Pre-clinical animal tests are used to assess drug efficacy and safety, but are limited by factors such as their suitability as a model for humans, robustness, cost, and ethical issues. While an organ-on-a-chip using human cells is promising for recapitulating human physiological conditions, it is highly desirable in investigations of the side effects of drugs to integrate more than one type of tissue using a designed circulatory system. We have developed a microfluidic device—an Integrated Heart/Cancer on a Chip (iHCC)—using human healthy heart cells (hCMs) and liver cancer cells (HepG2) to recapitulate the side effects of an anti-cancer drug, doxorubicin (DXR), to achieve individual cultures of cells from different tissues on a single device with three sets of artificial blood circulation loops, microfabrication technology for micro valves and a pump provides accurate fluid operation. Using improved soft lithography adopting numerical optimization simulation, the microfluidic device was fabricated with on-chip integration of pneumatic valves and a peristaltic micropump establishing precision fluid flow. The iHCC developed allows modelling of the side effects of DXR on heart cells caused by the production of toxic metabolites (doxorubicinol; DXRol) by HepG2 cells and the delivery of DXRol to heart cells via the circulation loop. Our findings open the door towards the development of a “Body-on-a-Chip.”

Non-alcoholic fatty liver disease (NAFLD) afflicts a significant percentage of the population; however, no effective treatments have yet been established because of the unsuitability of in vitro assays and animal experimental models. Here, we present an integrated-gut-liver-on-a-chip (iGLC) platform as an in vitro human model of the gut-liver axis (GLA) by co-culturing human gut and liver cell lines interconnected via microfluidics in a closed circulation loop, for the initiation and progression of NAFLD by treatment with free fatty acids (FFAs) for 1 and 7 days, respectively. Co-cultured Caco-2 gut-mimicking cells and HepG2 hepatocyte-like cells demonstrate the protective effects from apoptosis against FFAs treatment, whereas mono-cultured cells exhibit induced apoptosis. Phenotype and gene expression analyses reveal that the FFAs-treated gut and liver cells accumulated intracellular lipid droplets and show an increase in gene expression associated with a cellular response to copper ions and endoplasmic reticulum stress. As an in vitro human GLA model, the iGLC platform may serve as an alternative to animal experiments for investigating the mechanisms of NAFLD.

Digital micromirror device (DMD)-based grayscale lithography is a promising tool for 3-D photolithography of thick photoresists, because this technique provides a patterning solution for free-form 3-D microstructures. Among the numerous process parameters in DMD-based grayscale lithography, the exposure dose pattern corresponding to the grayscale mask pattern, the focal position in the photoresist, and the development time most strongly influence the final profile of the 3-D microstructure. However, finding the best combination of the three process parameters is a difficult and time-consuming task. In this paper, we propose a process optimization method for DMD-based grayscale lithography that is based on the 3-D photolithography simulation and sensitivity analysis. This optimization tool provides not only automatic process optimization for all three process parameters, i.e., the exposure dose pattern, the focal position, and the development time, but also a solution to improve fabrication accuracy for critical features by adopting a variable weight factor. Through a series of experiments, using a 20-μm-thick positive photoresist, the validity and effectiveness of the proposed optimization method and the improvement of the fabrication accuracy were successfully demonstrated.