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Current methods used to treat non-muscle invasive bladder cancer are inadequate due to a high recurrence rate after surgery and the occurrence of adverse events such as interstitial pneumonia following intravesical instillation therapy. Low-temperature plasma is a new form of physical therapy that provides a rich source of reactive oxygen species (ROS). Oxidative solutions, created by pre-treatment of aqueous media with plasma before application to target cells, lead to the destruction of cancer cells through oxidative stress pathways. This study focuses on the effects of plasma-activated media (PAM) in bladder cancer cells. PAM treatment increases oxidative stress that leads to cell cycle arrest and concomitantly depolarises the mitochondrial membrane leading to increased mitochondrial ROS production. Cell cycle arrest and increased mitochondrial ROS production led to an increase in caspase 3/cytochrome c activity, which might explain the induction of apoptosis in bladder cancer cells in vitro and in a bladder cancer tumour in vivo. These observations highlight the potential of plasma activated solutions as a new adjuvant therapy in the clinical treatment of bladder cancer.

The main bactericidal components of cold atmospheric plasma (CAP) are thought to be reactive oxygen and nitrogen species (RONS) and UV-radiation, both of which have the capacity to cause DNA damage and mutations. Here, the mutagenic effects of CAP on Escherichia coli were assessed in comparison to X- and UV-irradiation. DNA damage and mutagenesis were screened for using a diffusion-based DNA fragmentation assay and modified Ames test, respectively. Mutant colonies obtained from the latter were quantitated and sequenced. CAP was found to elicit a similar mutation spectrum to X-irradiation, which did not resemble that for UV implying that CAP-produced RONS are more likely the mutagenic component of CAP. CAP treatment was also shown to promote resistance to the antibiotic ciprofloxacin. Our data suggest that CAP treatment has mutagenic effects that may have important phenotypic consequences.

Refereed/Peer-reviewed This study compares how a helium plasma jet activates peracetic acid (PAA) from tetraacetylethylenediamine (TAED) and acetic acid (AA). Hydrogen peroxide (H2O2) generated from the plasma jets reacts with TAED resulting in the formation of PAA which further dissociates into AA. The by-product AA can also react with H2O2 to form PAA, which might also be useful for antimicrobial applications when coupled with plasma. Equivalent concentrations of TAED and AA solutions are used to compare the formation of PAA after activation with a helium plasma jet. Our results showed that the concentrations of both H2O2 and PAA in plasma-activated TAED (PAT) are higher than plasma-activated AA (PAAA), and that PAT is more efficient in reducing the growth of Pseudomonas aeruginosa and Staphylococcus aureus; the pathogens commonly found in wounds. The results are attributed to the presence of more acetyl donor groups in TAED, resulting in the formation of higher concentrations of PAA and H2O2.

Deposition chemistry from plasma is highly dependent on both the chemistry of the ions arriving at surfaces and the ion energy. Typically, when measuring the energy distribution of ions arriving at surfaces from plasma, it is assumed that the distributions are the same for all ionic species. Using ethyl acetate as a representative organic precursor molecule, we have measured the ion chemistry and ion energy as a function of pressure and power. We show that at low pressure (

Current methods used to treat non-muscle invasive bladder cancer are inadequate due to a high recurrence rate after surgery and occurrence of adverse events such as interstitial pneumonia following intravesical instillation therapy. Low-temperature plasma is a new form of physical therapy that provides a rich source of reactive oxygen species (ROS). Oxidative solutions, created by pre-treatment of aqueous media with plasma before application to target cells, lead to the destruction of cancer cells through oxidative stress pathways. This study focuses on the effects of plasma activated media (PAM) in bladder cancer cells. PAM treatment increases up regulation of p21 and down regulation of Cyclin D and CdK4 leading to cell cycle arrest, and concomitantly depolarises the mitochondrial membrane leading to increased mitochondrial ROS production. Cell cycle arrest and increased mitochondrial ROS production induce apoptosis in bladder cancer cells in vitro and in a bladder cancer tumour in vivo via the pro-apoptotic caspase 3/cytochrome c pathway. These observations highlight the potential of plasma activated solutions as a new adjuvant therapy in the clinical treatment of bladder cancer.

A conical assembly of six plasma jets arranged in a rectangular pattern for biomedical applications is presented. The conical configuration increases the separation distance between individual tubes within the assembly that reduces interference between individual plasma jets and enables the jets to converge at the output, facilitating more uniform treatment as opposed to plasma jet arrays operated in parallel. Electrical and optical diagnostics of the plasma discharges and measurements of H2O2 and [Formula: see text] production in de-ionized water are used to characterize the potential suitability of the device for biomedical applications. Particularly, it was found that the efficiency in H2O2 (an important bacterial disinfection agent) production by the conical assembly of six plasma jets was more than nine-fold higher compared to its single plasma jet counterpart and that this could be achieved at a biocompatible temperature of below 300 K. Therefore, the device may find use in biomedical applications, particularly where larger area treatments are required such as for certain wounds and cancer tumors that can span areas of tens of cm2.

