Cold plasma selectivity and the possibility of a paradigm shift in cancer therapy

Cancer metastasis: molecular mechanisms and therapeutic interventions

The metastatic cascade is a complicated process where cancer cells travel across multiple organs distant from their primary site of onset. Despite the wide acceptance of the 'seed and soil' theory, mechanisms driving metastasis organotropism remain mystery. Using breast cancer of different subtypes as the disease model, we characterized the 'metastatic profile of cancer cells' and the 'redox status of the organ microenvironment' as the primary determinants of cancer metastasis organotropism. Mechanically, we identified a positive correlation between cancer metabolic plasticity and stemness, and proposed oxidative stress as the selection power of cancer cells succeeding the metastasis cascade. Therapeutically, we proposed the use of pro-oxidative therapeutics in ablating cancer cells taking advantages of this fragile moment during metastasis. We comprehensively reviewed current pro-oxidative strategies for treating cancers that cover the first line chemo- and radio-therapies, approaches relying on naturally existing power including magnetic field, electric field, light and sound, nanoparticle-based anti-cancer composites obtained through artificial design, as well as cold atmospheric plasma as an innovative pro-oxidative multi-modal modality. We discussed possible combinations of pro-oxidative approaches with existing therapeutics in oncology prior to the forecast of future research directions. This paper identified the fundamental mechanics driving metastasis organotropism and proposed intervention strategies accordingly. Insights provided here may offer clues for the design of innovative solutions that may open a new paradigm for cancer treatment.

Cold Atmospheric Plasma in Oncology: A Review and Perspectives on Its Application in Veterinary Oncology

Cold atmospheric plasma (CAP) is emerging as an innovative approach for cancer treatment because of its selectivity for malignant cells and absence of significant adverse effects. While modern oncological therapies face challenges such as tumor heterogeneity and treatment resistance, CAP presents itself as a low-cost and environmentally sustainable alternative. Its mechanisms of action involve reactive oxygen and nitrogen species (RONS), UV radiation, and electromagnetic fields, which induce cell death. Preclinical and clinical studies have demonstrated the efficacy of CAP, with devices such as dielectric barrier discharge (DBD) and the plasma jet developed to minimize damage to healthy cells. Some CAP devices are already approved for clinical use, showing safety and efficacy. However, the standardization of treatments remains a challenge due to the variety of devices and parameters used. Although CAP has shown promising cytotoxic effects in vitro and in animal models, especially in different cancer cell lines, further research, particularly in vivo and in veterinary medicine, is needed to optimize its clinical use and maximize its efficacy in combating cancer.

Synergistic effects of cold atmospheric plasma and doxorubicin on melanoma: A systematic review and meta-analysis

Melanoma is responsible for the majority of skin cancer deaths, but there are ways to combat this deadly disease. One method is using anti-neoplastic agents, such as Doxorubicin (DOX). Unfortunately, DOX can be toxic and may lead to drug resistance. However, researchers are excited about the potential of Cold Atmospheric Plasma (CAP) treatment cancer cells and overcome drug resistance selectively. To better understand the effectiveness of the combination of CAP and DOX on melanoma cell viability, cytotoxicity, and cell death, we conducted a comprehensive evaluation and meta-analysis in this study. 41 studies out of 121 met our inclusion criteria. The pooled analysis found that CAP and DOX combination had a significant effect on cell viability (ES = 6.75, 95% CI 1.65 to 11.85, and I2 = 71%) and cytotoxicity (ES = 11.71, 95% CI 3.69 to 19.73, and I2 = 56%). however, no statistically significant association was found between cell death with combination treatment. Our studies have confirmed that the combined treatment of CAP and DOX has a synergistic effect on reducing cell viability and increasing cytotoxicity in melanoma cells. These results can assist researchers in selecting more effective treatment methods to address melanoma.

Anti-Tumor Effect of Non-Thermal Atmospheric Pressure Plasma-Activated Medium on Synovial Sarcoma: An In Vitro and In Vivo Study

Background/Objective: Anti-tumor effects of plasma-activated medium (PAM) were demonstrated using various malignant tumors. However, the anti-tumor effect of PAM on synovial sarcoma remains unclear. Therefore, we aimed to investigate the anti-tumor effects of PAM on synovial sarcoma and its underlying mechanisms, focusing on the quantitative analyses of both intracellular reactive oxygen species (ROS) and cell apoptosis. Methods: The human synovial sarcoma cell line HS-SY-II was used to investigate the cell viability after PAM treatment. We investigated the anti-tumor effects and side effects of local PAM injection in a synovial sarcoma xenograft murine model. Moreover, we observed PAM-induced intracellular ROS accumulation and cell apoptosis and assessed the involvement of intracellular ROS in the anti-tumor effects of PAM using an intracellular ROS scavenger. Results: PAM significantly decreased the viability of synovial sarcoma cells compared with untreated Dulbecco's modified Eagle medium. Local PAM injection into a synovial sarcoma xenograft murine model significantly suppressed tumor growth, including tumor volume (p < 0.001) and weight (p = 0.031), without side effects. Regarding anti-tumor mechanisms, PAM induced significant cell apoptosis and intracellular ROS accumulation (p < 0.001). The intracellular ROS scavenger significantly inhibited the anti-tumor effect of PAM (p < 0.001). Conclusions: We confirmed the anti-tumor effects of PAM on synovial sarcoma in vitro and in vivo, as well as the absence of side effects. The underlying mechanism was suggested to involve cell apoptosis induced by intracellular ROS accumulation. Considering the various clinical issues associated with the existing treatments of synovial sarcoma, PAM is a promising new option.

Non-thermal plasma as promising anti-cancer therapy against bladder cancer by inducing DNA damage and cell cycle arrest

Bladder cancer often recurs, necessitating innovative treatments to reduce recurrence. We investigated non-thermal plasma's potential as a novel anti-cancer therapy, focusing on plasma-activated solution (PAS), created by exposing saline to non-thermal plasma. Our study aims to elucidate the biological effects of PAS on bladder cancer cell lines in vitro, as well as the combination with mitomycin C (MMC), using clinically relevant settings. PAS treatment exerts a potent cytotoxic effect through the production of intracellular reactive oxygen species, resulting in DNA damage and subsequent induction of G1 cell cycle arrest/senescence. This is induced via upregulation of cell cycle checkpoint signalling and DNA damage repair pathways using LC-M/MS-based phospho-proteomics. Importantly, combining PAS with MMC reveals a synergistic effect (Combination Index of 0.59-0.67), suggesting the potential of utilizing PAS in combination therapies. Our findings demonstrate PAS's mode of action and suggest its potential as a promising treatment for bladder cancer, warranting further clinical studies.

Cold atmospheric plasma restores skewed macrophage polarization in triple negative breast cancers via enhancing KAT6A acetylation

Breast cancer is the most common cancer diagnosed and the second leading cause of death of cancer among women in the world, due to inappropriate diagnosis and choice of therapeutic approach. The molecular profiles of breast cancers may switch among subtypes during treatments, leading to a phenotype such as triple negative breast cancers (TNBCs) that is more difficult to treat. Cold atmospheric plasma (CAP) has been demonstrated by many studies on its efficacy in arresting the malignancies of multiple cancer types including TNBCs that lack surface receptor expression and are thus the most difficult to treat among breast cancers. By analyzing the genetic testing reports of a breast cancer clinical case misdiagnosed with BRCA1 mutation, we characterized the importance of KAT6A in driving disease progression of this patient. Through exploring genes differentially regulated under physical interactions between KAT6A and SMAD3, we proposed the KAT6A/SMAD3/IL6/CD163 molecular axis capable of driving macrophage M2 polarization in the immune microenvironment of breast cancers. Through examining the expression landscapes of KAT6A at both transcriptional and translational levels, we proposed a possible role of KAT6A acetylation in reducing its ability in acetylating SMAD3 and subsequent oncogenic roles. Through analyzing the whole transcriptome and acetylome of TNBC cells in response to CAP treatment, we predicted the efficacy of CAP in resolving TNBCs via increasing KAT6A acetylation, which were validated both in vitro and in vivo. Our study, for the first time, presented the role of CAP in re-polarizing macrophages from the M2 to M1 state in the microenvironment of breast cancers via elevating KAT6A acetylation, and warranted careful interpretation of patients' genetic testing reports by clinicians for the sake of minimizing mortalities due to inappropriate choice of therapeutic modalities.

