A Novel Nonenzymatic Hydrogen Peroxide Sensor Based on a Polypyrrole Nanowire-Copper Nanocomposite Modified Gold Electrode

A novel nonenzymatic hydrogen peroxide (H2O2) sensor has been fabricated by dispersing copper nanoparticles onto polypyrrole (PPy) nanowires by cyclic voltammetry (CV) to form PPy-copper nanocomposites on gold electrodes. Scanning electron microscopy (SEM) was used to characterize the morphologies of the PPy nanowires and the PPy-copper nanocomposite. The reactivity of the PPy-copper nanocomposite towards H2O2 was characterized by cyclic voltammetry and chronoamperometry. Effects of applied potential, the concentrations of detection solution upon the response currents of the sensor were investigated for an optimum analytical performance. It was proved that the PPy-copper nanocomposite showed excellent catalytic activity for the reduction of hydrogen peroxide (H2O2). The sensor showed a linear response to hydrogen peroxide in the concentration range between 7.0×10-6 and 4.3×10-3 mol L-1 with a high sensitivity, and a detection limit of 2.3×10-6 mol L-1. Experiment results also showed that the sensor had good stability

Dual-Amplification of Antigen -Antibody Interactions via Backfilling Gold Nanoparticles on (3-Mercaptopropyl) Trimethoxysilane Sol-Gel Functionalized Interface

Abstract A new dual-amplification strategy of electrochemical signaling from antigen -antibody interactions was proposed via backfilling gold nanoparticles on (3-mercaptopropyl) trimethoxysilane sol-gel (MPTS) functionalized interface. The MPTS was employed not only as a building block for the electrode surface modification but also as a matrix for ligand functionalization with first amplification. The second signal amplification strategy introduced in this study was based on the backfilling immobilization of nanogold particles to the immunosensor surface. Several coupling techniques, such as with nanogold but not MPTS or with MPTS but not nanogold, were investigated for the determination of carcinoembryonic antigen (CEA) as a model, and a very good result was obtained with nanogold and MPTS coupling immunosensor. With the noncompetitive format, the formation of the antigen -antibody complex by a simple onestep immunoreaction between the immobilized anti-CEA and CEA in sample solution introduced membrane potential change before and after the antigen -antibody interaction. Under optimal conditions, the proposed immunosensor exhibited a good electrochemical behavior to CEA in a dynamic concentration range of 4.4 to 85.7 ng/ mL with a detection limit of 1.2 ng/mL (at 3 d). Moreover, the precision, reproducibility and stability of the asprepared immunosensor were acceptable. Importantly, the proposed methodology would be valuable for diagnosis and monitoring of carcinoma and its metastasis

Bi-directional DNA Walking Machine and Its Application in an Enzyme-Free Electrochemiluminescence Biosensor for Sensitive Detection of MicroRNAs

Herein, a dual microRNA (miRNA) powered bi-directional DNA walking machine with precise control was developed to fabricate an enzyme-free biosensor on the basis of distance-based electrochemiluminescence (ECL) energy transfer for multiple detection of miRNAs. By using miRNA-21 as the driving force, the DNA walker could move forth along the track and generated quenching of ECL response due to the proximity between Au nanoparticles (AuNPs) and Mn²⁺ doped CdS nanocrystals (CdS:Mn NCs) film as the ECL emitters, realizing ultrasensitive determination of miRNA-21. Impressively, once miRNA-155 was introduced as the driving force, the walker could move back along the track automatically, and surface plasmon resonance (SPR) occurred owing to the appropriate large separation between AuNPs and CdS:Mn NCs, achieving an ECL enhancement and realizing ultrasensitive detection of miRNA-155. The bi-directional movement of the DNA walker on the track led to continuous distance-based energy transfer from CdS:Mn NCs film by AuNPs, which resulted in significant ECL signal variation of CdS:Mn NCs for multiple detection of miRNA-21 and miRNA-155 down to 1.51 fM and 1.67 fM, respectively. Amazingly, the elaborated biosensor provided a new chance for constructing controllable molecular nanomachines in biosensing, disease diagnosis, and clinical analysis

A Peptide Cleavage-Based Ultrasensitive Electrochemical Biosensor with an Ingenious Two-Stage DNA Template for Highly Efficient DNA Exponential Amplification

The direct transduction of a peptide cleavage event into DNA detection has always produced output DNA with some amino acid residues, which influence the DNA amplification efficiency in view of their steric hindrance effect. Here an ingenious two-stage DNA template was designed to achieve highly efficient DNA amplification by utilizing the DNA exponential amplification reaction (EXPAR) as a model. The usage of a two-stage DNA template not only accomplished the traditionally inefficient EXPAR triggered by output DNA with some amino acid residues but also simultaneously produced a newly identical DNA trigger without any amino acid residues to induce an extra efficient EXPAR, which significantly improved the DNA amplification efficiency, realizing the ultrasensitive detection of the target. On the basis of the proposed highly efficient DNA amplification strategy, a novel peptide cleavage-based electrochemical biosensor was constructed to ultrasensitively detect matrix metalloproteinases-7 (MMP-7). As a result, this developed assay demonstrated excellent sensitivity with a linear range from 0.1 pg·mL^–1 to 50 ng·mL^–1 and a detection limit down to 0.02 pg·mL^–1, which paved a novel avenue for constructing ultrasensitive peptide cleavage-based biosensors