An Electrochemical Sensor for the Detection of Cu²⁺ Based on Gold Nanoflowers-modifed Electrode and DNAzyme Functionalized Au@MIL-101 (Fe)

In this study, we developed an electrochemical sensor for sensitive detection of Cu²⁺ based on gold nanoflowers (AuNFs)-modified electrode and DNAzyme functionalized Au@MIL-101(Fe) (MIL: Materials of Institute Lavoisier). The AuNFs-modified indium tin oxide modified conductive glass electrode(AuNFs/ITO) prepared via electrodeposition showed improved electronic transport properties and provided more active sites to adsorb large amounts of oligonucleotide substrate (DNA1) via thiol-gold bonds. The stable Au@MIL-101(Fe) could guarantee the sensitivity because of its intrinsic peroxidase mimic property, while the Cu²⁺-dependent DNA-cleaving DNAzyme linked to Au@MIL-101(Fe) achieved the selectivity toward Cu²⁺. After the DNAzyme substrate strand (DNA2) was cleaved into two parts due to the presence of Cu²⁺, the oligonucleotide fragment linked to MIL-101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO. Due to the peroxidase-like catalytic activity of MIL-101(Fe) and the affinity recognition property of DNAzyme toward Cu²⁺, the electrochemical biosensor showed a sensitive detection range from 0.001 to 100 μM, a detection limit of 0.457 nM and a high selectivity, demonstrating its potential for Cu²⁺ detection in real environmental samples.