Cellular Response of Immune Cells in the Upper Respiratory Tract After Treatment with Cold Atmospheric Plasma In Vitro

Cold atmospheric plasma (CAP) has antimicrobial properties and is also known to stimulate the immune system. These properties could be useful for the development of a novel therapeutic or preventive strategy against respiratory infections in the upper respiratory tract (URT) such as ventilator-associated pneumonia (VAP) without inducing an immune overreaction. This study investigated the cellular responses of polymorphonuclear neutrophils (PMNs) after exposure to CAP in a three-dimensional (3D) model of the URT. In vitro experiments were conducted using PMNs isolated from human blood to assess cell migration, intracellular production of reactive oxygen species (ROS), NETosis, surface marker expression (CD11b, CD62L, and CD66b), and cell death with live cell imaging and flow cytometry. CAP was applied for 5 min using two distinct modalities: pressurized air plasma with a plasma intensive care (PIC) device and nebulized air plasma (NP) with a new humidity resistent surface microdischarge (SMD) plasma source, both developed by Terraplasma Medical GmbH. There were no significant signs of cell damage or overstimulation with either device under the conditions tested. However, the NP device caused milder effects on PMN functionality compared to the PIC device, but also demonstrated reduced antibacterial efficacy and reactive oxygen/nitrogen species (RONS) production, as analyzed with colorimetric/fluorimetric assay kits. These findings highlight a trade-off between the two CAP modalities, each with distinct advantages and limitations. Further studies are necessary to investigate these effects in the clinical setting and evaluate the long-term safety and efficacy of CAP treatment in the URT.

Microscopic mechanistic study of the penetration distributions for plasma reactive oxygen and nitrogen species based on sialic acid targeting on the cell membrane surface

The ability of cold atmospheric plasmas (CAPs) to produce a wide range of active constituents while maintaining a low or even room temperature of the gas has made it a novel research area of great interest. During plasma action, cancer cell membrane surface components are susceptible to oxidative modification by reactive oxygen and nitrogen species (RONS). In this study, the process of oxidative modification of membrane surface components sialic acid by RONS was investigated based on molecular dynamics simulations, and the penetration mechanism of long-lived particles ONOOH and its homolytic products at the membrane-water interface and the effect of appropriate electric field action were studied. The results showed that cancer cells with high sialic acid expression were less stable than healthy cells. Plasma treatment may promote the ONOOH homolysis process, and its homolysis product OH free radical is more likely to adsorb near sialic acid molecules by hydrogen bonding, resulting in oxidative modification. The interaction force between OH free radical and sialic acid molecules is stronger than ONOOH, which helps to further understand the oxidative modification reaction in membrane environment. At the same time, appropriate electric field stimulation can enhance the depth of penetration of RONS to more effectively treat the pathological state of biological tissues. The study proposes the use of membrane surface sialic acid as a cancer therapeutic target and provides guidance for improving the depth of RONS penetration and maximizing the survival of healthy cells, which contributes to the further clinical translation of plasma biomedicine.

Reactive oxygen species from non-thermal gas plasma (CAP): implication for targeting cancer stem cells

Cancer remains a major global health challenge, with the persistence of cancer stem cells (CSCs) contributing to treatment resistance and relapse. Despite advancements in cancer therapy, targeting CSCs presents a significant hurdle. Non-thermal gas plasma, also known as CAP, represents an innovative cancer treatment. It has recently gained attention for its often found to be selective, immunogenic, and potent anti-cancer properties. CAP is composed of a collection of transient, high-energy, and physically and chemically active entities, such as reactive oxygen species (ROS). It is acknowledged that the latter are responsible for a major portion of biomedical CAP effects. The dynamic interplay of CAP-derived ROS and other components contributes to the unique and versatile properties of CAP, enabling it to interact with biological systems and elicit various therapeutic effects, including its potential in cancer treatment. While CAP has shown promise in various cancer types, its application against CSCs is relatively unexplored. This review assesses the potential of CAP as a therapeutic strategy for targeting CSCs, focusing on its ability to regulate cellular states and achieve redox homeostasis. This is done by providing an overview of CSC characteristics and demonstrating recent findings on CAP's efficacy in targeting these cells. By contributing insights into the unique attributes of CSCs and the potential of CAP, this work contributes to an advanced understanding of innovative oncology strategies.

Interplay of Cellular Nrf2/NF-κB Signalling after Plasma Stimulation of Malignant vs. Non-Malignant Dermal Cells

Skin cancer is one of the most common malignancies worldwide. Cold atmospheric pressure Plasma (CAP) is increasingly successful in skin cancer therapy, but further research is needed to understand its selective effects on cancer cells at the molecular level. In this study, A431 (squamous cell carcinoma) and HaCaT (non-malignant) cells cultured under identical conditions revealed similar ROS levels but significantly higher antioxidant levels in unstimulated A431 cells, indicating a higher metabolic turnover typical of tumour cells. HaCaT cells, in contrast, showed increased antioxidant levels upon CAP stimulation, reflecting a robust redox adaptation. Specifically, proteins involved in antioxidant pathways, including NF-κB, IκBα, Nrf2, Keap1, IKK, and pIKK, were quantified, and their translocation level upon stimulation was evaluated. CAP treatment significantly elevated Nrf2 nuclear translocation in non-malignant HaCaT cells, indicating a strong protection against oxidative stress, while selectively inducing NF-κB activation in A431 cells, potentially leading to apoptosis. The expression of pro-inflammatory genes like IL-1B, IL-6, and CXCL8 was downregulated in A431 cells upon CAP treatment. Notably, CAP enhanced the expression of antioxidant response genes HMOX1 and GPX1 in non-malignant cells. The differential response between HaCaT and A431 cells underscores the varied antioxidative capacities, contributing to their distinct molecular responses to CAP-induced oxidative stress.

Optimization of the Treatment of Squamous Cell Carcinoma Cells by Combining Photodynamic Therapy with Cold Atmospheric Plasma

Actinic keratosis (AK) is characterized by a reddish or occasionally skin-toned rough patch on sun-damaged skin, and it is regarded as a precursor to squamous cell carcinoma (SCC). Photodynamic therapy (PDT), utilizing 5-aminolevulinic acid (ALA) along with red light, is a recognized treatment option for AK that is limited by the penetration depth of light and the distribution of the photosensitizer into the skin. Cold atmospheric plasma (CAP) is a partially ionized gas with permeability-enhancing and anti-cancer properties. This study analyzed, in vitro, whether a combined treatment of CAP and ALA-PDT may improve the efficacy of the treatment. In addition, the effect of the application sequence of ALA and CAP was investigated using in vitro assays and the molecular characterization of human oral SCC cell lines (SCC-9, SCC-15, SCC-111), human cutaneous SCC cell lines (SCL-1, SCL-2, A431), and normal human epidermal keratinocytes (HEKn). The anti-tumor effect was determined by migration, invasion, and apoptosis assays and supported the improved efficacy of ALA-PDT in combination with CAP. However, the application sequence ALA-CAP-red light seems to be more efficacious than CAP-ALA-red light, which is probably due to increased intracellular ROS levels when ALA is applied first, followed by CAP and red light treatment. Furthermore, the expression of apoptosis- and senescence-related molecules (caspase-3, -6, -9, p16INK4a, p21CIP1) was increased, and different genes of the junctional network (ZO-1, CX31, CLDN1, CTNNB1) were induced after the combined treatment of CAP plus ALA-PDT. HEKn, however, were much less affected than SCC cells. Overall, the results show that CAP may improve the anti-tumor effects of conventional ALA-PDT on SCC cells. Whether this combined application is successful in treating AK in vivo has to be carefully examined in follow-up studies.

