Droplet Reactors with Bioluminescent Enzymes for Real-Time Water Pollution Monitoring

• Main Authors: Anton S. Yakimov, Ivan A. Denisov, Anton S. Bukatin, Kirill A. Lukyanenko, Kirill I. Belousov, Igor V. Kukhtevich, Elena N. Esimbekova, Anatoly A. Evstrapov, Peter I. Belobrov
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Proceedings
• Subjects: early warning systems; luciferase; microfluidic droplet generator; emulsion; bioassay
• Online Access: https://www.mdpi.com/2504-3900/60/1/54

Early detection of pollutants in wastewater, water coming out of treatment facilities, drinking water, and water for agricultural needs is a challenging problem. Effective water quality monitoring requires development of new methods for express detection of pollutants. Enzymes from bioluminescent bacteria can be used for the development of new express enzyme-based bioassay systems. This work demonstrates, for the first time, a microfluidic chip to generate emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN-oxidoreductase) with reaction substrates. The developed chip generated “water-in-oil” emulsion droplets with a volume of 0.1 <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>L and a frequency of up to 12 droplets per second. A portable photomultiplier tube (PMT) was used to measure the bioluminescent signal in each individual droplet; the signal-to-noise ratio was 3000/1. The intensity of luminescence in droplets depended on the concentration of copper ions. The limit of detection (LOD) for copper sulfate was 1 mg/L. We showed that bioluminescent enzymatic reactions can be carried out in droplet reactors that can be applied for online monitoring of water quality. Thus, the suggested method of biological measurements has a good perspective for biosensing in general.