The mechanisms of plasma in medicine are broadly attributed to plasma-derived reactive oxygen and nitrogen species (RONS). In order to exert any intracellular effects, these plasma-derived RONS must first traverse a major barrier in the cell membrane. The cell membrane lipid composition, and thereby the magnitude of this barrier, is highly variable between cells depending on type and state (e.g. it is widely accepted that healthy and cancerous cells have different membrane lipid compositions). In this study, we investigate how plasma-derived RONS interactions with lipid membrane components can potentially be exploited in the future for treatment of diseases. We couple phospholipid vesicle experiments, used as simple cell models, with molecular dynamics (MD) simulations of the lipid membrane to provide new insights into how the interplay between phospholipids and cholesterol may influence the response of healthy and diseased cell membranes to plasma-derived RONS. We focus on the (i) lipid tail saturation degree, (ii) lipid head group type, and (iii) membrane cholesterol fraction. Using encapsulated molecular probes, we study the influence of the above membrane components on the ingress of RONS into the vesicles, and subsequent DNA damage. Our results indicate that all of the above membrane components can enhance or suppress RONS uptake, depending on their relative concentration within the membrane. Further, we show that higher RONS uptake into the vesicles does not always correlate with increased DNA damage, which is attributed to ROS reactivity and lifetime. The MD simulations indicate the multifactorial chemical and physical processes at play, including (i) lipid oxidation, (ii) lipid packing, and (iii) lipid rafts formation. The methods and findings presented here provide a platform of knowledge that could be leveraged in the development of therapies relying on the action of plasma, in which the cell membrane and oxidative stress response in cells is targeted. Refereed/Peer-reviewed

Electrically generated cold atmospheric plasma is being intensively researched for novel applications in biology and medicine. Significant attention is being given to reactive oxygen and nitrogen species (RONS), initially generated upon plasma-air interactions, and subsequently delivered to biological systems. Effects of plasma exposure are observed to millimeter depths within tissue. However, the exact nature of the initial plasma-tissue interactions remains unknown, including RONS speciation and delivery depth, or how plasma-derived RONS intervene in biological processes. Herein, we focus on current research using tissue and cell models to learn more about the plasma delivery of RONS into biological environments. We argue that this research is vital in underpinning the knowledge required to realize the full potential of plasma in biology and medicine. Physical effects of plasma can be seen to depths of several hundred micrometers within tissue.Plasma-derived RONS are likely to be delivered millimeters into tissues.Speciation reveals that RONS delivered by plasma into tissue fluid and tissue are predominately stable secondary RONS - for example, H 2 O 2 , NO 2 - , and NO 3 - .The plasma generation of RONS within a hydrated target is influenced by the target matrix that can enhance or reduce the RONS concentrations and act as a reservoir of RONS.It is likely that the concentration of these plasma-derived RONS exceeds hundreds of micromoles, even at depths of several millimeters within tissue.Oxygen concentration at the time of plasma treatment significantly influences RONS generation within a hydrated proteinaceous target. Refereed/Peer-reviewed

This study investigates how addition of a 2nd ground electrode in an argon plasma jet influences the production of hydrogen peroxide (H2O2) in deionised water (DIW). Briefly, plasma is ignited by purging argon gas through a quartz tube at 1 l min−1 and applying a sinusoidal voltage of 7 kV (peak–peak) at 23.5 kHz to a high voltage stainless steel needle electrode sealed inside the quartz tube surrounded by one or two copper ring(s) that served as the ground electrode(s) situated downstream of the high voltage electrode. The mechanisms of H2O2 production are investigated through the electrical and optical plasma properties and chemical analysis of the treated DIW. We discover that the addition of a 2nd ground electrode results in higher accumulation of charges on the inner wall surface of the quartz tube of the plasma jet assembly resulting in an increase in the discharge current and dissipated power. This further leads to an increase in the electron temperature that more than doubles the H2O2 production through dissociative recombination of water vapour molecules, whilst still maintaining a biological tissue tolerable gas temperature. The double ground electrode plasma jet is shown to be highly effective at reducing the growth of common wound pathogens (Pseudomonas aeruginosa and Staphylococcus aureus) in both planktonic and biofilm states whilst inducing a low level of cytotoxicity in HaCaT keratinocyte skin-like cells under certain conditions. The information provided in this study is useful in understanding the complex physicochemical processes that influence H2O2 production in plasma jets, which is needed to optimise the development of plasma sources for clinical applications.

Functionalizing medical devices with polypeptides to enhance their performance has become important for improved clinical success. The extracellular matrix (ECM) adhesion protein vitronectin (VN) is an effective coating, although the chemistry used to attach VN often reduces its bioactivity. In vivo, VN binds the ECM in a sequence-dependent manner with heparan sulfate (HS) glycosaminoglycans. We reasoned therefore that sequence-based affinity chromatography could be used to isolate a VN-binding HS fraction (HS9) for use as a coating material to capture VN onto implant surfaces. Binding avidity and specificity of HS9 were confirmed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR)-based assays. Plasma polymerization of allylamine (AA) to tissue culture-treated polystyrene (TCPS) was then used to capture and present HS9 as determined by radiolabeling and ELISA. HS9-coated TCPS avidly bound VN, and this layered surface supported the robust attachment, expansion, and maintenance of human pluripotent stem cells. Compositional analysis demonstrated that 6-O- and N-sulfation, as well as lengths greater than three disaccharide units (dp6) are critical for VN binding to HS-coated surfaces. Importantly, HS9 coating reduced the threshold concentration of VN required to create an optimally bioactive surface for pluripotent stem cells. We conclude that affinity-purified heparan sugars are able to coat materials to efficiently bind adhesive factors for biomedical applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1887-1896, 2018.

