Singlet-oxygen Plasma Afterglow Reaction Chamber for Disinfection and Sterilization

The capability of discharge-produced reactive oxygen species, in particular O2(a1), to effectively inactivate biological species has been empirically well-established. Disinfection and sterilization processes for instruments, surfaces, and wounds are essential in disease prevention to ensure destruction of microorganisms that can contaminate materials. Such microorganisms include spore-forming and non- spore-forming bacteria, viruses, fungi, and protozoa. Employing reactive oxygen species as a disinfectant is particularly exciting as it may prove to be one of the most versatile, safe, and low-cost disinfectants available. However, though reactive oxygen species have been empirically well-established by observing the outcome of oxygen plasma and plasma afterglow interactions with pathogens, the plasmas themselves have not been well interrogated. Insufficient quantitative understanding exists of reactive flow parameters required for reliable disinfection against a wide body of pathogens, and the biological inactivation mechanisms involved, to proceed with development of robust medical equipment. Critical parameters include, though are not limited to, reactive species densities, flow rates, mixtures, environmental conditions, and inactivation mechanisms. The lack of sufficient quantitative data has slowed the transition of this exciting disinfection technology to implementation as an affordable tool with wide societal benefit. The fundamental reason for a disconnect between the proven potential of reactive oxygen species and a well- quantified understanding of key biological inactivation parameters is inadequate and highly-inconsistent research tools utilized by microbiologists in the field of Plasma Medicine. To address this inadequacy, development of a standardized and well-instrumented biological inactivation toolset is proposed, enabling the capability of characterizing inactivation rates and mechanisms of reactive oxygen species against a wide body of pathogens. The toolset will be made widely available and be supported by well-calibrated diagnostic techniques for reactive oxygen species, as well as a detailed multi-physics computational model. The product will offer the user the ability to model test chamber dynamics prior to experiments, select desirable test conditions, and rapidly expose samples and contaminated tools to plasma afterglow, while monitoring reactive oxygen species levels with optical techniques. The Phase I project will proceed with the following crucial developmental tasks: (1) model and construct a test apparatus using largely existing laboratory equipment, (2) implement the apparatus and measure inactivation rates and associated reactive oxygen species levels for four biological species representative of a large cross-section of pathogens, (3) employ the experimental and computational results to develop a preliminary design for a plasma afterglow exposure chamber, and validate using a multi- physics model, and (4) develop a compact calibrated O2(a) diagnostic based on near-infrared spectroscopy using a filtered thermoelectrically-cooled InGaAs photodetector. Phase II will result in a compact mobile reactive oxygen exposure chamber for laboratory and clinical studies, which incorporates optical monitoring of reactive oxygen species levels and a computational model to characterize exposure conditions based on user specifications. The plasma technology will be adaptable and reconfigurable to other afterglow exposure technology using oxygen or air plasmas, and customized gas doses. Technological developments can also support medical tool sterilization chambers of various volumes, atmospheric plasma jet devices with a variety of configurations and gas mixtures, and custom- built experimental and commercial devices based on moderate to atmospheric pressure plasma.