Development of microfluidic devices for on-site water quality testing using glass molding process.

The demand for multi-point water quality monitoring is increasing to solve the global problem of safe drinking water supply and environmental water contamination by industries. Therefore, compact devices are needed for on-site water quality analysis. On-site devices require low cost and high durability because they are placed outdoors, exposing them to strong ultraviolet rays and a wide range of temperatures. Our previous study reported on a compact and low-cost water quality meter that uses microfluidic devices with resin to monitor chemicals. In this study, we extended the fabrication range of the glass molding method to fabricate a glass microfluidic device with a 300 µm deep channel on a 50 mm in diameter substrate for constructing a low-cost and high-durability device. Finally, we developed a low-cost, highly robust glass device with a diamond-like carbon-coated channel surface to measure residual chlorine. The experimental results indicated that this device can endure outdoor conditions and be attached to small internet of things devices for analyzing chemical substances, such as residual chlorine.

Development of a Microfluidic System Comprising Dialysis and Secretion Components for a Bioassay of Renal Clearance.

We have developed a microfluidic bioassay system that mimics glomerular filtration and tubular secretion in the kidney. The system consists of a peristaltic micropump (heart), a dialysis component (renal corpuscle), and a secretion component (renal proximal tubule). Analytes were separated by size using a dialysis membrane in the dialysis component. Model cells were cultured on a membrane in the secretion component, and active transport mediated by P-glycoprotein (P-gp) was confirmed using the P-gp substrate rhodamine 123 with or without the P-gp inhibitor quinidine sulfate. The system achieved both size separation and selective transport by P-gp on a single microchip. This proof-of-concept model may find applications in drug excretion assays, including studies of drug-drug interactions during tubular secretion.

Development of a Multichannel Dialysis Microchip for Bioassay of Drug Efficacy and Retention.

Here, we developed a multichannel dialysis microchip having three sets of dialysis systems, which consisted of three independent circulation channels with a common micropump. Each dialysis system was composed of a pneumatic micropump (heart), dialysis unit (renal corpuscle), and cell culture chamber (drug target) as well as circulation and dialysate channels to mimic the circulation system. Small molecules were successfully separated in parallel from macromolecules at the dialysis components. Anticancer tests using this microchip showed results that considered both serum protein-binding nature and drug activity. In the anticancer bioassay, the multichannel chip showed similar reproducible and reliable results as those of the single-channel system but with higher throughput.