Electrochemical nanosensors by integrating functional nucleic acids and nanomaterials hold a great promise in the fast detection of biomarkers, yet the current systems possess limitations on the accessibility of target–probe and probe–electrode interactions and the repeatability of detection. Herein, a host–guest assembly strategy is developed to build redox nanosensors for an immobilization‐free and ratiometric electrochemical detection system. Specifically, electroactive molecule (Em) guests are loaded in porous hosts of polydopamine nanoparticles (MPDA) to act as dual‐signal redox reporters. Hybrid DNA probes of G‐quadruplex and a single‐stranded anchor DNA are installed as gatekeepers for sealing the mesopores. Thereby, miRNA triggered Em release by strand displacement reactions and the homogeneous transportation of the hosts/guests to the electrode facilitate the generation of reference signal/response signal at different potentials. Concomitantly applied NIR irradiation boosts the electron transfer from MPDA to the electrode and results in a tenfold increase in the reference signal. Finally, the sensing system through the differential pulse voltammetry method achieves a highly repeatable detection (relative standard deviation 3.8%) of miRNA with a lower detection limit (362 × 10−15 m). This attractive system paves the way for rational designs of advanced electrochemical biosensors and smart diagnosis.

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