Plasma and Nanomaterials:Fabrication and Biomedical Applications

Application of plasma medicine has been actively explored during last several years. Treating every type of cancer remains a difficult task for medical personnel due to the wide variety of cancer cell selectivity. Research in advanced plasma physics has led to the development of different types of non-thermal plasma devices, such as plasma jets, and dielectric barrier discharges. Non-thermal plasma generates many charged particles and reactive species when brought into contact with biological samples. The main constituents include reactive nitrogen species, reactive oxygen species, and plasma ultra-violets. These species can be applied to synthesize biologically important nanomaterials or can be used with nanomaterials for various kinds of biomedical applications to improve human health. This review reports recent updates on plasma-based synthesis of biologically important nanomaterials and synergy of plasma with nanomaterials for various kind of biological applications

Differential Inactivation of Fungal Spores in Water and on Seeds by Ozone and Arc Discharge Plasma.

Seed sterilization is essential for preventing seed borne fungal diseases. Sterilization tools based on physical technologies have recently received much attention. However, available information is very limited in terms of efficiency, safety, and mode of action. In this study, we have examined antifungal activity of ozone and arc discharge plasma, potential tools for seed sterilization. In our results, ozone and arc discharge plasma have shown differential antifungal effects, depending on the environment associated with fungal spores (freely submerged in water or infected seeds). Ozone inactivates Fusarium fujikuroi (fungus causing rice bakanae disease) spores submerged in water more efficiently than arc discharge plasma. However, fungal spores associated with or infecting rice seeds are more effectively deactivated by arc discharge plasma. ROS generated in water by ozone may function as a powerful fungicidal factor. On the other hand, shockwave generated from arc discharge plasma may have greatly contributed to antifungal effects on fungus associated with rice seeds. In support of this notion, addition of ultrasonic wave in ozone generating water has greatly increased the efficiency of seed disinfection

Measurement of temperature and pH in water after ozone or arc discharge plasma treatment.

<p>A. Temperature of water after treatment with arc discharge plasma. Arc plasma was discharged at 10 kV and 12 Hz for 0.5, 1, 5, and 10 min or at 10 kV and different frequencies (6, 9, 12 Hz) for 30 min. B. pH of water after treated with ozone or arc discharge plasma for indicated time. Ozone injection rate was 1 lpm. Arc plasma was discharged at 10 kV and 12 Hz for 0.5, 1, 5, and 10 min or at 10 kV and different frequencies (6, 9, 12 Hz) for 30 min.</p

SEM analysis of seed surface after ozone or arc discharge plasma.

<p>A. Surface of rice seeds after treated with ozone (2 h) or arc discharge plasma (10 kV, 12 Hz for 30 min). Rice seeds with no treatment were used as control. Arrows indicate fungal spores. B. Set up for treatment with both ultrasonic wave and ozone in water. Ultrasonic wave was generated at 350 W power and 40 kHz frequency. C. Percentage of infected seeds after treated in water by both ultrasonic wave (indicated as Sonif.) and ozone (O₃) for 2 or 3 hrs. Each value was an average of 3 experimental replicates. Student t-test was performed between control and each treatment; ** p < 0.01.</p

Level of reactive species in water after ozone and arc discharge plasma.

<p>A. Concentration of ozone (ppm) present in water after ozone injection (1 lpm) for indicated time. All measurements were performed in 3 replicates. Student t-test was performed between each treatment time; ** p < 0.01. B. Relative level of ROS (OH radical, peroxynitrite, singlet oxygen) and RNS (nitric oxide) in water after ozone or arc plasma treatment compared to control (no treatment). All values on y-axis are the ratio between treatment and control (ratio = OD_wavelength of ozone or plasma treatment / OD_wavelength of control). All measurements were performed in 3 replicates.</p

(color online) Disinfection of rice seeds by arc discharge plasma treatment.

<p>A. Percentage of infected seeds after treated in water by arc plasma discharged at 10 kV and different frequencies (6, 9, 12 Hz) for 30 min (upper graph) or discharged at 10 kV and 12 Hz for 5, 10, 20, and 30 min (bottom graph). Each value was an average of 3 experimental replicates. Student t-test was performed between control and each treatment; * p< 0.05, ** p < 0.01. B. Fungal growth from rice seeds after treated with arc plasma discharged at 10 kV and different frequencies (6, 9, 12 Hz) for 30 min. C. Fungal growth from rice seeds after treated with arc plasma discharged at 10 kV and 12 Hz for 5, 10, 20, and 30 min. All plates were incubated at 25°C for 6 days and then imaged.</p

Germination of fungal spores after ozone or plasma treatment.

<p>Germination of <i>F</i>. <i>fujikuroi</i> spores after treatment with ozone (A) or arc discharge plasma (B). Germinated fungal spores were appeared as colonies on PDA plate and the number of colonies (CFU) was counted and converted to the log scale. Each value was an average of 3 experimental replicates and indicated on the bar. Student t-test was performed between control and each treatment; ** p < 0.01.</p

(color online) Disinfection of rice seeds by ozone treatment.

<p>A. Percentage of infected seeds after treated by ozone in water for 1 and 2 hrs (upper graph) or in water of different pH (3 and 10) and with different ozone injection rate (1 and 3 lpm) for 2 hrs (bottom graph). In upper graph, each value was an average of 3 experimental replicates. Student t-test was performed between control and each treatment; ** p < 0.01. B. Fungal growth from rice seeds after treated with ozone in water for 1 and 2 hrs. C. Fungal growth from rice seeds after treated with ozone in water of different pH (3 and 10) and ozone injection rate (1 and 3 lpm) for 2 hrs. All plates were incubated at 25°C for 6 days and then imaged.</p

(color online) Schematic view of the devices and treatment setting.

<p>A. Set-up for ozone treatment. Ozone generator was connected to an acryl container filled with fungal spore suspension or rice seeds. B. Set-up for treatment with arc discharge plasma. A high voltage DC power supply was connected to two electrodes submerged in spore or rice seeds suspension in the container. C. Voltage and current profile during arc discharge at 10 kV and 12 Hz.</p