A High-Efficiency Autocatalysis-Oriented Cascade Circuit via Reciprocal Hug-Amplification for Assay-to-Treat Application

Developing a DNA autocatalysis-oriented cascade circuit (AOCC) via reciprocal navigation of two enzyme-free hug-amplifiers might be desirable for constructing a rapid, efficient, and sensitive assay-to-treat platform. In response to a specific trigger (T), seven functional DNA hairpins were designed to execute three-branched assembly (TBA) and three isotropic hybridization chain reaction (3HCR) events for operating the AOCC. This was because three new inducers were reconstructed in TBA arms to initiate 3HCR (TBA-to-3HCR) and periodic T repeats were resultantly reassembled in the tandem nicks of polymeric nanowires to rapidly activate TBA in the opposite direction (3HCR-to-TBA) without steric hindrance, thereby cooperatively manipulating sustainable AOCC progress for exponential hug-amplification (1:3Nⁿ). Our experimental verifications manifested that the T-dependent AOCC amplifier achieved fast input transduction and efficient fluorescence readout. As predicted, the flexible programming of reactive hairpin species endowed the repeating nicks in productive 3HCR nanowires with great possibilities and accessibilities to graft tailored modular elements, such as G-rich AS1411 aptamers capable of adopting G-quadruplex conformations (G4) that readily facilitated the embedding of zinc(II) protoporphyrin IX (ZnPPIX), a kind of heme oxygenase-1 enzyme inhibitor. Thus, the cascading ZnPPIX/G4 entities acted as fluorescent signal reporters, photosensitizers and anticancer drugs, thereby creating an updated AOCC-based assay-to-treat platform for ultrasensitive biosensing, discernible cell imaging and efficient photodynamic therapy of cancer cells. This would offer a new paradigm to advance the rational integration of dynamic DNA assembly and amplifiable recycling circuits for applicable bioassay and theranostics.