Enhanced Antimicrobial Activity through Synergistic Effects of Cold Atmospheric Plasma and Plant Secondary Metabolites: Opportunities and Challenges

The emergence of antibiotic resistant microorganisms possesses a great threat to human health and the environment. Considering the exponential increase in the spread of antibiotic resistant microorganisms, it would be prudent to consider the use of alternative antimicrobial agents or therapies. Only a sustainable, sustained, determined, and coordinated international effort will provide the solutions needed for the future. Plant secondary metabolites show bactericidal and bacteriostatic activity similar to that of conventional antibiotics. However, to effectively eliminate infection, secondary metabolites may need to be activated by heat treatment or combined with other therapies. Cold atmospheric plasma therapy is yet another novel approach that has proven antimicrobial effects. In this review, we explore the physiochemical mechanisms that may give rise to the improved antimicrobial activity of secondary metabolites when combined with cold atmospheric plasma therapy.

Applications and recent advances in transdermal drug delivery systems for the treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic autoimmune disease predominantly based on joint lesions with an extremely high disability and deformity rate. Several drugs have been used for the treatment of rheumatoid arthritis, but their use is limited by suboptimal bioavailability, serious adverse effects, and nonnegligible first-pass effects. In contrast, transdermal drug delivery systems (TDDSs) can avoid these drawbacks and improve patient compliance, making them a promising option for the treatment of rheumatoid arthritis (RA). Of course, TDDSs also face unique challenges, as the physiological barrier of the skin makes drug delivery somewhat limited. To overcome this barrier and maximize drug delivery efficiency, TDDSs have evolved in terms of the principle of transdermal facilitation and transdermal facilitation technology, and different generations of TDDSs have been derived, which have significantly improved transdermal efficiency and even achieved individualized controlled drug delivery. In this review, we summarize the different generations of transdermal drug delivery systems, the corresponding transdermal strategies, and their applications in the treatment of RA.

Plasma Dermatology: Skin Therapy Using Cold Atmospheric Plasma

Cold atmospheric plasma-based plasma medicine has been expanding the diversity of its specialties. As an emerging branch, plasma dermatology takes advantage of the beneficial complexity of plasma constituents (e.g., reactive oxygen and nitrogen species, UV photons, and electromagnetic emission), technical versatility (e.g., direct irradiation and indirect aqueous treatment), and practical feasibility (e.g., hand-held compact device and clinician-friendly operation). The objective of this comprehensive review is to summarize recent advances in the CAP-dominated skin therapy by broadly covering three aspects. We start with plasma optimisation of intact skin, detailing the effect of CAP on skin lipids, cells, histology, and blood circulation. We then conduct a clinically oriented and thorough dissection of CAP treatment of various skin diseases, focusing on the wound healing, inflammatory disorders, infectious conditions, parasitic infestations, cutaneous malignancies, and alopecia. Finally, we conclude with a brief analysis on the safety aspect of CAP treatment and a proposal on how to mitigate the potential risks. This comprehensive review endeavors to serve as a mini textbook for clinical dermatologists and a practical manual for plasma biotechnologists. Our collective goal is to consolidate plasma dermatology’s lead in modern personalized medicine.

Potential generation of nano-sized mist by passing a solution through dielectric barrier discharge

Plasma medicine, a therapeutic technology that uses atmospheric-pressure plasma, is attracting much attention as an innovative tool for the medical field. Most of the plasma biomedical tools use direct effects, such as heat, optical stimulation, and reactive chemical species, on the lesion. Nanoparticulation techniques using indirect action by plasma, i.e., generation of electric fields, have the potential to be applied to promote transdermal absorption, where drugs pass through the barrier function of skin and penetrate into internal tissues. Here, we show a method to directly generate the nano-sized mist by passing a solution through the dielectric barrier discharge. This method enables us to produce the mist potentially in the nanometer size range for both water-based and oil-based solutions. Ease of mist generation was influenced by the plasma-induced changes in physical and chemical characteristics, including electrical conductivity, viscosity, and chemical species. We anticipate the developed method for nano-sized mist generation to provide a technique in the applications of the transdermal absorption system, including those related to pharmaceuticals and cosmetics.

