Autonomous Temporal Control of Hydrogen Sulfide Delivery.

Hydrogen sulfide (HS) is dichotomous in nature as it is lethal at higher concentrations, but at lower concentrations it shows a more cytoprotective nature. Due to its involvement in many physiological processes, it has recently risen to significance as a gasotransmitter alongside carbon monoxide (CO) and nitric oxide (NO). Experimentation using HS is thus important to generate in vitro and in vivo models for this ubiquitous gasotransmitter. However, laboratory studies involving HS are challenging due to the special handling conditions required to work with such a toxic gas. The use of chemical donors in the cell culture also show temporally varying release profiles, which are not optimal when trying to control HS in cell cultures lasting several days. Previously we applied microfluidics to deliver stable concentrations of HS, and in this work, we demonstrate a novel experimental method incorporating feedback control to precisely deliver HS that accounts for donor solution concentration decay.