Optimizing Microfluidic Gradient Generating Surface Plasmon Resonance (SPR) Chips for High-Throughput Biochemical Reaction Kinetics in Renal Physiology

Background: Motivated by the desire to study the activity of proteases, and protease inhibitors and activators in urine, we are developing a novel surface plasmon resonance technique which enables monitoring of these reactions over a wide range of simultaneous substrate concentrations, facilitating high-throughput measurement of proteolysis against peptides from protease-regulated macromolecules such as Epithelial Sodium Channel (ENaC). Methods: This study focuses on optimizing microfluidic chips for channel design, polydimethylsiloxane (PDMS) adhesion to glass, and gold-thin film sputter coating parameters while fabricating sensor chips. We developed a gradient generator chip design, which was cast from 3D-printed resin molds. BK7 glass slides were sputter coated with a gold thin-film. Both glass and PDMS were functionalized using oxygen plasma from a high voltage-high frequency generator to form covalent bonds. Results: We systematically examined effects of gold coaching thickness, and deposition time on sensor chip functionality. Our results demonstrate successful gradient generation, and assembly of biomolecule monolayers on the gold surface. Conclusion: Future work will integrate with the SPR design to measure real-world reaction kinetics, advancing our understanding of protease-substrate interaction and regulation in the kidney.