Cold atmospheric plasma (CAP) treatment is a rapidly expanding and emerging technology for cancer treatment. Direct CAP jet irradiation is limited to the skin and it can also be invoked as a supplement therapy during surgery as it only causes cell death in the upper three to five cell layers. However, the current cannulas from which the plasma emanates are too large for intracranial applications. To enhance efficiency and expand the applicability of the CAP method for brain tumors and reduce the gas flow rate and size of the plasma jet, a novel micro-sized CAP device (µCAP) was developed and employed to target glioblastoma tumors in the murine brain. Various plasma diagnostic techniques were applied to evaluate the physics of helium µCAP such as electron density, discharge voltage, and optical emission spectroscopy (OES). The direct and indirect effects of µCAP on glioblastoma (U87MG-RedFluc) cancer cells were investigated in vitro. The results indicate that µCAP generates short- and long-lived species and radicals (i.e., hydroxyl radical (OH), hydrogen peroxide (H₂O₂), and nitrite (NO₂⁻), etc.) with increasing tumor cell death in a dose-dependent manner. Translation of these findings to an in vivo setting demonstrates that intracranial µCAP is effective at preventing glioblastoma tumor growth in the mouse brain. The µCAP device can be safely used in mice, resulting in suppression of tumor growth. These initial observations establish the µCAP device as a potentially useful ablative therapy tool in the treatment of glioblastoma.

The study of cold atmospheric plasma (CAP) began about a decade ago. Currently, multiple applications of CAP have been discovered including biomedicine, nanomaterials, agriculture, and water purifications. At the current stage of these research fields, it is obvious that the next move will be CAP optimization for each specific application. For example, in the field of plasma-based cancer treatment, due to the different responses of cell lines, CAP can activate different biological pathways in different cells, i.e., to be selective. One of the most commonly used CAP types is the cold atmospheric plasma jet (CAPJ). However, without a full understanding of CAPJ physics, it is impossible to optimize the plasma for every application condition. Moreover, since each research team is equipped with its own CAPJ generator, the hardware behaviors vary significantly across researchers. Therefore, a complete big picture of CAPJ control and parameters is a critical milestone for future CAPJ optimization in these research fields. This Review provides a summary of how CAPJ parameters can be manipulated with the control inputs and hardware design to extend that the chemical compositions can be modified by the gas flow rate, discharge waveform, target properties, and local environment. Based on the control map summarized in this work, CAPJ users can easily optimize their device for a certain specific purpose, such as maximizing OH and H₂O₂ for cancer treatment or maximizing O₃ and ultraviolet for sterilization. Therefore, this study sheds light on the general theory of CAPJ control and can be a basis for future optimization of low-temperature plasma devices. Consideration of the plasma control based on machine learning methods has been receiving interest recently and certainly will become a future hot topic.

CAP is an ionized gas generated under atmospheric pressure conditions. Due to its reactive chemical components and near-room temperature nature, CAP has promising applications in diverse branches of medicine, including microorganism sterilization, biofilm inactivation, wound healing, and cancer therapy. Currently, hundreds of in vitro demonstrations of CAP-based cancer treatments have been reported. However, preclinical studies, particularly in vivo studies, are pivotal to achieving a final clinical application. Here, we comprehensively introduced the research status of the preclinical usage of CAP in cancer treatment, by primarily focusing on the in vivo studies over the past decade. We summarized the primary research strategies in preclinical and clinical studies, including transdermal CAP treatment, post-surgical CAP treatment, CAP-activated solutions treatment, and sensitization treatment to drugs. Finally, the underlying mechanism was discussed based on the latest understanding.

Cold atmospheric plasma (CAP) is an ionized gas, the product of a non-equilibrium discharge at atmospheric conditions. Both chemical and physical factors in CAP have been demonstrated to have unique biological impacts in cancer treatment. From a chemical-based perspective, the anti-cancer efficacy is determined by the cellular sensitivity to reactive species. CAP may also be used as a powerful anti-cancer modality based on its physical factors, mainly EM emission. Here, we delve into three CAP cancer treatment approaches, chemically based direct/indirect treatment and physical-based treatment by discussing their basic principles, features, advantages, and drawbacks. This review does not focus on the molecular mechanisms, which have been widely introduced in previous reviews. Based on these approaches and novel adaptive plasma concepts, we discuss the potential clinical application of CAP cancer treatment using a critical evaluation and forward-looking perspectives.

Cold atmospheric plasma (CAP) is a tunable source of reactive species and other physical factors. It exerts luxuriant biochemical effects on diverse cells, including bacterial cells, mammalian cells, and plant cells. Over the past decade, CAP has shown promising application in modern agriculture. Here, we focused on the state of the art of plasma agriculture, particularly the improvement of seed germination rates. Typical plasma sources, underlying physical principles, and the chemical and cellular mechanism of plasma’s effect on plants seeds have been discussed in depth.

Cold atmospheric plasma jet (CAPJ) is one of the latest and most promising techniques for potential cancer treatment and other biomedical applications. Due to the direct contact of air, the jet is sensitive to the parameters of the local environment such as relative humidity (RH). In a RH controlled chamber, the electron density of a helium CAPJ is measured using the Rayleigh microwave scattering method, and its optical emission spectroscopy (OES) is recorded using a spectrometer. A decreasing electron density along with the increasing RH is thus revealed, while the humidity effect on OES at a high discharge voltage is increased. These trends imply a shift of electron energy distribution function (EEDF) due to extra attachments of electrons as the physics behind such a phenomenon. This hypothesis is supported by a computation of the mean electron temperature and EEDF based on the electron density we measured and a plasma chemistry model. Therefore, this report is a basis of future CAPJ stabilization development, which is a necessity of reliable biomedical applications, such as an active control loop to make CAPJ immune to any accident environmental disturbance during a plasma-based cancer surgery.