The state-of-the-art of atmospheric pressure plasma for transdermal drug delivery

Plasma-enhanced transdermal drug delivery(TDD) presents advantages over traditional methods,including painless application, minimal skin damage, and rapid recovery of permeability. To harness its clinical potential, factors related to plasma’s unique properties, such as reactive species and electric fields, must be carefully considered.This review provides a concise summary of conventional TDD methods and subsequently offers a comprehensive examination of the current state-of-the-art in plasma-enhanced TDD. This includes an analysis of the impact of plasma on HaCaT human keratinocyte cells, ex vivo/in vivo studies, and clinical research on plasma-assisted TDD. Moreover, the review explores the effects of plasma on skin physical characteristics such as microhole formation, transepidermal water loss(TEWL), molecular structure of the stratum corneum(SC), and skin resistance. Additionally, it discusses the involvement of various reactive agents in plasma-enhanced TDD, encompassing electric fields,charged particles, UV/VUV radiation, heat, and reactive species. Lastly, the review briefly addresses the temporal behavior of the skin after plasma treatment, safety considerations, and potential risks associated with plasma-enhanced TDD.

Effect of gas components on the postdischarge temporal behavior of OH and O of a non-equilibrium atmospheric pressure plasma driven by nanosecond voltage pulses

OH radicals and O atoms are two of the most important reactive species of non-equilibrium atmospheric pressure plasma(NAPP),which plays an important role in applications such as plasma medicine.However,experimental studies on how the gas content affects the postdischarge temporal evolutions of OH and O in the noble gas ns-NAPP are very limited.In this work,the effect of the percentages of O_(2),N_(2),and H_(2)O on the amounts of OH and O productions and their post-discharge temporal behaviors in ns-NAPP is investigated by laser-induced fluorescence(LIF)method.The results show that the productions of OH and O increase and then decrease with the increase of O_(2)percentage.Both OH and O densities reach their maximum when about 0.8%O_(2)is added.Further increase of the O_(2)concentration results in a decrease of the initial densities of both OH and O,and leads to their faster decay.The increase of N_(2)percentage also results in the increase and then decrease of the OH and O densities,but the change is smaller.Furthermore,when the H_(2)O concentration is increased from 100 to 3000 ppm,the initial OH density increases slightly,but the OH density decays much faster,while the initial density of O decreases with the increase of the H_(2)O concentration.After analysis,it is found that OH and O are mainly produced through electron collisional dissociation.O(^(1)D)is critical for OH generation.O_(3)accelerates the consumption processes of OH and O at high O_(2)percentage.The addition of H_(2)O in the NAPP considerably enhances the electronegativity,while it decreases the overall plasma reactivity,accelerates the decay of OH,and reduces the O atom density.

Effect of power supply parameters on discharge characteristics and sterilization efficiency of magnetically driven rotating gliding arc

Plasma sterilization is a new generation of high-tech sterilization method that is fast,safe,and pollution free.It is widely used in medical,food,and environmental protection fields.Home air sterilization is an emerging field of plasma application,which puts higher requirements on the miniaturization,operational stability,and operating cost of plasma device.In this study,a novel magnetically driven rotating gliding arc(MDRGA)discharge device was used to sterilize Lactobacillus fermentation.Compared with the traditional gas-driven gliding arc,this device has a simple structure and a more stable gliding arc.Simulation using COMSOL Multiphysics showed that adding permanent magnets can form a stable magnetic field,which is conducive to the formation of gliding arcs.Experiments on the discharge performance,ozone concentration,and sterilization effect were conducted using different power supply parameters.The results revealed that the MDRGA process can be divided into three stages:starting,gliding,and extinguishing.Appropriate voltage was the key factor for stable arc gliding,and both high and low voltages were not conducive to stable arc gliding and ozone production.In this experimental setup,the sterilization effect was the best at 6.6 kV.A high modulation duty ratio was beneficial for achieving stable arc gliding.However,when the duty ratio exceeded a certain value,the improvement in the sterilization effect was slow.Therefore,considering the sterilization effect and energy factors comprehensively,we chose 80%as the optimal modulation duty ratio for this experimental device.

