Theranostics 2011; 1:363-370. doi:10.7150/thno/v01p0363

Research Paper

Transforming a Targeted Porphyrin Theranostic Agent into a PET Imaging Probe for Cancer

Jiyun Shi1,2,3 *, Tracy W.B. Liu1,2 *, Juan Chen2, David Green2, David Jaffray1,2, Brian C. Wilson1,2, Fan Wang3, Gang Zheng1,2 ✉

1. Department of Medical Biophysics, University of Toronto, Toronto, Canada;
2. Ontario Cancer Institute, University Health Network, Toronto, Canada;
3. Medical Isotopes Research Center, Peking University, Beijing, China.
* J. Shi and T. Liu contributed equally to this work.

Abstract

Porphyrin based photosensitizers are useful agents for photodynamic therapy (PDT) and fluorescence imaging of cancer. Porphyrins are also excellent metal chelators forming highly stable metallo-complexes making them efficient delivery vehicles for radioisotopes. Here we investigated the possibility of incorporating 64Cu into a porphyrin-peptide-folate (PPF) probe developed previously as folate receptor (FR) targeted fluorescent/PDT agent, and evaluated the potential of turning the resulting 64Cu-PPF into a positron emission tomography (PET) probe for cancer imaging. Noninvasive PET imaging followed by radioassay evaluated the tumor accumulation, pharmacokinetics and biodistribution of 64Cu-PPF. 64Cu-PPF uptake in FR-positive tumors was visible on small-animal PET images with high tumor-to-muscle ratio (8.88 ± 3.60) observed after 24 h. Competitive blocking studies confirmed the FR-mediated tracer uptake by the tumor. The ease of efficient 64Cu-radiolabeling of PPF while retaining its favorable biodistribution, pharmacokinetics and selective tumor uptake, provides a robust strategy to transform tumor-targeted porphyrin-based photosensitizers into PET imaging probes.

Keywords: Copper-64, Porphyrin, PET, Folate receptor, Peptides

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How to cite this article:
Shi J, Liu TWB, Chen J, Green D, Jaffray D, Wilson BC, Wang F, Zheng G. Transforming a Targeted Porphyrin Theranostic Agent into a PET Imaging Probe for Cancer. Theranostics 2011; 1:363-370. doi:10.7150/thno/v01p0363. Available from http://www.thno.org/v01p0363.htm