peer-reviewed

Nanoparticles, nanotubes, nanobelts, nanoneedles, nanosheets, nanowires, nanopillars: the variety of nanostructured interfaces that can be created and modified using plasma processes is virtually endless. This is great news for modern technologies because plasma-generated nanomaterials have unique properties that can benefit many industrial fields, ranging from electronics and photonics to medicine and biology. Using versatile plasma techniques to produce nanoengineered structures has many advantages over other conventional methods. This stems from the fact that plasma processes are environmentally friendly and time-efficient, capable of creating unique materials unachievable by other means. Plasma processes are also readily scalable and transferable to industrial use. In recent years, proactive approaches in this field have led to breakthroughs in plasma nanofabrication, generating nanoengineered materials with properties that could not be equaled via other techniques such as self-assembly or classic lithography. Refereed/Peer-reviewed

Silver nanoparticles (Ag-NPs) are used in a wide variety of products, prompting concerns regarding their potential environmental impacts. To accurately determine the toxicity of Ag-NPs it is necessary to differentiate between the toxicity of the nanoparticles themselves and the toxicity of ionic silver (Ag) released from them. This is not a trivial task given the reactive nature of Ag in solution, and its propensity for both adsorption and photo reduction. In the experiments reported here, we quantified the loss of silver from test solutions during standard ecotoxicity testing conducted using a variety of different test container materials and geometries. This sensitive 110mAg isotope tracing method revealed a substantial underestimation of the toxicity of dissolved Ag to the green algae Pseudokirchneriella subcapitata when calculated only on the basis of the initial test concentrations. Furthermore, experiments with surface-functionalized Ag-NPs under standard algal growth inhibition test conditions also demonstrated extensive losses of Ag-NPs from the solution due to adsorption to the container walls, and the extent of loss was dependent on Ag-NP surface-functionality. These results hold important messages for researchers engaged in both environmental and human nanotoxicology testing, not only for Ag-NPs but also for other NPs with various tailored surface chemistries, where these phenomena are recognized but are also frequently disregarded in the experimental design and reporting. Refereed/Peer-reviewed

To understand the role of surface chemistry on cell behavior and the associated molecular mechanisms, we developed and utilized a surface chemical gradient of amine functional groups by carefully adjusting the gas composition of 1,7-octadiene (OD) and allylamine (AA) of the plasma phase above a moving substrate. The chemical gradient surface used in the present work shows an increasing N/C ratio and wettability from the OD side toward the AA side with no change in surface topography. Under standard culture conditions (with serum), human adipose-derived stem cells (hASCs) adhesion and spreading area increased toward the AA side of the gradient. However, there were no differences in cell behavior in the absence of serum. These results, supported by the trends in proteins adsorption on the gradient surface, demonstrated that surface chemistry affects the response of hASCs through cell-adhesive serum proteins, rather than interacting directly with the cells. The expression of p-ERK and the osteogenic differentiation increased toward the AA side of the gradient, while adipogenic differentiation decreased in the same direction; however, when the activation of ERK1/2 was blocked by PD98059, the levels of osteogenic or adipogenic differentiation on different regions of the chemical gradient were the same. This indicates that ERK1/2 may be an important downstream signaling pathway of surface chemistry directed stem cell fate. Refereed/Peer-reviewed

Poly(2-oxazoline)s are emerging revolutionary biomaterials, exhibiting comparable and even superior properties to well-established counterparts. Overcoming current tedious wet synthesis methods, we report solvent-free and substrate independent, plasma polymerised nano-scale biocompatible polyoxazoline coatings capable of controlling protein and cell adhesion, and significantly reducing biofilm build up. Refereed/Peer-reviewed

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 ¼2) was achieved at a pressure of 100mTorr in the RPR.