Realtime RONS monitoring of cold plasma-activated aqueous media based on time-resolved phosphorescence spectroscopy

Besides many efforts on the detection and quantification of reactive oxygen and nitrogen species (RONSs) in the aqueous media activated by the cold atmospheric plasma, to get a better insight into the dominant mechanism and reactive species in medical applications, a challenge still remains in monitoring the real-time evaluation of them. To this end, in the present work, relying on the photonic technology based on the time-resolved phosphorescence spectroscopy, real-time tracking of RONSs concentration in treated aqueous media is achieved by following the dissolved oxygen (DO) production/consumption. Using a photonic-based dissolved oxygen sensor, the dependence of real-time RONS concentration evaluation of plasma activated medium on plasma nozzle distance, non-thermal plasma jet exposure time, various culture media, and presence of cells is investigated. Analyzing the results, the activation parameters including the time of reaching maximum RONS concentration after treatment and defined activation parameter [Formula: see text] of the treated media for each case is measured and compared together. Moreover, employing the scavengers related to two involved ROSs, the dominant chemical reactions as well as ROS contributed in the DMEM medium is determined. As a promising result, the obtained correlation between the real-time DO level and viability and toxicity of the cancer cells, MCF-7 breast cancer cells, could enable us to exploit the present photonic setup as an alternative technique for the biological assessment.

Zwitterionic-hydrogel-based sensing system enables real-time ROS monitoring for ultra-long hypothermic cell preservation

Hypothermic preservation (HP) is highly desired for the maintenance of the viability of living cell specimens, e.g. rare cells in whole-blood samples or therapeutic cells, in an unfrozen state. However, the extension of the viable preservation time is a challenge because of the multiple injuries suffered by hypothermically preserved cells. Here, based on a dynamic bond crosslinked zwitterionic hydrogel, we established a sensing preservation system that could monitor the levels of reactive oxygen species (ROS) via real-time electronic signals and intelligent control of antioxidant addition, to completely prevent an excess of ROS in the whole-cell specimen. Furthermore, the hydrogel-based system can counter the extracellular-matrix-loss-induced anoikis of living cells. Based on the design aimed at affording protection against two primary HP injuries (i.e. ROS overproduction and anoikis) to cells, this system extended the preservation time of cell specimens under refrigerated conditions to 24 days. After preservation, the use of a mild cell retrieval process guaranteed the activity of the preserved living cells. This work not only possesses the potential to facilitate intelligent cell-based clinical applications, but also paves the way for the preparation of living materials that can host programmed cells with long-term survival. STATEMENT OF SIGNIFICANCE: An intelligent system based on a zwitterionic sensing hydrogel is established, which can afford ultra-long hypothermic cell-preservation times of up to 24 days. The system enables the real-time monitoring of ROS overproduction and intelligent antioxidant addition, because of the merging of the smart hydrogel with a computer intelligent detection and control system. Furthermore, the automatic addition of an antioxidant according to the ROS-signal changes produced by the ZBA hydrogel effectively prevented HP lesions, including ROS over-production and ECM loss, in the preserved living cells. Subsequently, the system could also be gently dissociated, to retrieve the preserved cells. This work provides a solution for the real-time monitoring and long-term HP of living specimens, which holds the promise of benefiting cell-based medicine and the development of genetically programmed cell-based living materials.

Proposing an Affordable Plasma Device for Polymer Surface Modification and Microbial Inactivation

This study proposes an affordable plasma device that utilizes a parallel-plate dielectric barrier discharge geometry with a metallic mesh electrode, featuring a straightforward 3D-printed design. Powered by a high-voltage supply adapted from a cosmetic plasma device, it operates on atmospheric air, eliminating the need for gas flux. Surface modification of polyethylene treated with this device was characterized and showed that the elemental composition after 15 min of plasma treatment decreased the amount of C to ~80 at% due to the insertion of O (~15 at%). Tested against Candida albicans and Staphylococcus aureus, the device achieved a reduction of over 99% in microbial load with exposure times ranging from 1 to 10 min. Simultaneously, the Vero cell viability remained consistently high, namely between 91% and 96% across exposure times. These results highlight this device's potential for the surface modification of materials and various infection-related applications, boasting affordability and facilitating effective antimicrobial interventions.

Cold Atmospheric Plasma Induces Growth Arrest and Apoptosis in Neurofibromatosis Type 1-Associated Peripheral Nerve Sheath Tumor Cells

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder resulting from mutations in the NF1 gene. Patients harboring these mutations are predisposed to a spectrum of peripheral nerve sheath tumors (PNSTs) originating from Schwann cells, of which malignant peripheral nerve sheath tumors (MPNSTs) are the deadliest, with limited treatment options. Therefore, an unmet need still exists for more effective therapies directed at these aggressive malignancies. Cold atmospheric plasma (CAP) is a reactive oxygen species (ROS) and reactive nitrogen species (RNS) generating ionized gas that has been proposed to be a potential therapeutic modality for cancer. In this study, we sought to determine the effects of CAP on NF1-associated PNSTs. Utilizing established mouse and human cell lines to interrogate the effects of CAP in both in vitro and in vivo settings, we found that NF1-associated PNSTs were highly sensitive to CAP exposure, resulting in cell death. To our knowledge, this is the first application of CAP to NF1-associated PNSTs and provides a unique opportunity to study the complex biology of NF1-associated tumors.

Cold atmospheric plasma enhances SLC7A11-mediated ferroptosis in non-small cell lung cancer by regulating PCAF mediated HOXB9 acetylation

Lung cancer is a leading cause of cancer death worldwide, with high incidence and poor survival rates. Cold atmospheric plasma (CAP) technology has emerged as a promising therapeutic approach for cancer treatment, inducing oxidative stress in malignant tissues without causing thermal damage. However, the role of CAP in regulating lung cancer cell ferroptosis remains unclear. Here, we observed that CAP effectively suppressed the growth and migration abilities of lung cancer cells, with significantly increased ferroptotic cell death, lipid peroxidation, and decreased mitochondrial membrane potential. Mechanistically, CAP regulates SLC7A11-mediated cell ferroptosis by modulating HOXB9. SLC7A11, a potent ferroptosis suppressor, was markedly reduced by HOXB9 knockdown, while it was enhanced by overexpressing HOXB9. The luciferase and ChIP assays confirmed that HOXB9 can directly target SLC7A11 and regulate its gene transcription. Additionally, CAP enhanced the acetylation modification level of HOXB9 by promoting its interaction with acetyltransferase p300/CBP-associated factor (PCAF). Acetylated HOXB9 affects its protein ubiquitination modification level, which in turn affects its protein stability. Notably, the upregulation of SLC7A11 and HOXB9 mitigated the suppressive effects of CAP on ferroptosis status, cell proliferation, invasion, and migration in lung cancer cells. Furthermore, animal models have also confirmed that CAP can inhibit the progression of lung cancer in vivo. Overall, this study highlights the significance of the downregulation of the HOXB9/SLC7A11 axis by CAP treatment in inhibiting lung cancer, offering novel insights into the potential mechanisms and therapeutic strategies of CAP for lung cancer.

Plasma-generated RONS in liquid transferred into cryo-microneedles patch for skin treatment of melanoma

Malignant melanoma is the most lethal form of skin cancer. As a promising anti-cancer agent, plasma-activated water (PAW) rich in reactive oxygen and nitrogen species (RONS) has shown significant potential for melanoma treatment. However, rapid decay of RONS and inefficient delivery of PAW in conventional injection methods limit its practical applications. To address this issue, here we report a new approach for the production of plasma-activated cryo-microneedles (PA-CMNs) patches using custom-designed plasma devices and processes. Our innovation is to incorporate PAW into the PA-CMNs that are fabricated using a fast cryogenic micro-molding method. It is demonstrated that PA-CMNs can be easily inserted into skin to release RONS and slow the decay of RONS thereby prolonging their bioactivity and effectiveness. The new insights into the effective melanoma treatment suggest that the rich mixture of RONS within PA-CMNs prepared by custom-developed hybrid plasma-assisted configuration induces both ferroptosis and apoptosis to selectively kill tumor cells. A significant inhibition of subcutaneous A375 melanoma growth was observed in PA-CMNs-treated tumor-bearing nude mice without any signs of systemic toxicity. The new approach based on PA-CMNs may potentially open new avenues for a broader range of disease treatments.

Cold Atmospheric Plasma: An Emerging Immunomodulatory Therapy

Cold atmospheric plasma (CAP) is a novel technology that generates a unique combination of reactive oxygen and nitrogen species (ROS/RNS), electric fields, and UV radiation. CAP has shown promise in regulating the immune system and has potential clinical applications in wound healing, cancer treatment, and infection control. This review provides an overview of the immunological regulation activity of CAP, highlighting its substantial impact on cytokines production, immune cell phagocytosis, and immune cell proliferation. CAP has also been demonstrated to have potent therapeutic effect in anti‐inflammation, wound repair, viral and bacterial infections. Furthermore, CAP has been investigated as an adjuvant therapy for tumor treatment, eliciting a robust antitumor immune response and remarkable synergistic effects in diverse combination therapies. Further research is needed to fully understand the mechanisms underlying the effects of CAP on the immune system and to optimize its clinical application.