Temporal electric field of a helium plasma jet by electric field induced second harmonic(E-FISH)method

Electric field is an important parameter of plasma,which is related to electron temperature,electron density,excited species density,and so on.In this work,the electric field of an atmospheric pressure plasma jet is diagnosed by the electric field induced second harmonic(E-FISH)method,and the time-resolved electric field under different conditions is investigated.When positive pulse voltage is applied,the electric field has a peak of about 25 kV cm-1at the rising edge of the voltage pulse.A dark channel is left behind the plasma bullet and the electric field in the dark channel is about 5 kV cm-1.On the other hand,when negative pulse voltage is applied,the electric field has a peak of-16 kV cm-1when the negative voltage is increased to-8 kV.A relatively bright channel is left behind the plasma head and the electric field in this relatively bright channel is about-6 kV cm-1.When the pulse rising time increases from 60 to 200 ns,the peak electric field at both the rising edge and the falling edge of the voltage decreases significantly.When 0.5%of oxygen is added to the main working gas helium,the peak electric field at the rising edge is only about 15 kV cm-1.On the other hand,when 0.5%nitrogen is added,the peak electric field increases especially at the falling edge of the voltage pulse,where it increases reversely from-12 to-16 kV cm-1(the minus sign only represents the direction of electric field).

Plasma-activated hydrogel:fabrication,functionalization,and effective biological model

Hydrogels are biomaterials with 3D networks of hydrophilic polymers.The generation of hydrogels is turning to the development of hydrogels with the help of enabling technologies.Plasma can tailor the hydrogels’properties through simultaneous physical and chemical actions,resulting in an emerging technology of plasma-activated hydrogels(PAH).PAH can be divided into functional PAH and biological tissue model PAH.This review systematically introduces the plasma sources,plasma etching polymer surface,and plasma cross-linking involved in the fabrication of PAH.The‘diffusion-drift-reaction model’is used to study the microscopic physicochemical interaction between plasma and biological tissue PAH models.Finally,the main achievements of PAH,including wound treatment,sterilization,3D tumor model,etc,and their development trends are discussed.

On the green aurora emission of Ar atmospheric pressure plasma

The Ar atmospheric pressure plasma was found to be an excellent laboratorial source for green aurora emission.However,the characteristic and production mechanism of the green aurora emission of the Ar atmospheric pressure plasma are still not clear.In this work,an Ar plasma in a long glass tube which emits intense green aurora light is investigated.With the long glass tube,it can be concluded that the green aurora emission in the Ar plasma is not owing to the mixture of Ar plasma plume with the surrounding air.It is also found that the green aurora emission often appeared beyond the active electrode when the active electrode is placed at the downstream of the gas flow.The green emission disappears when the traces amount of O_(2) or N_(2)(about 0.05%–0.07%)is added to Ar.This is because the O_(2) molecules deactivate the upper state O(^(1)S),which results in the decrease of the green emission.On the other hand,when N_(2) is added,Ar metastable atoms are quenched by N_(2),which results in the decrease of O atoms and eventually leads to the decrease of the green emission intensity.The intensity of the green aurora emission increases when the driving voltage frequency increases from 1 to 10 k Hz.More importantly,it is found that the green aurora emission is not affected when a grounded stainless steel needle is in contact with the plasma plume.Thus,the green emission is not driven electrically.All these findings are helpful for the understanding of the physics and its applications of atmospheric pressure plasma jet in space physics,laser physics and other application areas.

