WFU Physics Colloquium

TITLE: Lab-on-Bead Processing of Encoded Chemical Libraries: Drug Discovery at the Nanoscopic Level

SPEAKER: Professor Jed Macosko,

TIME: Thursday Feb. 21, 2008 at 4:00 PM

PLACE: Room 101 in Olin Physical Laboratory

To hasten the discovery of new drugs, our lab has developed a method that we call "Lab-on-Bead", which allows us to process and screen encoded chemical libraries. In this method, individual 100-200 nm fluorescent bead are each functionalized with multiple copies of a unique DNA sequence. These unique sequences are used to hybridize to DNA or PNA (peptide nucleic acid) encoded chemical libraries that are synthesized by our collaborators. Since each bead is monoclonal with respect to its unique hybridization DNA, only one type of encoded chemical will hybridize to each bead. Thus, by isolating individual beads that bind tightly to target molecules, and by amplifying and sequencing their unique hybridization DNA, the accompanying encoded molecules can be identified.

Currently our research is focused on how to isolate individual beads for amplification and sequencing. We have built a combined AFM and fluorescent microscope, and we use this instrument to image and manipulate target-binding beads. We found that "skewering" beads with the tip of an AFM probe is an effective way to move the bead from the target-binding surface to a separate compartment for PCR amplification. Our results demonstrate that the ~1000 DNA molecules attached to these beads 1) hybridize enough encoded molecules to cause tight target-binding and 2) template a sufficient PCR product for normal gel electrophoresis and DNA sequencing. This means that our maximal screening rate is 1010 compounds per day, per AFM. Moreover, as part of an ongoing collaboration, a microfluidic device is being developed in our lab that will miniaturize this drug-screening methodology and allow for parallel processing.