Trackable and Targeted Phage as Positron Emission Tomography (PET) Agent for Cancer Imaging

Abstract

The recent advancement of nanotechnology has provided unprecedented opportunities for the development of nanoparticle enabled technologies for detecting and treating cancer. Here, we reported the construction of a PET trackable organic nanoplatform based on phage particle for targeted tumor imaging. Method: The integrin αvβ3 targeted phage nanoparticle was constructed by expressing RGD peptides on its surface. The target binding affinity of this engineered phage particle was evaluated in vitro. A bifunctional chelator (BFC) 1,4,7,10-tetraazadodecane-N,N',N",N"'-tetraacetic acid (DOTA) or 4-((8-amino-3,6,10,13,16,19-hexaazabicyclo [6.6.6] icosane-1-ylamino) methyl) benzoic acid (AmBaSar) was then conjugated to the phage surface for 64Cu2+ chelation. After 64Cu radiolabeling, microPET imaging was performed in U87MG tumor model and the receptor specificity was confirmed by blocking experiments. Results: The phage-RGD demonstrated target specificity based on ELISA experiment. According to the TEM images, the morphology of the phage was unchanged after the modification with BFCs. The labeling yield was 25 ± 4% for 64Cu-DOTA-phage-RGD and 46 ± 5% for 64Cu-AmBaSar-phage-RGD, respectively. At 1 h time point, 64Cu-DOTA-phage-RGD and 64Cu-AmBaSar-phage-RGD have comparable tumor uptake (~ 8%ID/g). However, 64Cu-AmBaSar-phage-RGD showed significantly higher tumor uptake (13.2 ± 1.5 %ID/g, P<0.05) at late time points compared with 64Cu-DOTA-phage-RGD (10 ± 1.2 %ID/g). 64Cu-AmBaSar-phage-RGD also demonstrated significantly lower liver uptake, which could be attributed to the stability difference between these chelators. There is no significant difference between two tracers regarding the uptake in kidney and muscle at all time points tested. In order to confirm the receptor specificity, blocking experiment was performed. In the RGD blocking experiment, the cold RGD peptide was injected 2 min before the administration of 64Cu-AmBaSar-phage-RGD. Tumor uptake was partially blocked at 1 h time point. Phage-RGD particle was also used as the competitive ligand. In this case, the tumor uptake was significantly reduced and the value was kept at low level consistently. Conclusion: In this report, we constructed a PET trackable nanoplatform based on phage particle and demonstrated the imaging capability of these targeted agents. We also demonstrated that the choice of chelator could have significant impact on imaging results of nano-agents. The method established in this research may be applicable to other receptor/ligand systems for theranostic agent construction, which could have an immediate and profound impact on the field of imaging/therapy and lay the foundation for the construction of next generation cancer specific theranostic agents.

Crosslinked multilamellar liposomes for controlled delivery of anticancer drugs

“…The process for preparing radiolabeled liposomes is shown in Figure 6A. The bifunctional chelator AmBaSar was used in the 64 Cu labeling due to the superior in vivo stability of 64 Cu-AmBaSar over other 64 Cu-chelator, such as 64 Cu-DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) [42, 43]. As shown in Figure 6B, the PET images were obtained at several time points (1, 3, 24 h) after intravenous injection of 64 Cu-AmBaSar-labeled ULs, DLLs, or CMLs.…”

A potent immunotoxin targeting fibroblast activation protein for treatment of breast cancer in mice

“…Radiolabeling of αFAP‐PE38 was performed based on a previously reported method for AmBaSar‐mediated 64 Cu labeling of proteins and peptides . Positron emission tomography (PET) imaging of the mice was performed using a rodent scanner (Concorde Microsystems).…”

Cytoreductive Chemotherapy Improves the Biodistribution of Antibodies Directed against Tumor Necrosis in Murine Solid Tumor Models

“…BaBaSar-N-hydroxysulfosuccinimidyl (BaBaSar-OSSu) was synthesized by activating BaBaSar with EDC and Sulfo-NHS at a molar ratio of 5:5:4 as reported previously (19, 23). Without purification, BaBaSar-OSSu was cooled to 4 °C and added to chTNT-3 in 0.1 M borate buffer, pH 8.5.…”

“…All 64 Cu labeling reactions for DOTA-chTNT-3 and Sar-chTNT-3 were performed using the same protocol (23). In brief, 100–200 μg DOTA-chTNT-3 or BaBaSar-chTNT-3 were loaded with 64 CuCl 2 (37–74 MBq 64 Cu per 50 μg antibody) in 0.1 N ammonium acetate buffer, pH 5.5.…”