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Here a sensing strategy with the integration of photosensitizer and electrochemical analysis was present. The photosensitizer, Zinc(II) tetraphenylporphyrin (ZnTCPP), was functionalized graphene oxide (GO) to form complex (ZnTCPP/GO) as the electrode material and generated singlet-oxygen (1O 2) in the presence of air under light illumination. Due to the special electronic structure of 1O 2 , hydroquinone (HQ) could react with 1O 2 to produce electrochemically-detectable products, benzoquinone (BQ). Meanwhile, the formed BQ could be reduced on the electrode, completing the redox cycling. The ZnTCPP/GO modified ITO electrode produces a stable and enhanced photocurrent signal under 420 nm irradiation in air-saturated buffer, compared with in N 2 -saturated buffer. On the other hand, l -glutathione (GSH) as a signalling molecule plays important role in physiological process, which was employed as model to investigated the sensing performance. Coupling with HQ oxidized by 1O 2 , a GSH sensor was constructed on the basis the redox cycling of HQ. A sensitive reduction of photocurrent is observed with the addition of GSH, due to the GSH could be oxidized by the generated 1O 2 to form GSSG. The biosensor displayed good performance in a broad concentration range of 0–150 μM, with a lower detection limit of 1.3 μM at an S/N ratio of 3, and could be used in practical application. This work affords a platform for constructing the biosensor with 1O 2 instead of enzyme via on/off light switching. Electrochemical biosensor based on singlet oxygen generated by molecular photosensitizers was designed for l -glutathione detection with signal amplification. [Display omitted] • A electrochemical biosensor based on singlet oxygen (1O 2) generated by molecular photosensitizers was designed. • Photosensitizers, Zinc(II) tetraphenylporphyrin, generated 1O 2 in the presence of air under light illumination. • The signal was amplified by hydroquinone which was oxidized by 1O 2 and then reduced on the electrode, completing the cycling. • The use of catalytic photosensitizers could instead of enzyme used in complex environment, and switch the light to control the signal. • The sensor showed good performance. [ABSTRACT FROM AUTHOR]

S-nitrosothiols (RSNO) as the potential nitric oxide (NO) storage, transfer and delivery vehicles under physiological condition have been identified as important in a number of disease states. However, a detection and quantification of RSNO method with simple and sensitive in biological media is currently lacking. A novel electrochemical sensing platform based on ionic liquid (IL) and copper porphyrin (PorCu) decorated cuprous oxide (Cu 2 O) nanocomposites was developed to detect RSNO under physiological condition. In this system, RSNO were decomposed by Cu(I) in IL/PorCu/Cu 2 O to release NO, following the generated NO could be oxidized on the electrode to generate current signal. By taking advantage of the synergetic effect of IL, PorCu and Cu 2 O, the sensor exhibited excellent sensitivity and linearity toward various RSNO species in phosphate buffer solution (PBS), pH 7.4. A low detection limit for N-Acetyl-3-(nitrososulfanyl)valine (SNAP), S-nitrosocysteine (CysNO) and S-nitrosoglutathione (GSNO) was 110 nM, 20 nM and 67 nM (S/N = 3), respectively. Furthermore, this method displayed good selectivity, which could be used in complex application. The detection scheme with the features of high sensitivity and ease of operation, implies the potential of IL/PorCu/Cu 2 O for further various complex physiological studies. A novel electrochemical sensing platform based on porphyrin decorated Cu 2 O as nano-catalyst and electrode material was developed for sensitive S-Nitrosothiols detection under physiological pH. [Display omitted] • A electrochemical biosensor based on ionic liquid and porphyrin modified Cu 2 O (IL/PorCu/Cu 2 O) as nanocrystals was designed. • The IL/PorCu/Cu 2 O composite has high catalytic activity toward RSNO. • By taking advantage of the synergy of IL, PorCu and Cu 2 O, the sensor exhibited excellent sensitivity and selectivity. • The method could be used in complex matrix. • The sensor showed good performance. [ABSTRACT FROM AUTHOR]

Conventional immunochromatographic assays (ICAs) based on gold nanoparticles (GNPs) suffer from the disadvantage of low sensitivity. In this work, a highly sensitive ICA based on polydopamine coated zirconium metal-organic frameworks labeled antibodies (ZrPA-Ab) as a novel probe was developed for visual determination of deoxynivalenol (DON). The ZrPA was synthesized via an oxidative self-polymerized assembly (OPMA) strategy using porphyrin functionalized zirconium metal-organic frameworks (Zr-MOFs, MOF-525) and polydopamine (PDA). The Abs could directly attach to the ZrPA surface owing to the large specific surface area, excellent water-stability and bio-compatibility of the ZrPA, on this basis, a sensitive, precise and reliable immunoassay method can be developed for rapid and selective detection of DON. Under optimized conditions, a non-linear calibration curve was obtained in the range of 0–50 ng/mL DON concentration with an IC 50 of 1.22 ng/mL, and the visual detection limit was 0.18 ng/mL, which was about 8-times more sensitive than that of the conventional GNPs-based ICA. Finally, the proposed ZrPA-ICA was successfully applied for the detection of DON in pig hind legs meat, green bean, maize and millet samples, revealing the feasible and reliable application of this biosensor in different food matrices. Thus, this work broadens the possibilities for the use of MOFs as a novel labeling carrier in immunoassays. Image 1 • A Zr-MOFs-polydopamine (ZrPA) based sensor was employed for deoxynivalenol detection. • The ZrPA shares the merits of excellent water-stability and water-dispersibility. • This assay has an 8-fold improved sensitivity than gold nanoparticles (GNPs)-sensor. • The approach exhibited high selectivity and excellent food sample application ability. • This work expands the application of MOFs as a novel label in immunoassays. [ABSTRACT FROM AUTHOR]

Herein, a cost-effective, simple and sensitive electrochemical sensing platform was established based on aptamer - target recognition and target-triggering signal amplification strategy for protein detection. Due to the high affinity between the aptamer and target, the assistant DNA1 (a1) could release from a1-aptamer duplex and trigger the following DNA circuits. The strand displacement and branch migration reaction brought assistant DNA3 (a3) released. Eventually, a large number of duplex structures of a3−Hairpin DNA3 were formed on the surface of electrode. Consequently, the capture DNA on the surface of platinum nanoparticles could hybridize with the unfolded DNA fragment of Hairpin DNA3 on the sensor surface, resulting in the electrochemical signal readout of H 2 O 2 reduction. Using thrombin as a model target, under the optimal conditions, this method exhibited a linear detection range from 0.5 pM to 300 nM with a detection limit of 0.17 pM. The proposed detection strategy was enzyme-free and exhibited good selectivity and sensitivity for a variety of protein targets detection by using corresponding DNA-based affinity probes, which makes it possible to apply the sensor for sensitivity detection of analytes in bioassays. A novel electrochemical sensing platform based on target-triggering cascade enzyme-free signal amplification strategy was developed for sensitive protein detection. [Display omitted] • Electrochemical detection of thrombin using target-triggering cascade enzyme-free signal amplification strategy was proposed. • The method was PCR-free, enzyme-free, low cost, and without the need for any additional separation steps. • The sensor for thrombin showed good performance. [ABSTRACT FROM AUTHOR]