Droplet Microfluidic Device for Chemoenzymatic Sensing

Abstract

The rapid detection of pollutants in water can be performed with enzymatic probes, the catalytic light-emitting activity of which decreases in the presence of many types of pollutants. Herein, we present a microfluidic system for continuous chemoenzymatic biosensing that generates emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN–oxidoreductase) with substrates required for the reaction. The developed chip generates “water-in-oil” emulsion droplets with a volume of 0.1 μL and a frequency of up to 12 drops per minute as well as provides the efficient mixing of reagents in droplets and their distancing. The bioluminescent signal from each individual droplet was measured by a photomultiplier tube with a signal-to-noise ratio of up to 3000/1. The intensity of the luminescence depended on the concentration of the copper sulfate with the limit of its detection of 5 μM. It was shown that bioluminescent enzymatic reactions could be carried out in droplet reactors in dispersed streams. The parameters and limitations required for the bioluminescent reaction to proceed were also studied. Hereby, chemoenzymatic sensing capabilities powered by a droplet microfluidics manipulation technique may serve as the basis for early-warning online water pollution systems.

Homogeneous, heterogeneous, and enzyme catalysis in microfluidics droplets

“…Microfluidic droplets have unique chemical properties that are analogous to test tubes or microplates, where the signals from many droplets are averaged to provide higher sensitivity and detection limits [58–62] . Microfluidic technology also has the following advantages [63] : (1) significantly reduced sample/reagent volume and ultrahigh analytical throughput [64] ; (2) precise control of heat and mass transport [65] ; (3) different functional modules can be easily integrated into microfluidic instruments [66] ; (4) rapid temperature equilibration and mixing of reactants with efficient heat and mass transfer [67] ; and (5) extraction of the thermodynamic and kinetic information of enzymes through the high‐throughput extraction of reactants, allowing unbiased analysis and analysis of the reactants, which allows the thermodynamic study of fragile enzymes [68] . In this section, we review the organic synthesis processes enabled by biological enzymes in microfluidics, including homogeneous w/w interfaces and heterogeneous w/o interfaces.…”

Activation and Switching of Supramolecular Chemical Signals in Multi-Output Microfluidic Devices

“…as their interaction products are extremely sensitive to a variety of factors, such as concentration and ratio of components [ 22 , 28 , 29 ], solvent [ 30 ], pH [ 31 ], among others. Nonequilibrium microfluidic confinement allows the simultaneous application of these factors to synthesize and modify soft matter structures [ 32 , 33 , 34 , 35 , 36 ]. By varying microchip operation parameters, we can use various mixing strategies for polymers, colloids and related low-molecular compounds, such as electrolytes [ 35 , 37 , 38 , 39 , 40 ].…”

Orientational Behavior of Nematic Liquid Crystals in Two-Phase Microfluidic Systems

“…[1,2]. Надмолекулярноорганизованные системы на основе жидких кристаллов (ЖК) в микрожидкостных «чипах» находят применение в фотонике [3,4], в качестве биосенсоров [5][6][7] и систем защитной маркировки [8,9], а также в качестве компонентов люминесцентных термометров [10,11] и темплатов для получения полимерных микрочастиц [12].…”