Real-Time In Situ Sequential Fluorescence Activation Imaging of Cyt c and Caspase-9 with a Gold-Selenium-Bonded Nanoprobe.

Apoptosis, as a very important mode of programmed death, is closely associated with many diseases. Real-time in situ monitoring of the dynamic change of the apoptotic process remains a great challenge. Herein, a nanoprobe based on the gold-selenium (Au-Se) bond was developed for a sequential fluorescence activation imaging of cytochrome c (Cyt c) and caspase-9, two important apoptotic signaling molecules, to monitor the progression of apoptosis. The Cyt c aptamer and caspase-9-cleavable peptide chains labeled with two dyes were modified onto the surface of gold nanoparticles (Au NPs) by the Au-Se bond, which can be activated by upstream Cyt c and downstream caspase-9 to trigger fluorescence recovery. The Au-Se nanoprobe exhibited good specificity and stability. Compared with the traditional nanoprobe based on the gold-sulfur (Au-S) bond, the interference of biological thiols on the Au-Se nanoprobe can be effectively avoided. Importantly, the Au-Se nanoprobe can image the sequential changes of the two markers in situ in real time during cell apoptosis. This work provides an effective tool for the accurate and real-time detection of apoptosis and is conducive to the in-depth study of the relationship between apoptosis and disease.