A new strategy to prevent biofilm and clot formation in medical devices: The use of atmospheric non-thermal plasma assisted deposition of silver-based nanostructured coatings.

In industrialized countries, health care associated infections, the fourth leading cause of disease, are a major health issue. At least half of all cases of nosocomial infections are associated with medical devices. Antibacterial coatings arise as an important approach to restrict the nosocomial infection rate without side effects and the development of antibiotic resistance. Beside nosocomial infections, clot formation affects cardiovascular medical devices and central venous catheters implants. In order to reduce and prevent such infection, we develop a plasma-assisted process for the deposition of nanostructured functional coatings on flat substrates and mini catheters. Silver nanoparticles (Ag NPs) are synthesized exploiting in-flight plasma-droplet reactions and are embedded in an organic coating deposited through hexamethyldisiloxane (HMDSO) plasma assisted polymerization. Coating stability upon liquid immersion and ethylene oxide (EtO) sterilization is assessed through chemical and morphological analysis carried out by means of Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In the perspective of future clinical application, an in vitro analysis of anti-biofilm effect has been done. Moreover, we employed a murine model of catheter-associated infection which further highlighted the performance of Ag nanostructured films in counteract biofilm formation. The anti-clot performances coupled by haemo- and cytocompatibility assays have also been performed.

Plasma activated water triggers plant defence responses.

Nowadays, one of the main challenges is moving towards an eco-sustainable agriculture, able to preserve the food production through a reduced use of pesticides. Current global food sustenance by intensive agriculture is mainly based on economic crop monocultures and drastically reduces the biodiversity, increasing the yield losses due to the presence of biotic and abiotic stresses. A technology based on plasma activated water (PAW), characterized by the presence in liquid of reactive oxygen and nitrogen species, was tested to try to ensure yield stability also enhancing the plant resistance responses and to promote an eco-sustainable management of plant diseases. In PAW-treated micropropagated periwinkle shoots, periwinkle and grapevine plants, qRT-PCR and small RNAs high-throughput sequencing were used to analyse the differential expression of genes involved in the major plant defence pathways. The results indicate that PAW treatment enhances the plant defence responses and provide an encouraging framework for future applications in plant disease management programs.

Enhanced Electrospinning of Active Organic Fibers by Plasma Treatment on Conjugated Polymer Solutions.

Realizing active, light-emitting fibers made of conjugated polymers by the electrospinning method is generally challenging. Electrospinning of plasma-treated conjugated polymer solutions is here developed for the production of light-emitting microfibers and nanofibers. Active fibers from conjugated polymer solutions rapidly processed by a cold atmospheric argon plasma are electrospun in an effective way, and they show a smoother surface and bead-less morphology, as well as preserved optical properties in terms of absorption, emission, and photoluminescence quantum yield. In addition, the polarization of emitted light and more notably photon waveguiding along the length of individual fibers are remarkably enhanced by electrospinning plasma-treated solutions. These properties come from a synergetic combination of favorable intermolecular coupling in the solutions, increased order of macromolecules on the nanoscale, and resulting fiber morphology. Such findings make the coupling of the electrospinning method and cold atmospheric plasma processing on conjugated polymer solutions a highly promising and possibly general route to generate light-emitting and conductive micro- and nanostructures for organic photonics and electronics.

Plasma-activated Ringer's Lactate Solution Displays a Selective Cytotoxic Effect on Ovarian Cancer Cells.

Epithelial Ovarian Cancer (EOC) is one of the leading causes of cancer-related deaths among women and is characterized by the diffusion of nodules or plaques from the ovary to the peritoneal surfaces. Conventional therapeutic options cannot eradicate the disease and show low efficacy against resistant tumor subclones. The treatment of liquids via cold atmospheric pressure plasma enables the production of plasma-activated liquids (PALs) containing reactive oxygen and nitrogen species (RONS) with selective anticancer activity. Thus, the delivery of RONS to cancer tissues by intraperitoneal washing with PALs might be an innovative strategy for the treatment of EOC. In this work, plasma-activated Ringer's Lactate solution (PA-RL) was produced by exposing a liquid substrate to a multiwire plasma source. Subsequently, PA-RL dilutions are used for the treatment of EOC, non-cancer and fibroblast cell lines, revealing a selectivity of PA-RL, which induces a significantly higher cytotoxic effect in EOC with respect to non-cancer cells.

Gas Plasma Technology-An Asset to Healthcare During Viral Pandemics Such as the COVID-19 Crisis?

