A cell surface-targeted MNAzyme-aptamer system for highly sensitive and visual detection of cancer cells via nucleolin activation.

Cancer has become a major disease that seriously threatens human health and life worldwide. Cytological diagnosis serves as a cornerstone for clinical oncology. However, conventional cytomorphological evaluation and immunohistochemistry (IHC) remain time-consuming and inadequate for large-scale screening and rapid on-site precision diagnosis. Consequently, novel cytological technologies integrating morphological and molecular information are urgently needed to enable rapid, accurate, and scalable detection. To address this need, we report here a tumor detection strategy based on the MNAzyme-aptamer system, featuring in situ assembly and dual-mode signal output (fluorescence and colorimetric). In this design, MNAzyme is anchored onto tumor cell membranes via cholesterol moieties. Upon target recognition, the AS1411 aptamer undergoes a conformational change from its duplex state to specifically bind nucleolin, which is overexpressed on tumor cell surfaces. This binding event triggers a proximity-induced assembly that activates MNAzyme cleavage activity, thereby initiating efficient catalytic signal amplification. The system exploits stable membrane anchoring coupled with a target-activated "switch" mechanism, thereby minimizing false positives from nonspecific binding. This strategy significantly enhances detection efficiency and accuracy while accommodating both high-sensitivity instrumental analysis and low-cost visual screening, offering a promising approach to advance cancer diagnostics.