Toward a Microparticle-Based System for Pooled Assays of Small Molecules in Cellular Contexts

Abstract

Experimental approaches to the discovery of small molecule probes and drug candidates often use biochemical or cell-based screening of large libraries (>105) of small molecules. Small molecules of interest are tested one at a time in individual wells of a microtiter plate, at a significant cost in time and resources. Furthermore, evaluation of large numbers of compounds in such assays requires robust cellular or biochemical screening formats that may not be relevant to the contexts found in human patients. We envision a solution to these issues that involves a pooled system of small molecule screening, which would require development of numerous new technologies, and solutions to several key challenges. We report here that a microparticle-based screening system can allow for screening of small molecules in such a pooled fashion, analogous to the pooled screens of genetic reagents that have been powerfully deployed in recent years. We developed a cleavable linker that can link small molecules of interest to silica microparticle beads; a DNA tag encoding the identity of the small molecule on each bead that was attached to the silica beads through a photocleavable linker to enable its amplification; and a bead-based fluorescent sensor that can report on the activity of small molecules in cells. We suggest that this pooled small molecule screening system could ultimately be useful for drug and probe discovery, allowing rapid and inexpensive screening of small molecules in assays of relevance to human diseases.

Particle Templated Emulsification enables Microfluidic-Free Droplet Assays

“…For example, it is not currently possible to perform droplet additions as are often conducted with microfluidics, requiring that all reaction components be introduced before encapsulation; this requires that reagents be compatible and stable until the droplets can be generated and, in the case of troublesome combinations, can often be addressed by quickly mixing and emulsifying the sample on ice. Alternatively, reactive components that can be triggered externally with light or heat can be used 13 . PTE thus provides a flexible and scalable method for conducting droplet assays accessible to non-experts.…”