Nonthermal Atmospheric Pressure Plasma Treatment of Endosteal Implants for Osseointegration and Antimicrobial Efficacy: A Comprehensive Review

The energy state of endosteal implants is dependent on the material, manufacturing technique, cleaning procedure, sterilization method, and surgical manipulation. An implant surface carrying a positive charge renders hydrophilic properties, thereby facilitating the absorption of vital plasma proteins crucial for osteogenic interactions. Techniques to control the surface charge involve processes like oxidation, chemical and topographical adjustments as well as the application of nonthermal plasma (NTP) treatment. NTP at atmospheric pressure and at room temperature can induce chemical and/or physical reactions that enhance wettability through surface energy changes. NTP has thus been used to modify the oxide layer of endosteal implants that interface with adjacent tissue cells and proteins. Results have indicated that if applied prior to implantation, NTP strengthens the interaction with surrounding hard tissue structures during the critical phases of early healing, thereby promoting rapid bone formation. Also, during this time period, NTP has been found to result in enhanced biomechanical fixation. As such, the application of NTP may serve as a practical and reliable method to improve healing outcomes. This review aims to provide an in-depth exploration of the parameters to be considered in the application of NTP on endosteal implants. In addition, the short- and long-term effects of NTP on osseointegration are addressed, as well as recent advances in the utilization of NTP in the treatment of periodontal disease.

Cold atmospheric plasma stabilizes mismatch repair for effective, uniform treatment of diverse colorectal cancer cell types

Mismatch Repair (MMR) mechanisms play a pivotal role in rectifying DNA replication errors and maintaining the stability of DNA microsatellite structure. Colorectal cancer (CRC) can be characterized into microsatellite stability (MSS) and microsatellite instability (MSI) subtypes based on the functionality of MMR. MSI CRC notably exhibits enhanced chemotherapy resistance, attributable to diminished MMR-related protein expression. Cold atmospheric plasma (CAP) has emerged as a promising treatment modality, demonstrating efficacy in inducing apoptosis in various cancer cells. However, the therapeutic impact of CAP on MSI colorectal cancer, and the underlying mechanisms remain elusive. In this study, we investigated the effects of CAP on MSI (MC38, HCT116, and LOVO) and MSS (CT26 and HT29) CRC cell lines. We are probing into the products of CAP treatment. Our findings indicate that CAP treatment induces comparable effects on apoptosis, reactive oxygen species (ROS), and reactive nitrogen species (RNS), as well as the expression of apoptosis-related proteins in both MSI and MSS cells. Mechanistically, CAP treatment led to an elevation in the expression of mismatch repair proteins (MLH1 and MSH2), particularly in MSI cells, which notably have been proven to facilitate the activation of apoptosis-related proteins. Collectively, our study reveals that CAP enhances apoptotic signaling and induces apoptosis in MSI colorectal cancer cells by upregulating the expression of MMR-related proteins, thereby reinforcing MMR stabilization.

Comparative assessment of direct and indirect cold atmospheric plasma effects, based on helium and argon, on human glioblastoma: an in vitro and in vivo study

Recent research has highlighted the promising potential of cold atmospheric plasma (CAP) in cancer therapy. However, variations in study outcomes are attributed to differences in CAP devices and plasma parameters, which lead to diverse compositions of plasma products, including electrons, charged particles, reactive species, UV light, and heat. This study aimed to evaluate and compare the optimal exposure time, duration, and direction-dependent cellular effects of two CAPs, based on argon and helium gases, on glioblastoma U-87 MG cancer cells and an animal model of GBM. Two plasma jets were used as low-temperature plasma sources in which helium or argon gas was ionized by high voltage (4.5 kV) and frequency (20 kHz). In vitro assessments on human GBM and normal astrocyte cell lines, using MTT assays, flow cytometry analysis, wound healing assays, and immunocytochemistry for Caspase3 and P53 proteins, demonstrated that all studied plasma jets, especially indirect argon CAP, selectively induced apoptosis, hindered tumor cell growth, and inhibited migration. These effects occurred concurrently with increased intracellular levels of reactive oxygen species and decreased total antioxidant capacity in the cells. In vivo results further supported these findings, indicating that single indirect argon and direct helium CAP therapy, equal to high dose Temozolomide treatment, induced tumor cell death in a rat model of GBM. This was concurrent with a reduction in tumor size observed through PET-CT scan imaging and a significant increase in the survival rate. Additionally, there was a decrease in GFAP protein levels, a significant GBM tumor marker, and an increase in P53 protein expression based on immunohistochemical analyses. Furthermore, Ledge beam test analysis revealed general motor function improvement after indirect argon CAP therapy, similar to Temozolomide treatment. Taken together, these results suggest that CAP therapy, using indirect argon and direct helium jets, holds great promise for clinical applications in GBM treatment.

Low-Temperature Plasma Techniques in Biomedical Applications and Therapeutics: An Overview

Plasma, the fourth fundamental state of matter, comprises charged species and electrons, and it is a fascinating medium that is spread over the entire visible universe. In addition to that, plasma can be generated artificially under appropriate laboratory techniques. Artificially generated thermal or hot plasma has applications in heavy and electronic industries; however, the non-thermal (cold atmospheric or low temperature) plasma finds its applications mainly in biomedicals and therapeutics. One of the important characteristics of LTP is that the constituent particles in the plasma stream can often maintain an overall temperature of nearly room temperature, even though the thermal parameters of the free electrons go up to 1 to 10 keV. The presence of reactive chemical species at ambient temperature and atmospheric pressure makes LTP a bio-tolerant tool in biomedical applications with many advantages over conventional techniques. This review presents some of the important biomedical applications of cold-atmospheric plasma (CAP) or low-temperature plasma (LTP) in modern medicine, showcasing its effect in antimicrobial therapy, cancer treatment, drug/gene delivery, tissue engineering, implant modifications, interaction with biomolecules, etc., and overviews some present challenges in the field of plasma medicine.

Ozone mediates the anticancer effect of air plasma by triggering oxidative cell death caused by H2O2 and iron

Cold atmospheric plasmas and plasma-treated solutions (PTSs) have emerged as promising approaches in cancer treatment because of their tumor-selective actions. While oxidative stress is critical for their effects, the precise mechanisms, including chemical mediators, remain obscure. Previously, we reported that air plasma-activated medium (APAM) exhibited tumor-selective anticancer activity. The fragmentation of mitochondria and their asymmetrical assembly around the peripheral regions of the damaged nucleus, namely, monopolar perinuclear mitochondrial clustering (MPMC), proceed to the effect. Subsequently, we found that APAM had a substantial amount of O3 in addition to hydrogen peroxide (H2O2), nitrile (NO2-), and nitrate (NO3-). In the present study, we investigated the possible role of O3 in the anticancer effect. For this purpose, we created a nitrogen oxide-free ozonated medium ODM. ODM exhibited potent cytotoxicity against various cancer but not nonmalignant cells. ODM also increased MPMC, hydroxyl radicals, lipid peroxides, and their shifts to perinuclear sites in cancer cells. Catalase and iron chelation prevented these events and cytotoxicity. ODM also decreases the intracellular labile irons while increasing those within mitochondria. ODM had substantial H2O2, but this oxidant failed to cause MPMC and cytotoxicity. These results show that ODM can mimic the effects of APAM, including MPMC and tumor-selective anticancer effects. The findings suggest that O3 is critical in mediating the anticancer effects of APAM by triggering oxidative cell death caused by H2O2 and iron.

