Preliminary biological evaluation of ¹⁸F-AlF-NOTA-MAL-Cys-Annexin V as a novel apoptosis imaging agent

A novel annexin V derivative (Cys-Annexin V) with a single cysteine residue at its C-terminal has been successfully labeled site-specifically with NOTA-maleimide aluminum [¹⁸F]fluoride complexation and evaluated it as a novel apoptosis agent in vitro and in vivo. The total synthesis time of ¹⁸F-AlF-NOTA-MAL-Cys-Annexin V from [¹⁸F]fluoride was about 65 min. The tracer was stable in vitro and it was excreted through renal in normal mice. The rate of the tracer bound to erythrocytes with exposed phosphatidylserine was 89.36±0.61% and this binding could be blocked by unlabeled Cys-Annexin V. In rats treated with cycloheximide, there were 6.23±0.23 times (n=4) increase in hepatic uptake of the tracer as compared to normal rats at 1h p.i. The uptake of the tracer in liver also could be blocked by co-injection of unlabeled Cys-Annexin V. These results indicated the favorable characterizations such as convenient synthesis and specific apoptotic cells targeting of¹⁸F-AlF-NOTA-MAL- Cys-Annexin V were suitable for its further investigation in clinical apoptosis imaging.