title: Enzyme kinetic measurements using a droplet-based microfluidic system with a concentration gradient.
abstract: In this paper, we propose a microfluidic device that is capable of generating a concentration gradient followed by parallel droplet formation within channels with a simple T-junction geometry. Linear concentration gradient profiles can be obtained based on fluid diffusion under laminar flow. Optimized conditions for generating a linear concentration gradient and parallel droplet formation were investigated using fluorescent dye. The concentration gradient profile under diffusive mixing was dominated by the flow rate at sample inlets, while parallel droplet formation was affected by the channel geometry at both the inlet and outlet. The microfluidic device was experimentally characterized using optimal layout and operating conditions selected through a design process. Furthermore, in situ enzyme kinetic measurements of the β-galactosidase-catalyzed hydrolysis of resorufin-β-d-galactopyranoside were performed to demonstrate the application potential of our simple, time-effective, and low sample volume microfluidic device. We expect that, in addition to enzyme kinetics, drug screening and clinical diagnostic tests can be rapidly and accurately performed using this droplet-based microfluidic system.
authors.affiliation: Department of Bionano Engineering, Hanyang University, Ansan 426-791, South Korea.
authors.forename: Minh-Phuong Ngoc
authors.initials: MP
authors.lastname: Bui
authors.forename: Cheng Ai
authors.initials: CA
authors.lastname: Li
authors.forename: Kwi Nam
authors.initials: KN
authors.lastname: Han
authors.forename: Jaebum
authors.initials: J
authors.lastname: Choo
authors.forename: Eun Kyu
authors.initials: EK
authors.lastname: Lee
authors.forename: Gi Hun
authors.initials: GH
authors.lastname: Seong
mesh_terms: D004798:Enzymes / Q000737:chemistry*; D007700:Kinetics; D044085:Microfluidics / Q000379:methods*
chemical_list: D004798:Enzymes