Hemin on graphene nanosheets functionalized with flower-like MnO2 and hollow AuPd for the electrochemical sensing lead ion based on the specific DNAzyme

Herein, integrated with DNAzyme highly specific to metal ions, hemin@reduced graphene oxide (hemin@rGO) functionalized with flower-like MnO2 and hollow AuPd (hAuPd-fMnO(2)-hemin@rGO) was used as electroactive probe and electrocatalyst to construct a universal platform for metal ion detection (lead ion Pb2+ as the model). The proposed strategy with generality was mainly based on two aspects. Firstly, the designed probe not only showed high stability and excellent peroxidase-like activity originating from hemin, fMnO(2) and hAuPd, but also possessed intrinsic redox performance from hemin, which resulted in the promotion of electron transfer and the enhancement of the response signal readout. Secondly, due to the introduction of Pb2+, Pb2+-dependent DNAzyme bound in the electrode surface could be specifically identified and cleaved by Pb2+, and the remained fragment (its supplementary sequence is a single-strand DNA S3) captured the nanocomposites S3-hAuPd-fMnO(2)-hemin@rGO by the hybridization reaction. Therefore, combined the cooperative catalysis of fMnO(2), hAuPd and hemin to H2O2 reduction with highly specific interaction of Pb2+-dependent DNAzyme, the proposed Pb2+ biosensor showed significant improvement of electrochemical analytical performance, which was involved in wide dynamic response in the range of 0.1 pM-200 nM, low detection limit of 0.034 pM, high sensitivity and high specificity. This could facilitate the universal strategy to be a promising method for detection of other metal ions, only changing the corresponding DNAzyme specific to them. (C) 2016 Elsevier B.V. All rights reserved.