PAMAM-Based DNA Fluorescence Nanoprobe for Rapid Whole Cellular APE1 Detection and Imaging

Apurinic/apyrimidinic endonuclease 1/redox effector factor 1 (APE1/ref-1, APE1), a vital protein for DNA repair and cellular redox regulation, is frequently overexpressed in tumor cells, underscoring the importance of developing sensitive detection methods for early cancer diagnosis. However, the rapid detection and visualization of nuclear APE1 in tumor cells are still challenging. In this study, we successfully developed a novel DNA fluorescent nanoprobe based on polyamidoamine (PAMAM) for the rapid detection of cytoplasmic and nuclear APE1. The PAMAM surface was modified with arginine (Arg), named PR, and its hydrophobic core encapsulated the 1,6,7,12-tetrachloroperylene tetracarboxylic acid dianhydride (TA) dye to construct fluorescent nanoparticles (TPR). Furthermore, an APE1-responsive dsDNA (SP) was linked on the TPR surface, containing apurinic/apyrimidinic sites (AP sites) and the black hole quencher 2 (BHQ2) and ensuring that fluorescence remains off in the absence of APE1. TPR-SP exhibited a detection range of 0.125-25 U mL^-1 and a detection limit as low as 0.03 U mL^-1. Compared with the Arg-free nanoprobes (TP-SP), TPR-SP significantly accelerated endocytosis and nuclear penetration, reducing the APE1 detection time to one-quarter (from 2 to 0.5 h). Notably, the APE1 signal in the whole nucleus can also be significantly detected. Thus, the TPR nanoprobe achieves the rapid enrichment and amplification of fluorescence signals, leading to highly sensitive whole cellular APE1 detection. This innovative and efficient detection method greatly expands the technological means for early cancer detection.