Proximity ligation-responsive catalytic hairpin assembly-guided DNA dendrimers for synergistically amplified electrochemical biosensing

Abstract

Herein, we report a specific and sensitive electrochemical aptasensor through the proximity ligation-responsive catalytic hairpin assembly (PLCHA) to guide the construction of functional DNA dendrimers (DNADS), which remarkably facilitates the anchoring and entrapping of synergistic amplifiers, Pt nanoparticles (PtNPs) and manganese(III) meso-tetrakis (N-methyl-pyridinium-2-yl)-porphyrin (MnTMPyP). Using thrombin (TB) as analyte model, the proximity ligation with its specific aptamers tethered in two affinity probes (A1 and A2) dependently output a sequence-specific fuel strand (F*) to activate PLCHA of two DNA hairpins (H1 and H2) through F*-mediated strand displacement. With unpaired toeholds of the formed duplexes, two PtNPs-functionalized single strands (S1@PtNPs) and S2@PtNPs) sequentially hybridize one another, allowing the “bottom-up” self-assembly of this DNADS to entrap mimicking peroxidase MnTMPyP in numerous duplex scaffolds. Upon treated with hydrogen peroxide (H2O2), the oxidation of 4-chloro-1-naphthol (4-CN) was greatly promoted by the synergistic catalysis of PtNPs and MnTMPyP, generating significantly enhanced electrochemical signal for reliable quantitation of TB in a linear range of 1 fM to 100 nM with a high sensitivity down to 10.7 aM. Based on PLCHA-directed DNADS for the stable loading of signal amplifiers, this rational detection route would pave a new avenue to monitor various disease-related proteins, enzymes or small molecules.