Effects of cold atmospheric-pressure plasma in combination with doxorubicin drug against breast cancer cells in vitro and invivo

Cold atmospheric plasma (CAP) has been suggested for medical applications that can be applied indirectly through plasma-activated medium (PAM) and recently it has been introduced as an innovative therapeutic approach for all cancer types. Studies have exhibited that ROS/RNS are key factors in CAP-dependent apoptosis; nevertheless, ROS/RNS stability are weak. Combination therapy is considered an effective strategy to overcome these problems. In the present research, we revealed that the combination of CAP and doxorubicin (DOX) significantly induces the apoptosis of breast cancer cells both in vitro and in vivo. Our results indicated that both Ar and He/O2 CAP treatment as well as DOX drug alone reduced cell growth. CAP/PAM treatment in combination with DOX induced apoptosis in MCF-7 breast cancer cells and 4T1-implanted BALB/c mice, resulting in a significant increase in antitumor activity. The apoptotic effects of CAP-DOX on MCF-7 cells were inferred from altered expression of BAX and cleaved-caspase-3 which mechanistically take place through the mitochondrial pathway mediated by Bcl-2 family members. Besides, the BAX/BCL-2 ratio is significantly higher in the simultaneous treatment of CAP and DOX. This ratio was equal to 2.82 ± 0.24, 2.54 ± 0.30, and 11.27 ± 0.31 for treatment with DOX, He/O2 plasma, and combination treatment, respectively. Additionally, the tumor growth rate of He/O2-PAM + DOX and Ar-PAM + DOX treatments was significantly inhibited by PAM-injection, and the tumor growth rate of PAM alone or DOX alone was slightly reduced. It can be concluded that the effect of PAM + DOX may increase the anticancer activity and decrease the dose required for the chemotherapeutic treatment.

Molecular dynamics simulation of the transmembrane transport process of reactive species under the synergistic effect of plasma oxidation and an electric field

Cold atmospheric pressure plasma (CAP)-assisted cancer therapy has become a popular topic in plasma biomedical research. Membrane lipid oxidation and local electric fields are two important factors in plasma-cell interactions, and the study of their synergistic effect is highly significant for optimizing the regulatory mechanism of the plasma-induced apoptosis of cancer cells. In this paper, a model of oxidized phospholipids was established, and the transmembrane process of reactive species was simulated by the classical molecular dynamics (MD) method under the conditions of oxidation and an electric field. The results showed that hydrophilic reactive oxygen species could not penetrate the membrane lipids through oxidation. The formation of electroporation provided a new channel for reactive species to penetrate the membrane, and the oxidation effect reduced the electric field threshold of membrane electroporation. Our simulation could provide theoretical support for the plasma-induced apoptosis of cancer cells at the microscopic level, provide mechanistic guidance for the practical application of plasma-induced cancer therapy, and promote the development of CAP in the field of cancer therapy.

Health assessment of rice cultivated and harvested from plasma-irradiated seeds

This study provides the health effects assessment of rice cultivated from plasma-irradiated seeds. The rice (Oryza sativa L.) cultivated from seeds with plasma irradiation showed a growth improvement (slope-ratios of with plasma to without plasma were 1.066, 1.042, and 1.255 for tiller, and earing, and ripening periods, respectively) and an 4% increase in yield. The cultivated rice was used for repeated oral administrations to mice for 4-week period. Distilled water and rice cultivated from seeds without plasma irradiation were also used as control. The weights of the lung, kidney, liver, and spleen, with corresponding average values of 0.22 g, 0.72 g, 2.1 g, and 0.17 g for w/ plasma group and 0.22 g, 0.68 g, 2.16 g, and 0.14 g for w/o plasma group, respectively, showing no effect due to the administration of rice cultivated from plasma-irradiated seeds. Nutritional status, liver function, kidney function, and lipid, neutral fat profiles, and glucose metabolism have no significant difference between with and without plasma groups. These results show no obvious subacute effects were observed on rice grains cultivated and harvested from the mother plant that experienced growth improvement by plasma irradiation. This study provides a new finding that there is no apparent adverse health effect on the grains harvested from the plasma-irradiated seeds.

Nanosecond pulsed cold atmospheric plasma jet suppresses proliferation and migration of human glioblastoma cells via apoptosis promotion and EMT inhibition

Glioblastoma (GBM) is one of the most aggressive and challenging cancers to treat. Despite extensive research on dozens of cancer cells, including GBM, the effect of cold atmospheric plasma (CAP) on the invasive migration of GBM cells has received limited attention, and the underlying mechanisms remain poorly understood. This study aims to investigate the potential molecular mechanism of ns-CAPJ in inhibiting the invasive migration of human GBM cells. The findings indicate that ns-CAPJ significantly reduces GBM cell invasion and migration, and induces apoptosis in GBM cells. Further mechanistic studies demonstrate a direct correlation between the suppression of the epithelial-mesenchymal transition (EMT) signaling pathway and ns-CAPJ's inhibitory effect on GBM cell invasion and migration. Additionally, combined with the N-acetyl cysteine (NAC, a ROS inhibitor) assay, we found that the ROS stimulated by the ns-CAPJ plays an important role in suppressing the EMT process. This work is expected to provide new insight into understanding the molecular mechanisms of how ns-CAPJ inhibits the proliferation and migration of human GBM cells.

Investigating the impact of inbuilt cold atmospheric pressure plasma on molecular assemblies of tryptophan enantiomers: in vitro fabrication of self-assembled supramolecular structures

The advancements in understanding the phenomenon of plasma interactions with matter, coupled with the development of CAPP devices, have resulted in an interdisciplinary research topic of significant importance. This has led to the integration of various fields of science, including plasma physics, chemistry, biomedical sciences, and engineering. The reactive oxygen species and reactive nitrogen species generated from cold atmospheric plasma on interaction with biomolecules like proteins and peptides form various supramolecular structures. CAPP treatment of amino acids, which are the fundamental building blocks of proteins, holds potential in creating self-assembled supramolecular architectures. In this work, we demonstrate the process of self-assembly of aromatic amino acid tryptophan (Trp) enantiomers (l-tryptophan and d-tryptophan) into ordered supramolecular assemblies induced by the reactive species generated by a cold atmospheric pressure helium plasma jet. These enantiomers of tryptophan form organized structures as evidenced by FE-SEM. To assess the impact of CAPP treatment on the observed assemblies, we employed various analytical techniques such as zeta potential, dynamic light scattering and FTIR spectroscopy. Also, photoluminescence and time-resolved lifetime measurements revealed the transfiguration of individual Trp enantiomers. The LC-ESI-QTOF-MS analysis demonstrated that CAPP irradiation led to the incorporation of oxygenated ions into the pure Trp molecule. These studies of the self-assembly of Trp due to ROS and RNS interactions will help us to understand the assembly environment. This knowledge may be utilized to artificially design and synthesize highly ordered functional supramolecular structures using CAPP.

Medical gas plasma technology: Roadmap on cancer treatment and immunotherapy

Despite continuous therapeutic progress, cancer remains an often fatal disease. In the early 2010s, first evidence in rodent models suggested promising antitumor action of gas plasma technology. Medical gas plasma is a partially ionized gas depositing multiple physico-chemical effectors onto tissues, especially reactive oxygen and nitrogen species (ROS/RNS). Today, an evergrowing body of experimental evidence suggests multifaceted roles of medical gas plasma-derived therapeutic ROS/RNS in targeting cancer alone or in combination with oncological treatment schemes such as ionizing radiation, chemotherapy, and immunotherapy. Intriguingly, gas plasma technology was recently unraveled to have an immunological dimension by inducing immunogenic cell death, which could ultimately promote existing cancer immunotherapies via in situ or autologous tumor vaccine schemes. Together with first clinical evidence reporting beneficial effects in cancer patients following gas plasma therapy, it is time to summarize the main concepts along with the chances and limitations of medical gas plasma onco-therapy from a biological, immunological, clinical, and technological point of view.

Basic research and clinical exploration of cold atmospheric plasma for skin wounds

Skin wounds, such as burns, diabetic foot ulcers, pressure sores, and wounds formed after laser or surgical treatment, comprise a very high proportion of dermatological disorders. Wounds are treated in a variety of ways; however, some wounds are greatly resistant, resulting in delayed healing and an urgent need to introduce new alternatives. Our previous studies have shown that cold atmospheric plasma (CAP) has antibacterial activity and promotes cell proliferation, differentiation, and migration in vitro. To further advance the role of CAP in wound healing, we evaluated the safety and efficacy of CAP in vitro by irradiation of common refractory bacteria on the skin, irradiation of normal skin of rats and observing reactions, treatment of scald wounds in rats, and treating clinically common acute wounds. Our findings revealed that CAP can eliminate refractory skin bacteria in vitro; CAP positively affected wound healing in a rat scalding wound model; and direct CAP irradiation of low intensity and short duration did not lead to skin erythema or edema. CAP promises to be a new, economical, and safe means of wound treatment.

