Magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified alpha-Fe2O3/Fe3O4 heterogeneous nanoparticles for sensitive detection of Ni2+

A magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified alpha-Fe2O3/Fe3O4 heterogeneous nanoparticles was successfully fabricated to detect Nickel(II) (Ni2+). The phase composition and magnetic properties of alpha-Fe2O3/Fe3O4 heterogeneous nanoparticles controllably prepared by the citric acid (CA) sol-gel method were investigated in detail. The alpha-Fe2O3/Fe3O4 heterogeneous nanoparticles were modified by using trisodium citrate as reducing agent, and the magnetically induced self-assembly alpha-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/alpha-Fe2O3/Fe3O4-Au/S1/BSA/S2 electrochemical sensing platform was constructed and differential pulse voltammetry was applied for electrochemical detection. Under the optimum experimental parameters, the detection range of the biosensor was 100 pM-10 mu M (R-2 = 0.9978) with the limit of detection of 55 pM. The biosensor had high selectivity, acceptable stability, and reproducibility (RSD = 4.03%).