PEI protected aptamer molecular probes for contrast-enhanced in vivo cancer imaging.

Aptamers have emerged as promising molecular probes for cancer diagnosis. However, their application for in vivo cancer imaging remains limitation due to the poor stability in blood and the degradation by nucleases. In the present study, we generated PEI/aptamer molecular complexes for cancer imaging in vivo by using deoxyribonuclease (DNase)-activatable fluorescence probes (DFProbes) to monitor DNA degradation. The results showed that the complexes with PEI at the N/P ratio from 3.8 to 15 effectively prevented the degradation of DFProbes both in vitro and in vivo. Moreover, PEI successfully protected TD05 aptamers from DNase degradation without affecting its specific recognition of Ramos cells. In tumor bearing mice, PEI/aptamer molecular complexes further demonstrated superior passive tumor targeting and extended circulation time as compared with free aptamer. Hence, the well-defined PEI/aptamer probe is a novel strategy to deliver targeted aptamer for tumor diagnosis and imaging in vivo.