Microfluidic System to Deliver Aqueous Superoxide

Francisco J. Chaparro-Carrasquillo1, Rebekah Wilson2, Edward Chainani2, Geoffrey Beck2, and Alexander Scheeline2. (1) Chemistry & Chemical Engineering, University of Puerto Rico at Mayaguez, Bo. Guaniquilla, BZN. A-359, Aguada, PR 00602, (2) Chemistry, University of Illinois at Urbana-Champaign, 600 S. Matthews Ave., Box 48-5 MC 712, Urbana, IL 61801

Reactive oxygen species (ROS) are natural by-products of cellular metabolism which are highly reactive chemicals containing oxygen. Superoxide radical (O2-), is one such ROS, and can be generated in aqueous solution in many ways, most commonly by using the enzyme xanthine oxidase to reduce oxygen to superoxide. However, superoxide attacks xanthine oxidase which eventually decreases the production of superoxide and generates hydrogen peroxide instead. Also, superoxide reacts with itself and dismutates rapidly to hydrogen peroxide (H2O2) and molecular oxygen (O2), with a pH-dependent rate constant. Potassium superoxide (KO2) in highly alkaline solutions, where the rate of dismutation is very slow, has been demonstrated to be a stable source of superoxide. To be useful experimentally, superoxide must be brought to biological pH while avoiding its dismutation. In a microfluidic device under development, alkaline KO2 is introduced into a channel, where a two step buffer system rapidly drops the pH to around 7-8 at the outlet. Immobilized catalase in the flow path removes hydrogen peroxide produced by dismutation. The device aims to provide concentrated superoxide on demand to biological systems where oxidative stress is implicated such as cell cultures for investigating aging, inflammation, neurological disorders, heart disease, as well as hearing loss.