Current Status and Future Trends of Cold Atmospheric Plasma as an Oncotherapy

Cold atmospheric plasma (CAP), a redox modulation tool, is capable of inhibiting a wide spectrum of cancers and has thus been proposed as an emerging onco-therapy. However, with incremental successes consecutively reported on the anticancer efficacy of CAP, no consensus has been made on the types of tumours sensitive to CAP due to the different intrinsic characteristics of the cells and the heterogeneous design of CAP devices and their parameter configurations. These factors have substantially hindered the clinical use of CAP as an oncotherapy. It is thus imperative to clarify the tumour types responsive to CAP, the experimental models available for CAP-associated investigations, CAP administration strategies and the mechanisms by which CAP exerts its anticancer effects with the aim of identifying important yet less studied areas to accelerate the process of translating CAP into clinical use and fostering the field of plasma oncology.

Improving physio-mechanical and biological properties of 3D-printed PLA scaffolds via in-situ argon cold plasma treatment

As a bone tissue engineering material, polylactic acid (PLA) has received significant attention and interest due to its ease of processing and biocompatibility. However, its insufficient mechanical properties and poor wettability are two major drawbacks that limit its extensive use. For this purpose, the present study uses in-situ cold argon plasma treatment coupled with a fused deposition modeling printer to enhance the physio-mechanical and biological behavior of 3D-printed PLA scaffolds. Following plasma treatment, field emission scanning electron microscopy images indicated that the surface of the modified scaffold became rough, and the interlayer bonding was enhanced. This resulted in an improvement in the tensile properties of samples printed in the X, Y, and Z directions, with the enhancement being more significant in the Z direction. Additionally, the root mean square value of PLA scaffolds increased (up to 70-fold) after plasma treatment. X-ray photoelectron spectroscopy analysis demonstrated that the plasma technique increased the intensity of oxygen-containing bonds, thereby reducing the water contact angle from 92.5° to 42.1°. The in-vitro degradation study also demonstrated that argon plasma treatment resulted in a 77% increase in PLA scaffold degradation rate. Furthermore, the modified scaffold improved the viability, attachment, and proliferation of human adipose-derived stem cells. These findings suggest that in-situ argon plasma treatment may be a facile and effective method for improving the properties of 3D-printed parts for bone tissue engineering and other applications.

The Development of Nonthermal Plasma and Tirapazamine as a Novel Combination Therapy to Treat Melanoma In Situ

Although melanoma accounts for only 5.3% of skin cancer, it results in >75% of skin-cancer-related deaths. To avoid disfiguring surgeries on the head and neck associated with surgical excision, there is a clear unmet need for other strategies to selectively remove cutaneous melanoma lesions. Mohs surgery is the current treatment for cutaneous melanoma lesions and squamous and basal cell carcinoma. While Mohs surgery is an effective way to remove melanomas in situ, normal tissue is also excised to achieve histologically negative margins. This paper describes a novel combination therapy of nonthermal plasma (NTP) which emits a multitude of reactive oxygen species (ROS) and the injection of a pharmaceutical agent. We have shown that the effects of NTP are augmented by the DNA-damaging prodrug, tirapazamine (TPZ), which becomes a free radical only in conditions of hypoxemia, which is often enhanced in the tumor microenvironment. In this study, we demonstrate the efficacy of the combination therapy through experiments with B16-F10 and 1205 Lu metastatic melanoma cells both in vitro and in vivo. We also show the safety parameters of the therapy with no significant effects of the therapy when applied to porcine skin. We show the need for the intratumor delivery of TPZ in combination with the surface treatment of NTP and present a model of a medical device to deliver this combination therapy. The importance of functional gap junctions is indicated as a mechanism to promote the therapeutic effect. Collectively, the data support a novel therapeutic combination to treat melanoma and the development of a medical device to deliver the treatment in situ.

Non-Thermal Plasma Application in Medicine-Focus on Reactive Species Involvement

Non-thermal plasma (NTP) application in medicine is a dynamically developing interdisciplinary field. Despite the fact that basics of the plasma phenomenon have been known since the 19th century, growing scientific attention has been paid in recent years to the use of plasma in medicine. Three most important plasma-based effects are pivotal for medical applications: (i) inactivation of a broad spectrum of microorganisms, (ii) stimulation of cell proliferation and angiogenesis with lower plasma treatment intensity, and (iii) inactivation of cells by initialization of cell death with higher plasma intensity. In this review, we explain the underlying chemical processes and reactive species involvement during NTP in human (or animal) tissues, as well as in bacteria inactivation, which leads to sterilization and indirectly supports wound healing. In addition, plasma-mediated modifications of medical surfaces, such as surgical instruments or implants, are described. This review focuses on the existing knowledge on NTP-based in vitro and in vivo studies and highlights potential opportunities for the development of novel therapeutic methods. A full understanding of the NTP mechanisms of action is urgently needed for the further development of modern plasma-based medicine.

Unraveling the Transport Properties of RONS across Nitro-Oxidized Membranes

The potential of cold atmospheric plasma (CAP) in biomedical applications has received significant interest, due to its ability to generate reactive oxygen and nitrogen species (RONS). Upon exposure to living cells, CAP triggers alterations in various cellular components, such as the cell membrane. However, the permeation of RONS across nitrated and oxidized membranes remains understudied. To address this gap, we conducted molecular dynamics simulations, to investigate the permeation capabilities of RONS across modified cell membranes. This computational study investigated the translocation processes of less hydrophilic and hydrophilic RONS across the phospholipid bilayer (PLB), with various degrees of oxidation and nitration, and elucidated the impact of RONS on PLB permeability. The simulation results showed that less hydrophilic species, i.e., NO, NO₂, N₂O₄, and O₃, have a higher penetration ability through nitro-oxidized PLB compared to hydrophilic RONS, i.e., HNO₃, s-cis-HONO, s-trans-HONO, H₂O₂, HO₂, and OH. In particular, nitro-oxidation of PLB, induced by, e.g., cold atmospheric plasma, has minimal impact on the penetration of free energy barriers of less hydrophilic species, while it lowers these barriers for hydrophilic RONS, thereby enhancing their translocation across nitro-oxidized PLB. This research contributes to a better understanding of the translocation abilities of RONS in the field of plasma biomedical applications and highlights the need for further analysis of their role in intracellular signaling pathways.

Non-Thermal Atmospheric Pressure Plasma Application in Endodontics

The failure of endodontic treatment is frequently associated with the presence of remaining microorganisms, mainly due to the difficulty of eliminating the biofilm and the limitation of conventional irrigation solutions. Non-thermal atmospheric pressure plasma (NTPP) has been suggested for many applications in the medical field and can be applied directly to biological surfaces or indirectly through activated liquids. This literature review aims to evaluate the potential of NTPP application in Endodontics. A search in the databases Lilacs, Pubmed, and Ebsco was performed. Seventeen manuscripts published between 2007 and 2022 that followed our established inclusion criteria were found. The selected manuscripts evaluated the use of NTPP regarding its antimicrobial activity, in the direct exposure and indirect method, i.e., plasma-activated liquid. Of these, 15 used direct exposure. Different parameters, such as working gas and distance from the apparatus to the substrate, were evaluated in vitro and ex vivo. NTPP showed a disinfection property against important endodontic microorganisms, mainly Enterococcus faecalis and Candida albicans. The antimicrobial potential was dependent on plasma exposure time, with the highest antimicrobial effects over eight minutes of exposure. Interestingly, the association of NTPP and conventional antimicrobial solutions, in general, was shown to be more effective than both treatments separately. This association showed antimicrobial results with a short plasma exposure time, what could be interesting in clinical practice. However, considering the lack of standardization of the direct exposure parameters and few studies about plasma-activated liquids, more studies in the area for endodontic purposes are still required.