We investigated a new approach to control protein and cell attachment inside 96-well polystyrene plates. The wells were first coated with bovine serum albumin (BSA) to inhibit cell and protein attachment. The BSA-coated wells were then treated with a helium microplasma jet for increasing times that resulted in gradual removal of BSA from the surface. It was found that the amount of enzyme and cell attachment could be controlled in the wells where BSA was only partially removed by the microplasma jet. In addition to the surface coverage of BSA, the new surface chemistry induced by the microplasma jet treatment also had an important role in the control of enzyme and cell attachment. In summary, microplasma jet treatment of BSA-coated polystyrene wells is a simple and effective method for controlling enzyme and cell attachment. This might find use for high-throughput screening of new cell culture platforms where control over the level protein, enzyme or cell adherence is needed in order to maintain a specific cell function. Refereed/Peer-reviewed

Here, a reaction-based indicator displacement hydrogel assay (RIA) was developed for the detection of hydrogen peroxide (H2O2) via the oxidative release of the optical reporter Alizarin Red S (ARS). In the presence of H2O2, the RIA system displayed potent biofilm inhibition for Methicillin-resistant Staphylococcus aureus (MRSA), as shown through an in vitro assay quantifying antimicrobial efficacy. This work demonstrated the potential of H2O2-responsive hydrogels containing a covalently bound diol-based drug for controlled drug release.

We explore how to configure an argon atmospheric-pressure plasma jet for enhancing its production of hydrogen peroxide (H2O2) in deionised water (DIW). The plasma jet consists of a quartz tube of 1.5 mm inner diameter and 3 mm outer diameter, with an upstream internal needle electrode (within the tube) and a downstream external cylindrical electrode (surrounding the tube). The plasma is operated by purging argon through the glass tube and applying a sinusoidal AC voltage to the internal needle electrode at 10 kV (peak–peak) with a frequency of 23.5 kHz. We study how the following operational parameters influence the production rate of H2O2 in water: tube length, inter-electrode separation distance, distance of the ground electrode from the tube orifice, distance between tube orifice and the DIW, argon flow rate and treatment time. By examining the electrical and optical properties of the plasma jet, we determine how the above operational parameters influence the major plasma processes that promote H2O2 generation through electron-induced dissociation reactions and UV photolysis within the plasma core and in the plasma afterglow; but with a caveat being that these processes are highly dependent on the water vapour content from the argon gas supply and ambient environment. We then demonstrate how the synergistic action between H2O2 and other plasma generated molecules at a plasma induced low pH in the DIW is highly effective at decontaminating common wound pathogens Gram-positive Staphylococus aureus and Gram-negative Pseudomonas aeruginosa. The information presented in this study is relevant in the design of medical plasma devices where production of plasma reactive species such as H2O2 at physiologically useful concentrations is needed to help realise the full clinical potential of the technology.

Functionalising surfaces using polymeric thin films is an industrially important field. One technique for achieving nanoscale, controlled surface functionalization is plasma deposition. Plasma deposition has advantages over other surface engineering processes, including that it is solvent free, substrate and geometry independent, and the surface properties of the film can be designed by judicious choice of precursor and plasma conditions. Despite the utility of this method, the mechanisms of plasma polymer growth are generally unknown, and are usually described by chemical (i.e., radical) pathways. In this review, we aim to show that plasma physics drives the chemistry of the plasma phase, and surface-plasma interactions. For example, we show that ionic species can react in the plasma to form larger ions, and also arrive at surfaces with energies greater than 1000 kJ∙mol–1 (>10 eV) and thus facilitate surface reactions that have not been taken into account previously. Thus, improving thin film deposition processes requires an understanding of both physical and chemical processes in plasma.[Figure not available: see fulltext.] Refereed/Peer-reviewed

Skin has a remarkable capacity for regeneration; however, with an ever aging population, there is a growing burden to the healthcare system from chronic wounds. Novel therapies are required to address the problems associated with nonhealing chronic wounds. Novel wound dressings that can encourage increased reepithelialization could help to reduce the burden of chronic wounds. A suite of chemically defined surfaces have been produced using plasma polymerization, and the ability of these surfaces to support the growth of primary human skin cells has been assessed. Additionally, the ability of these surfaces to modulate cell migration and morphology has also been investigated. Keratinocytes and endothelial cells were extremely sensitive to surface chemistry showing increased viability and migration with an increased number of carboxylic acid functional groups. Fibroblasts proved to be more tolerant to changes in surface chemistry; however, these cells migrated fastest over amine-functionalized surfaces. The novel combination of comprehensive chemical characterization coupled with the focus on cell migration provides a unique insight into how a material's physicochemical properties affect cell migration. Refereed/Peer-reviewed

Plasma polymerization was used to coat a melt electrospun polycaprolactone scaffold to improve cell attachment and organization. Plasma polymerization was performed using an amine containing monomer, allylamine, which then allowed for the subsequent immobilization of biomolecules, i.e., heparin and fibroblast growth factor-2. The stability of the plasma-polymerized amine-coating was demonstrated by X-ray photoelectron spectroscopy analysis and imaging time-of-flight secondary ion mass spectrometry revealed that a uniform plasma amine-coating was deposited throughout the scaffold. Based upon comparison with controls, it was evident that the combination scaffold aided cell ingress and the formation of distinct fibroblast and keratinocyte layers.

