Magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified α-Fe2O3/Fe3O4heterogeneous nanoparticles for sensitive detection of Ni2.

A magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified α-Fe2O3/Fe3O4heterogeneous nanoparticles was successfully fabricated to detect Nickel(II) (Ni2+). The phase composition and magnetic properties of α-Fe2O3/Fe3O4heterogeneous nanoparticles controllably prepared by the citric acid (CA) sol-gel method were investigated in detail. The α-Fe2O3/Fe3O4heterogeneous nanoparticles were modified by using trisodium citrate as reducing agent, and the magnetically induced self-assembly α-Fe2O3/Fe3O4-Au nanocomposites were obtained. The designed Ni2+-dependent DNAzyme consisted of the catalytic chain modified with the thiol group (S1-SH) and the substrate chain modified with methylene blue (S2-MB). The MGCE/α-Fe2O3/Fe3O4-Au/S1/BSA/S2 electrochemical sensing platform was constructed and differential pulse voltammetry (DPV) was applied for electrochemical detection. Under the optimum experimental parameters, the detection range of the biosensor was 100 pM-10 µM (R2= 0.9978) with the limit of detection (LOD) of 55 pM. The biosensor had high selectivity, acceptable stability, and reproducibility (RSD = 4.03%).