Ju Hun Yeon

Drug Permeability Assay Using Microhole-Trapped Cells in a Microfluidic Device

As orally administered drugs must be absorbed from the intestine into the blood circulation, permeability assays of drug candidates have been widely used in the early screening stages of drug discovery. In this study, a microfluidic device was developed for the drug permeability assay, considering the in vivo delivery path of drugs in humans. A microhole array for cell trapping was fabricated using the poly(dimethylsiloxane) (PDMS) molding technique by mimicking the intestinal epithelial cell membrane. On the basis of mathematical simulations, the configuration of the microfluidic device, including a microhole array and a mixing channel, was optimized to trap cells firmly in each microhole. At the flow rate under optimal conditions, cells were effectively trapped in a microhole array without cell damage. We measured the permeability of 10 drugs, including those with high and low permeability in microchannels, and compared the results with the reported values of permeability in the human and rat intestine. Most drugs had a high p value (p > 0.4), and only a few drugs had a low p value less than 0.05 by t test. Though their measured permeabilities are not the same as those in vivo human intestine, it shows that in vivo permeabilities in the human and rat intestine are highly correlated with those measured by the microfluidic device (R(2) = 0.9013 and R(2) = 0.8765, respectively). Also, the fraction of the dose absorbed in the human intestine (F(a)) indicated that the drug permeability measured using this device was significantly correlated (R(2) = 0.9641) with those in human subjects. As the microfluidic assay system is dependent on cells trapped inside a microhole array, it is a valuable tool in drug discovery as well as an alternative to animal testing.

Hepatotoxicity assay using human hepatocytes trapped in microholes of a microfluidic device.

Hepatocytes have been used for in vitro hepatotoxicity assays because of their ability to sustain intact liver‐specific functions. Here, we demonstrate a hepatotoxicity assay system using primary human hepatocytes trapped in microholes of a microfluidic device, providing a microscale in vivo liver‐like environment. We performed microfluidic hepatotoxicity assays of several drugs, including acetaminophen, verapamil, diclofenac, and benzopyrene, all of which are known to specifically affect hepatic function. The drug sensitivities in hepatocytes and HepG2 cells were measured by calculating the live cell fraction at various drug concentrations. The results indicated that hepatocytes were more sensitive to these drugs than HepG2 cells. The lethal concentration 50 values for all drugs tested were similar to those from the in vitro toxicity data with human hepatocytes obtained from the literature. Furthermore, we developed a mathematical hepatotoxicity model based on the time‐dependent cell death profiles measured by our device. This novel assay system enabled us to analyze in vivo‐like hepatotoxicity in a microfluidic device by exploiting microstructures to mimic the microenvironment of the liver.

A Simple Pipetting-based Method for Encapsulating Live Cells into Multi-layered Hydrogel Droplets

Here, we present a simple pipetting-based approach for generating multi-layered core-shell hydrogel droplets composed of alginate for outer shell and collagen for culturing cells inside. By using a multi-hole plastic substrate and by pipetting, multi-layered hydrogel droplets were generated in a simple and rapid manner. HEK293 cells, which are human embryonic kidney cells, were cultured for 14 days in double-layered hydrogel droplet with high viability. Cancer cells were co-cultured with epithelial cells in multi-layered hydrogel droplets and applied for drug tests with curcumin. As epithelial cells protect cancer cells from anti-cancer drugs, co-cultured cells showed lower sensitivity to curcumin. We developed a simple and easy method for creating complex hydrogel particles for 3D multicellular co-culture and developed an alternative method for drug testing in vivo.