Reagentless, sensitive and multiplexed analysis of gyrB and K-ras gene biomarkers is achieved based on the proximity changes of two different redox-tags to the electrode surface upon DNA hybridizations, and the presence of the two gene biomarkers also acts as inputs and activates the logic gate.

Reproducible electrochemically encoded quantum dot (QD) barcodes were prepared by using the reverse-micelle synthetic approach. The encoding elements, Zn 2+ , Cd 2+ , Pb 2+ were confined within a single QD, which eliminates the cumbersome encapsulation process used by other common nanoparticle-based barcode preparation schemes. The distinct voltammetric stripping patterns of Zn 2+ , Cd 2+ , Pb 2+ at distinguishable potentials with controllable current intensities offer excellent encoding capability for the prepared electrochemical (EC) QDs. Additionally, the simultaneous modification of the QD barcode surface with organic ligands during the preparation process make them potentially useful in biomedical research. For proof of concept of their application in bioassays, the EC QD barcodes were further employed as tags for an immunoassay of a cancer marker, carcinoembryonic antigen (CEA). The voltammetric stripping response of the dissolved bardcode tags was proportional to log[CEA] in the range from 0.01 ng mL −1 to 80 ng mL −1 , with a detection limit of 3.3 pg mL −1 . The synthesized EC QD barcodes hold considerable potentials in biodetection, encrypted information and product tracking.

We present an ultrasensitive aptasensor for electronic monitoring of proteins through a dual amplified strategy in this paper. The target protein thrombin is sandwiched between an electrode surface confined aptamer and an aptamer-enzyme-carbon nanotube bioconjugate. The analytical signal amplification is achieved by coupling the signal amplification nature of multiple enzymes with the biocatalytic signal enhancement of redox-recycling. Our novel dramatic signal amplification strategy, with a detection limit of 8.3 fM, shows about 4 orders of magnitude improvement in sensitivity for thrombin detection compared to other universal single enzyme-based assay. This makes our approach an attractive alternative to other common PCR-based signal amplification in ultralow level of protein detection.

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