The COVID-19 crisis profoundly disguised the vulnerability of human societies and healthcare systems in the situation of a pandemic. In many instances, it became evident that the quick and safe reduction of viral load and spread is the foremost principle in the successful management of such a pandemic. However, it became also clear that many of the established routines in healthcare are not always sufficient to cope with the increased demand for decontamination procedures of items, healthcare products, and even infected tissues. For the last 25 years, the use of gas plasma technology has sparked a tremendous amount of literature on its decontaminating properties, especially for heat-labile targets, such as polymers and tissues, where chemical decontamination often is not appropriate. However, while the majority of earlier work focused on bacteria, only relatively few reports are available on the inactivation of viruses. We here aim to provide a perspective for the general audience of the chances and opportunities of gas plasma technology for supporting healthcare during viral pandemics such as the COVID-19 crisis. This includes possible real-world plasma applications, appropriate laboratory viral test systems, and critical points on the technical and safety requirements of gas plasmas for virus inactivation.

Plasma activated water as resistance inducer against bacterial leaf spot of tomato.

Plant bacterial diseases are routinely managed with scheduled treatments based on heavy metal compounds or on antibiotics; to reduce the negative environmental impact due to the use of such chemical compounds, as pollution or selection of antibiotic resistant pathogens, the integrated control management is required. In the frame of a sustainable agriculture the use of bacterial antagonists, biological agents, plant defence response elicitors or resistant host plant genotypes are the most effective approaches. In this work, cold atmospheric pressure plasma (CAP) was applied to sterile distilled water, inducing the production of a hydrogen peroxide, nitrite and nitrate, and a pH reduction. In particular, an atmospheric pressure dielectric barrier discharge (DBD) has been used to produce plasma activated water (PAW), that was firstly assayed in in vitro experiments and then in planta through application at the root apparatus of tomato plants, against Xanthomonas vesicatoria (Xv), the etiological agent of bacterial leaf spot. Moreover, the transcription abundance of five genes related to the plant defense was investigated in response to PAW treatment. PAW did not show direct antimicrobial activity against Xv in in vitro experiments, but it enhanced the tomato plants defenses. It was effective in reducing the disease severity by giving relative protections of ca. 61, 51 and 38% when applied 1 h, 24 h and 6 days before the experimental inoculation, respectively. In addition, the experiments highlighted the pal gene involvement in response to the PAW treatments and against the pathogen; its transcription levels resulted significantly high from 1 to 48 h until their decrease 192 h after PAW application.

The Effect of Cold Atmospheric Plasma (CAP) Treatment at the Adhesive-Root Dentin Interface.

PURPOSE: To investigate the use of a cold atmospheric plasma (CAP) source in a clinically realistic endodontic procedure to enhance the bond strength of a dental adhesive in root canal restoration. MATERIALS AND METHODS: CAP was generated by a handheld DBD-jet prototype specifically designed for biomedical applications. Extracted monoradicular teeth were standardized through crown sectioning and root canal shaping before being embedded in epoxy resin cylinders using a custom molding procedure designed to ensure the accurate alignment of the specimens. Afterwards, the dentin surface was conditioned according to different protocols including (or not, in controls) chelating agents (EDTA or IP6) and CAP treatment (180 s). Then a self-etch adhesive was applied, followed by a luting material to seal the root canal. Both materials were light cured. Tooth sections were obtained from coronal and middle portions of the root canal, and the push-out test was used to evaluate the bond strength between the adhesive and dentin. RESULTS: Push-out results demonstrated that plasma treatment greatly improved (> twofold) the mechanical properties of the adhesive-dentin interface along the whole length of the root canal. Contact angle measurements and SEM analyses showed that plasma treatment facilitated adhesive permeation into dentinal tubules, hence enhancing the effects of the bonding procedure. CONCLUSIONS: Although investigations on long-term bond stability after CAP treatment and clinical studies are required, the present study indicates that CAP devices may be useful in clinical endodontic treatment.

Non-equilibrium atmospheric pressure plasma as innovative method to crosslink and enhance mucoadhesion of econazole-loaded gelatin films for buccal drug delivery.

In this paper we developed an innovative, effective and rapid one-step approach to crosslink mucoadhesive gelatin films for buccal drug delivery. The method, which involves the application of non-equilibrium pressure plasma for 3 or 5 minutes/side, was compared with a classical approach based on the use of a chemical crosslinking agent, namely genipin. Econazole nitrate (ECN), an imidazole antifungal agent used for the treatment of skin infections and mucosal candidiasis, was selected as model drug. X-Ray Diffraction characterization performed on the drug-containing gelatin films revealed that ECN undergoes to a topotactic transformation into Econazole (EC) immediately after mixing with gelatin suggesting the occurrence of an acid-base reaction between drug and gelatin during film processing. Plasma treatment, as well as genipin crosslinking, did not provoke any further variation of EC structure. However, plasma exposure significantly improved films adhesiveness and allowed to reach mucoadhesive strength values more than double with respect to those obtained with genipin, ascribable to the presence of polar and hydrophilic groups on the plasma treated film's surface. A residence time of at least 48 h was obtained by properly selecting the plasma exposure times. These results, together with the in-vitro data showing retention of antifungal efficacy against a strain of Candida albicans, demonstrated that plasma treatment was a valid and rapid alternative, easy to scale-up, to chemical crosslinking methods for the production of highly mucoadhesive gelatin-based films.

