Final Report Summary - CT-PROBES (Protease Activated X-Ray Contrast Agents for Molecular Imaging of Vulnerable Atherosclerotic Plaques and Cancer Development using Spectral CT)
The focus of this project was the synthesis and characterization and application of new classes contrast reagents that enable cancer detection with X-ray computed tomography (CT) scanners. The compounds generated were targeted to cysteine cathepsin proteases, enzymes that are highly elevated in cancer, they were engineered to irreversible bind the proteases as a result of the protease activity thus served as selective molecular reporters.
X-ray CT instruments are among the most available, efficient and cost-effective imaging modalities in hospitals. The field of CT molecular imaging agents is emerging relying mainly on detection of gold and bismuth nanoparticles, iodine and gadolinium labeled compounds. However, the low sensitivity of CT scanners to contrast reagents makes molecular imaging using CT a challenging task.
We have generated two libraries of probes, one labeled with iodine and the other with gold nanoparticles. Both libraries target and bind the active proteases through a small targeting moiety that consisting of a recognition peptide sequence and a binding electrophilic part. After chemical and biochemical evaluations; we selected the most potent and stable probes of each library to proceed to non-invasive imaging in cancer mice models. CT contrast from the tumor could be detected after systemic injection of targeted probes from both libraries. The specific signal increased over time and was significant higher compared to controls particles lacking the targeting element. Contrast agent concentrations and sub-cellular localization within the tumor cells was detected using transmission electron microscopy (TEM). Thus, we were able to generate CT molecular imaging probes that report on protease activity within tumors bearing mice.
X-ray CT instruments are among the most available, efficient and cost-effective imaging modalities in hospitals. The field of CT molecular imaging agents is emerging relying mainly on detection of gold and bismuth nanoparticles, iodine and gadolinium labeled compounds. However, the low sensitivity of CT scanners to contrast reagents makes molecular imaging using CT a challenging task.
We have generated two libraries of probes, one labeled with iodine and the other with gold nanoparticles. Both libraries target and bind the active proteases through a small targeting moiety that consisting of a recognition peptide sequence and a binding electrophilic part. After chemical and biochemical evaluations; we selected the most potent and stable probes of each library to proceed to non-invasive imaging in cancer mice models. CT contrast from the tumor could be detected after systemic injection of targeted probes from both libraries. The specific signal increased over time and was significant higher compared to controls particles lacking the targeting element. Contrast agent concentrations and sub-cellular localization within the tumor cells was detected using transmission electron microscopy (TEM). Thus, we were able to generate CT molecular imaging probes that report on protease activity within tumors bearing mice.