Search

We present the concept of a versatile drug-loaded composite hydrogel that can be activated using an argon-based cold atmospheric plasma (CAP) jet to deliver both a drug and CAP-generated molecules, concomitantly, in a tissue target. To demonstrate this concept, we utilized the antibiotic gentamicin that is encapsulated in sodium polyacrylate (PAA) particles, which are dispersed within a poly(vinyl alcohol) (PVA) hydrogel matrix. The final product is a gentamicin-PAA-PVA composite hydrogel suitable for an on-demand triggered release using CAP. We show that by activating using CAP, we can effectively release gentamicin from the hydrogel and also eradicate the bacteria effectively, both in the planktonic state and within a biofilm. Besides gentamicin, we also successfully demonstrate the applicability of the CAP-activated composite hydrogel loaded with other antimicrobial agents such as cetrimide and silver. This concept of a composite hydrogel is potentially adaptable to a range of therapeutics (such as antimicrobials, anticancer agents, and nanoparticles) and activatable using any dielectric barrier discharge CAP device.

Here we present a novel plasma treatment regime– plasma fractionation, analogous to the concept of dose fractionation in radiotherapy, which could see application in plasma-based cancer treatment. In plasma fractionation, a single acute dose of plasma is divided into multiple small dosages (fractionated dosages) and administered to the cells in vitro at 24-hour intervals. We utilised a helium plasma jet and studied the effects of plasma fractionation in an immortalised keratinocyte line (HaCaT) and a squamous cell carcinoma line (A431). The effects were assessed over three cell seeding densities – 8000, 3500 and 1000 cells/well. Our results show that, at all seeding densities, plasma fractionation produced lower levels of cell death in both cell types compared to the same dose administered as a single plasma treatment. This highlights the potential of plasma fractionation as a potentially safer method to conduct plasma treatments in future. We also show that A431 cells were more sensitive to a single acute plasma treatment than HaCaT cells, at cell densities that are sub-confluent (1000 cells/well). A similar difference in sensitivity between HaCaT cells and A431 cells was not observed on exogenous treatment with hydrogen peroxide, pointing to the importance of other shorter-lived plasma components.

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.

Cold atmospheric plasmas have attracted significant worldwide attention for their potential beneficial effects in cancer therapy. In order to further improve the effectiveness of plasma in cancer therapy, it is important to understand the generation and transport of plasma reactive species into tissue fluids, tissues and cells, and moreover the rates and depths of delivery, particularly across physical barriers such as skin. In this study, helium (He) plasma jet treatment of a 3D cancer tumour, grown on the back of a live mouse, induced apoptosis within the tumour to a depth of 2.8 mm. The He plasma jet was shown to deliver reactive oxygen species through the unbroken skin barrier before penetrating through the entire depth of the tumour. The depth and rate of transport of He plasma jet generated H2O2, NO3 - and NO2 -, as well as aqueous oxygen [O2(aq)], was then tracked in an agarose tissue model. This provided an approximation of the H2O2, NO3 -, NO2 - and O2(aq) concentrations that might have been generated during the He plasma jet treatment of the 3D tumour. It is proposed that the He plasma jet can induce apoptosis within a tumour by the 'deep' delivery of H2O2, NO3 - and NO2 - coupled with O2(aq); the latter raising oxygen tension in hypoxic tissue.

Herein, we employed UV-Vis spectroscopy to monitor real-time changes in the oxygen tension and concentration of reactive oxygen and nitrogen species (RONS) in deionized (DI) water during treatments with helium (He) and argon (Ar) gas and plasma jets. He and Ar gas jets are both shown to de-oxygenate DI water with He being more efficient than Ar, whilst the plasma jets deliver and regulate the concentrations of hydrogen peroxide (H_2O_2), nitrite (NO_2^-) and nitrate (NO_3^-) in deionized (DI) water....

There is a growing literature database that demonstrates the therapeutic potential of cold atmospheric plasma (herein referred to as plasma). Given the breadth of proposed applications (eg from teeth whitening to cancer therapy) and vast gamut of plasma devices being researched, it is timely to consider plasma interactions with specific components of the cell in more detail. Plasma can produce highly reactive oxygen and nitrogen species (RONS) such as the hydroxyl radical (OH•), peroxynitrite (ONOO−) and superoxide (O2-) that would readily modify essential biomolecules such as DNA. These modifications could in principle drive a wide range of biological processes. Against this possibility, the reported therapeutic action of plasmas are not underpinned by a particularly deep knowledge of the potential plasma-tissue,-cell or-biomolecule interactions.