In Vitro and In Vivo Enhancement of Temozolomide Effect in Human Glioblastoma by Non-Invasive Application of Cold Atmospheric Plasma

Glioblastoma (GBM) is one of the most aggressive forms of adult brain cancers and is highly resistant to treatment, with a median survival of 12-18 months after diagnosis. The poor survival is due to its infiltrative pattern of invasion into the normal brain parenchyma, the diffuse nature of its growth, and its ability to quickly grow, spread, and relapse. Temozolomide is a well-known FDA-approved alkylating chemotherapy agent used for the treatment of high-grade malignant gliomas, and it has been shown to improve overall survival. However, in most cases, the tumor relapses. In recent years, CAP has been used as an emerging technology for cancer therapy. The purpose of this study was to implement a combination therapy of CAP and TMZ to enhance the effect of TMZ and apparently sensitize GBMs. In vitro evaluations in TMZ-sensitive and resistant GBM cell lines established a CAP chemotherapy enhancement and potential sensitization effect across various ranges of CAP jet application. This was further supported with in vivo findings demonstrating that a single CAP jet applied non-invasively through the skull potentially sensitizes GBM to subsequent treatment with TMZ. Gene functional enrichment analysis further demonstrated that co-treatment with CAP and TMZ resulted in a downregulation of cell cycle pathway genes. These observations indicate that CAP can be potentially useful in sensitizing GBM to chemotherapy and for the treatment of glioblastoma as a non-invasive translational therapy.

Atmospheric Pressure Plasma Irradiation Facilitates Transdermal Permeability of Aniline Blue on Porcine Skin and the Cellular Permeability of Keratinocytes with the Production of Nitric Oxide

The transdermal delivery system of nutrients, cosmetics, and drugs is particularly attractive for painless, noninvasive delivery and sustainable release. Recently, atmospheric pressure plasma techniques have been of great interest to improve the drug absorption rate in transdermal delivery. Currently, plasma-mediated changes in the lipid composition of the stratum corneum are considered a possible mechanism to increase transdermal permeability. Nevertheless, its molecular and cellular mechanisms in transdermal delivery have been largely confined and still veiled. Herein, we present the effects of cold plasma on transdermal transmission on porcine skin and the cellular permeability of keratinocytes and further demonstrate the production of nitric oxide from keratinocytes. Consequently, argon plasma irradiation for 60 s resulted in 2.5-fold higher transdermal absorption of aniline blue dye on porcine skin compared to the nontreated control. In addition, the plasma-treated keratinocytes showed an increased transmission of high-molecular-weight molecules (70 and 150 kDa) with the production of nitric oxide. Therefore, these findings suggest a promoting effect of low-temperature plasma on transdermal absorption, even for high-molecular-weight molecules. Moreover, plasma-induced nitric oxide from keratinocytes is likely to regulate transdermal permeability in the epidermal layer.

Analgesic effect of topical lidocaine is enhanced by cold atmospheric plasma pretreatment in facial CO2 laser treatments

BACKGROUND

Topical anesthesia is widely used in many dermatological and cosmetic procedures. Nevertheless, the stratum corneum serves as the skin barrier, impedes the transdermal drug delivery greatly, and results in insufficient analgesia. Cold atmospheric plasma (CAP) has been researched as a transdermal drug delivery promoter with ex vivo experiments for a few years, while clinical trials are scarce.

AIMS

To assess the efficacy and safety of CAP as a pretreatment to improve the transdermal absorption of topical anesthetic cream before the CO₂ laser treatment for postacne scars in the human body.

PATIENTS/METHODS

Twenty patients, seeking full facial laser treatment for atrophic acne scars, underwent a randomized split-face study. One side of the face was pretreated by CAP before topical anesthetic cream was applied, and the other side was applied with topical anesthetic cream only as control. After that, the subjects went through full-face fractional CO₂ laser treatment of postacne scars. They were asked to score the pain on a visual analogue scale (VAS) after the laser treatment to measure the anesthesia effects which indicates the transdermal absorption of the cream. Possible adverse effects of the plasma were recorded during the pretreatment including associated pain, heat, erythema, and edema.

RESULTS

The VAS score of the treated side was statistically lower (5.1 ± 2.1) compared with the nontreated side (6.3 ± 1.9), with a mean difference of 1.3 (95% confidence interval [CI], 0.6-1.9; P < .0001). No severe adverse event was reported, and all the disturbing sensations and symptoms (pain, heat, and edema) were evaluated as mild with no mean score surpassing 4.0.

