Protease-Activated Agents

Excitation-emission matrix of visible emission QDs.

The goal of this project is to develop biologically responsive nanostructures that can sense and respond to the activity of proteolytic enzymes in their biological environments, providing novel tools to both detect and treat disease. It is believed that such structures will have a wide range of applications in cancer diagnostics, in developmental biology, and in elucidating the molecular basis of a number of diseases, particularly cancer. This effort is the ongoing extension of a CBEN collaboration involving bioengineers (West and Drezek) and a chemist (Colvin). Our prior efforts have demonstrated the proof of principle of creating gold-QD complexes with functional imaging capability. The project is now progressing to more expansive applications as well as basic science to uncover the fundamentals of the behavior. Over the next 2 years this group will work toward broadening its funding base, as well as exploring a wider range of possible uses for this new capability. Activities will include the development of NIR QDs for in vivo imaging. A limitation of currently available QD systems is the low penetration depth of the relevant wavelengths of light through tissue, particularly the sources used for excitation of the materials. The group is developing materials with substantially red-shifted excitation and emission spectra for use in in vivo imaging. We have also created nanostructured reporters that respond to targeted proteolytic enzymes. Aggregates of nanoparticles can be linked through proteolytically degradable peptides, allowing disruption of the aggregate structure in response to specific, targeted proteolytic enzymes. This can lead to optical signals through dequenching of a fluorophore such as a QD. We have developed nanostructures that respond to the presence of proteolytic enzymes associated with cancer metastasis and invasion linking QD-gold conjugates using proteolytically degradable peptides. Optical responses have been assessed in enzyme solutions and also in cultures of metastatic tumor cells and normal fibroblasts. In the next year, we plan to move into in vivo tumor imaging.

Participating Researchers:

• Jennifer West
• Vicki Colvin
• Rebekah Drezek