A novel RhB@MOF-808 fluorescent probe for the rapid detection of dopamine and Fe3

Dopamine (DA) and Fe³⁺ as the important bioactive ingredients, playing an indispensable role in human metabolism. Therefore, developing the accurate detection of DA and Fe³⁺ is of great significance for disease screening. Herein, we put forward a simple, rapid, and sensitive fluorescent detection strategy for the detection of dopamine and Fe³⁺ based on Rhodamine B-modified MOF-808 (RhB@MOF-808). RhB@MOF-808 produced strong fluorescence at 580 nm, and the fluorescence was significantly quenched after DA or Fe³⁺ was added, which was regarded as a static quenching process. Detection limits are as low as 60.25 nM and 48.34 nM, respectively. Furthermore, based on the responses of DA and Fe³⁺ to the probe, molecular logic gates were successfully designed. More importantly, RhB@MOF-808 had excellent cell membrane permeability and had been successfully used to label DA and Fe³⁺ in Hela cells, which presented a potential biological application value as a fluorescent probe for detecting DA and Fe³⁺.

SERS determination of dopamine using metal-organic frameworks decorated with Ag/Au noble metal nanoparticle composite after azo derivatization with p-aminothiophenol

A specific surface-enhanced Raman scattering (SERS) assay for dopamine (DA) based on an azo derivatization reaction is proposed for the first time by preparation of p-aminothiophenol (PATP)-modified composite SERS substrate, composed of metal-organic framework (MIL-101) decorated with Au and Ag nanoparticles. As the result, the SERS method for detection of the azo reaction between PATP and DA exhibits superior sensitivity, selectivity, and stability. A reasonable linearity in the range 10^-6 to 10^-10 mol∙L^-1 is achieved, and the limit of detection is 1.2 × 10^-12 mol∙L^-1. The reactive SERS assay is free from interference in complex physiological fluid. The feasibility of the proposed SERS method for the detection of DA levels in fetal bovine serum (FBS) samples and human serum samples is validated by HPLC-MS methods, displaying promising application potential in early disease diagnosis.

Detection of pollutants in water bodies: electrochemical detection or photo-electrochemical detection?

The massive discharge of pollutants including endocrine-disrupting chemicals (EDCs), heavy metals, pharmaceuticals and personal care products (PPCPs) into water bodies is endangering the ecological environment and human health, and needs to be accurately detected. Both electrochemical and photo-electrochemical detection methods have been widely used for the detection of these pollutants, however, which one is better for the detection of different environmental pollutants? In this feature article, different electrochemical and photo-electrochemical detection methods are summarized, including the principles, classification, common catalysts, and applications. By summarizing the advantages and disadvantages of different detection methods, this review provides a guide for other researchers to detect pollutants in water bodies by using electrochemical and photo-electrochemical analysis.

Gold nanoparticles decorated bimetallic CuNi-based hollow nanoarchitecture for the enhancement of electrochemical sensing performance of nitrite

Gold nanoparticles (AuNPs) decorated bimetallic CuNi-based hollow nanoarchitecture (CNHN) are reported for the first time as a nonenzymatic sensor for the quantification of nitrite in neutral solution . The CNHN was prepared via a convenient calcining routine using the bimetallic CuNi-MOFs as a coprecursor. The unique chemical structure of hollow CNHN with high specific surface area and abundant terminal amino groups effectively avoid the aggregation of AuNPs and facilitate the subsequent adsorption of nitrite. The Au/CNHN exhibited high electrocatalytic activity towards nitrite oxidation due to the synergetic catalytic effect of AuNPs and CNHN. Chronoamperometric detection of nitrite at the Au/CNHN/GCE achieved a lower linear calibration range of 0.05 to 1.15 mM, with an LOD of 0.017 μM compared with previous reports. The proposed method obtained satisfactory recoveries for nitrite determination in practical applications, which was verified by UV-Vis spectrophotometry. The prepared sensor based on Au/CNHN featured favorable selectivity and stability, which provides a promising approach for real sample analysis. Graphical abstract.

