Amplified and Specific Staining of Protein Dimerization on Cell Membrane Catalyzed by Responsively Installed DNA Nanomachines for Cancer Diagnosis.

In situ staining of protein dimerization on cell membrane has an important significance in accurate diagnosis during perioperative period, yet facile integration of specific recognition function and local signal conversion/amplification abilities on membrane surface remains a great challenge. Herein, a two-stage catalytic strategy is developed by installing DNA nanomachines and employing. Specifically, dual-aptamer-assisted DNA scaffold perform a "bispecific recognition-then-computing" operation and the output signal initiate a membrane-anchored biocatalysis for self-assembly of DNA catalytic converters, that is, G-quadruplex nanowire/hemin DNAzyme. Then, localized-deposition of chromogenic polydopamine is chemically catalyzed by horseradish peroxidase-mimicking DNAzyme and guided by supramolecular interactions between conjugate rigid plane of G-tetrad and polydopamine oligomer. The catalytic products exhibit nanofiber morphology with a diameter of 80-120 nm and a length of 1-10 µm, and one-to-one localize on DNA scaffold for amplified and specific staining of protein dimers. The bispecific staining leads to a higher (≈3.4-fold) signal intensity than traditional immunohistochemistry, which is beneficial for direct visualization. Moreover, an efficient discrimination ability of the bispecific staining strategy is observed in co-culture model staining. This study provides a novel catalytic method for controlling deposition of chromogens and paves a new avenue to sensitively stain of protein-protein interactions in disease diagnosis.