Rolling circle amplification combined with nanoparticle aggregates for highly sensitive identification of DNA and cancer cells

An electrochemical biosensor based on rolling circle amplification (RCA) and nanoparticle aggregates for highly sensitive identification of DNA and cancer cells were established in this work. First, a sandwich-type DNA complexes containing target DNA was constructed on the surface of the magnetic beads. Second, one part of the primer in the sandwich-type DNA complexes induced the RCA in the system. Then the long RCA products were digested to construct another sandwich-type DNA complex for the electrochemical detection. Differential pulse voltammetry (DPV) peaks with high signal intensity were obtained, and the signal intensities were found to be dependent on the amount of Fc, which is related to the concentration of target DNA. Under the optimum conditions, the electrochemical signal intensity was increased with the increase of the concentration of target DNA: A detection limit of 2.8 x 10(-18) M of target DNA was achieved. Combined with aptamers technology, the proposed signal amplification strategy was also used for the identification of cancer cells with the detection limit of 100 Ramos cells mL(-1). (C) 2012 Elsevier B.V. All rights reserved.