Bio-assisted preparation of efficiently architectured nanostructures of γ-Fe2O3 as a molecular recognition platform for simultaneous detection of biomarkers

Magnetic nanoparticles of iron oxide (γ-Fe2O3) have been prepared using bio-assisted method and their application in the field of biosensors is demonstrated. Particularly in this work, different nanostructures of γ-Fe2O3 namely nanospheres (NS), nanograsses (NG) and nanowires (NW) are prepared using a bio-surfactant namely Furostanol Saponin (FS) present in Fenugreek seeds extract through co-precipitation method by following "green" route. Three distinct morphologies of iron oxide nanostructures possessing the same crystal structure, magnetic properties, and varied size distribution are prepared and characterized. The resultant materials are analyzed using field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Fourier transform infrared spectroscopy. Moreover, the effect of reaction time and concentration of FS on the resultant morphologies of γ-Fe2O3 nanostructures are systematically investigated. Among different shapes, NWs and NSs of γ-Fe2O3 are found to exhibit better sensing behaviour for both the individual and simultaneous electrochemical detection of most popular biomarkers namely dopamine (DA) and uric acid (UA). Electrochemical studies reveal that γ-Fe2O3 NWs showed better sensing characteristics than γ-Fe2O3 NSs and NGs in terms of distinguishable voltammetric signals for DA and UA with enhanced oxidation current values. Differential pulse voltammetric studies exhibit linear dependence on DA and UA concentrations in the range of 0.15-75 µM and 5 μM - 0.15 mM respectively. The detection limit values for DA and UA are determined to be 150 nM and 5 µM. In addition γ-Fe2O3 NWs modified electrode showed higher sensitivity, reduced overpotential along with good selectivity towards the determination of DA and UA even in the presence of other common interferents. Thus the proposed biosensor electrode is very easy to fabricate, eco-friendly, cheaper and possesses higher surface area suggesting the unique structural patterns of γ-Fe2O3 nanostructures to be a promising candidate for electrochemical bio-sensing and biomedical applications.

Photo-electrochemical detection of dopamine in human urine and calf serum based on MIL-101 (Cr)/carbon black

A new photo-electrochemical sensor based on MIL-101(Cr) MOF/carbon black (CB) is fabricated and characterized. By using differential pulse voltammetry, dopamine (DA) can be effectively detected using a photo-electrochemical MIL-101(Cr)/CB sensor under visible light. The CB acts as the electron bridge to combine with the large specific surface area and photo-catalytic feature of MOF, which contribute to the improvements of sensitivity of DA detection. The concentration of the catalyst, pH value, accumulation potential, and accumulation time were also optimized. Furthermore, the electrochemical performances of MIL-101(Cr)/CB sensor was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scan rate, electrochemically active surface area (ECSA), and amperometric responses. A detection limit of 0.38 nM (LOD = 3 s_b/S, s_b = 0.028) and a working range of 1 nM to 2.22 μM has been achieved. The MIL-101(Cr)/CB sensor exhibits excellent reproducibility, stability, and selectivity and also has satisfactory recovery rate for the analysis of real samples including calf serum and human urine. Graphical abstract.

Nanopattern-Assisted Direct Growth of Peony-like 3D MoS2/Au Composite for Nonenzymatic Photoelectrochemical Sensing

The chalcogenide material MoS₂ has been recognized as a promising candidate for photoelectrochemical (PEC) applications due to its enhanced photocatalytic and electrocatalytic activities. However, few reports have been focused on the designated catalytic MoS₂ for the nonenzymatic PEC sensing of small molecules. Here, we report on a novel in situ and fab-free method for the direct growth of three-dimensional (3D) porous Peony-like MoS₂ nanosheets supported by nanohole-patterned TiO₂ and composited with gold deposits. The direct growth resulted in enhanced electrical conductivity between the substrate and 3D-standing MoS₂ nanosheets and thus the uniform distribution of gold electrodeposits from the MoS₂ lattice. The hybrid 3D MoS₂/gold nanocomposite demonstrated enhanced abundance of exposed catalytic edge sites and improved optic and electrical coupling, which ultimately led to excellent photoelectrochemical activities. We performed full characterization of the morphology, crystallinity, lattice configuration, and optical properties of hybrid MoS₂ nanosheets via field emission scanning microscope, high-resolution transmission electron microscopy, and energy-dispersive X-ray, Raman, and UV-vis spectroscopies. The 3D COMSOL simulation also confirmed enhanced electric field distribution at the interface of the proposed 3D MoS₂/gold nanocomposite electrode in comparison with other morphologies. We acquired the Peony-like 3D MoS₂/Au composite for photoelectrochemical sensing of glucose in buffer and diluted plasma solutions with a very low limit of detection of 1.3 nM and superb sensitivity in plasma. Overall, we have successfully synergized both electrical and optical merits from individual components to form a novel composite, which offered an effective scaffold for the development of PEC sensors.

Quantitative detection of procalcitonin using an electrochemical immunosensor based on MoO3/Au@rGO nanocomposites

In this work, a sandwich-type electrochemical immunosensor for the detection of procalcitonin (PCT) is constructed layer-by-layer with a novel label based on MoO₃/Au@rGO nanocomposites.