Refine
Year of publication
Document Type
- Article (25)
- Doctoral Thesis (5)
Has Fulltext
- yes (30)
Is part of the Bibliography
- no (30)
Keywords
- plasma medicine (30) (remove)
Institute
- Klinik und Poliklinik für Chirurgie Abt. für Viszeral-, Thorax- und Gefäßchirurgie (8)
- Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie/Plastische Operationen (7)
- Institut für Hygiene und Umweltmedizin (5)
- Klinik und Poliklinik für Orthopädie und Orthopädische Chirurgie (3)
- Institut für Physik (2)
- Klinik und Poliklinik für Chirurgie Abt. für Unfall- und Wiederherstellungschirurgie (2)
- Institut für Biochemie (1)
- Institut für Immunologie u. Transfusionsmedizin - Abteilung Immunologie (1)
- Institut für Pharmakologie (1)
- Klinik und Poliklinik für Urologie (1)
AbstractPlasma medicine refers to the application of nonequilibrium plasmas at approximately body temperature, for therapeutic purposes. Nonequilibrium plasmas are weakly ionized gases which contain charged and neutral species and electric fields, and emit radiation, particularly in the visible and ultraviolet range. Medically-relevant cold atmospheric pressure plasma (CAP) sources and devices are usually dielectric barrier discharges and nonequilibrium atmospheric pressure plasma jets. Plasma diagnostic methods and modelling approaches are used to characterize the densities and fluxes of active plasma species and their interaction with surrounding matter. In addition to the direct application of plasma onto living tissue, the treatment of liquids like water or physiological saline by a CAP source is performed in order to study specific biological activities. A basic understanding of the interaction between plasma and liquids and bio-interfaces is essential to follow biological plasma effects. Charged species, metastable species, and other atomic and molecular reactive species first produced in the main plasma ignition are transported to the discharge afterglow to finally be exposed to the biological targets. Contact with these liquid-dominated bio-interfaces generates other secondary reactive oxygen and nitrogen species (ROS, RNS). Both ROS and RNS possess strong oxidative properties and can trigger redox-related signalling pathways in cells and tissue, leading to various impacts of therapeutic relevance. Dependent on the intensity of plasma exposure, redox balance in cells can be influenced in a way that oxidative eustress leads to stimulation of cellular processes or oxidative distress leads to cell death. Currently, clinical CAP application is realized mainly in wound healing. The use of plasma in cancer treatment (i.e. plasma oncology) is a currently emerging field of research. Future perspectives and challenges in plasma medicine are mainly directed towards the control and optimization of CAP devices, to broaden and establish its medical applications, and to open up new plasma-based therapies in medicine.
Molecular Mechanisms of the Efficacy of Cold Atmospheric Pressure Plasma (CAP) in Cancer Treatment
(2020)
In this work the mechanisms leading to the generation of the various reactive oxygen and nitrogen species (RONS) in a cold atmospheric plasma (CAP) jet and means to control their composition were studied. The investigated CAP jet kinpen is typically operated with Ar feed gas (pure or with molecular admixtures), driven at a frequency of approximately 1 MHz and features fast ionization waves or guided streamers, traveling at velocities of several km/s. The complex reaction networks were investigated by numerical and experimental techniques. Detailed experimental, analytical and computational investigations on the mass and heat transport in the plasma plume were performed: A novel analytical approach to diffusion in jet flows, the non-dispersive path mapping approximation (NDPM) was developed. The method for the first time allows for an estimation of the ambient species density in the near-field of jets that feature a non-homogeneous flow-field. The NDPM approximation was employed for the evaluation of laser induced fluorescence measurements on OH. Through combining measurements and NDPM approximation, this approach yielded an estimation for the ambient species density at the position of the guided streamers, not only in the laminar, but also in the (standard) turbulent operating regime. Accurate measurements of the temporally averaged ambient species density and temperature in the plasma plume were obtained by quantitative Schlieren measurements. The method yields temperature values with sub-Kelvin accuracy and, through combination with computational fluid dynamics (CFD) simulations, allowed for an estimation of the calorimetric power of the jet. In order to obtain a defined environment for the jet to operate in, a