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. Refereed/Peer-reviewed

Amine containing plasma polymer films are of interest due to their ability to bind biomolecules either covalently or electrostatically. One issue with generating such plasma polymers is the need to generate sufficient amine density on the surface to enable binding, while simultaneously maintaining the chemical, physical stability of the surface in aqueous media. Here we investigate the relationship between plasma parameters, film stability for two commonly used monomers, allylamine AA, ethylenediamine EDA. Plasma polymer films from AA, EDA were produced at radio frequency RF powers between 2 and 20 W at a constant monomer flowrate. Deposition rate, ion flux, ion energy, plasma phase mass spectrometry were used to investigate the plasma-surface interactions. Film stability was assessed by comparing X-ray photoelectron spectroscopy XPS, atomic force microscopy AFM measurements before, after washing in phosphate buffered saline PBS. The results show that films generated from EDA plasmas are generally unstable in aqueous media, while films generated from AA plasmas exhibit higher stability, particularly those deposited at high RF power. The chemical, physical stability of the films is then related to the mechanisms of deposition, the energy density provided to the surface during film growth.

Functionalizing medical devices with polypeptides to enhance their performance has become important for improved clinical success. The extracellular matrix (ECM) adhesion protein vitronectin (VN) is an effective coating, although the chemistry used to attach VN often reduces its bioactivity. In vivo, VN binds the ECM in a sequence-dependent manner with heparan sulfate (HS) glycosaminoglycans. We reasoned therefore that sequence-based affinity chromatography could be used to isolate a VN-binding HS fraction (HS9) for use as a coating material to capture VN onto implant surfaces. Binding avidity and specificity of HS9 were confirmed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR)-based assays. Plasma polymerization of allylamine (AA) to tissue culture-treated polystyrene (TCPS) was then used to capture and present HS9 as determined by radiolabeling and ELISA. HS9-coated TCPS avidly bound VN, and this layered surface supported the robust attachment, expansion, and maintenance of human pluripotent stem cells. Compositional analysis demonstrated that 6-O- and N-sulfation, as well as lengths greater than three disaccharide units (dp6) are critical for VN binding to HS-coated surfaces. Importantly, HS9 coating reduced the threshold concentration of VN required to create an optimally bioactive surface for pluripotent stem cells. We conclude that affinity-purified heparan sugars are able to coat materials to efficiently bind adhesive factors for biomedical applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1887-1896, 2018.

The quantification of primary and secondary amines in plasma polymerized allylamine and plasma copolymers of allylamine/octadiene films was carried out using chemical derivatization followed by X-ray photoelectron spectroscopy. Data was analyzed using a combination of the peak-fit-analysis method (PFA) and the quantitative-elemental-analysis method (QEA). The latter method overestimates the secondary amine contribution, since it does not account for the additional reaction of TFAA with OH groups that may be present as a result of surface aging effects. In the current work the PFA method has been extended to enable the separation of –OH groups and secondary amines, thus allowing for a more precise determination of the secondary amine groups even after surface aging.

Plasma processing is widely used to provide novel surface modifications to materials for a variety of applications. Typically, the systems used to carry out these modifications are poorly characterised. Here we describe the basics of a global model for a capacitively coupled asymmetric parallel plate radiofrequency plasma system routinely used to produce plasma polymers. An analytical global model was developed for argon, for which cross-sections are known, at a constant pressure of 1 Pa, and includes an electrical model and a power balance. The main parameters of interest were ion flux and self-bias voltages. The argon modelling results were then compared to experimental results for a range of operating gases (argon, oxygen, amines, acids, alcohols, ethers, siloxanes) including both saturated and unsaturated compounds with molecular weights ranging from 40 to 162 g · mol−1, for different inter-electrode separations and from 2 to 50 W using an Impedans OctIV probe. Importantly, it is shown that the RF power transfer efficiency is dependent on the gas. The results show that the argon model results can be used to predict the plasma parameters for other gases when the RF power transfer efficiency is taken into account.