A novel flexible plasma array for large-area uniform treatment of an irregular surface

In this work,we demonstrate a flexible multi-pin plasma generator with movable electrodes,which can change the shape of the electrode array freely,and then provide a large-area uniform plasma for the treatment of surfaces of different shapes.Discharge characteristics including U-I waveforms and discharge images and sterilization performance under three different electrode configurations(flat-flat,flat-curve,curve-curve)are investigated.Very similar results are acquired between the flat-flat configuration and the curve-curve configuration,which is much better than that under flat-curve configuration.This flexible multi-pin plasma generator offers a simple method to treat different irregularly shaped surfaces uniformly with a single device.Moreover,this device provides a foundation for developing a self-adaption large-scale uniform plasma generator by further introducing automatic adjustment of the position of every electrode driven by motors with discharge current feedback in the following study.Thus it will promote the applications of atmospheric-pressure cold plasmas significantly.

On the chronological understanding of the homogeneous dielectric barrier discharge

Dielectric barrier discharges(DBD)are widely utilised non‐equilibrium atmospheric pressure plasmas with a diverse range of applications,such as material processing,surface treatment,light sources,pollution control,and medicine.Over the course of several decades,extensive research has been dedicated to the generation of homogeneous DBD(H‐DBD),focussing on understanding the transition from H‐DBD to filamentary DBD and exploring strategies to create and sustain H‐DBD.This paper first discusses the in-fluence of various parameters on DBD,including gas flow,dielectric material,surface conductivity,and mesh electrode.Secondly,a chronological literature review is presented,highlighting the development of H‐DBD and the associated understanding of its un-derlying mechanisms.This encompasses the generation of H‐DBD in helium,nitrogen,and air.Lastly,the paper provides a brief overview of multiple‐current‐pulse(MCP)behaviours in H‐DBD.The objective of this article is to provide a chronological un-derstanding of homogeneous dielectric barrier discharge(DBD).This understanding will aid in the design of new experiments aimed at better comprehending the mechanisms behind H‐DBD generation and ultimately assist in achieving large‐volume H‐DBD in an air environment.

Plasma-activated ethanol solution and it's decontamination effect

Ethanol solution as a disinfectant has been widely used in various fields.However,it has a significant bactericidal capability only when the volume fraction of ethanol is around 70%-75%.For such high concentration of ethanol solution,it has an irritating smell.When it is used for applications such as wound disinfection,it causes a stinging sensation.Low concentrations of ethanol solution are less irritating,but it is also less effective at killing bacteria.In this study,an idea for producing a green,efficient and less irritating disinfectant is proposed.It is based on a plasma-activated low-concentration ethanol solution(PAES).It is found that the plasma-activated 10% volume fraction of ethanol solution can kill more than seven orders of magnitude of Escherichia coli,while the untreated 10% volume fraction of ethanol solution has no bactericidal effect.Besides,the PAES's activity remains unchanged after being stored at -20℃ for three days.Further investigation shows that new compositions including peracetic acid,peroxynitrite,hydrogen peroxide and acetic acid are detected in the PAES,which together are playing the main role of the excellent and prolonged bactericidal effect.

A non‐equal gap distance dielectric barrier discharge:Between cone‐shape and cylinder‐shape electrodes

A non‐equal gap distance dielectric barrier discharge(DBD)between cone‐shape and a cylinder‐shaped electrodes is reported.The DBD is driven by a nanosecond voltage pulse.When the pulse frequency is 500 Hz or lower,ladder‐shape plasma with multiple plasma layers is generated within the gap,with a distance increasing from 1 to 7 mm.According to high‐speed photographs of the plasma captured by an intensified charge‐coupled camera detector camera,the ladder‐shaped plasma is formed owing to propa-gation of ring‐shaped plasma from the region of the short‐gap distance to the region of long‐gap distance with regular variations in its propagation speed.The propagation speed drops to zero and lasts for about 20-30 ns at the region of each plasma layer,which results in bright plasma layers.The electric field of the plasma layer at the region of the different gap distance is evaluated according to the optical emission intensity ratio R_(391)/_(394)of N_(2)^(+)at 391 nm and N_(2) at 394 nm.The obtained electric field drops from 8.1 to 6.4 kV/mm when the plasma is propagated from regions of gap distance of 2-5 mm.When the pulse frequency is increased to 1 kHz or higher,the discharge changes into a filamentary mode and the multiple‐layer plasma disappears.