shielding gas device was designed in this work, which creates a gas curtain of defined composition around the plasma plume. The plasma dynamics on the ns timescale was investigated by phase resolved optical measurements. The effect of different shielding compositions ranging from pure N2 to pure O2 on guided streamer propagation was investigated. An electrostatic focusing mechanisms was discovered, which promotes the propagation of guided streamers along the channels formed by a noble gas in the plume of plasma jets operating in electronegative gases (such as air or O2). Two zero-dimensional (volume averaged) models were developed: First, the local processes in the guided streamer were modeled using an electron impact reaction kinetic model, which is closely correlated to densities of metastable argon (Ar*) obtained by laser atom absorption measurements. This first model shows that Ar* is the species which dominantly drives the plasma chemistry in the plasma plume. This is exploited in the second plug-flow reaction kinetics model, which is employed to investigate the formation of long-living RONS and uses an Ar* source term as sole energy input. The model uses the previous experimental data on mass and heat transport and temporal dynamics as input and is in turn verified by quantitative FTIR absorption measurements on O3, NO2, N2O, HNO3 and N2O5 in the far-field of the jet, where large absorption lengths can be achieved using a multi pass cell. For the evaluation of the zero-dimensional model, the time-of-flight of RONS from their generation to reaching the multi pass cell was determined using CFD simulations. The insight gained through this combined experimental-modeling approach on the reaction networks revealed relevant control parameters and enabled adjusting the plasma chemistry towards a desired RONS output. Through choosing appropriate feed-gas admixtures and shielding gas compositions, it is possible to generate an NOx-dominated plasma chemistry, although the jet usually produces a strongly O/O3-dominated chemistry. Understanding and controlling the plasma chemistry of cold atmospheric plasma sources for medical applications is not only essential for research, but is also the key for designing future plasma sources for specific medical applications that yield an optimum efficacy and avoid potential side effects of plasma treatment.
Multiple evidence in animal models and in humans suggest a beneficial role of cold physical
plasma in wound treatment. Yet, risk assessment studies are important to further foster therapeutic
advancement and acceptance of cold plasma in clinics. Accordingly, we investigated the long-term
side effects of repetitive plasma treatment over 14 consecutive days in a rodent full-thickness ear
wound model. Subsequently, animals were housed for 350 days and sacrificed thereafter. In blood,
systemic changes of the pro-inflammatory cytokines interleukin 1β and tumor necrosis factor α
were absent. Similarly, tumor marker levels of α-fetoprotein and calcitonin remained unchanged.
Using quantitative PCR, the expression levels of several cytokines and tumor markers in liver,
lung, and skin were found to be similar in the control and treatment group as well. Likewise,
histological and immunohistochemical analysis failed to detect abnormal morphological changes
and the presence of tumor markers such as carcinoembryonic antigen, α-fetoprotein, or the neighbor
of Punc 11. Absence of neoplastic lesions was confirmed by non-invasive imaging methods such as
anatomical magnetic resonance imaging and positron emission tomography-computed tomography.
Our results suggest that the beneficial effects of cold plasma in wound healing come without apparent
side effects including tumor formation or chronic inflammation.
Despite continuous advances in therapy, malignant melanoma is still among the deadliest
types of cancer. At the same time, owing to its high plasticity and immunogenicity, melanoma is
regarded as a model tumor entity when testing new treatment approaches. Cold physical plasma is a
novel anticancer tool that utilizes a plethora of reactive oxygen species (ROS) being deposited on the
target cells and tissues. To test whether plasma treatment would enhance the toxicity of an established
antitumor therapy, ionizing radiation, we combined both physical treatment modalities targeting
B16F10 murine melanoma cell in vitro. Repeated rather than single radiotherapy, in combination
with gas plasma-introduced ROS, induced apoptosis and cell cycle arrest in an additive fashion. In
tendency, gas plasma treatment sensitized the cells to subsequent radiotherapy rather than the other
way around. This was concomitant with increased levels of TNFα, IL6, and GM-CSF in supernatants.