CONCLUSION

Plasma pretreatment of 5 minutes before topical anesthetic cream application gives significant pain reduction during the laser procedures, showing the potential effects of CAP on promoting transdermal drug delivery, with no obvious adverse effects reported.

The emerging potential of cold atmospheric plasma in skin biology

The maintenance of skin integrity is crucial to ensure the physiological barrier against exogenous compounds, microorganisms and dehydration but also to fulfill social and aesthetic purposes. Besides the development of new actives intended to enter a formulation, innovative technologies based on physical principles have been proposed in the last years. Among them, Cold Atmospheric Plasma (CAP) technology, which already showed interesting results in dermatology, is currently being studied for its potential in skin treatments and cares. CAP bio-medical studies gather several different expertise ranging from physics to biology through chemistry and biochemistry, making this topic hard to pin. In this review we provide a broad survey of the interactions between CAP and skin. In the first section, we tried to give some fundamentals on skin structure and physiology, related to its essential functions, together with the main bases on cold plasma and its physicochemical properties. In the following parts we dissected and analyzed each CAP parameter to highlight the already known and the possible effects they can play on skin. This overview aims to get an idea of the potential of cold atmospheric plasma technology in skin biology for the future developments of dermo-cosmetic treatments, for example in aging prevention.

Transdermal delivery of topical lidocaine in a mouse model is enhanced by treatment with cold atmospheric plasma

BACKGROUND

Topical anesthetics are widely used in dermatology and cosmetology to alleviate the pain from nonsurgical cosmetic procedures, while the transdermal drug delivery is limited by the skin barrier. Cold atmospheric plasma (CAP) is a potential approach used for skin pretreatment to enhance transdermal delivery of topical medications.

AIMS

To assess the efficacy of CAP as a pretreatment to improve the transdermal delivery of topical anesthetic.

METHODS

First, we conducted ex vivo permeation studies on 30 mice with a Franz cell diffusion experiment. CAP irradiations of different intensity and duration were pretreated on the epidermal layer of mice before topical lidocaine applied, with the control group received no pretreatment. The amount of drug penetrated through the skin and drug flux were determined by high-performance liquid chromatography. Then, we treated 3 living mice with CAP followed by application of methylene blue cream (MB) and used skin biopsies to measure penetration depth by microscope. Last, we measured the transepidermal water loss (TEWL) of mouse skin in vivo before and after CAP treatment to observe its effect on the skin barrier function.

RESULTS

In the permeation study, the transdermal flux of lidocaine was enhanced to 1.97 times of the control samples by CAP pretreatment. We also observed that the accumulative amount of lidocaine varied with the duration of the CAP treatment in a biphasic manner. In the MB penetration study, significant amount of MB deposition was observed under the epidermis and deeper parts of the skin after CAP pretreatment compared with the control sample. A sharp increase in TEWL value was observed directly after the CAP treatment, but 30 minutes later, it began to decrease and recovered to baseline in the next 3 hours, indicating that the skin barrier property had been changed reversibly.

CONCLUSIONS

Our studies suggested that the transdermal absorption of topical lidocaine can be efficiently and safely enhanced by pretreatment of the skin with CAP. We believe that CAP could be used as an assistance to improve analgesia in dermatology.

Cold atmospheric pressure (physical) plasma in dermatology: where are we today?

Cold atmospheric pressure plasma is physical plasma (essentially ionized gas) created at room temperature and atmospheric pressure, and it has complex effects on cells, tissues, and living organisms. These effects are studied extensively for medical and dermatological use. This article reviews current achievements and new trends in clinical dermatological cold plasma research, discusses the basics of plasma physics and plasma engineering, and describes the most important areas of laboratory plasma research to provide a well-rounded understanding of the nature, present applications, and future promise of this exciting, emerging technology.

Applications of cold atmospheric plasma for transdermal drug delivery: a review

Although transdermal drug delivery would be very useful for the treatment of many diseases, in practice it is difficult to accomplish for the obstruction of the stratum corneum. The application of cold atmospheric plasma (CAP) as a pretreatment to the skin surface helps to enhance the delivery of topically applied drugs into the skin and the systemic circulation. CAP can change the skin properties to improve drug penetration by various different effects based on its multiple components. This review first introduces the skin barrier properties and some traditional transdermal drug delivery strategies. Next what is known about the application of CAP in transdermal drug delivery has been summarized, including the mechanisms and possible side effects. We believe that CAP could be developed as a non-invasive and efficient pretreatment to improve the transdermal permeation of drugs in clinical practice, although more research needs to be done to overcome the challenges. Graphical Abstract.

