Search

The influence of the liquid composition on the chemical and morphological properties of copper-based nanostructures synthesized by a non-equilibrium atmospheric plasma treatment is investigated and discussed. The synthesis approach is simple and environmentally friendly, employs a non-equilibrium nanopulsed atmospheric pressure plasma jet as a contactless cathode and a Cu foil as immersed anode. The process was studied using four distinct electrolyte solutions composed of distilled water and either NaCl + NaOH, NaCl only or NaOH only at two different concentrations, without the addition of any copper salts. CuO crystalline structures with limited impurities (e.g. Cu and Cu(OH)2 phases) were produced from NaCl + NaOH containing solutions, mainly CuO and CuCl2 structures were synthesized in the electrolyte solution containing only NaCl and no synthesis occurred in solutions containing only NaOH. Both aggregated and dispersed nanostructures were produced in the NaCl + NaOH and NaCl containing solutions. Reaction pathways leading to the formation of the nanostructures are proposed and discussed.

Amine/amide-rich coatings possessing good biocompatibility are of high interest in the medical field. A new type of coatings with high content of NH groups has been prepared in a single step plasma process. Deposition is performed by atmospheric pressure plasma which is coupled to aerosol injection of liquid precursor. The method is applied for the polymerization of N,N'-methylenebisacrylamide precursor. The surface analyses, including X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR), show polymerization of the precursor with formation of amide-rich coatings with up to 8 at.% of N-containing groups. The coatings are stable in phosphate buffer saline (PBS) solution and characterized by improved biocompatibility to STEM cells.

The aim of this work was to evaluate cold atmospheric plasma bactericide activity towards biofilm formation on soft reline oral palatal obturators. Plasma was generated using two dielectric barrier discharge and tested against the oral biofilm formers Streptococcus mutans and Aggregatibacter actinomycetemcomitans. Relines were either plasma treated before being infected with 24 h biofilm, or infected with 90 min (early) or 24 h (mature) biofilm prior to be plasma treated for 30, 60, or 120 s. Bacteria numbers and viability were evaluated by Colonies Forming Units counts (CFU) and quantitative colorimetric metabolic 2,3-bis (2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenyl amino) carbonyl]-2H-tetrazolium hydroxide assay (XTT). cytocompatibility was assayed towards human primary fibroblasts and keratinocytes cultivated on plasma-treated specimens by colorimetric metabolic 3-(4,5-Dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay and light microscopy. Results demonstrated that both plasma sources were effective. Plasma treatment of sterile reline affected bacterial adhesion, reducing CFU number and viability by 2 logs and by 50%, in comparison with untreated controls (p < 0.05). Plasma efficacy was marked against early biofilm: after 120 s, CFUs were reduced by 3 logs, and viability decreased by about 60% (p < 0.05). Significant results were also observed for mature biofilm: CFUs and viability were reduced by approximately 2 logs and 40% (p < 0.05), after 120 s exposure. Lastly, MTT did not show any toxic effect on human cells. Thus, plasma could represent a very promising skill for soft reline shutters decontamination.

A single step process for the deposition of nanocomposite coatings with silver nanoparticles (AgNPs) embedded in a plasma-polymerized polyacrylic acid (pPAA) matrix and performed using a non-equilibrium atmospheric pressure plasma jet is presented. Acrylic acid (AA) and AgNPs dispersed in ethanol (EtOH) are used as precursors and are separately injected in the plasma region directly; Ar is used as plasma gas and also as carrier gas for both precursors. Scanning electron microscopy (SEM) and ATR-FTIR analysis show the deposition of a micrometric pPAA coating on the polyethylene (PE) film used as substrate; AgNPs embedded in the polymeric matrix are visible in SEM pictures and their presence is confirmed by XPS and EDS analysis. X-ray photoelectron spectroscopy (XPS) also highlights a high retention of carboxylic groups in the pPAA chemical structure and the surface oxidation of AgNPs. Preliminary results of the antibacterial activity of the co-deposited coatings are presented.