Cold atmospheric pressure plasma jets (plasma) operated in ambient air provide a rich source of reactive oxygen and nitrogen species (RONS), which are known to influence biological processes important in disease. In the plasma treatment of diseased tissue such as subcutaneous cancer tumors, plasma RONS need to first traverse an interface between the plasma-skin surface and second be transported to millimeter depths in order to reach deep-seated diseased cells. However, the mechanisms in the plasma generation of RONS within soft tissues are not understood. In this study, we track the plasma jet delivery of RONS into a tissue model target and we delineate two processes: Through target delivery of RONS generated (primarily) in the plasma jet and in situ RONS generation by UV photolysis within the target. We demonstrate that UV photolysis promotes the rapid generation of RONS in the tissue model target's surface after which the RONS are transported to millimeter depths via a slower molecular process. Our results imply that the flux of UV photons from plasma jets is important for delivering RONS through seemingly impenetrable barriers such as skin. The findings have implications not only in treatments of living tissues but also in the functionalization of soft hydrated biomaterials such as hydrogels and extracellular matrix derived tissue scaffolds. Refereed/Peer-reviewed

This paper reports a method for producing protein arrays on antifouling PEO-like coatings using a “non-contact” atmospheric pressure helium microplasma array. ToF-SIMS characterization of PEO-like coatings after short plasma treatment revealed the antifouling plasma polymer was largely modified/removed within the microplasma-exposed regions. Incubation of microplasma-patterned PEO-like coatings with a fluorescently labeled streptavidin resulted in selective and uniform protein adsorption within the modified regions. A protein sensing application was demonstrated where a target red fluorescent protein (RFP) was only captured on the anti-RFP functionalized regions. This indicates the adsorbed antibody protein on the microplasma-treated PEO-like regions retained its bioactivity.

Growth factors (GFs) play an important role in biological processes such as cell proliferation, differentiation and angiogenesis. GFs are known to bind to glycosaminoglycans (GAGs) in the extracellular matrix, aiding projection from degradation and pooling the GFs for quick response to biological stimuli in vivo. GFs are typically expensive and have a relatively short half-life in culture media, requiring regular replenishment. Here the cooperative binding of GF to a plasma polymerised surface decorated with heparin, and the subsequent culture of primary human dermal fibroblasts (HDFs) is investigated. A simple one-step technique suitable for coating a wide range of different substrates was utilised. Substrates such as culture-ware, scaffolds, bandages and devices for implantation could be coated. The modified surface was compared to standard culture techniques of addition of GF to the media. Results demonstrate that surface bound heparin and FGF-2 have a greater effect on cell proliferation especially at reduced serum concentrations. With performance equivalent to supplementing the media achieved at as little as 1% total FGF-2 added. The protective cooperative effect of FGF-2-GAG bound to modified surface at the interface could lead to reduced costs by reduction of FGF-2 required. Furthermore, for applications such as chronic non-healing wounds, bandages can be produced modified by plasma and decorated with GAGs that could utilise and protect important GFs. This would effectively re-introduce important biomolecules which are protected by GAG binding into a harsh environment. Refereed/Peer-reviewed

An oxygen plasma treatment was employed to modify the surface of carbon electrodes used in capacitive deionization (CDI). X-ray photoelectron spectroscopy analysis of samples showed that oxygen plasma is mainly attaching oxygenated groups on the PTFE binder used in these electrodes. By functionalizing the binder it can increase the hydrophilicity of the electrode surface and increase the available specific surface area. 2.5 min of plasma treatment resulted in the largest improvement of CDI performance of electrodes. Thermodynamic study of CDI performance showed that the modified electrodes followed Langmuir and Freundlich isotherms resulting from the increased interaction between the enhanced electrodes and water. The kinetic study showed that the CDI process followed a pseudo-first order adsorption kinetics. The calculated adsorption rate constants suggested that plasma modification can accelerate ion adsorption of electrodes. Refereed/Peer-reviewed

This multi-centre investigation explores the variability that results from using the power/flow rate ratio (W/F) to describe plasma treatment and plasma polymerization processes. Results from fourteen reactors of different design and spread across ten laboratories, showed that the chemistry of the treated and deposited polymer/plasma polymer films is highly variable between reactor systems, and that there was no clear pattern linking these variations to other properties of the reactor systems (e.g. pressure, volume, electrode configuration). Although W/FM provides a useful rule-of-thumb for process optimization within a single system, it does not provide sufficient information to enable the same plasma polymer to be produced on a different system.

We report a systematic study of the plasma polymerization of ethyl α-bromoisobutyrate (EBIB) to produce thin film coatings capable of serving as ATRP initiation surfaces, for which they must contain α-bromoisobutyryl functional groups. In the deposition of polymeric coatings by plasma polymerization there generally occurs considerable fragmentation of precursor(“monomer”) molecules in the plasma; and the retention of larger structural elements is challenging, particularly when they are inherently chemically labile. Empirical principles such as low plasma power and low pressure are usually utilized. However, we show that the α-bromoisobutyryl structural moiety is labile in a plasma gas phase and in low pressure plasma conditions, below the collisional threshold, there is little retention. At higher pressure, in contrast, fragmentation of this structural motif appears to be reduced substantially, and coatings useful for ATRP initiation were obtained. Mass spectrometry analysis of the composition of the plasma phase revealed that the desired structural moiety can be retained through the plasma, if the plasma conditions are steered toward ions of the precursor molecule. Whereas at low pressure the plasma polymer assembles mainly from various neutral (radical) fragments, at higher pressure the deposition occurs from hyperthermal ions, among which the protonated intactmolecular ion is the most abundant. At higher pressure, a substantial population of ions has low kinetic energy, leading to “soft landing” and thus less fragmentation. This study demonstrates that relatively complex structural motifs in precursor molecule scan be retained in plasma polymerization if the chemical and physical processes occurring in the plasma phase are elucidated and controlled such that desirable larger structural elements play a key role in the film deposition. Refereed/Peer-reviewed

