A Homogenous Microarray for Enzymatic Functional Assays

Microarrays as an emerging research tool promises to play a pivotal role in the post genomic era. However, in spite of the fast development of this technology special requirements, such as the immobilization and delivery of bio-reagents on the chip surface limit the utilization of microarrays, especially for small chemical compound libraries. We have developed a unique homogenous microarray system that overcomes these limitations and can be used to array most biofunctional molecules, such as small chemical compounds, peptides and proteins without pre-immobilization. A standard microscope slide containing up to 5000 microarray dots, with volumes less than 2 nanoliter each and acting as individual reaction centers, can be printed with standard DNA arrayer. An aerosol deposition technology was adapted to deliver extremely small volumes of biofluids uniformly into each reaction center. The fluorescence based reaction signals were then scanned and analyzed with standard DNA scanner and DNA array analyzing software. With this platform, we demonstrated that this chip format could be used for not only screening individual but also multiple enzymatic activities simultaneously with different fluorescent tagged small peptide libraries. We further demonstrated that this system could be a very powerful ultra high throughput screening tool for drug discovery, with which we identified potential “hits” after screening chips printed with small chemical compounds against caspases 1 and 3. This highly sensible chip is also able to monitor caspase protein expression profiles by activating the peptide chips with cell lysates undergoing apoptosis.