In vitro analysis of nonthermal plasma as a disinfecting agent

Plasma bioscience and its application to medicine

Nonthermal atmospheric pressure biocompatible plasma (NBP), alternatively called bio-cold plasma, is a partially ionized gas that consists of charged particles, neutral atoms and molecules, photons, an electric field, and heat. Recently, nonthermal plasma-based technology has been applied to bioscience, medicine, agriculture, food processing, and safety. Various plasma device configurations and electrode layouts has fast-tracked plasma applications in the treatment of biological and material surfaces. The NBP action mechanism may be related to the synergy of plasma constituents, such as ultraviolet radiation or a reactive species. Recently, plasma has been used in the inactivation of viruses and resistant microbes, such as fungal cells, bacteria, spores, and biofilms made by microbes. It has also been used to heal wounds, coagulate blood, degrade pollutants, functionalize material surfaces, kill cancers, and for dental applications. This review provides an outline of NBP devices and their applications in bioscience and medicine. We also discuss the role of plasma-activated liquids in biological applications, such as cancer treatments and agriculture. The individual adaptation of plasma to meet specific medical requirements necessitates real-time monitoring of both the plasma performance and the target that is treated and will provide a new paradigm of plasma-based therapeutic clinical systems.

Opposite effects of non-thermal plasma on cell migration and collagen production in keloid and normal fibroblasts

Recent progress in the understanding non-thermal plasma (NTP) properties prompted its application in the treatment of various diseases. However, therapeutic effect of NTP on keloid cells has not been reported previously. We sought to investigate the effect of NTP treatment on keloid by comparing cell migration and collagen production of keloid (KFs) and normal fibroblasts (NFs) and determined the regulatory pathways involved. We assessed NTP effects on cell migration in KFs and NFs by the wound healing assay and measured the expression of the epidermal growth factor receptor (EGFR), signal transducer and activator of transcription-3 (STAT3), and collagen by western blot. Expression of the transforming growth factor-β and Type I collagen following NTP treatment was determined by reverse transcription-polymerase chain reaction, immunofluorescence staining, and the Sircol collagen assay. NTP treatment increased cell migration and collagen production of NFs. However, it reduced these parameters in KFs. NTP reduced the expression of EGFR, STAT3, and Type I collagen in KFs but increased their levels in NFs. We revealed that NTP suppressed KF cell migration via down-regulation of EGFR and STAT3 and reduced collagen production via supressing transforming growth factor-β. Our data suggest that NTP may be a new therapeutic strategy for keloids.

Comparative Effects of Non-Thermal Atmospheric Pressure Plasma on Migration and Invasion in Oral Squamous Cell Cancer, by Gas Type

PURPOSE

The fourth state of matter, plasma is known as an ionized gas with electrons, radicals and ions. The use of non-thermal plasma (NTP) in cancer research became possible because of the progresses in plasma medicine. Previous studies on the potential NTP-mediated cancer therapy have mainly concentrated on cancer cell apoptosis. In the present study, we compared the inhibitory effect of NTP on cell migration and invasion in the oral squamous cancer cell lines.

MATERIALS AND METHODS

We used oral squamous cancer cell lines (SCC1483, MSKQLL1) and different gases (N₂, He, and Ar). To investigate the mechanism of plasma treatment, using different gases (N₂, He, and Ar) which induces anti-migration and anti-invasion properties, we performed wound healing assay, invasion assay and gelatin zymography.

RESULTS

The results showed that NTP inhibits cancer cell migration and invasion of oral squamous cancer cell. In addition, focal adhesion kinase expression and matrix metalloproteinase-2/9 activity were also inhibited.

CONCLUSION

The suppression of cancer cell invasion by NTP varied depending on the type of gas. Comparison of the three gases revealed that N₂ NTP inhibited cell migration and invasion most potently via decreased expression of focal adhesion kinase and matrix metalloproteinase activity.

