Magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified <i>α</i> -Fe ₂ O ₃ /Fe ₃ O ₄ heterogeneous nanoparticles for sensitive detection of Ni ²⁺

Abstract

Abstract A magnetically induced self-assembly DNAzyme electrochemical biosensor based on gold-modified α -Fe 2 O 3 /Fe 3 O 4 heterogeneous nanoparticles was successfully fabricated to detect Nickel(II) (Ni 2+ ). The phase composition and magnetic properties of α -Fe 2 O 3 /Fe 3 O 4 heterogeneous nanoparticles controllably prepared by the citric acid (CA) sol–gel method were investigated in detail. The α -Fe 2 O 3 /Fe 3 O 4 heterogeneous nanoparticles were modified by using trisodium citrate as reducing agent, and the magnetically induced self-assembly α -Fe 2 O 3 /Fe 3 O 4 –Au nanocomposites were obtained. The designed Ni 2+ -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 -Fe 2 O 3 /Fe 3 O 4 –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 μ 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%).