A challenge in cancer therapy is the destruction of tumours, where there is the potential issue of cancer cells residing within hypoxic tissue. The concept of hypoxic regions within tumours dates back to 1909 and it has long been suspected that under low oxygen tension, cells are “afforded” radiation protection. It has been shown many decades ago, that raising the concentration of oxygen in tissues can significantly improve the outcomes in radiotherapy. For example, in 1953, a meta-analysis of 83 randomised trials showed a clear benefit from raising tissue oxygen tension during radiation therapy, with the clearest benefits seen in cancers of neck and head [1]. However, there are only a limited number of ways to raise oxygen tension in tissues, which include breathing pure oxygen at or above standard temperature and pressure, or hypoxic modification by the means of an administered drug (e.g. nimorazole) [2, 3, 4]. Recently, we (and other research groups) have shown that cold atmospheric plasma jets not only readily deliver reactive oxygen and nitrogen species (RONS) into tissue, but concomitantly raise the oxygen tension in tissue. Combined RONS and oxygen delivery, may significantly elevate oxidative stress in cancer cells, resulting in destruction of these cells within hypoxic tumours. In this presentation, I will provide a brief historical overview of research on the modification of hypoxia in cancers; I will then discuss results that have shown how plasma jets can be used to treat hypoxia in tumours (through delivery of RONS and oxygen into tissues). I will also discuss the potential opportunities, challenges and limitations of the plasma technology for treatment of hypoxic cancer tumours.

The reduced pressure synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) with sheet-like morphology has been achieved with the introduction of an amphiphilic triblock copolymer into the oxidant thin film. Addition of the copolymer not only results in an oxidant thin film which remains liquid-like under reduced pressure but also induces structured growth during film formation. PEDOT films were polymerized using the vacuum vapor phase polymerization (VPP) technique, in which we show that maintaining a liquid-like state for the oxidant is essential. The resulting conductivity is equivalent to commercially available indium tin oxide (ITO) with concomitant optical transmission values. PEDOT films can be produced with a variety of thicknesses across a range of substrate materials from plastics to metals to ceramics, with sheet resistances down to 45 Ω/□ (ca. 3400 S·cm−1), and transparency in the visible spectrum of >80% at 65 nm thickness. This compares favorably to ITO and its currently touted replacements. Refereed/Peer-reviewed

Subretinal transplantation of functioning retinal pigment epithelial (RPE) cells grown on a synthetic substrate is a potential treatment for age-related macular degeneration (AMD), a common cause of irreversible vision loss in developed countries. Plasma polymers give the opportunity to tailor the surface chemistry of the artificial substrate whilst maintaining the bulk properties. In this study, plasma polymers with different functionalities were investigated in terms of their effect on RPE attachment and growth. Plasma polymers of acrylic acid (AC), allyl amine (AM) and allyl alcohol (AL) were fabricated and characterised using X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Octadiene (OD) hydrocarbon films and tissue culture polystyrene were used as controls. Wettability varied from hydrophobic OD to relatively hydrophilic AC. XPS demonstrated four very different surfaces with the expected functionalities. Attachment, proliferation and morphological examination of an RPE cell line and primary RPE cells were investigated. Both cell types grew on all surfaces, with the exception of OD, although the proliferation rate of primary cells was low. Good epithelial morphology was also demonstrated. Plasma polymerised films show potential as cell carrier surfaces for RPE cells in the treatment of AMD. Refereed/Peer-reviewed

The control of cell-material interactions is the key to a broad range of biomedical interactions. Gradient surfaces have recently been established as tools allowing the high-throughput screening and optimization of these interactions. In this paper, we show that plasma polymer gradients can reveal the subtle influence of surface chemistry on embryonic stem cell behavior and probe the mechanisms by which this occurs. Lateral gradients of surface chemistry were generated by plasma polymerization of diethylene glycol dimethyl ether on top of a substrate coated with an acrylic acid plasma polymer using a tilted slide as a mask. Gradient surfaces were characterized by X-ray photoelectron spectroscopy, infrared microscopy mapping and profilometry. By changing the plasma polymerization time, the gradient profile could be easily manipulated. To demonstrate the utility of these surfaces for the screening of cell-material interactions, we studied the response of mouse embryonic stem (ES) cells to these gradients and compared the performance of different plasma polymerization times during gradient fabrication. We observed a strong correlation between surface chemistry and cell attachment, colony size and retention of stem cell markers. Cell adhesion and colony formation showed striking differences on gradients with different plasma polymer deposition times. Deposition time influenced the depth of the plasma film deposited and the relative position of surface functional group density on the substrate, but not the range of plasma-generated species. Refereed/Peer-reviewed

Dr. S. A. Al-Bataineh, E. J. Szili, P. J. Gruner, R. D. Short, D. A. Steele Mawson Institute, University of South Australia, Mawson Lakes, SA 5095, Australia Fax: þ61 (0)8 8302 5689; E-mail: sameer.al-bataineh@unisa.edu.au C. Priest, H. J. Griesser Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia N. H. Voelcker Flinders University, School of Chemical and Physical Sciences, Bedford Park, SA 5042, Australia Current address: Mawson Institute, University of South Australia, Mawson Lakes, SA 5095, Australia 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 250mm in diameter and separated by 500mm) 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.