With ambient mass spectrometry, we followed the transport of neutral gas species and ionic species through a 3.2 mm thick agarose tissue model target during He non-thermal atmospheric pressure plasma (NT-APP) jet treatment. We found that the neutral gas species are unable to efficiently penetrate the agarose target. But both positively and negatively charged ionic species readily penetrate through the agarose target, following an initial time-lag period of several minutes. Interestingly, we also found that the ionic species are easily hydrated. The trends in the He NT-APP jet transport of ionic species observed in this study correlate well with the He NT-APP jet transport of reactive oxygen and nitrogen species (RONS) through agarose tissue model targets that was investigated in previous studies. Therefore, mass spectrometry might prove to be a useful tool in the future for analyzing the dosages of NT-APP-generated RONS in real biological tissues.

Despite growing interest in the application of atmospheric plasma jets as medical treatment strategies, there has been comparatively little research on the potential genotoxic and cytotoxic effects of plasma jet treatment. In this study, we have employed the cytokinesis block micronucleus cytome (CBMN-Cyt) assay with WIL2-NS B lymphoblastoid cells to test the potential genotoxicity, as well as the cytotoxicity, of toxic species generated in cell culture media by an argon (Ar) plasma jet. Elevated levels of cell death (necrosis) and occurrence of chromosomal damage (micronuclei MN, nculeoplasmic bridge NPBs and nuclear bus, Nbuds) were observed when cells were exposed to plasma jet-treated media. These results provide a first insight into how we might measure the genotoxic and cytotoxic effect of plasma jet treatments (both indirect and direct) in dividing human cells.

The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as “sparging.” He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine.

The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine.

There is significant optimism that cold atmospheric (ionised gas) plasma could play a role in the treatment of life-threatening diseases, such as non-healing chronic wounds and cancers. The medical benefits from plasma are thought to arise from the reactive oxygen and nitrogen species (RONS) generated by plasma upon interaction with air and liquids. However, it is unclear what RONS are delivered by plasma into tissue fluid and tissue, and their rate of delivery. This knowledge is needed to develop safe and effective plasma therapies. In this investigation, a simple approach was proposed to monitor the dynamic changes in the concentrations of RONS and dissolved oxygen within tissue-like fluid and tissue during plasma treatment. A plasma “jet” device was shown to non-invasively transport RONS and oxygen deep within tissue (to millimetre depths). However, tissue fluid directly treated with the plasma jet was deoxygenated due to the gas flow purging oxygen out of the fluid. Monitoring and controlling the plasma delivery of both RONS and oxygen into tissue fluid and tissue is necessary to avoid hypoxia in open wound treatment, to achieve targeted destruction of cancerous cells within solid tumours and to oxygenate oxygen-starved tissue to stimulate tissue regeneration. J.-S. Oh, E. J. Szili, N. Gaur, S.-H. Hong, H. Furuta, H. Kurita, A. Mizuno, A. Hatta and R. D. Short, How to assess the plasma delivery of RONS into tissue fluid and tissue, J. Phys. D 49, 304005 (2016)

The efficacy of helium (He) and argon (Ar) plasma jets are being investigated for different healthcare applications including wound and cancer therapy, sterilisation and surface disinfections. Current research points to a potential link between the generation of reactive oxygen and nitrogen species (RONS) and outcomes in a range of biological and medical applications. As new data accrue, further strengthening this link, it becomes important to understand the controlled delivery of RONS into solutions, tissue fluids and tissues. This paper investigates the use of He and Ar plasma jets to deliver three RONS (hydrogen peroxide—H2O2, nitrite—$\text{NO}_{2}^{-}$ and nitrate—$\text{NO}_{3}^{-}$ ) and molecular oxygen (O2) directly into deionised (DI) water, or indirectly into DI water through an agarose target. The DI water is used in place of tissue fluid and the agarose target serves as a surrogate of tissue. Direct plasma jet treatments deliver more RONS and O2 than the through-agarose treatments for equivalent treatments times. The former only deliver RONS whilst the plasma jets are ignited; the latter continues to deliver RONS into the DI water long after the plasmas are extinguished. The He plasma jet is more effective at delivering H2O2 and $\text{NO}_{2}^{-}$ directly into DI water, but the Ar plasma jet is more effective at nitrating the DI water in both direct and through-agarose treatments. DI water directly treated with the plasma jets is deoxygenated, with the He plasma jet purging more O2 than the Ar plasma jet. This effect is known as 'sparging'. In contrast, for through-agarose treatments both jets oxygenated the DI water. These results indicate that in the context of direct and indirect plasma jet treatments of real tissue fluids and tissue, the choice of process gas (He or Ar) could have a profound effect on the concentrations of RONS and O2. Irrespective of operating gas, sparging of tissue fluid (in an open wound) for long prolonged periods during dire

