Cold Plasma: Clean Technology to Destroy Pathogenic Micro-organisms

Cold Plasma for the Modification of the Surface Roughness of Microparticles

Cold plasma treatment is commonly used for sterilization. However, another potential of cold plasma treatment is surface modification. To date, several efforts have been directed toward investigating the effect of cold plasma treatment in modifying the surfaces of films. Here, the impact of suspension properties and parameters of cold plasma treatment on the changes of surfaces of monodisperse polymeric microparticles is tested. The plasma treatment did not touch the surface chemistry of the monodisperse polymeric microparticles. The concentration of suspensions of 1 mg/mL was determined to relate to a stronger effect of the plasma treatment on the roughness of the microparticles. Microparticles with an average diameter of 20 μm show a roughness increase with the plasma treatment time. However, a plasma treatment time longer than 15 min damages the microparticles, as observed in particles with an average diameter of 20 and 50 μm. We finally prototyped monodisperse microparticles to deliver drugs to the nasal mucosa by studying the effect of roughness in their (undesired) self-adhesion and (desired) adhesion with tissue. A moderate roughness, with an average peak-to-valley distance of 500 nm, appears to be the most effective in reducing the detachment forces with nasal tissue by up to 5 mN.

Utility of devices for onychomycosis: a review

Onychomycosis is difficult to treat due to long treatment durations, poor efficacy rates of treatments, high relapse rates, and safety issues when using systemic antifungal agents. Device-based treatments are targeted to specific regions of the nail, have favorable safely profiles, and do not interfere with systemic agents. They may be an effective alternative therapy for onychomycosis especially with increasing reports of squalene epoxidase gene mutations and potential resistance to terbinafine therapy. In this review, we discuss four devices used as antifungal treatments and three devices used as penetration enhancers for topical agents. Lasers, photodynamic therapy, microwaves, and non-thermal plasma have the capacity to inactivate fungal pathogens demonstrated through in vivo studies. Efficacy rates for these devices, however, remain relatively low pointing toward the need to further optimize device or usage parameters. Ultrasound, nail drilling, and iontophoresis aid in improving the permeability of topical agents through the nail and have been investigated as adjunctive therapies. Due to the paucity in clinical data, their efficacy in treating onychomycosis has not yet been established. While the results of clinical studies point toward the potential utility of devices for onychomycosis, further large-scale randomized clinical trials following regulatory guidelines are required to confirm current results.

Detoxification of mycotoxins in agricultural products by non-thermal physical technologies: a review of the past five years

Mycotoxins produced by Aspergillus spp., Penicillium spp. and Fusarium spp. with small molecular weight and thermal stability, are highly toxic and carcinogenic secondary metabolites. Mycotoxins have caused widespread concern regarding food safety internationally because of their adverse effects on the health of humans and animals, and the major economic losses they cause. There is an urgent need to find ways to reduce or eliminate the impact of mycotoxins in food and feed without introducing new safety issues, or reducing nutritional quality. Non-thermal physical technology is the basis for new techniques to degrade mycotoxins, with great potential for practical detoxification applications in the food industry. Compared with conventional thermal treatments, non-thermal physical detoxification technologies are easier to apply and effective, with less adverse impact on the nutritional value of agricultural products. The advantages, limitations and development prospects of these new detoxification technologies are discussed. Further studies are recommended to standardize the treatment conditions for each detoxification technology, evaluate the safety of the degradation products, and to combine different detoxification technologies to achieve synergistic effects. This will facilitate realization of the great potential of the new technologies and the development of practical applications.

Cold atmospheric plasma: Its time-dependent effects on the elimination of bacterial colony on periodontal manual scalers

Background

This in vitro study investigated the time-dependent bactericidal effects of cold atmospheric argon plasma treatment of periodontal hand scalers as well as the scanning electron microscopic view of the scaler tip surfaces before and after plasma treatment.

Materials and Methods

The study used 34 periodontal hand scalers which were divided into test and control groups. The scaler tips were inoculated with Escherichia coli and Staphylococcus aureus bacteria, following which the scalers in the control and test groups were subjected to conventional sterilization and argon plasma sterilization, respectively. Varying exposure times of plasma treatment were done on the test group samples to evaluate the minimum time required for complete sterilization. Subsequently, streaks were made on plate count agar using each of these instruments. The agar plates were then kept in an incubator for 24 h, following which bacterial colony count was assessed (colony-forming units/mL). Furthermore, the scanning electron microscopic (SEM) view of the scaler tip was studied before and after plasma treatment.