Single-walled carbon nanotubes (SWCNTs) and polyaniline (PANI) composites with different proportions of SWCNTs were synthesized by in situ polymerization. The resultant composites were characterized by Fourier TransformInfrared (FTIR) spectroscopy and theirmorphology was studied by transmission electronmicroscopy (TEM). Their specific surface areas were determined by N2 adsorption/desorption tests and the mesoporous structure of the composites was analyzed using the Barrett-Joyner-Halenda (BJH) method. A band shift in the FTIR spectrum indicates a strong interaction between PANI and SWCNTs. The mesopore volume was increased by introducing PANI into the SWCNTs. Cyclic voltammetry (CV) was carried out to study their electrochemical properties. The SWCNT/PANI composites obtained exhibited reversible electrochemical and faster ion transport properties, even in a neutral aqueous environment. This is probably due to /pi - /pi interaction between the PANI backbone and the graphite-like structure of carbon nanotubes. Finally, a capacitive deionization (CDI) test was conducted in a batch mode bench-scale cell. The electrodes made from SWCNT/PANI composites showed a higher ion electrosorption capacity than those made from SWCNTs alone and the composite electrodes can be easily regenerated, indicating excellent recyclability. Refereed/Peer-reviewed

Surface density gradients of streptavidin (SAV) were created on solid surfaces and demonstrated functionality as a bioconjugation platform. The surface density of immobilized streptavidin steadily increased in one dimension from 0 to 235 ng cm−2 over a distance of 10 mm. The density of coupled protein was controlled by its immobilization onto a polymer surface bearing a gradient of aldehyde group density, onto which SAV was covalently linked using spontaneous imine bond formation between surface aldehyde functional groups and primary amine groups on the protein. As a control, human serum albumin was immobilized in the same manner. The gradient density of aldehyde groups was created using a method of simultaneous plasma copolymerization of ethanol and propionaldehyde. Control over the surface density of aldehyde groups was achieved by manipulating the flow rates of these vapors while moving a mask across substrates during plasma discharge. Immobilized SAV was able to bind biotinylated probes, indicating that the protein retained its functionality after being immobilized. This plasma polymerization technique conveniently allows virtually any substrate to be equipped with tunable protein gradients and provides a widely applicable method for bioconjugation to study effects arising from controllable surface densities of proteins. Refereed/Peer-reviewed

There is considerable interest in the spatial control of plasma polymerisation such as to produce sub-millimetre features with high fidelity, versatility and reproducibility, for example, for arrays or writable specific patterns. This study reports the design of a microcavity plasma device and a method for its fabrication, with the device comprising a single cavity of � 400 mm diameter. The device can be fabricated within a short time and at low cost in a standard laboratory, with no need for a clean room facility. The device is capable of multiple operations in plasma polymerisation mode. XPS imaging combined with small-spot ROI analysis showed localised thin film deposition of an acrylic acid plasma polymer with good retention of carboxylate groups from the monomer. The device can be configured with flexibility and addressedforplasma polymer writing of complex patterns.

Vacuum vapour phase polymerisation (V-VPP) was used to synthesis high conductivity poly(3,4-ethylenedioxythiophene) (PEDOT) on glycol/oxidant coated substrates. Thermo gravimetric analysis (TGA) indicated that up to 15 wt.-% glycol was able to complex with the Fe(Tos)3 oxidant solution and that this loading produced PEDOT with the highest conductivity, namely 1487 S cm-1. Further addition beyond 15 wt.-% resulted in an unbounded excess of glycol which appeared to inhibit the polymerisation process, resulting in reduced doping levels and conductivity. XPS data showed that glycol was incorporated within the PEDOT matrix after polymer synthesis, and that this may contribute to the high conductivity achieved using the V-VPP technique. XPS data also confirmed that the highest conductivity coincided with the highest recorded doping level, d = 28.4%. Refereed/Peer-reviewed

The manner by which plasma polymers grow in the very first stages of deposition is a topic which has been almost overlooked. We show using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) that in the early stages of plasma deposition there are significant differences in the way plasma polymers grow from two amine-containing compounds onto silicon wafers. By AFM it is shown that films grown from n-heptylamine (HA) initially show 'island-like' growth before a continuous smooth film is formed. In contrast, films from allylamine grow smoothly from the very earliest stages. XPS data show substantial differences of plasma polymer chemistry in close proximity to the silicon surface manifested in the formation of NH + 3 and NO x species which are more abundant in films of HA. We present a possible explanation for these results based upon post-plasma surface phenomena in the case of HA.

Selected ion flow tube mass spectrometry (SIFT-MS) and proton transfer reaction mass spectrometry (PTR-MS) are used to explore ion-molecule reactions in low temperature and pressure plasmas of hexamethyldisiloxane. These techniques shed new light on possible reactions taking place within such plasma environments and validate many of the reaction pathways previously advocated based upon plasma-phase MS. However, SIFT-MS and PTR-MS results draw attention to the possible importance of the H 3 O + ion in initiating the formation of oligomeric ions, a point previously missed in plasma-MS studies.

