We have developed new tools to interrogate the effects of small molecules on biological function (Figure 1). These include cell- and protein-based high-throughput screening, on chip immunoassays and high-throughput biocatalysis on a microarray platform (Lee et al. Proc. Natl. Acad. Sci. USA 102, 983-987 (2005); Sukumaran et al. J. Biomol. Screen. 14, 668-678 (2009)]. With respect to the cell-based screening platform, we developed (in collaboration with Doug Clark’s group at UC Berkeley) a miniaturized three-dimensional (3D) cellular array chip (the DataChip, Figure 2) that has been used for in vitro toxicological assessment of drug candidates and other chemicals in high-throughput [Lee et al. Proc. Natl. Acad. Sci. USA 105, 59-63 (2008)]. Although recent emphasis has been placed on understanding cellular metabolism in 3D, relatively little effort has been spent using 3D cultures to study cytotoxicity, particularly at very small volumes consistent with high-throughput screening. Furthermore, we have recently begun to investigate the toxicity of compounds on human stem and progenitor cells in comparison to their differentiated progeny.
We also developed a novel chip design that enables interrogation of differential expression of various drug-metabolizing enzymes (DMEs) in the human liver. Such information is relevant to inter-individual variability in drug pharmacokinetic profiles, drug efficacy and toxicity. Specifically, we developed the “Transfected Enzyme and Metabolism Chip” (TeamChip), which predicts potential metabolism-induced drug or drug-candidate toxicity [Kwon et al. Nat. Commun. 5, 3739 (2014)]. The TeamChip is prepared by delivering genes into miniaturized three-dimensional cellular microarrays on a micropillar chip using recombinant adenoviruses in a complementary microwell chip (Figure 3). The device enables users to manipulate the expression of individual and multiple human metabolizing-enzyme genes (such as CYP3A4, CYP2D6, CYP2C9, CP1A2, CYP2E1, and UGT1A4) in THLE-2 cell microarrays. To identify specific enzymes involved in drug detoxification, we created 84 combinations of metabolic-gene expressions in a combinatorial fashion on a single microarray (Figure 4). Thus, the TeamChip platform can provide critical information necessary for evaluating metabolism-induced toxicity in a high-throughput manner.