In this study, atmospheric pressure non-thermal plasma treatment of electrospun poly(L-lactic acid) scaffolds is used to improve scaffold hydrophilicity and to introduce carboxyl groups on scaffold surface. Thermo-mechanical properties, morphology, hydrophilicity, and water uptake of the plasma-treated scaffolds are studied. The amount of carboxyl functional groups on the scaffold surface is evaluated using fluorescein isothiocyanate conjugation and microdensitometry. The effect of plasma treatment on mouse embryonic fibroblast morphology is assessed through image analysis. Results show an enhancement of scaffold biocompatibility, demonstrating that atmospheric plasma technology is a flexible process that can be integrated in “in-line” procedures of biomaterial fabrication and functionalization.

Electrospun gelatin nanofibers attract great interest as a natural biomaterial for cartilage and tendon repair despite their high solubility in aqueous solution, which makes them also difficult to crosslink by means of chemical agents. In this work, we explore the efficiency of non-equilibrium atmospheric pressure plasma in stabilizing gelatin nanofibers. We demonstrate that plasma represents an innovative, easy and environmentally friendly approach to successfully crosslink gelatin electrospun mats directly in the solid state. Plasma treated gelatin mats display increased structural stability and excellent retention of fibrous morphology after immersion in aqueous solution. This method can be successfully applied to induce crosslinking both in pure gelatin and genipin-containing gelatin electrospun nanofibers, the latter requiring an even shorter plasma exposure time. A complete characterization of the crosslinked nanofibres, including mechanical properties, morphological observations, stability in physiological solution and structural modifications, has been carried out in order to get insights on the occurring reactions triggered by plasma.

High-speed and Schlieren imaging have been used to visualize ignition transients, discharge behavior and flow fields of a plasma device integrating a low-power inductively coupled plasma torch, generating a high temperature thermal plasma, with a quenching device, able to cool the gaseous effluent down to biocompatible temperatures for effective use in biomedical applications.

Intense and energetic atmospheric plasma was achieved by jet-to-jet coupling using an array of plasma jets arranged in an axisymmetric structure. To highlight the effects of pulse repetition frequency, peak voltage and mass flow rate on the transition from a coupled mode to an uncoupled one, qualitative results coming from iCCD imaging of a nanopulsed Gatling machine gun-like plasma source will be shown. Moreover, results on surface modifications and bacterial inactivation will be presented.

Water soluble polymers may display interesting properties (e.g. thermal, mechanical, biocompatibility, etc.) that make them useful in different fields where, however, the stability of the material in a aqueous environment is often required. Chemical modification of the polymer molecular chains are commonly applied to introduce interchain bridging (crosslinks) that impart water resistance to the material. However, these methods are time-consuming and often make use of toxic chemical agents. Recently, it has been reported that non-equilibrium plasma treatments, commonly used to modify the chemical structure and the reactivity of polymer surfaces, are able to induce formation of radicals, which may recombine, producing unsaturation and crosslinking1. In this work we focus on the use of atmospheric pressure non-equilibrium plasmas to crosslink pullulan. Pullulan is a water soluble polysaccharide whose biodegradability, biocompatibility, low oxygen permeability and high temperature resistance make it very attractive for food technology, pharmaceutical application, environmental remediation and filtration. Results will be presented concerning the treatment of pullulan in form of electrospun mat with a Dielectric Barrier Discharge plasma source, inserted in a properly designed chamber, operated in environment air at atmospheric pressure and driven by a HV amplifier connected to a function generator with a microsecond rise time. In order to evaluate the effects of electrical parameters and treatment time on the degree of crosslinking in pullulan, several operating conditions were investigated. The crosslinking degree of plasma treated electrospun samples was evaluated: (i) from the capability of the pullulan fibers to preserve their morphology upon water exposure; (ii) through weight loss and swelling degree measurements; (iii) by monitoring the change of mechanical properties of electrospun mat after plasma treatment.