Influence of pulse characteristics and power density on stratum corneum permeabilization by dielectric barrier discharge

BACKGROUND

In recent years, the medical use of cold atmospheric plasma has received much attention. Plasma sources can be suited for widely different indications depending on their physical and chemical characteristics. Being interested in the enhancement of drug transport across the skin by plasma treatment, we evaluated three dielectric barrier discharges (DBDs) as to their potential use in permeabilizing human isolated stratum corneum (SC).

METHODS

Imaging techniques (electrochemical and redox-chemical imaging, fluorescence microscopy), transepithelial electrical resistance measurements and permeation studies were employed to study the permeabilizing effect of different DBD-treatments on SC.

RESULTS

Filamentous μs-pulsed DBDs induced robust pore formation in SC. Increasing the power of the μs-pulsed DBD lead to more pronounced pore formation but might increase the risk of undesired side-effects. Plasma permeabilization was much smaller for the ns-pulsed DBD, which left SC samples largely intact.

CONCLUSIONS

The comparison of different DBDs provided insight into the mechanism of DBD-induced SC permeabilization. It also illustrated the need to tailor electrical characteristics of a DBD to optimize it for a particular treatment modality. For future applications in drug delivery it would be beneficial to monitor the permeabilization during a plasma treatment.

GENERAL SIGNIFICANCE

Our results provide mechanistic insight into the potential of an emerging interdisciplinary technology - plasma medicine - as a prospective tool or treatment option. While it might become a safe and pain-free method to enhance skin permeation of drug substances, this is also a mechanism to keep in mind when tailoring plasma sources for other uses.

Fractional laser-assisted percutaneous drug delivery via temperature-responsive liposomes

Liposomes are used for transdermal delivery of drugs and vaccines. Our objective was to develop temperature-responsive (TR) liposomes to achieve temperature-dependent, controlled release of an encapsulated drug, and use fractional laser irradiation to enhance transdermal permeability of these liposomes. TR-liposomes prepared using a thermosensitive polymer derived from poly-N-isopropylacrylamide, N,N-dimethylacrylamide, egg phosphatidylcholine, and dioleoylphosphatidylethanolamine, delivered fluorescein isothiocyanate-conjugated ovalbumin (OVA-FITC) as a model drug. Effect of temperature on liposome size and drug release rate was estimated at two temperatures. Transdermal permeation through hairless mouse skin, with and without CO₂ fractional laser irradiation, and penetration into Yucatan micro-pig skin were investigated using Franz cell and fluorescence microscopy. Dynamic light scattering showed that mean liposome diameter nearly doubled from 190 to 325 nm between 37 and 50 °C. The rate and amount of OVA-FITC released from TR-liposomes were higher at 45 °C that those at 37 °C. Transdermal permeation of OVA-FITC across non-irradiated skin from both TR- and unmodified liposomes was minimal at 37 °C, but increased at 45 °C. Laser irradiation significantly increased transdermal permeation of both liposome groups at both temperatures. Fluorescence microscopy of frozen biopsy specimens showed deeper penetration of FITC from unmodified liposomes compared to that from polymer-modified liposomes. Rhodamine accumulation was not observed with polymer-modified liposomes at either temperature. Temperature-dependent controlled release of an encapsulated drug was achieved using the TR-liposomes. However, TR-liposomes showed lower skin permeability despite higher hydrophobicity. Fractional laser irradiation significantly increased the transdermal permeation. Additional studies are required to control liposome size and optimize transdermal permeation properties.

Finger evolution of a gas bubble driven by atmospheric pressure plasma

We report the generation and evolution of a finger-shaped bubble in liquid by dielectric discharge setup. The spherical gas bubble is deformed into a finger-shaped bubble after the ignition of plasma. The presence of the filamentary discharge in the bubble not only provides the local heating to the bubble, it also changes the distribution of the electric field in the bubble and the bubble mutually provides the pathway to the discharge. The reduced surface tension on the liquid-gas interface due to the rise of temperature by plasma heating and the nonuniform electric field caused by the presence of filamentary discharge might induce the concave-shaped bubble. We also observe the formation of the quasi-two-dimensional bubble, which is generated from the bubble and attached on one side of the electrodes. It is found that the discharge induces the growth of the periodic fluctuations in the thin layer of gas.