Plasma medicine

Plasma medicine is an innovative and emerging field combining plasma physics, life sciences and clinical medicine to use physical plasma for therapeutic applications. Initial experiments confirm that plasma can be effective in in vivo antiseptics without affecting surrounding tissue and, moreover, stimulating tissue regeneration. Based on sophisticated basic research on plasma-tissue interaction, first therapeutic applications in wound healing, dermatology and dentistry will be opened.

Plasma, described as the fourth state of matter, comprises charged species, active molecules and atoms and is also a source of UV-photons. These plasma-generated active species are useful for several bio-medical applications such as sterilization of implants and surgical instruments as well as modifying biomaterial surface properties. Sensitive applications of plasma, like subjecting human body or internal organs to plasma treatment for medical purposes, are also possible. This possibility is profoundly being investigated by research groups worldwide under the highly-interdisciplinary research field called 'plasma medicine'.

Research fields
Progress in life sciences is increasingly caused by utilization of unrelated technologies and knowledge. In this spirit, microelectronics, optics, material sciences or nanotechnology became key technologies in modern medicine. A similar trend is expected now concerning plasma technology. Actually, plasma medicine is emerging worldwide as an independent medical field - comparable to the launch of laser technology into medicine years ago.

Plasma medicine can be subdivided into three main fields:
 * 1) Non-thermal atmospheric-pressure direct plasma for medical therapy
 * 2) Plasma-assisted modification of bio-relevant surfaces
 * 3) Plasma-based bio-decontamination and sterilization

Non-thermal atmospheric-pressure plasma for medical therapy
Recently, one of challenges is the application of non-thermal plasmas directly on the surface of human body or on internal organs. Whereas for surface modification and biological decontamination both low-pressure and atmospheric pressure plasmas can be used, for direct therapeutic applications only atmospheric pressure plasma sources are applicable.

One such plasma source that can be applied on human body is based on the dielectric barrier discharge (DBD) principle. A conventional DBD device comprises two planar electrodes with at least one of them covered with a dielectric material and the electrodes are separated by a small gap which is called the discharge gap. However, for medical application of DBD devices, the human body itself can serve as one of the two electrodes making it sufficient to devise plasma sources that consist of only one electrode covered with a dielectric such as alumina or quartz. DBD for medical applications such as for treatment of skin diseases and wounds, tumor treatment and disinfection of skin surface are currently under investigation.

The high reactivity of plasma is a result of different plasma components: electromagnetic radiation (UV/VUV, visible light, IR, high-frequency electromagnetic fields, etc.) on the one hand and ions, electrons and reactive chemical species, primarily radicals, on the other. Besides surgical plasma application like argon plasma coagulation (APC), which is based on high-intensity lethal plasma effects, first and sporadic non-thermal therapeutic plasma applications are documented in literature. However, the basic understanding of mechanisms of plasma effects on different components of living systems is in the early beginning. Especially for the field of direct therapeutic plasma application, a fundamental knowledge of the mechanisms of plasma interaction with living cells and tissue is essential as a scientific basis.

First therapeutic approaches of plasma medicine: dermatology and wound healing
Initial experiments confirm the fact that infectious agents can be killed without adverse reactions on surrounding healthy body cells. Furthermore, it is possible to stimulate physiological and biochemical processes in living tissues by plasma treatment under special conditions. This opens the possibility to use plasma to support wound healing as well as to treat several skin diseases. Therefore, application-oriented research is directed to develop an integrated concept of plasma-based wound treatment comprising both superficial wound cleaning and antiseptics and stimulation of tissue regeneration in deeper tissue layers. On a solid scientific basis, further therapeutic plasma applications e.g. in dentistry, or surgery, will be opened during the next years

Plasma-assisted modification of bio-relevant surfaces
Plasma-assisted modification of bio-relevant materials is an established technique to optimize the biofunctionality of implants or to qualify polymer surfaces for cell culturing and tissue engineering. Plasma-based methods and processes for sterilization, decontamination or reprocessing of medical and diagnostic devices, pharmaceutical products or packaging materials are under development worldwide. Both fields are more or less indirect medical plasma applications.

Interdisciplinary basic research on plasma interaction with living matter
Based on knowledge about mechanisms of antimicrobial plasma activity, current research in plasma medicine is mainly focussed on the following fields:


 * Selective inactivation of infectious agents in the close presence of living tissue (in vivo antisepsis)
 * Direct interaction of active plasma components with biochemical and physiological processes influencing growth and vitality of cells and tissue
 * Indirect influencing of cells and tissue via changes of the vital environment (physiological liquids) of cells and tissue through physical plasma.

Combination of plasma technology and plasma diagnostics with cell biological, biochemical and chemical analytical techniques based on in vitro models using microorganisms as well as cell and tissue cultures, will facilitate a sophisticated evaluation of biological plasma effects.

To achieve sustained success of plasma medicine, for any potential therapeutic application optimal plasma composition (radicals, irradiation, temperature, etc.), useful application rate and acceptable relation between desired therapeutic effects and adverse reactions have to be found. This can be realized only in close collaboration between plasma physicists, life scientists and clinical physicians.