Eva Stoffels

We investigated the long‐term behaviour of vascular cells (endothelial and smooth muscle) after exposure to a cold atmospheric plasma source. The cells were treated through a gas‐permeable membrane, in order to simulate intravenous treatment with a gas plasma‐filled catheter. Such indirect treatment resulted in (dose‐dependent) apoptosis and necrosis in smooth muscle cells; these effects were visible 6–10 h after exposure. We ascribed cell damage to poisoning by active nitrogen species. A not yet resolved phenomenon of total (irreversible) cell inactivation without necrosis was observed in endothelial cells. Conditions for non‐inflammatory plasma treatment (no cell necrosis) can be realized. Furthermore, the current experiments have brought new insights in the mechanism of cell detachment, which was observed in many previous studies. magnified image

A nonthermal atmospheric plasma, designed for biomedical applications, was tested for its antimicrobial activity against biofilm cultures of a key cariogenic bacterium Streptococcus mutans. The Strep. mutans biofilms were grown with and without 0.15% sucrose. A chlorhexidine digluconate rinse (0.2%) was used as a positive antimicrobial reference. The presence of sucrose and the frequency of plasma application during growth were shown to have a significant effect on the response to treatment and antibacterial activity. A single plasma treatment for 1 min on biofilms cultured without sucrose caused no re-growth within the observation period. However, with either single or repeated plasma treatments of 1 min, on biofilms cultured with 0.15% sucrose, growth was only reduced. In summary, there may be a role for nonthermal plasma therapies in dental procedures. Sucrose and associated growth conditions may be a factor in the survival of oral biofilms after treatment.

This article surveys current applications of gas discharges in various medical procedures. Various designs of non‐equilibrium plasma sources are described, with special attention to cold plasma devices. In “tissue processing”, two approaches are distinguished: thermal processing, such as heat‐induced coagulation, desiccation, cutting and ablation, and non‐thermal processing, based on sub‐lethal plasma effects on living cells. The latter technique requires special low‐power sources, which operate at the body temperature.

UV excimer lamps are efficient and economical narrowband sources of UVB and UVC radiation. Potentially, these lamps may be used in bacterial disinfection or in minor cosmetic procedures, but safety tests are necessary. For this purpose, cellular damage induced by the UV radiation is assessed. 3T3 mouse fibroblasts are used as a model system. It is found that lethal damage occurs above a certain wavelength-dependent threshold dose. Furthermore, the antioxidant balance of the cells is influenced; glutathione levels are usually depleted, both under and above the lethal threshold. A striking increase of glutathione level is observed after UVC irradiation. This is attributed to an enhanced repair activity as a response to acute oxidative stress induced by UVC. In contrast to UVC, low-power irradiation with UVB seems to induce very little cellular damage

In this survey we analyse the status quo of gas plasma applications in medical sciences. Plasma is a partly ionized gas, which contains free charge carriers (electrons and ions), active radicals, and excited molecules. So-called nonthermal plasmas are particularly interesting, because they operate at relatively low temperatures and do not inflict thermal damage to nearby objects. In the past two decades nonthermal plasmas have made a revolutionary appearance in solid state processing technology. The recent trends focus on using plasmas in health care, for "processing" of medical equipment and even living tissues. The major goal of tissue treatment with plasmas is nondestructive surgery: controlled, high-precision removal of diseased sections with minimum damage to the organism. Furthermore, plasmas allow fast and efficient bacterial inactivation, which makes them suitable for sterilization of surgical tools and local disinfection of tissues. Much research effort must be undertaken before these techniques will become common in medicine, but it is expected that a novel approach to surgery will emerge from plasma science.

Interactions of a small-size, non-thermal plasma (plasma needle) with living cells in culture are studied. We have demonstrated the non-destructive character of the plasma needle: under moderate conditions (low-power and low concentration of molecular species) the plasma needle does not heat biological samples and does not induce cell death. Treatment of living cells is restricted to the cell exterior (membrane). As a result of the interactions of plasma radicals with cell adhesion molecules, cell attachment is temporarily interrupted; the loose cells can be removed, reattached or transferred. This effect may prove very useful in fine surgery, where a part of the tissue must be removed with high-precision, without damage to the adjacent cells and without inflammatory reaction.