Microplasma Bubbles: Reactive Vehicles for Biofilm Dispersal

Area of Science:

• Plasma science and technology
• Aquatic microbiology
• Biotechnology

Background:

• Cold atmospheric-pressure plasmas interact with water, generating reactive oxygen and nitrogen species (RONS).
• RONS are crucial for transferring plasma reactivity to solutions, enabling applications like pathogen inactivation and biofilm removal.
• Scaling plasma-based biofilm removal to complex systems like aquaculture tanks presents challenges in species delivery and maintaining inhabitant health.

Purpose of the Study:

• To investigate the efficacy of underwater microplasma bubbles as a delivery system for reactive plasma species in complex aquatic environments.
• To assess the impact of microplasma bubbles on biofilm reduction and the health of fish in a multispecies system.
• To identify key bioactive species responsible for biofilm inactivation.

Main Methods:

• Generation of underwater microplasma bubbles using a dielectric barrier discharge microplasma-bubble reactor (4.0 kV).
• Application of microplasma bubbles and plasma-activated water (PAW) to artificial and living surfaces with biofilms.
• Assessment of biofilm reduction, prevention of new biofilm formation, and fish health status in a custom-made fish tank.
• Analysis of generated reactive species, including hydrogen peroxide, ozone, nitrite, nitrate, and nitric oxide.

Main Results:

• Underwater microplasma bubbles effectively delivered reactive plasma species to target biofilm sites.
• Both microplasma bubbles and PAW significantly reduced existing pathogenic biofilm load (∼83% and 60%, respectively) and prevented new biofilm formation.
• Daily application of microplasma bubbles in a fish tank reduced biofilm-infected areas by 80-90% and improved fish health.
• Nitric oxide was identified as a critical species triggering biofilm cell release and inactivation.

Conclusions:

• Underwater microplasma bubbles serve as efficient transport vehicles for reactive plasma species in complex aquatic systems.
• This technology offers a viable method for biofilm control in aquaculture, promoting both water quality and fish health.
• Plasma-induced nitric oxide plays a key role in the antibiofilm mechanism.