A voltammetric immunoassay for the carcinoembryonic antigen using silver(I)-terephthalate metal-organic frameworks containing gold nanoparticles as a signal probe.

A voltammetric immunoassay for the carcinoembryonic antigen (CEA) was developed using silver metal-organic frameworks (Ag-MOFs) as a signal probe. The Ag-MOFs contained a substantial amount of Ag(I) whose electrochemical signal was relatively stable. Therefore, the Ag-MOFs were viable signal probes. The signal can be detected without previous acid dissolution and preconcentration steps. This simplifies the detection steps and reduces the detection time. If CEA binds to its antibody on the modified electrode, the signal for Ag(I) becomes reduced. Measurements were best performed at a potential as low as 0.07 V (vs. SCE) which made the electrode hardly sensitive to potential electroactive interferents. Under optimized conditions, the method included a wide linear response range (0.05 to 120 ng mL-1) and a low detection limit of 8.0 fg mL-1 (S/N = 3). The synthesis of Ag-MOFs is relatively simple, and Ag-MOFs are not only used as nanocarriers for immobilizing anti-CEA but also acted as electroactive materials for a signal probe. The voltammetric immunoassay is stable, inexpensive, sensitive, and selective. Based on these advantages, the method holds great promise for applications in the point-of-care disease and environmental monitoring. Graphical abstract Schematic presentation of a novel electrochemical immunoassay for the carcinoembryonic antigen (CEA) using silver metal-organic frameworks (Ag-MOFs) as a signal probe.

Preparation of a nanocomposite material consisting of cuprous oxide, polyaniline and reduced graphene oxide, and its application to the electrochemical determination of hydrogen peroxide.

A method is described for the preparation of a nanocomposite material consisting of cuprous oxide/polyaniline/reduced graphene oxide (Cu2O/PANI/rGO). Aniline was employed as both the precursor for PANI and the reducing agent for Cu2+ and graphene oxide. A glassy carbon electrode was modified with the nanocomposite material. Chronoamperometric studies with the modified electrode showed it to enable an efficient electroreduction of hydrogen peroxide at -0.2 V vs. saturated calomel electrode. All measurements were performed in the absence of oxygen. Figures of merit include a wide linear response range (0.8 µM to 12.78 mM) and a low limit of detection of 0.5 µM (S/N = 3). Graphical abstract Cuprous oxide/polyaniline/reduced graphene oxide nanocomposites were synthesized through one-step process for fabricating an nonenzymatic electrochemical sensor for hydrogen peroxide.

A Dual-Signaling Electrochemical Aptasensor Based on an In-Plane Gold Nanoparticles-Black Phosphorus Heterostructure for the Sensitive Detection of Patulin.

Patulin (PAT), a type of mycotoxin existing in foodstuffs, is harmful to food safety and human health. Thus, it is necessary to develop sensitive, selective and reliable analytical methods for PAT detection. In this study, a sensitive aptasensor based on a dual-signaling strategy was fabricated, in which a methylene-blue-labeled aptamer and ferrocene monocarboxylic acid in the electrolyte acted as a dual signal, for monitoring PAT. To improve the sensitivity of the aptasensor, an in-plane gold nanoparticles-black phosphorus heterostructure (AuNPs-BPNS) was synthesized for signal amplification. Due to the combination of AuNPs-BPNS nanocomposites and the dual-signaling strategy, the proposed aptasensor has a good analytical performance for PAT detection with the broad linear range of 0.1 nM-100.0 µM and the low detection limit of 0.043 nM. Moreover, the aptasensor was successfully employed for real sample detection, such as apple, pear and tomato. It is expected that BPNS-based nanomaterials hold great promise for developing novel aptasensors and may provide a sensing platform for food safety monitoring.