Murine JAWS dendritic cells cultured in these supernatants showed an increased expression of cell
surface activation markers, such as MHCII and CD83. For PD-L1 and PD-L2, increased expression
was observed. Our results are the first to suggest an additive therapeutic effect of gas plasma and
radiotherapy, and translational tumor models are needed to develop this concept further.
Cold physical plasma (CPP) technology is of high promise for various medical applications.
The interplay of specific components of physical plasma with living cells, tissues and organs on a structural and functional level is of paramount interest with the aim to induce therapeutic effects in a controlled and replicable fashion.
In contrast to other medical disciplines such as dermatology and oromaxillofacial surgery, research reports on CPP application in orthopaedics are scarce.
The present implementation of CPP in orthopaedics involves surface modifications of orthopaedic materials and biomaterials to optimize osseointegration. In addition, the influence of CPP on musculoskeletal cells and tissues is a focus of research, including possible adverse reactions and side effects. Its bactericidal aspects make CPP an attractive supplement to current treatment regimens in case of microbial inflammations such as periprosthetic joint infections. Attributed anticancerogenic and pro-apoptotic effects underline the clinical relevance of CPP as an additive in treating malignant bone lesions.
The present review outlines ongoing research in orthopaedics involving CPP; it distinguishes considerations for safe application and the need for more evidence-based research to facilitate robust clinical implementation.
Cold medical gas plasmas are under pre-clinical investigation concerning their hemostatic activity and could be applied for intra-operative bleeding control in the future. The technological leap innovation was their generation at body temperature, thereby causing no thermal harm to the tissue and ensuring tissue integrity. This directly contrasts with current techniques such as electrocautery, which induces hemostasis by carbonizing the tissue using a heated electrode. However, the necrotized tissue is prone to fall, raising the risk of post-operative complications such as secondary bleedings or infection. In recent years, various studies have reported on the ability of medical gas plasmas to induce blood coagulation, including several suggestions concerning their mode of action. As non-invasive and gentle hemostatic agents, medical gas plasmas could be particularly eligible for vulnerable tissues, e.g., colorectal surgery and neurosurgery. Further, their usage could be beneficial regarding the prevention of post-operative bleedings due to the absence or sloughing of eschar. However, no clinical trials or individual healing attempts for medical gas plasmas have been reported to pave the way for clinical approvement until now, despite promising results in experimental animal models. In this light, the present mini-review aims to emphasize the potential of medical gas plasmas to serve as a hemostatic agent in clinical procedures. Providing a detailed overview of the current state of knowledge, feasible application fields are discussed, and possible obstacles are addressed.
Reactive species generated by medical gas plasma technology can be enriched in liquids for use in oncology targeting disseminated malignancies, such as metastatic colorectal cancer. Notwithstanding, reactive species quantities depend on the treatment mode, and we recently showed gas plasma exposure in conductive modes to be superior for cancer tissue treatment. However, evidence is lacking that such a conductive mode also equips gas plasma-treated liquids to confer augmented intraperitoneal anticancer activity. To this end, employing atmospheric pressure argon plasma jet kINPen-treated Ringer’s lactate (oxRilac) in a CT26-model of colorectal peritoneal carcinomatosis, we tested repeated intraabdominal injection of such remotely or conductively oxidized liquid for antitumor control and immunomodulation. Enhanced reactive species formation in conductive mode correlated with reduced tumor burden in vivo, emphasizing the advantage of conduction over the free mode for plasma-conditioned liquids. Interestingly, the infiltration of lymphocytes into the tumors was equally enhanced by both treatments. However, significantly lower levels of interleukin (IL)4 and IL13 and increased levels of IL2 argue for a shift in intratumoral T-helper cell subpopulations correlating with disease control. In conclusion, our data argue for using conductively over remotely prepared plasma-treated liquids for anticancer treatment.