The Regulatory Mechanism of Cold Plasma in Relation to Cell Activity and Its Application in Biomedical and Animal Husbandry Practices

As an innovative technology in biological applications, cold plasma is widely used in oral treatment, tissue regeneration, wound healing, and cancer therapy, etc., because of the adjustable composition and temperature which allow the plasma to react with bio-objects safely. Reactive oxygen species (ROS) produced by cold plasma regulate cell activity in an intensity- and time-dependent manner. A low level of ROS produced by cold plasma treatment within the appropriate intensities and times promotes proliferation of skin-related cells and increases angiogenesis, which aid in the acceleration of the wound healing process, while a high level of ROS produced by cold plasma treatment performed at a high intensity or over a long period of time inhibits the proliferation of endothelial cells, keratinocytes, fibroblasts, and cancer cells. Moreover, cold plasma can regulate stem cell proliferation by changing niche interface and producing nitric oxide directly. However, the molecular mechanism of cold plasma regulating cell activity and its potential application in the field of animal husbandry remain unclear in the literature. Therefore, this paper reviews the effects and possible regulatory mechanisms of cold plasma on the activities of endothelial cells, keratinocytes, fibroblasts, stem cells, and cancer cells to provide a theoretical basis for the application of cold plasma to skin-wound healing and cancer therapy. In addition, cold plasma exposure at a high intensity or an extended time shows excellent performances in killing various microorganisms existing in the environment or on the surface of animal food, and preparing inactivated vaccines, while cold plasma treatment within the appropriate conditions improves chicken growth and reproductive capacity. This paper introduces the potential applications of cold plasma treatment in relation to animal-breeding environments, animal health, their growth and reproduction, and animal food processing and preservation, which are all beneficial to the practice of animal husbandry and guarantee good animal food safety results.

An omics approach to delineating the molecular mechanisms that underlie the biological effects of physical plasma

The use of physical plasma to treat cancer is an emerging field, and interest in its applications in oncology is increasing rapidly. Physical plasma can be used directly by aiming the plasma jet onto cells or tissue, or indirectly, where a plasma-treated solution is applied. A key scientific question is the mechanism by which physical plasma achieves selective killing of cancer over normal cells. Many studies have focused on specific pathways and mechanisms, such as apoptosis and oxidative stress, and the role of redox biology. However, over the past two decades, there has been a rise in omics, the systematic analysis of entire collections of molecules in a biological entity, enabling the discovery of the so-called "unknown unknowns." For example, transcriptomics, epigenomics, proteomics, and metabolomics have helped to uncover molecular mechanisms behind the action of physical plasma, revealing critical pathways beyond those traditionally associated with cancer treatments. This review showcases a selection of omics and then summarizes the insights gained from these studies toward understanding the biological pathways and molecular mechanisms implicated in physical plasma treatment. Omics studies have revealed how reactive species generated by plasma treatment preferentially affect several critical cellular pathways in cancer cells, resulting in epigenetic, transcriptional, and post-translational changes that promote cell death. Finally, this review considers the outlook for omics in uncovering both synergies and antagonisms with other common cancer therapies, as well as in overcoming challenges in the clinical translation of physical plasma.

Selective Effects of Cold Atmospheric Plasma on Bone Sarcoma Cells and Human Osteoblasts

BACKGROUND

The use of cold atmospheric plasma (CAP) in oncology has been intensively investigated over the past 15 years as it inhibits the growth of many tumor cells. It is known that reactive oxidative species (ROS) produced in CAP are responsible for this effect. However, to translate the use of CAP into medical practice, it is essential to know how CAP treatment affects non-malignant cells. Thus, the current in vitro study deals with the effect of CAP on human bone cancer cells and human osteoblasts. Here, identical CAP treatment regimens were applied to the malignant and non-malignant bone cells and their impact was compared.

METHODS

Two different human bone cancer cell types, U2-OS (osteosarcoma) and A673 (Ewing's sarcoma), and non-malignant primary osteoblasts (HOB) were used. The CAP treatment was performed with the clinically approved kINPen MED. After CAP treatment, growth kinetics and a viability assay were performed. For detecting apoptosis, a caspase-3/7 assay and a TUNEL assay were used. Accumulated ROS was measured in cell culture medium and intracellular. To investigate the influence of CAP on cell motility, a scratch assay was carried out.

RESULTS

The CAP treatment showed strong inhibition of cell growth and viability in bone cancer cells. Apoptotic processes were enhanced in the malignant cells. Osteoblasts showed a higher potential for ROS resistance in comparison to malignant cells. There was no difference in cell motility between benign and malignant cells following CAP treatment.

CONCLUSIONS

Osteoblasts show better tolerance to CAP treatment, indicated by less affected viability compared to CAP-treated bone cancer cells. This points toward the selective effect of CAP on sarcoma cells and represents a further step toward the clinical application of CAP.

Cold Atmospheric Plasma Triggers Apoptosis via the Unfolded Protein Response in Melanoma Cells

Cold atmospheric plasma (CAP) describes a partially ionized gas carrying large amounts of reactive oxygen (ROS) and nitrogen species (RNS). Numerous studies reported strong antitumor activity of CAP, thus rendering it a promising approach for tumor therapy. Although several cellular mechanisms of its cytotoxicity were identified in recent years, the exact molecular effects and contributing signaling pathways are yet to be discovered. We discovered a strong activation of unfolded protein response (UPR) after CAP treatment with increased C/EBP homologous protein (CHOP) expression, which was mainly caused by protein misfolding and calcium loss in the endoplasmic reticulum. In addition, both ceramide level and ceramide metabolism were reduced after CAP treatment, which was then linked to the UPR activation. Pharmacological inhibition of ceramide metabolism resulted in sensitization of melanoma cells for CAP both in vitro and ex vivo. This study identified a novel mechanism of CAP-induced apoptosis in melanoma cells and thereby contributes to its potential application in tumor therapy.

Portable Cold Atmospheric Plasma Patch-Mediated Skin Anti-Inflammatory Therapy

Although plasma is a promising technology in various fields, its clinical application is restricted by several limitations. A cold atmospheric plasma (CAP) patch is fabricated to help overcome hurdles, especially when treating skin diseases. This patch has surface dielectric barrier discharge, which generates reactive oxygen species (ROS) and reactive nitrogen species (RNS) on a flexible polymer film surface on which the embedded electrode induces a locally strong electric field. The effect of the CAP patch on psoriasis is also evaluated. The distinct characteristics of psoriasis between the lesion and non-lesion area allow the CAP patch to be suitable for only lesion area for its treatment. The CAP patch induces the opening of calcium channels in keratinocytes, thereby restoring abnormal keratinocyte differentiation and the collapse of the tight junction; thus, alleviating psoriatic symptoms. In addition, the favorable effect is due to the induction of ROS/RNS by the CAP patch, not the electric field generated during plasma generation. The findings indicate that the proposed portable CAP patch can help treat inflammatory skin disorders, especially psoriasis. As this can be used easily as a combination therapy with existing drugs, it may help reduce side effects caused by existing drugs.

Thomson microwave scattering for diagnostics of small plasma objects enclosed within glass tubes

In this work, coherent microwave scattering in the Thomson regime was demonstrated for small-scale plasmas enclosed within a glass tube and validated using a well-known hairpin resonator probe technique. The experiments were conducted in a DC discharge tube with a diameter of 1.5 cm and a length of 7 cm. Thomson microwave scattering (TMS) diagnostics yielded electron number densities of about 5.9 × 10¹⁰ cm^-3, 2.8 × 10¹⁰ cm^-3, and 1.8 × 10¹⁰ cm^-3 for air pressures in the discharge tube of 0.2, 0.5, and 2.5 Torr, respectively. Measurements using the TMS technique were consistent across the tested microwave frequencies of 3-3.9 GHz within the margin of error associated with non-idealities of the IQ mixer utilized in the circuit. The corresponding densities measured with the hairpin resonator probe were 4.8 × 10¹⁰, 3.8 × 10¹⁰, and 2.6 × 10¹⁰ cm^-3. Discrepancies between the two techniques were within 30% and can be attributed to inaccuracies in the sheath thickness estimation required for correct interpretation of the hairpin resonator probe results.

