A novel sensing strategy for sensitive detection of mucin 1 protein (MUC1) and MCF-7 cells based on electrochemiluminescence (ECL) resonance energy transfer (ERET) from bis(2,2'-bipyridine)-(5-aminophenanthroline)ruthenium(II) (Ru1) to graphene oxide (GO) was proposed. The MUC1 aptamer was covalently combined with Ru1 (Ru1-aptamer) using aqueous carbodiimide coupling chemistry. Due to the strong noncovalent interaction between the Ru1-aptamer and GO, the ECL of Ru1 was efficiently quenched because of the ERET. In the presence of a target MUC1 protein, the binding between the Ru1-aptamer and MUC1 disturbed the interaction between the Ru1-aptamer and GO. These interactions led to the release of the Ru1-aptamer from GO, and resulted in the restoration of Ru1 ECL. This was shown to detect MUC1 protein sensitively in a linear range from 64.9 to 1036.8 nM with a detection limit of 40 nM. With further application in the detection of MCF-7 cells, the presented method could respond at concentrations as low as 30 cancer cells per mL. By substituting the aptamer and the corresponding target, this method could be conveniently extended for the sensitive detection of other biomolecules.

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Herein, fluorescent gold nanoclusters (AuNCs) and horseradish peroxidase (HRP) were simultaneously embedded into self-assembled dipeptide supramolecular films of N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) on the surface of ITO electrodes (Fmoc-FF/AuNCs/HRP) by using a simple single-step process. In the films, both the fluorescence property of AuNCs and the bioelectrocatalytic property of HRP were well maintained and could be reversibly regulated by pH-sensitive structural changes in the Fmoc-FF hydrogel films. Cu­(II)/EDTA in the solution could lead to the aggregation/disaggregation of AuNCs and further quenching/dequenching the fluorescence signal from the films. Meanwhile, the blue complexes formed by Cu­(II) and EDTA could produce a UV–vis signal in the solution. In addition, the coordinated Cu­(II) in the films enhanced the electrocatalytic capacity toward the reduction of H2O2 and could switch the current signal. A biomolecular logic circuit was built based on the smart film electrode system by using pH, the concentrations of EDTA, Cu­(II) and H2O2 as inputs, while the fluorescence intensity (FL), current (I) and UV–vis extinction (E) of the solution as outputs. Various logic devices were fabricated using the uniform platform, consisting of an encoder/decoder, demultiplexer, dual-transfer gate, keypad lock, digital comparator, half adder, and controlled NOT (CNOT) gate. Specifically, an electronic three-value logic gate, gullibility (ANY) gate, was first mimicked in this biocomputing system. This work not only demonstrated the construction of a new type of multivalued logic gate by using a dipeptide micromolecular matrix but also provided a new approach for designing sophisticated biologic functions, establishing smart multianalyte biosensing or fabricating biology information processing through the use of a simple film system.

Two rapid and sensitive enzyme-linked immunosorbent assays (ELISA) and an immunochromatographic assay (ICA) for the detection of chlortetracycline (CTC) residues in edible animal tissues were developed based on a monoclonal antibody (MAb) produced by using the chlortetracycline-bovine serum albumin (CTC-BSA) conjugate as the immunogen. A total of 50% inhibiting concentration (IC(50)) of the modified ELISA was 0.66 ng ml(-1) and the recoveries from spiked chicken muscle and liver were 78.8-92.2% and 80.3-90.2%, respectively. The corresponding coefficient variations (CVs) were 3.2-9.5% and 6.5-10.2%. The detection limit was 0.06 ng g(-1) in chicken muscle and 0.07 ng g(-1) in liver. However, the detection limit of ICA was 0.12 ng ml(-1), and the recoveries in negative samples spiked at concentrations of 10, 50 and 100 ng g(-1) ranged from 79.0% to 88.6% for muscle samples and from 75.2% to 87.0% for liver samples. The cut-off values for the test lines were 80 ng g(-1) and the analysis can be completed within 5-10 min. Comparisons with an HPLC method were performed by testing 200 swine muscle samples and chicken muscle samples from local markets, and an agreement rate of 99.5% was obtained between the three methods.

The development of efficient and mild methods to assemble C–N bonds represents an important and appealing goal in modern synthetic chemistry.