Nanoliter homogenous ultra-high throughput screening microarray for lead discoveries and IC50 profiling

Microfluidic technologies offer the potential for highly productive and low-cost ultra-high throughput screening and high throughput selectivity profiling. Such technologies need to provide the flexibility of plate-based assays as well as be less expensive to operate. Presented here is a unique microarray system (the Reaction Biology [Malvern, PA] DiscoveryDot), which runs over 6,000 homogeneous reactions per 1" x 3" microarray using chemical libraries or compound dilutions printed in 1-nl volumes. A simple and rapid piezo-activation method delivers from 30 to 300 pl of biochemical targets and detector chemistries to each reaction. The fluorescent signals are detected and analyzed with conventional microarray scanners and software. The DiscoveryDot platform is highly customizable, and reduces consumption of targets and reaction chemistries by >40-fold and the consumption of compounds by >10,000-fold, compared to 384-well plate assay. We demonstrate here that the DiscoveryDot platform is compatible with conventional large-volume well-based reactions, with a Z' factor of >0.6 for many enzymes, such as the caspase family enzymes, matrix metalloproteinase, serine proteases, kinases, and histone deacetylases. The platform is well equipped for 50% inhibitory concentration (IC50) profiling studies of enzyme inhibitors, with up to 10 dilution conditions of each test compound printed in duplicate, and each microarray chip can generate over 300 IC50 measurements against a given target.