Analysis of a nano-pulsed DBD Plasma jet for endoscopy and impact of excitation parameters

Cold atmospheric plasma induces various dose-dependent effects on living cells, from proliferation to necrosis. These effects are of interest in the field of therapeutic flexible endoscopy, although implementing an effective plasma delivery system represents a technical challenge. This work studies the impact of critical parameters on plume intensity, delivered reactive species (RS), and current administered to the target for the use of plasma in endoscopy. A 2 m long dielectric barrier discharge plasma jet was studied upon nano-pulsed high voltage excitation to increase plasma reactivity. The peak voltage, gas gap, pulse repetition frequency, and pulse width were varied while the power dissipated by the system and the optical emissions (with imaging and spectrometry) were measured. Two configurations were compared: the first one with the plume exiting freely in air, and the second one with the plume impinging an electrical equivalent of the human body. Finally, the current flowing through the capillary was measured at regular intervals along the tube with a Rogowski coil. Results show that (a) a conductive target increases the ratio of RS produced over the dissipated power, (b) increasing the pulse repetition frequency does not improve the RS production per pulse (e.g. through a synergetic, memory effect), (c) increasing the pulse width does not influence RS production but increases the dissipated power, and (d) current linearly leaks through the tube walls, and leaks are lower with nano-pulsed compared to sinusoidal excitation. Reactance and capacitance values of the system are analyzed based on the electrical equivalent circuit approach. Finally, displacement and discharge currents are discussed to bring power dissipation mechanisms to light and compare them between configurations. The conclusions drawn are important for the future design of safe and effective endoscopic plasma devices.

Modulation of Reactive Oxygen Species in Cancers: Recent Advances

Oxidation-reduction reactions played a significant role in the chemical evolution of life forms on oxygenated earth. Cellular respiration is dependent on such redox reactions, and any imbalance leads to the accumulation of reactive oxygen species (ROS), resulting in both chronic and acute illnesses. According to the International Agency for Research on Cancer (IARC), by 2040, the global burden of new cancer cases is expected to be around 27.5 million, with 16.3 million cancer deaths due to an increase in risk factors such as unhealthy lifestyle, environmental factors, aberrant gene mutations, and resistance to therapies. ROS play an important role in cellular signalling, but they can cause severe damage to tissues when present at higher levels. Elevated and chronic levels of ROS are pertinent in carcinogenesis, while several therapeutic strategies rely on altering cellular ROS to eliminate tumour cells as they are more susceptible to ROS-induced damage than normal cells. Given this selective targeting potential, therapies that can effectively modulate ROS levels have been the focus of intense research in recent years. The current review describes biologically relevant ROS, its origins in solid and haematological cancers, and the current status of evolving antioxidant and pro-oxidant therapies in cancers.

Novel epigenetic therapeutic strategies and targets in cancer

The critical role of dysregulated epigenetic pathways in cancer genesis, development, and therapy has typically been established as a result of scientific and technical innovations in next generation sequencing. RNA interference, histone modification, DNA methylation and chromatin remodelling are epigenetic processes that control gene expression without causing mutations in the DNA. Although epigenetic abnormalities are thought to be a symptom of cell tumorigenesis and malignant events that impact tumor growth and drug resistance, physicians believe that related processes might be a key therapeutic target for cancer treatment and prevention due to the reversible nature of these processes. A plethora of novel strategies for addressing epigenetics in cancer therapy for immuno-oncological complications are currently available - ranging from basic treatment to epigenetic editing. - and they will be the subject of this comprehensive review. In this review, we cover most of the advancements made in the field of targeting epigenetics with special emphasis on microbiology, plasma science, biophysics, pharmacology, molecular biology, phytochemistry, and nanoscience.

Open Questions in Cold Atmospheric Plasma Treatment in Head and Neck Cancer: A Systematic Review

Over the past decade, we witnessed a promising application of cold atmospheric plasma (CAP) in cancer therapy. The aim of this systematic review was to provide an exhaustive state of the art of CAP employed for the treatment of head and neck cancer (HNC), a tumor whose late diagnosis, local recurrence, distant metastases, and treatment failure are the main causes of patients’ death. Specifically, the characteristics and settings of the CAP devices and the in vitro and in vivo treatment protocols were summarized to meet the urgent need for standardization. Its molecular mechanisms of action, as well as the successes and pitfalls of current CAP applications in HNC, were discussed. Finally, the interesting emerging preclinical hypotheses that warrant further clinical investigation have risen. A total of 24 studies were included. Most studies used a plasma jet device (54.2%). Argon resulted as the mostly employed working gas (33.32%). Direct and indirect plasma application was reported in 87.5% and 20.8% of studies, respectively. In vitro investigations were 79.17%, most of them concerned with direct treatment (78.94%). Only eight (33.32%) in vivo studies were found; three were conducted in mice, and five on human beings. CAP showed pro-apoptotic effects more efficiently in tumor cells than in normal cells by altering redox balance in a way that oxidative distress leads to cell death. In preclinical studies, it exhibited efficacy and tolerability. Results from this systematic review pointed out the current limitations of translational application of CAP in the urge of standardization of the current protocols while highlighting promising effects as supporting treatment in HNC.

Emerging innovations in cold plasma therapy against cancer: A paradigm shift

Cancer is one of the major causes of mortality, accounting for ∼ 9.5 million deaths globally in 2018. The spectrum of conventional treatment for cancer includes surgery, chemotherapy and radiotherapy. Recently, cold plasma therapy surfaced as a novel technique in the treatment of cancer. The FDA approval of the first trial for the use of cold atmospheric plasma (CAP) in cancer therapy in 2019 is evidence of this. This review highlights the mechanisms of action of CAP. Additionally, its applications in anticancer therapy have been reviewed. In summary, this article will introduce the readers to the exciting field of plasma oncology and help them understand the current status and prospects of plasma oncology.

Cold Atmospheric Plasma Targeting Hematological Malignancies: Potentials and Problems of Clinical Translation

Cold atmospheric plasma is an ionized gas produced near room temperature; it generates reactive oxygen species and nitrogen species and induces physical changes, including ultraviolet, radiation, thermal, and electromagnetic effects. Several studies showed that cold atmospheric plasma could effectively provoke death in a huge amount of cell types, including neoplastic cells, via the induction of apoptosis, necrosis, and autophagy. This technique seems able to destroy tumor cells by disturbing their more susceptible redox equilibrium with respect to normal cells, but it is also able to cause immunogenic cell death by enhancing the immune response, to decrease angiogenesis, and to provoke genetic and epigenetics mutations. Solutions activated by cold gas plasma represent a new modality for treatment of less easily reached tumors, or hematological malignancies. Our review reports on accepted knowledge of cold atmospheric plasma’s effect on hematological malignancies, such as acute and chronic myeloid leukemia and multiple myeloma. Although relevant progress was made toward understanding the underlying mechanisms concerning the efficacy of cold atmospheric plasma in hematological tumors, there is a need to determine both guidelines and safety limits that guarantee an absence of long-term side effects.

Non-invasive medical gas plasma augments bladder cancer cell toxicity in preclinical models and patient-derived tumor tissues

INTRODUCTION

Medical gas plasma therapy has been successfully applied to several types of cancer in preclinical models. First palliative tumor patients suffering from advanced head and neck cancer benefited from this novel therapeutic modality. The gas plasma-induced biological effects of reactive oxygen and nitrogen species (ROS/RNS) generated in the plasma gas phase result in oxidation-induced lethal damage to tumor cells.

OBJECTIVES

This study aimed to verify these anti-tumor effects of gas plasma exposure on urinary bladder cancer.

METHODS

2D cell culture models, 3D tumor spheroids, 3D vascularized tumors grown on the chicken chorion-allantois-membrane (CAM) in ovo, and patient-derived primary cancer tissue gas plasma-treated ex vivo were used.

RESULTS

Gas plasma treatment led to oxidation, growth retardation, motility inhibition, and cell death in 2D and 3D tumor models. A marked decline in tumor growth was also observed in the tumors grown in ovo. In addition, results of gas plasma treatment on primary urothelial carcinoma tissues ex vivo highlighted the selective tumor-toxic effects as non-malignant tissue exposed to gas plasma was less affected. Whole-transcriptome gene expression analysis revealed downregulation of tumor-promoting fibroblast growth factor receptor 3 (FGFR3) accompanied by upregulation of apoptosis-inducing factor 2 (AIFm2), which plays a central role in caspase-independent cell death signaling.

CONCLUSION

Gas plasma treatment induced cytotoxicity in patient-derived cancer tissue and slowed tumor growth in an organoid model of urinary bladder carcinoma, along with less severe effects in non-malignant tissues. Studies on the potential clinical benefits of this local and safe ROS therapy are awaited.