Advanced medical devices, treatments and therapies demand an understanding of the role of interfacial properties on the cellular response. This is particularly important in the emerging fields of cell therapies and tissue regeneration. In this study, we evaluate the role of surface nanotopography on the fate of human dental pulp derived stem cells (hDPSC). These stem cells have attracted interest because of their capacity to differentiate to a range of useful lineages but are relatively easy to isolate. We generated and utilized density gradients of gold nanoparticles which allowed us to examine, on a single substrate, the influence of nanofeature density and size on stem cell behavior. We found that hDPSC adhered in greater numbers and proliferated faster on the sections of the gradients with higher density of nanotopography features. Furthermore, greater surface nanotopography density directed the differentiation of hDPSC to osteogenic lineages. This study demonstrates that carefully tuned surface nanotopography can be used to manipulate and guide the proliferation and differentiation of these cells. The outcomes of this study can be important in the rational design of culture substrates and vehicles for cell therapies, tissue engineering constructs and the next generation of biomedical devices where control over the growth of different tissues is required. Refereed/Peer-reviewed

Protein adsorption to biomaterials is critical in determining their suitability for specific applications, such as implants or biosensors. Here, we show that surface nanoroughness can be tailored to control the covalent binding of proteins to plasma-deposited polyoxazoline (PPOx). Nanoengineered surfaces were created by immobilizing gold nanoparticles varying in size and surface density on PPOx films. To keep the surface chemistry consistent while preserving the nanotopography, all substrates were overcoated with a nanothin PPOx film. Bovine serum albumin was chosen to study protein interactions with the nanoengineered surfaces. The results demonstrate that the amount of protein bound to the surface is not directly correlated with the increase in surface area. Instead, it is determined by nanotopography-induced geometric effects and surface wettability. A densely packed array of 16 and 38 nm nanoparticles hinders protein adsorption compared to smooth PPOx substrates, while it increases for 68 nm nanoparticles. These adaptable surfaces could be used for designing biomaterials where proteins adsorption is or is not desirable. Refereed/Peer-reviewed

Correction for ‘Rapid fabrication of functionalised poly(dimethylsiloxane) microwells for cell aggregate formation’ by A. Forget et al., Biomater. Sci., 2017, 5, 828–836.

Cell aggregates reproduce many features of the natural architecture of functional tissues, and have therefore become an important in vitro model of tissue function. In this study, we present an efficient and rapid method for the fabrication of site specific functionalised poly(dimethylsiloxane) (PDMS) microwell arrays that promote the formation of insulin-producing beta cell (MIN6) aggregates. Microwells were prepared using an ice templating technique whereby aqueous droplets were frozen on a surface and PDMS was cast on top to form a replica. By employing an aqueous alkali hydroxide solution, we demonstrate exclusive etching and functionalisation of the microwell inner surface, thereby allowing the selective absorption of biological factors within the microwells. Additionally, by manipulating surface wettability of the substrate through plasma polymer coating, the shape and profile of the microwells could be tailored. Microwells coated with antifouling Pluronic 123, bovine serum albumin, collagen type IV or insulin growth factor 2 were employed to investigate the formation and stability of MIN6 aggregates in microwells of different shapes. MIN6 aggregates formed with this technique retained insulin expression. These results demonstrate the potential of this platform for the rapid screening of biological factors influencing the formation and response of insulin-producing cell aggregates without the need for expensive micromachining techniques. Refereed/Peer-reviewed

Tuning the material properties in order to control the cellular behavior is an important issue in tissue engineering. It is now well-established that the surface chemistry can affect cell adhesion, proliferation, and differentiation. In this study, plasma polymerization, which is an appealing method for surface modification, was employed to generate surfaces with different chemical compositions. Allylamine (AAm), acrylic acid (AAc), 1,7-octadiene (OD), and ethanol (ET) were used as precursors for plasma polymerization in order to generate thin films rich in amine (−NH2), carboxyl (−COOH), methyl (−CH3), and hydroxyl (−OH) functional groups, respectively. The surface chemistry was characterized by X-ray photo electron spectroscopy (XPS), the wettability was determined by measuring the water contact angles (WCA) and the surface topography was imaged by atomic force microscopy (AFM). The effects of surface chemical compositions on the behavior of human adipose-derive stem cells (hASCs) were evaluated in vitro: Cell Count Kit-8 (CCK-8) analysis for cell proliferation, F-actin staining for cell morphology, alkaline phosphatase (ALP) activity analysis, and Alizarin Red S staining for osteogenic differentiation. The results show that AAm-based plasma-polymerized coatings can promote the attachment, spreading, and, in turn, proliferation of hASCs,as well as promote the osteogenic differentiation of hASCs, suggesting that plasma polymerization is an appealing method for the surface modification of scaffolds used in bone tissue engineering. Refereed/Peer-reviewed