Plasma

The term "plasma" has several meanings in science. In biology it refers to the karyo- or cytoplasm, in medicine to the blood plasma. In physics, however, the term "plasma" refers to an electrically conductive gas consisting of positive and negative ions, electrons, and excited and neutral atoms and molecules. Plasma is also called the 4th state of matter.

Physical plasmas are widespread in nature. About 99% of all visible matter in the universe exists in the plasma state. Most natural plasmas are hot, e.g. stars and lightning. An example of a cold plasma is the aurora borealis (called Northern Lights or Aurora borealis in the northern hemisphere; Southern Lights, Aurora australis, in the southern hemisphere) is a luminous phenomenon caused by excited nitrogen and oxygen atoms in the high atmosphere (electrometeor), which is produced in polar regions when accelerated charged particles . Plasmas can be artificially created for technical and medical purposes.

Basically, depending on the gas temperature, plasmas can be divided into:

• cold plasma (temperatures around 40°C) and
• hot plasma.

Medical use:

Hot plasmas (argon plasma coagulation) have been used for a long time in gastroenterology and surgery, e.g. for endoscopic stopping of internal bleeding but also cutting, liver resections or polypectomies.

Cold plasmas (temperatures around 40°C) have only been used in recent years. Cold plasmas are composed of heat rays, visible light, UV rays, electromagnetic radiation, reactive radicals, and ions and electrons (Wiegend C et al. 2017).

The development of cold atmospheric plasmas (cold atmospheric plasmas abbreviated CAP or KAP) has led to the application of a new field of application and research, plasma medicine. The preferred plasma gas is air. For special applications, however, other gases such as argon or helium and mixtures can also be used. The plasma gases ionize and dissociate due to the energy of the plasma arc. The result of the action is, for example, chemical changes on the surface of biological structures.

The temperatures for direct (non-thermal) therapeutic application on the human body (KAPs) are in the range of body temperature. Numerous studies on cold physical plasma demonstrate a strong antibacterial, anti-inflammatory, and wound-healing effect (Matthes R et al. 2013).

Recent studies indicate the wound healing-promoting use of cold atmospheric plasma in epidermolysis bullosa systrophica.

Thus, cold plasmas (KAPs) are particularly suitable for decontamination of biological and technical surfaces. KPAs are able to kill microorganisms. These are probably killed by the occurring ROS and RNS, such as atomic oxygen, ozone, hydroxyl radicals and nitrite.

Also in dentistry, cold plasma can be used for antisepsis. It can be used especially against biofilms that form on teeth or implants.

Furthermore, KAPs can selectively induce apoptosis in tumor cells in a dose-dependent manner. In this respect, this technology could also be applied to oncological issues (Gay-Mimbrera J et al. 2016).

Since 2013, devices have been available that have received approval in accordance with the Medical Devices Act. Thus, the medical electrical device can be placed on the market as an approved plasma medical device.

Cold plasma can be produced in 2 ways:

Barrier discharge = dialectically impeded discharge: a voltage is built up between 2 flat electrodes, one electrode is thereby covered by an insulating layer

Plasma jet device: a gas such as argon or helium flowing through a nozzle is ionized by means of an applied high voltage.

1. Gay-Mimbrera J et al (2016) Clinical and Biological Principles of Cold Atmospheric Plasma Application in Skin Cancer. Adv Ther33:894-909.
2. Matthes R et al (2013) Antimicrobial efficacyof two surface barrier discharges with air plasma against in vitro biofilms.PLoS One 8:e70462.
3. Weighing C et al (2017) Plasma medicine. Coldplasma for the treatment of skin infections. Act Derdatol 43: 339-345
4. Yan D et al (2017) Cold atmospheric plasma, a novel promising anti-cancer treatment modality. Oncotarget 8: 15977-15995.