The structure, fluid-dynamic behavior, temperature, and radiation emission of a cold atmospheric pressure plasma jet driven by high-voltage pulses with rise time and duration of a few nanoseconds have been investigated. Intensified charge-coupled device (iCCD) imaging revealed that the discharge starts when voltage values of 5–10 kV are reached on the rising front of the applied voltage pulse; the discharge then propagates downstream the source outlet with a velocity around $10^{7}$ – $10^{8}$ cm/s. Light emission was observed to increase and decrease periodically and repetitively during discharge propagation. The structure of the plasma plume presents a single front or either several branched subfronts, depending on the operating conditions; merging results of investigations by means of Schlieren and iCCD imaging suggests that branching of the discharge front occurs in spatial regions where the flow is turbulent. By means of optical emission spectroscopy, discharge emission was observed in the ultraviolet-visible (UV-VIS) spectral range (N2, N2+, OH, and NO emission bands); total UV irradiance was lower than 1 $\mu $ W/ $\mathrm{cm}^{2}$ even at short distances from the device outlet (

Summary form only given.Material science applied to regenerative medicine and tissue engineering study the achievement of biocompatible artificial tissues to improve, self-repair or favour cellular therapies. Various studies prove plasma ability to modify polymeric scaffold surface, with an improvement of hydrophilicity and surface roughness demonstrated by a reduction of contact angle and by an increase of surface energy without altering bulk properties. Furthermore, it was demonstrated that cell cultures on plasma modified scaffolds display better proliferation and viability compared to pristine materials. In this work we focus on the use of atmospheric pressure non-thermal plasma for surface modification of electrospun poly(L-lactic acid) (PLLA) non-woven mats. The electrospinning technology allows to fabricate scaffolds of polymeric materials with highly porous structure, interconnected pores and large specific surface area, that mimic extracellular matrix (ECM). In this work results will be presented concerning the process of exposure of electrospun scaffolds to the plasma region generated by three different plasma sources operated at atmospheric pressure: a floating electrode dielectric barrier discharge (FE-DBD), a linear corona discharge and a DBD roller. A high voltage generator capable of producing pulses with a rise rate in the order of some kV/ns has been used. All the sources are easily scaled-up in the frame of a “large area treatment” approach. Plasma sources characterization has been carried out through a wide set of measurements, changing operating conditions, geometry and plasma gas composition, as the fundamental stage in a multi-step approach for process optimization. In this work, results on the effect of plasma treatment on morphology, thermo-mechanical and surface properties of PLLA electrospun nanofibrous mats will be presented. Results for the introduction of COOH functional group on PLLA electrospun scaffold and for the proliferation of rat embryonic stem cells (RESCs) grown on plasma treated and untreated PLLA electrospun scaffolds will be presented and discussed.

Summary form only given. In recent years, increasing efforts have been dedicated to atmospheric pressure non-thermal plasma (NTP) modification of biomaterials to promote cell adhesion and proliferation; while low-pressure plasma is already an established technology in this field, NTP are raising interest because of their easy handling, effectiveness and low operational costs. Moreover, the possibility of locally modifying the surface, creating patterns to induce controlled cell growth, would be of great interest for some application of these materials. In this work NTP local modification of borosilicate glass cell culture coverslips (size 24x24 mm) has been performed with three non-equilibrium atmospheric pressure plasma sources: a single electrode plasma jet, a dielectric barrier discharge (DBD), both connected to a high voltage pulse generator, and a commercial plasma jet (kINPen 09, Neoplas Tools GmbH); surface wettability before and after plasma treatment has been studied using water contact angle (WCA) measurement. To analyze plasma treatment localization with the two different plasma jets, four regions (quadrants) were identified onto each slide and the plasma discharge was oriented towards only one of these. Results suggest a decrease of WCA in the region directly exposed to the plasma jet, while the remaining area doesn't show any significant variation of surface wettability. With these sources the localization efficiency is strongly influenced by the distance between the source outlet and the substrate: increasing the stand-off results in a more localized surface modification. While in the case of the single electrode Ar plasma jet a relevant reduction of WCA was obtained only in the region exposed to the jet even for very short treatment time, with the kINPen 09, operated in Ar, there was no significant difference between the quadrant exposed to the plasma jet and the remaining area. Finally, results for the DBD treatment are presented: since the DBD high voltage electrode was as large as the whole glass slide, treatment localization was obtained by employing as grounded counter electrode a metal layer (12x12 mm, a quarter of the glass slide) placed below one of the quadrants. As a result, plasma generation was limited to the area of the glass above the grounded counter electrode and only in this region a drastic WCA reduction was measured, while no significant variation was observed in the remaining quadrants. Results suggest the possibility to realize patterned modification of large surfaces using DBD sources with suitably shaped grounded counter.