Plasma in Dentistry: Brief History and Current Status.

We briefly discuss the history of cold atmospheric plasma (CAP) applications in dentistry. The reasons for seeking innovative solutions in dentistry are reported, highlighting results showing the potential of plasma along with some still-open questions. Finally, we suggest the next steps on the road from the laboratory to the dental chair.

Cold Atmospheric Plasma Induces Apoptosis and Oxidative Stress Pathway Regulation in T-Lymphoblastoid Leukemia Cells.

Cold atmospheric plasma (CAP) has shown its antitumor activity in both in vitro and in vivo systems. However, the mechanisms at the basis of CAP-cell interaction are not yet completely understood. The aim of this study is to investigate CAP proapoptotic effect and identify some of the molecular mechanisms triggered by CAP in human T-lymphoblastoid leukemia cells. CAP treatment was performed by means of a wand electrode DBD source driven by nanosecond high-voltage pulses under different operating conditions. The biological endpoints were assessed through flow cytometry and real-time PCR. CAP caused apoptosis in Jurkat cells mediated by p53 upregulation. To test the involvement of intrinsic and/or extrinsic pathway, the expression of Bax/Bcl-2 and caspase-8 was analyzed. The activation of caspase-8 and the upregulation of Bax and Bcl-2 were observed. Moreover, CAP treatment increased ROS intracellular level. The situation reverts after a longer time of treatment. This is probably due to compensatory cellular mechanisms such as the posttranscriptional upregulation of SOD1, CAT, and GSR2. According to ROS increase, CAP induced a significant increase in DNA damage at all treatment conditions. In conclusion, our results provide a deeper understanding of CAP potential in the oncological field and pose the basis for the evaluation of its toxicological profile.

Atmospheric Pressure Non-Equilibrium Plasma as a Green Tool to Crosslink Gelatin Nanofibers.

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.

Poly-l-Lactic Acid Nanofiber-Polyamidoamine Hydrogel Composites: Preparation, Properties, and Preliminary Evaluation as Scaffolds for Human Pluripotent Stem Cell Culturing.

Electrospun poly-l-lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide-end capped AGMA1, a biocompatible polyamidoamine with arg-gly-asp (RGD)-reminiscent repeating units. The resultant mixture is finally cured giving PLLA-AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short-term undifferentiated cultures of human pluripotent stem cells in feeder-free conditions.

Investigation of the antimicrobial activity at safe levels for eukaryotic cells of a low power atmospheric pressure inductively coupled plasma source.

Low power atmospheric pressure inductively coupled thermal plasma sources integrated with a quenching device (cold ICP) for the efficient production of biologically active agents have been recently developed for potential biomedical applications. In the present work, in vitro experiments aimed at assessing the decontamination potential of a cold ICP source were carried out on bacteria typically associated with chronic wounds and designed to represent a realistic wound environment; further in vitro experiments were performed to investigate the effects of plasma-irradiated physiological saline solution on eukaryotic cells viability. A thorough characterization of the plasma source and process, for what concerns ultraviolet (UV) radiation and nitric oxide production as well as the variation of pH and the generation of nitrates and nitrites in the treated liquid media, was carried out to garner fundamental insights that could help the interpretation of biological experiments. Direct plasma treatment of bacterial cells, performed at safe level of UV radiation, induces a relevant decontamination, both on agar plate and in physiological saline solution, after just 2 min of treatment. Furthermore, the indirect treatment of eukaryotic cells, carried out by covering them with physiological saline solution irradiated by plasma, in the same conditions selected for the direct treatment of bacterial cells does not show any noticeable adverse effect to their viability. Some considerations regarding the role of the UV radiation on the decontamination potential of bacterial cells and the viability of the eukaryotic ones will be presented. Moreover, the effects of pH variation, nitrate and nitrite concentrations of the plasma-irradiated physiological saline solution on the decontamination of bacterial suspension and on the viability of eukaryotic cells subjected to the indirect treatment will be discussed. The obtained results will be used to optimize the design of the ICP source for an effective production of reactive species, while keeping effluent temperature and UV radiation at values compatible with biomedical treatments.