The Penn Center for
Molecular Discovery

Institute for Medicine and Engineering
1024 Vagelos Research Laboratories
The University of Pennsylvania
Philadelphia, PA 19104

Tel 215-573-5702 (office)
Tel 215-573-5704 (lab)
Fax 215-573-7227

Email pcmd@seas.upenn.edu

Microarray Screening: Scott L. Diamond, PhD.

The Diamond laboratory has developed a methodology to screen chemical libraries on microarrays (Gosalia and Diamond, PNAS 2003). Chemical compounds within individual nanoliter droplets of glycerol can be microarrayed onto glass slides at 400 spots/cm². Using aerosol deposition, subsequent reagents and water are metered into each reaction center in order to rapidly assemble diverse multicomponent reactions without cross-contamination or the need for surface linkage. This proteomics technique allows for the kinetic profiling of protease mixtures, protease – substrate interactions, and high throughput screening reactions.

Exploiting the low volatility of glycerol droplets on glass, we have created discrete reaction volumes via contact printing. Each droplet had an average volume of 1.6 nL after microarraying. A 16x24 array of 200 um diameter spots with 500 µm center-to-center spacing, equivalent to a 384-well plate format, occupied less than 1-cm². In kinetic applications on a microarray, the need to initiate tens of thousands of reactions at once is not easily accommodated by the use of piezo dispensing micropipettes or ink-jet engines that have exacting surface tension or viscosity requirements and are prone to clogging. To solve the problem of rapid sample delivery to these small nonspreading droplets, we deposited onto the arrays using aerosol deposition. In this approach, the aerosolization of the sample resulted in a fine mist with a median droplet diameter of 18 µm (~3 pL). Aerosol droplets deposited evenly on and around the glycerol spots and rapidly evaporated within 7 seconds without mixing between spots.