The helium (He) atmospheric-pressure plasma jet (APPJ) delivery of reactive oxygen and nitrogen species (RONS) and molecular oxygen (O2) in deionized (DI) water was monitored in real time using in situ UV absorption spectroscopy. The He APPJ was used to treat DI water directly and through an agarose target as a surrogate for tissue (e.g., a skin barrier). For direct treatment, the RONS were generated immediately in the DI water, and the concentration of RONS continued to increase during the He APPJ treatment. But there was only a very minor increase in the total RONS concentration detected after the plasma and gas flow were switched off. The agarose target delayed the generation of RONS into the DI water, but the total RONS concentration continued to increase long after (25 min) the plasma and gas flow were switched off. Direct treatment deoxygenated the DI water, whereas treatment through agarose resulted in oxygenation of the DI water. A dynamic change in the ratio of H2O2, NO2 -, NO3 -, and O2 was detected in the DI water during He APPJ treatment and 25 min after the He and gas flow were switched off for both direct and through-agarose treatment. These results have implications for the plasma treatment of real tissue where the dynamic changes in the RONS and O2 concentrations within the tissue and tissue fluid could affect cellular and physiological processes.

We demonstrated the efficacy of using a simple experimental approach, involving UV absorption spectroscopy, to monitor the transport of reactive oxygen and nitrogen species (RONS) through an agarose film (as surrogate for real tissue) into deionized (DI) water. The experiment involved placing a 4 mm thick agarose film over a quartz cuvette filled with DI water. The agarose film was exposed to a non-thermal, He atmospheric-pressure plasma jet (APPJ) and the UV absorption of the DI water was recorded in real-time. Our results indicate an accumulation of RONS within the agarose film during APPJ exposure and a subsequent time-lapsed release of RONS into the DI water. Curve fitting of the UV spectra suggested the APPJ transported and / or generated at least four RONS (NaNO2, HNO3, H2O2 and O2) through the 4 mm thick agarose film. Our approach of analyzing the delivery depth of RONS through synthetic tissue targets might find use in the future development of APPJ medical therapies and for improving our understanding of APPJ interactions with soft tissue.

The influence of protein and molecular, ground state oxygen (O-2) on the plasma generation, and transport of reactive oxygen and nitrogen species (RONS) in tissue are investigated. A tissue target, comprising a 1mm thick gelatin film (a surrogate for real tissue), is placed on top of a 96-well plate; each well is filled with phosphate buffered saline (PBS, pH 7.4) containing one fluorescent or colorimetric reporter that is specific for one of three RONS (i.e., H2O2, NO2-, or OH center dot) or a broad spectrum reactive oxygen species reporter (2,7-dichlorodihydrofluorescein). A helium cold atmospheric plasma (CAP) jet contacts the top of the gelatin surface, and the concentrations of RONS generated in PBS are measured on a microplate reader. The data show that H2O2, NO2-, or OH center dot are generated in PBS underneath the target. Independently, measurements are made of the O-2 concentration in the PBS with and without the gelatin target. Adding bovine serum albumin protein to the PBS or gelatin shows that protein either raises or inhibits RONS depending upon the O-2 concentration. Our results are discussed in the context of plasma-soft tissue interactions that are important in the development of CAP technology for medicine, biology, and food manufacturing. (C) 2015 AIP Publishing LLC.

Introduction: Diabetes mellitus is a metabolic disorder leading to multiple health conditions including diabetic foot ulcers (DFUs), which often become infected. Current therapies are ineffective and contribute to antimicrobial resistance (AMR). Therefore, new non-antibiotic treatments are required. Cold Atmospheric Plasma (CAP), an ionised gas, has the potential to resolve infection by delivering reactive species (RS) such as hydrogen peroxide (H2O2) deep into the wound. CAP can also be used to deliver antimicrobial drugs from a hydrogel dressing also known as plasma-activated hydrogel therapy (PAHT). Aim: To investigate the potential of a PAHT for the treatment of infected DFUs. Methods: A systematic review compared two bacterial detection techniques – 16S rRNA gene sequencing and conventional culture. The physical (electrical and optical) and chemical (RS delivery) characteristics of CAP jet were studied. Povidone-iodine (PVP-I) solution and PVP-I from a hydrogel (i.e. PVP-I–PAHT) exposed to CAP were assessed using UV-visible spectroscopy and agarose-starch assays. The antibacterial efficiency of PVP-I–PAHT was assessed using checkerboard synergy assay, Kirby-Bauer Assay, and a wound biofilm model. Results: The review demonstrated the Staphylococcal spp. and Pseudomonas spp. predominance in DFUs. A low-power CAP jet, which can deliver up to 1.91 mM of H2O2 in solution was established. A potential formation of hypoiodous acid (HOI) was shown upon the interaction of PVP-I with CAPproduced H2O2. Complete eradication of an immature biofilm and a log 2 reduction against 1 hour incubated mature biofilms were observed with PVP-I–PAHT. Conclusion: This is the first study to investigate the properties of plasma-activated PVP-I and the anti-microbial activity of PVP-I–PAHT against the bacteria specific to DFUs. It also highlights the role of H2O2 and HOI in CAP–PVP-I treatment of DFUs. An existing antimicrobial (PVP-I) was repurposed with non-antibiotic CAP technology whic