Ultrasensitive homogeneous electrochemiluminescence biosensor based on DNAzyme walker-regulated interface reaction...

Sensitive detection methods for trace heavy metal ions in complex samples are of great interest. Herein, a homogeneous electrochemiluminescence (ECL) biosensor based on DNAzyme walker-mediated interface reaction rate regulation strategy has been developed for copper ions (Cu²⁺). Ruthenium bipyridine-doped silica nanoparticles modified with Cu²⁺-activated DNAzyme (Cu-DNAzyme) and its substrate sequence (Cu-Sub) are designed as ECL nanoprobes. Negatively charged Cu-Subs on nanoprobes can effectively prevent ECL reaction of ruthenium bipyridine with coreactant and negatively charged electrode due to steric hindrance and electrostatic repulsion. When Cu²⁺ ions exists, the Cu-DNAzyme walker is activated, cyclically cleaving Cu-Subs and thereby enhancing the ECL performance of nanoprobes, resulting in signal amplification. The biosensor enables sensitive Cu²⁺ ions detection from 0.1 nM to 10 mM with a detection limit of 0.025 nM. Cu²⁺ ions in real samples have been detected with satisfactory results, and it is promising for heavy metal ions detection in complex samples.