Results

A complete elimination of bacterial load (Gram-positive as well as Gram-negative) from the instrument surface was achieved by the plasma exposure time of 15-20 s. SEM analysis did not show a significant difference before and after plasma treatment as not many organic residues were present on the scaler tip.

Conclusion

Cold atmospheric pressure plasma is an efficient and time-saving method of sterilization, capable of destroying both Gram-positive and Gram-negative bacteria.

A comprehensive study on decontamination of food-borne microorganisms by cold plasma

Food-borne microorganisms are one of the biggest concern in food industry. Food-borne microorganisms such as Listeria monocytogenes, Escherichia coli, Salmonella spp., Vibrio spp., Campylobacter jejuni, Hepatitis A are commonly found in food products and can cause severe ailments in human beings. Hence, disinfection of food is performed before packaging is performed to sterilize food. Traditional methods for disinfection of microorganisms are based on chemical, thermal, radiological and physical principles. They are highly successful, but they are complex and require more time and energy to accomplish the procedure. Cold plasma is a new technique in the field of food processing. CP treatments has no or very low effect on physical, chemical and nutritional properties of food products. This paper reviews the effect of plasma processing on food products such as change in colour, texture, pH level, protein, carbohydrate, and vitamins. Cold plasma by being a versatile, effective, economical and environmentally friendly method provides unique advantages over commercial food processing technologies for disinfection of food.

Plasma bioscience for medicine, agriculture and hygiene applications

Nonthermal biocompatible plasma (NBP) sources operating in atmospheric pressure environments and their characteristics can be used for plasma bioscience, medicine, and hygiene applications, especially for COVID-19 and citizen. This review surveyed the various NBP sources, including a plasma jet, micro-DBD (dielectric barrier discharge) and nanosecond discharged plasma. The electron temperatures and the plasma densities, which are produced using dielectric barrier discharged electrode systems, can be characterized as 0.7 ~ 1.8 eV and (3-5) × 1014-15 cm-3, respectively. Herein, we introduce a general schematic view of the plasma ultraviolet photolysis of water molecules for reactive oxygen and nitrogen species (RONS) generation inside biological cells or living tissues, which would be synergistically important with RONS diffusive propagation into cells or tissues. Of the RONS, the hydroxyl radical [OH] and hydrogen peroxide H2O2 species would mainly result in apoptotic cell death with other RONS in plasma bioscience and medicines. The diseased biological protein, cancer, and mutated cells could be treated by using a NBP or plasma activated water (PAW) resulting in their apoptosis for a new paradigm of plasma medicine.

Evaluation of Virucidal Efficacy of Cold Plasma on Bacteriophage Inside a Three-Layered Sterilization Chamber

Traditional disinfection methods against pathogens have numerous shortcomings, and inventive methods like cold plasma are required for virus inactivation. Here, an atmospheric pressure 13.56 MHz radio-frequency hollow cathode (RF–HC) cold plasma device has been used to build a cold plasma sterilization device, and its virucidal activity is assessed against P2 bacteriophage, a model surrogate for pathogenic viruses. The heart of this device contains a three-layered sterilization chamber which is a rectangular parallelopiped of 42 × 32 × 30 cm³. Optimization experiments were performed to make each corner of this chamber completely virus free after cold plasma treatment. This two-pronged study was conducted to establish the requirement of minimum vol. % H₂O₂ in minimum time for the complete elimination of phages inside this sterilization chamber even when plasma is not in the direct line of sight. In initial experiments, the effect of the direct plasma line of sight was seen as the top and bottom layers showing less phage killing as compared to the middle of the sterilization chamber. Complete sterilization of bacteriophage, in all the three layers inside the sterilization chamber, was achieved by plasma treatment with 6% H₂O₂ for 10 min in 80 watts of plasma operating power. It was also seen that 6% H₂O₂ mist alone is not sufficient to provide a high degree of sterilization, and normal water mist combined with cold plasma can provide a higher level of sterilization at each corner of the chamber.

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.