Cerasome Spherical Nucleic Acid Nanostructure-Based AND Logic Gate-Guided Dual-DNAzyme Walker for Accurate Cancer Cell Identification

Spherical nucleic acids that consist of high-density oriented strands allow for tailoring of DNA computation and nanomachines and provide a unique nanoscale platform for biosensing and bioimaging. Herein, we report the construction of a core–shell-nanostructured dual-emission quantum dot-loaded cerasome spherical nucleic acid (QD2@C-SNA), and its use as an intracellular nanobiosensor via AND gate-guided dual-DNAzyme walker-mediated resonance energy transfer at the spherical nanoscale interface. QD2@C-SNA has an inner core (∼123 nm) of red- and green-emission quantum dot-layered cerasome and an outer shell (∼6 nm) of DNAzyme-AP site-DNAzyme/cDNA probe and a quencher-labeled substrate. In the presence of dual markers (inputs), namely, apurinic/apyrimidinic endonuclease 1 (APE1) and miRNA, the SNA shell performs an operation of AND gate-guided dual-DNAzyme walking: APE1 cleaves the AP site on DNAzyme-AP site-DNAzyme, exposing a middle toehold on cDNA; the middle toehold-mediated miRNA/cDNA hybridization displaces dual strands of DNAzyme from the duplex; the dual-DNAzyme walkers stochastically move along the substrate tracks, leaving the quenchers away from the SNA. This operation eliminates resonance energy transfer at the nanoscale core–shell interface, and the cerasome core outputs dual quantum dot-based ratiometric fluorescence: the reactivated green fluorescence relative to the constant red fluorescence, which is imaged by confocal laser scanning microscopy. As such, single-entity detection of dual endogenous markers is accomplished by the QD2@C-SNA nanobiosensor, and cancer/normal cells as well as cancer cell subtypes are well differentiated, showing improved imaging contrast and accuracy.