Atmospheric pressure plasmas have been developed in the last decades for many material treatment applications such as cleaning and activation of surfaces, interaction with in-vivo and in vitro tissues and, as such, they play an increasing role in disinfection and sterilization of surfaces. Heat sensitive polymers can be plasma treated with the final aim of microbial inactivation: given for granted such a capability for many different atmospheric pressure plasma sources, in this work, we focus on the investigation of the effectiveness of the treatment of a polyethylene (PE) polymer foil commonly used for pharmaceutical packaging by means of a Dielectric Barrier Discharge (DBD) operated on a “large area” at atmospheric pressure in ambient air. For effectiveness of the treatment we considered the uniformity of the variation of water contact angle (WC) induced by the plasma on different positions of the treated area (for example, 160×300 mm) and the capability not to affect negatively the properties of the plasma treated packaging material in terms of weldability (for example, hot plate weldability). The surface of the polymer foil has been characterized by measuring the variation of water contact angle (WCA) in different position on the treated sample; Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) has been used to investigate the surface oxidation of the treated samples; moreover, polymer weldability after plasma treatment has been tested on a packaging machine that includes a contact hot plate. This procedure allowed correlating surface oxidation with polymer weldability and with plasma treatment parameters. Results show that it is possibile to select geometrical (DBD gap width; for example, 2mm) and generator operating conditions (for example, 12kV, 100Hz) suitable to obtain uniform change in WCA (for example from 98.2° to 55°) while maintaining good weldability for the treated material. Aging of the treated polymer for what concerns WCA has also been considered, together with treatment time compatible with the final industrial on-line treatment, forming and welding process.

The effect of an atmospheric pressure non-equilibrium plasma on human mesenchymal stem cells was investigated. A dielectric barrier discharge non-equilibrium plasma source driven by two different high-voltage pulsed generators was used and cell survival, senescence, proliferation, and differentiation were evaluated. Cells deprived of the culture medium and treated with nanosecond pulsed plasma showed a higher mortality rate, while higher survival and retention of proliferation were observed in cells treated with microsecond pulsed plasma in the presence of the culture medium. While a few treated cells showed the hallmarks of senescence, unexpected delayed apoptosis ensued in cells exposed to plasma-treated medium. The plasma treatment did not change the expression of OCT4, a marker of mesenchymal stem cell differentiation.

In the present study, the comparison between a conventional wet-chemical method and a non-equilibrium atmospheric pressure plasma process for the conjugation of biomolecules on the surface of poly(L-lactic acid) (PLLA) electrospun fibers is reported. Physico-chemical and morphological characteristics of chemically and plasma functionalized mats are studied and compared with those of pristine mats. The efficiency in biomolecules immobilization is assessed by the covalent conjugation of an antibody (anti-CD10) on the functionalized PLLA fibers. The achieved results highlight that the proposed plasma process enables antibodies to be successfully immobilized on the surface of PLLA fibers, demonstrating that non-equilibrium atmospheric pressure plasma can be an effective, highly flexible and environmentally friendly alternative to the still widely employed wet-chemical methods for the conjugation of biomolecules onto biomaterials.