Session: ASME Undergraduate Student Design Expo

Paper Number: 175907

Dynamic Rons Behavior in Helium Plasma-Activated Water for Therapeutic Applications 

Dielectric barrier discharge (DBD) plasma is an emerging noninvasive treatment option that is being utilized in several medical applications, including: wound sterilization, cell proliferation, targeting of lesions, and inflammation regulation. These therapeutic properties stem from the formation of radicals known as reactive oxygen and nitrogen species (RONS), which are produced when the plasma jet interacts with surrounding air molecules. This means, varying the concentration of certain RONS influences the healing properties of DBD plasma, tailoring plasma technology to maximize wound-healing benefits. In order to control RONS makeup, the plasma set-up can be manipulated, including variations in exposure time, distance of plasma jet from the wound surface, and the power of the plasma jet. Using distilled water to model the wound surface, plasma-activated water (PAW) was generated at set time intervals and absorbance spectroscopy was employed to examine the relationship between helium plasma exposure-time treatment and RONS concentration (H2O2, NO3, NO2). As peak intensities are unique to each RONS, wavelength ranges were established for H2O2 (245-290 nm), NO2 (220-245 nm), and NO3 (200-215 nm), by determining its peak intensities, aligning with research literature about these RONS characteristics. 

A custom DBD plasma torch was designed using a quartz tube with options for the working gas to flow in along with two electrodes separated by the tube wall that acted as a dielectric material. The inner electrode was made of tungsten and the outer electrode was a copper tape that was placed around the tube. The torch was integrated with a high-voltage power supply (7-8 KV, 30-40 kHz), gas-flow control (10 SLPM), and plasma monitoring through an oscilloscope. Plasma power was measured by using a 1000:1 voltage reducer that measured the input voltage across a ballast resistor (100 k Ohm). In order to understand the capacitive nature of DBD plasma, both current and voltages were measured before and after the plasma to find the phase difference between the voltage curves to calculate the input plasma power. For a typical plasma operation, the power was measured between 20-30 W. 

In order to conduct the treatment experiment, 6 milliliters of distilled water was exposed to plasma torch for 5, 10, or 15 minutes. Three samples per exposure time condition were run through a spectrophotometer (Shimadzu 1900i) to analyze its absorption frequency from 190-400 nanometers. The main focus of this experiment was absorbance spectroscopy, where the calibration curves of different concentrations of H2O2, NO3, NO2 (RONS) were compared to absorbance frequencies of set 5 min, 10 min, and 15 min helium PAW for helium plasma-activated water, demonstrating the correlation between RONS and peak intensities in helium PAW. 

However, the results revealed unexpected complexities driven by the multifaceted nature of helium plasma. The results with helium plasma-activated water showed inconsistent rather than the positive trend seen in previous work with nitrogen plasma-activated water as time exposure increased. In some cases, the 10 minute helium plasma-activated water demonstrated an overall higher concentration than 5-min hPAW and 15-min hPAW (e.g. 10-minute NO3 concentration > 2.2 mg/L; ~215% increase in NO3 concentration compared to 5-min treatments), but in other samples, the 10-minute helium plasma-activated water had a lower overall concentration than the 15-min hPAW (e.g. 10 min NO3 concentration < 0.7 mg/L). In order to quantify variations in helium plasma-water interactions, the RONS concentration for each sample recorded for a specific experimental condition was determined and analyzed by its coefficient of variation, varying from ~18% to 62.28% CV rate across the different time conditions. Experimental evidence in this study aligns with findings in published research, revealing temperature and humidity as potential factors behind these variations; these variations show that careful real-time monitoring in a controlled environment is needed for consistent RONS delivery to maximize the healing impact of plasma technology on the wound. This project presents calibration curves, curve-fitting routines, and insights into the dynamic behavior of plasma in order to fully understand its therapeutic potential for the wound-healing process. 

 

Presenting Author: Sahana Prasad Adrian Wilcox High School

Presenting Author Biography: As a researcher in Intelliscience Institute working under Dr. Syed Zaidi at San Jose State University, my research activities revolve around investigating the formation of reactive species in helium plasma-activated water for therapeutic optimization. Recently, I have been focusing on quantifying the dynamic nature of helium plasma in plasma-water interactions to understand the controlled conditions required to maximize the wound-healing benefits of plasma technology. In my future academic and research career, I will continue working in plasma medicine field.

Authors:

Sohail Zaidi San Jose State University
Sahana Prasad Adrian Wilcox High School