An emerging field of plasma medicine is discussed, where non-equilibrium plasmas are shown to be able to initiate, promote, control, and catalyze various complex behaviors and responses in biological systems. More importantly, it will be shown that plasma can be tuned to achieve the desired medical effect, especially in medical sterilization and treatment of different kind of skin diseases. Wound healing and tissue regeneration can be achieved following various types of plasma treatment in a multitude of wound pathologies. Non-equilibrium plasmas will be shown to be non-destructive to tissue, safe, and effective in inactivation of various parasites and foreign organisms.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppap.200700154

Applied Plasma Medicine

This introductory review on plasma health care is intended to provide the interested reader with a summary of the current status of this emerging field, its scope, and its broad interdisciplinary approach, ranging from plasma physics, chemistry and technology, to microbiology, biochemistry, biophysics, medicine and hygiene. Apart from the basic plasma processes and the restrictions and requirements set by international health standards, the review focuses on plasma interaction with prokaryotic cells (bacteria), eukaryotic cells (mammalian cells), cell membranes, DNA etc. In so doing, some of the unfamiliar terminology—an unavoidable by-product of interdisciplinary research—is covered and explained. Plasma health care may provide a fast and efficient new path for effective hospital (and other public buildings) hygiene— helping to prevent and contain diseases that are continuously gaining ground as resistance of pathogens to antibiotics grows. The delivery of medically active 'substances' at the molecular or ionic level is another exciting topic of research through effects on cell walls (permeabilization), cell excitation (paracrine action) and the introduction of reactive species into cell cytoplasm. Electric fields, charging of surfaces, current flows etc can also affect tissue in a controlled way. The field is young and hopes are high. It is fitting to cover the beginnings in New Journal of Physics, since it is the physics (and non- equilibrium chemistry) of room temperature atmospheric pressure plasmas that have made this development of plasma health care possible.

/pdf/plasma-medicine-an-introductory-review-16ncxlrbef.pdf

Plasma medicine: an introductory review

Plasmas for medicine

Mechanisms of plasma interaction with living tissues and cells can be quite complex, owing to the complexity of both the plasma and the tissue. Thus, unification of all the mechanisms under one umbrella might not be possible. However, the authors are attempting to make first steps in this direction. In this paper, analysis of interaction of floating electrode dielectric barrier discharge (FE-DBD) with living tissues and cells is presented and biological and physical mechanisms are discussed. In physical mechanisms, charged species are identified as the major contributors to the desired effect and a mechanism of this interaction is proposed. Biological mechanisms are also addressed and a hypothesis of plasma selectivity and its effects is offered.

https://iopscience.iop.org/article/10.1088/1367-2630/11/11/115020/pdf

Physical and biological mechanisms of direct plasma interaction with living tissue

Atomic Spectra Database

An atmospheric low-temperature microwave plasma torch has been developed and applied to disinfection. The size of the plasma output is relatively large (35 mm in diameter). Ar gas at a flow rate of 2.2 slm and 85 W microwave power are used. Plasma discharges are produced between the tip of each electrode and the inner surface of the cylinder. When an Escherichia coli culture is placed for 2 min at 20 mm below the torch, where the gas temperature is sufficiently cool, the bacteria are almost completely killed within a 40 mm diameter circle. The UV radiation is one of the major players responsible for killing bacteria, others being the reactive species and the charged particles.

Characterization of microwave plasma torch for decontamination

A mechanism for sterilizing Escherichia coli by a flowing postdischarge and UV radiation of argon plasma at atmospheric pressure was investigated by analyzing the surviving cells and the potassium leakage of cytoplasmic material and by morphological observation. Inactivation of E. coli results from the destruction of the cytoplasmic membrane and the outer membrane under plasma exposure and the destruction of nucleic acids by exposure to ultraviolet radiation from the plasma source.

Sterilization mechanism for Escherichia coli by plasma flow at atmospheric pressure

Research on low-temperature atmospheric plasma sources (LTAPS) has grown strongly over the last few years, in part driven by possible medical 'in vivo' applications. LTAPS offer new technology for medicine and biomedical engineering. Important application examples include in situ production of reactive molecules and ions, delivery at the molecular level, contact-free and self-sterilizing devices. An important issue is the efficient bactericidal effect of LTAPS, which has already been studied widely in vitro. In spite of the many investigations, details of the plasma effect on bacteria are still largely unknown. To contribute to a better understanding of the sterilization process, we investigated the morphological changes of bacteria using atomic force microscopy before and after plasma treatment at high resolution. We examined both gram-positive and gram-negative bacteria at different plasma exposure times. Additionally, the effect of UV radiation as one agent in the plasma was investigated separately. Our results suggest that several sterilizing mechanisms exist and they proceed at different timescales.

https://iopscience.iop.org/article/10.1088/1367-2630/11/11/115023/pdf

The effect of low-temperature plasma on bacteria as observed by repeated AFM imaging

A coaxial cable for microwave transmission type of atmospheric low-temperature plasma source was developed. The plasma source has the advantages of portability, simple configuration, and ability to operate with a wide range of gases and mixtures of such gases. It mainly consists of a cavity, a quartz discharge tube, a coaxial cable, a microwave power source, and a gas supply system. Using this plasma source, the authors tried to clarify its sterilization efficacy against Geobacillus stearothermophilus. A log reduction number of G. stearothermophilus of at least 5 (10/sup -5/) was obtained under the following operating conditions: gas flow rate of argon of 14 SL/min, input power is 400 W, and substrate surface temperature of 353 K. Distributions of temperature and velocities of gas were also measured two-dimensionally by using an E-type thermocouple and a Pitot tube, respectively. The temperature distributions and the peak value of temperature were found to be influenced by the gas flow rate and the kinds of gas mixtures.

Takuya Urayama

Papers

Characterization of microwave plasma torch for decontamination

Sterilization mechanism for Escherichia coli by plasma flow at atmospheric pressure

The effect of low-temperature plasma on bacteria as observed by repeated AFM imaging

Sterilization efficacy of a coaxial microwave plasma flow at atmospheric pressure

Characterization of Low‐Temperature Microwave Plasma Treatment With and Without UV Light for Disinfection