Fundamentals of plasma disinfection for the inactivation of viruses in aerosol particles: Influence of liquid films
Biophysics
Final Report Abstract
The purpose of this project was to investigate the fundamentals of cold atmospheric plasma (CAP) for virus inactivation in aerosol particles. CAP has attracted significant attention in biomedical applications, including wound healing, sterilization, cancer therapy, and antibacterial treatment. The COVID-19 pandemic further intensified interest in CAP, particularly for aerosol and surface sterilization, due to its effectiveness and environmental compatibility. To enhance the efficiency of plasma-based disinfection, optimizing plasma composition is essential. Therefore, within this DFG project, we demonstrated precise control over the plasma chemical profile by optimizing electrical parameters, such as applied voltage and frequency, and by adjusting the gas composition with a controlled ratio of nitrogen, oxygen, and argon. Reactive plasma species were characterized using Fourier Transform Infrared (FTIR) and UV-Vis spectroscopy. Additionally, the study investigated the aerosol polymerization of acrylamide (AM) into polyacrylamide (PAM) as a model reaction to evaluate the reactivity of different plasma-generated species. The highest polymerization yield was achieved under plasma conditions with a maximum concentration of NO₂, whereas the presence of OH radicals resulted in significantly lower yields, likely due to their brief lifespan. The transient nature of OH radicals cause substantial challenges for experimental studies, as their direct observation and detailed investigation are difficult. To address this challenge, the second part of the project employed Molecular Dynamics (MD) simulations to investigate the interactions between plasma-generated species and surrounding liquid layers at the atomic level. The simulations revealed that OH radicals, upon interacting with water molecules, engage in hydrogen atom exchange, thereby regenerating new OH radicals. This process establishes a dynamic equilibrium that sustains radical activity in aqueous environments. In contrast, H₂O₂ remains highly stable due to strong hydrogen bonding with water, leading to a lower diffusion rate compared to OH radicals. Furthermore, both OH radicals and H₂O₂ effectively penetrate the water layer, it means they could reach the biomolecule surfaces with diffusion coefficients of 0.789 Ų/ps and 0.148 Ų/ps, respectively. The focus of our simulations was to investigate the interactions of OH radicals and H₂O₂ with water for two main reasons. First, the short lifespan of OH radicals presents significant challenges for experimental investigation and characterization. Therefore, we use simulations as an alternative tool to study their behavior at the atomic level. Second, the current reactive force fields in MD simulations do not adequately describe the reactions of NOₓ species with water or biological molecules. We are actively working to refine and develop these force fields to extend their applicability to nitrogen species in future studies.
Publications
-
Advancing DBD Plasma Chemistry: Insights into Reactive Nitrogen Species such as NO2, N2O5, and N2O Optimization and Species Reactivity through Experiments and MD Simulations. Environmental Science & Technology, 58(36), 16087-16099.
Shaban, Masoom; Merkert, Nina; van Duin, Adri C. T.; van Duin, Diana & Weber, Alfred P.
