A pro-gastrin-releasing peptide imprinted photoelectrochemical sensor based on the in situ growth of gold nanoparticles on a MoS2 nanosheet surface.

Lamellar MoS2 nanosheets were successfully prepared by hydrothermal synthesis using 1-(3-mercaptopropyl)-3-methyl-imidazolium bromine (MIMBr) ionic liquid as a sulfur source and a morphology control agent, and sodium molybdate as a molybdenum source. Gold nanoparticles were assembled on the surface of MoS2 nanosheets by the in situ reduction of chloroauric acid at low temperatures to successfully fabricate AuNP/2D-MoS2 nanocomposites, thus improving photoelectrochemical response. AuNP/2D-MoS2 nanocomposites were used as photoelectrically active materials modified onto a glassy carbon electrode surface to construct a photoelectrochemical (PEC) sensor. Then, using 1-(N-pyrrolpropyl)-3-methyl-imidazolium bromine (PMIMBr) ionic liquid as a functional monomer and pro-gastrin-releasing peptide (Pro-GRP) as a template, a molecularly imprinted polymerized ionic liquid film was electrochemically deposited on an AuNP/2D-MoS2/GCE surface. Upon removing the templates, a molecularly imprinted photoelectrochemical sensor was constructed for the sensing of a tumor marker, pro-gastrin-releasing peptide. Experimental conditions including ascorbic acid concentration, polymerization conditions, incubation time, and pH value of the incubation solution have been optimized. Under the optimized conditions, the molecularly imprinted photoelectrochemical sensor can specifically detect the target protein Pro-GRP in the range of 0.02 ng mL-1-5 ng mL-1 with a detection limit of 0.0032 ng mL-1 (S/N = 3). The practicability of this photoelectrochemical sensor was demonstrated by accurately determining Pro-GRP in human serum samples.

ZnS/C/MoS2 Nanocomposite Derived from Metal-Organic Framework for High-Performance Photo-Electrochemical Immunosensing of Carcinoembryonic Antigen.

A hexafluorophosphate ionic liquid is used as a functional monomer to prepare a metal-organic framework (Zn-MOF). Zn-MOF is used as a template for MoS2 nanosheets synthesis and further carbonized to yield light-responsive ZnS/C/MoS2 nanocomposites. Zn-MOF, carbonized-Zn-MOF, and ZnS/C/MoS2 nanocomposites are characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction pattern, scanning electron microscopy (SEM), element mapping, Raman spectroscopy, X-ray photoelectron spectroscopy, fluorescence, and nitrogen-adsorption analysis. Carcinoembryonic antigen (CEA) is selected as a model to construct an immunosensing platform to evaluate the photo-electrochemical (PEC) performances of ZnS/C/MoS2 nanocomposites. A sandwich-type PEC immunosensor is fabricated by immobilizing CEA antibody (Ab1 ) onto the ZnS/C/MoS2 /GCE surface, subsequently binding CEA and the alkaline phosphatase-gold nanoparticle labeled CEA antibody (ALP-Au-Ab2 ). The catalytic conversion of vitamin C magnesium phosphate produces ascorbic acid (AA). Upon being illuminated, AA can react with photogenerated holes from ZnS/C/MoS2 nanocomposites to generate a photocurrent for quantitative assay. Under optimized experimental conditions, the PEC immunosensor exhibits excellent analytical characteristics with a linear range from 2.0 pg mL-1 to 10.0 ng mL-1 and a detection limit of 1.30 pg mL-1 (S/N = 3). The outstanding practicability of this PEC immunosensor is demonstrated by accurate assaying of CEA in clinical serum samples.

Ionic liquid and spatially confined gold nanoparticles enhanced photoelectrochemical response of zinc-metal organic frameworks and immunosensing squamous cell carcinoma antigen.

Metal-organic framework nanocrystal (Zn-MOF) was synthesized by using 3,3'-{(propane-1,3-diyl)bis[1-(4-carboxybenzyl)-1H-imidazol-3-ium]} hexafluorophosphate ionic liquid as the functional monomer and Zn2+ as the central metal ion under hydrothermal conditions. Spatially confined gold nanoparticles (Au-NP) were prepared by in-situ reduction of chloroauric acid in the nanopores of Zn-MOF using acetic acid as the reducing agent to fabricate Au-NP@Zn-MOF nanocomposites. Au-NPs@Zn-MOF was further functionalized with 1H-imidazolium-1,3-bis(2-aminoethyl)bromide ionic liquid (IBABr) to prepare IBABr-Au@Zn-MOF nanocomposites. All abovementioned nanomaterials were thoroughly characterized by TEM, SEM, XPS, FTIR, and nitrogen-adsorption surface area analysis. IBABr-Au@Zn-MOFnanocomposites were then deposited onto a glassy carbon electrode and used as the photoactive element to fabricate a label-free photoelectrochemical (PEC) immunosensor by immobilizing anti-squamous cell carcinoma antigen (anti-SCCA). The PEC sensing principle is based on the photocurrent decline due to the blocking effect of SCCA on the electron and mass transfer after binding SCCA to anti-SCCA. The photocurrent variation related to the specific recognition of SCCA shows a linear relationship to the logarithm of SCCA concentration in the range of 5.0 pg mL-1 to 15.0 ng mL-1. The detection limit is as low as 2.34 pg mL-1. Such a signal-off PEC immunosensor is highly selective, sensitive, stable, and reproducible towards SCCA detection. Its performance is comparable to enzyme-linked immunosorbent assay from the studies on clinical samples. This immunosensor is promising for the label-free determining SCCA in clinical human serum samples.