We report a novel, versatile method for generating number density gradients of individual gold (Au) and silver (Ag) nanoparticles by a two-step method. First, a chemical gradient of amine surface functional groups is deposited by plasma copolymerization. Second, a density gradient of nanoparticles is formed by the immersion of the chemical gradient in solutions of nanoparticles. Chemical characterization by X-ray photoelectron spectroscopy and morphological analysis by atomic force microscopy shows that nanoparticle density closely follows the change in nitrogen surface concentration across the gradients. We also demonstrate that it is possible to control the slope of the gradients by using nanoparticle solutions of different concentrations. Important for technological and research applications, this method can be used with nanoparticles of various sizes and different materials. In addition, the use of plasma deposition allows such gradients to be generated on any type of substrate. Refereed/Peer-reviewed

This report addresses the challenge of using microplasma jets to modify surfaces with precise chemistries over exact areas. We explore how different treatment conditions (time and distance) and operational parameters (voltage and frequency) influence the spatial modification of a model polymer (polystyrene) in terms of size, degree and nature of the surface modification. At 4.5 kV pk―pk , the visible glow of the microplasma jet was confined to within the capillary tube (tube inner diameter = 0.7 mm) and resulted in a narrower area of treatment compared to when the visible glow extended 3 mm into the ambient atmosphere at 8.0 kV pk―pk . Short treatment times of 15 s or less, longer capillary tube-sample separation distances of several mm and lower frequencies of 5―10 kHz were also required to reduce expansion of treatment. Low concentrations of carboxylates (

Using perhaps the most comprehensive data set for the plasma polymerisation of acrylic acid (AA) currently available, the hypothesis that different plasma regimes for AA may be revealed by plotting the deposition rate normalised by flow rate (Rm/F) against the composite parameter of (W/F) 1, where W is the plasma power, is explored. The analyses possibly support the view that an apparent activation energy Ea can be obtained from the plot at low W, but based on other data (notably, mass spectrometry and ion flux) the processes that are on-going in this regime are interpreted differently. Refereed/Peer-reviewed

A micro-cavity discharge array (2500 cavities of 50 µm2 size) was operated in neon at atmospheric pressure to modify polystyrene (PS), fluorinated ethylene–propylene co-polymer (FEP) and polytetrafluoroethylene(PTFE) polymer surfaces and, with the injection of a polymerisable monomer (acrylic acid), to deposit patterned, thin polymeric coatings. The aim of this study was to investigate the utility of these micro-discharge sources in the surface treatment of polymers and for the patterned deposition of polymeric material. The influence of the driving frequency, treatment time and sample-array distance on polymer surface treatment was investigated. X-ray photoelectron spectroscopy (XPS) was used to explore the surface chemistry of the treated polymer surfaces and of the polymer deposits. It was found that increasing themicro-cavity discharge source driving frequency and/or treatment time and decreasing the sample-arraydistance all led to a significant decrease in surface energy as determined by water contact angle measurements. For a period of time, post treatment surface hydrophilicity degraded due to the well known“ageing effect” but stabilized after two days. Finally, it was demonstrated that the device could be used forthe localized, array sized, deposition of acrylic acid. High resolution XPS analysis of the deposit registered a C1s spectra typical of poly(acrylic acid) with a prominent peak centred at approximately 289.3 eV indicating a relatively high level retention of the original monomer functionality. These results demonstrate that microcavity discharges, operated at or near atmospheric pressure, can be used to both modify and locally depositpolymeric material. Refereed/Peer-reviewed

The interactions of glycosaminoglycans (GAGs) with proteins underlie a wide range of important biological processes. However, the study of such binding reactions has been hampered by the lack of a simple frontline analysis technique. Previously, we have reported that cold plasma polymerization can be used to coat microtiter plate surfaces with allyl amine to which GAGs (e.g., heparin) can be noncovalently immobilized retaining their ability to interact with proteins. Here, we have assessed the capabilities of surface coats derived from different ratios of allyl amine and octadiene (100:0 to 0:100) to support the binding of diverse GAGs (e.g., chondroitin-4-sulfate, dermatan sulfate, heparin preparations, and hyaluronan) in a functionally active state. The Link module from TSG-6 was used as a probe to determine the level of functional binding because of its broad (and unique) specificity for both sulfated and nonsulfated GAGs. All of the GAGs tested could bind this domain following their immobilization, although there were clear differences in their protein-binding activities depending on the surface chemistry to which they were adsorbed. On the basis of these experiments, 100% allyl amine was chosen for the generation of a microtiter plate-based "sugar array"; X-ray photoelectron spectroscopy revealed that similar relative amounts of chondroitin-4-sulfate, dermatan sulfate, and heparin (including two selectively de-sulfated derivatives) were immobilized onto this surface. Analysis of four unrelated proteins (i.e., TSG-6, complement factor H, fibrillin-1, and versican) illustrated the utility of this array to determine the GAG-binding profile and specificity for a particular target protein.