Non-thermal atmospheric pressure plasma inhibits thyroid papillary cancer cell invasion via cytoskeletal modulation, altered MMP-2/-9/uPA activity

Plasma, the fourth state of matter, is defined as a partially or completely ionized gas that includes a mixture of electrons and ions. Advances in plasma physics have made it possible to use non-thermal atmospheric pressure plasma (NTP) in cancer research. However, previous studies have focused mainly on apoptotic cancer cell death mediated by NTP as a potential cancer therapy. In this study, we investigated the effect of NTP on invasion or metastasis, as well as the mechanism by which plasma induces anti-migration and anti-invasion properties in human thyroid papillary cancer cell lines (BHP10-3 and TPC1). Wound healing, pull-down, and Transwell assays demonstrated that NTP reduced cell migration and invasion. In addition, NTP induced morphological changes and cytoskeletal rearrangements, as detected by scanning electron microscopy and immunocytochemistry. We also examined matrix metalloproteinase (MMP)-2/-9 and urokinase-type plasminogen activator (uPA) activity using gelatin zymography, uPA assays and RT-PCR. FAK, Src, and paxillin expression was detected using Western blot analyses and immunocytochemistry. NTP decreased FAK, Src, and paxillin expression as well as MMP/uPA activity. In conclusion, NTP inhibited the invasion and metastasis of BHP10-3 and TPC1 cells by decreasing MMP-2/-9 and uPA activities and rearranging the cytoskeleton, which is regulated by the FAK/Src complex. These findings suggest novel actions for NTP and may aid in the development of new therapeutic strategies for locally invasive and metastatic cancers.

Effect of atmospheric pressure non-equilibrium plasmas on Neisseria gonorrhoeae

In this study, the sterilizing effect of atmospheric pressure nonequilibrium plasmas (APNPs) on Neisseria gonorrhoeae (N. gonorrhoeae) was preliminarily examined and the possible mechanisms were explored. N. gonorrhoeae FA1090, FA19 and MS11 were treated by APNPs and their survival rate was analyzed by using CFUs counting and structurally studied by laser scanning confocal microscopy. The morphological changes of bacterial cell membrane and wall were studied under TEM. Our results showed that APNPs had strong sterilizing effect on N. gonorrhoeae. The survival rate of MS11 in N. gonorrhoeae liquid medium was 60.65% after disinfection with the APNPs for 5 min, whereas, the survival rate of FA19 was 92.60% and the rate of FA1090 was 96.40%. The survival rate of MS11 was 21.13% after exposure to APNPs for 6 min, whereas the survival rate of FA19 was 31.60% and the rate of FA1090 was 91.00%. N. gonorrhoeae was structurally damaged after treatment with APNPs. It is concluded that APNPs is able to effectively and quickly kill the N. gonorrhoeae, and the killing effect is related to the architectural damage of cell membrane.

Use of atmospheric non-thermal plasma as a disinfectant for objects contaminated with methicillin-resistant Staphylococcus aureus

BACKGROUND

Health care-associated infections because of methicillin-resistant strains of Staphylococcus aureus (MRSA) are increasing worldwide despite current infection control measures. Novel methods for disinfection of MRSA would be useful.

METHODS

We tested the effectiveness of atmospheric, non-thermal plasma discharge at killing S aureus, including USA300 strains, and at disinfecting experimentally contaminated hospital pagers.

RESULTS

Exposure of S aureus to plasma at different concentrations and for varying lengths of time resulted in up to a 4- to 5-log(10) kill on tryptic soy agar plates within 10 minutes and was not toxic to epithelial cells. USA300 strains of MRSA were more resistant to plasma-based killing than other tested strains. Disinfection of hospital pagers experimentally coated with clinically relevant amounts of MRSA could be achieved in as little as 30 seconds.

CONCLUSION

Generation of plasma is a promising method for disinfection of objects or surfaces that warrants further study in hospital settings. The USA300 strains of S aureus may be more resistant to disinfection than other strains.