Jinmao You

Facile and Sensitive Fluorescence Sensing of Alkaline Phosphatase Activity with Photoluminescent Carbon Dots Based on Inner Filter Effect

A simple and sensitive fluorescent assay for detecting alkaline phosphatase (ALP) based on the inner filter effect (IFE) has been proven, which is conceptually different from the previously reported ALP fluorescent assays. In this sensing platform, N-doped carbon dots (CDs) with a high quantum yield of 49% were prepared by one-pot synthesis and were directly used as a fluorophore in IFE. p-Nitrophenylphosphate (PNPP) was employed to act as an ALP substrate, and its enzyme catalytic product (p-nitrophenol (PNP)) was capable of functioning as a powerful absorber in IFE to influence the excitation of fluorophore (CDs). When in the presence of ALP, PNPP was transformed into PNP and induced the absorption band transition from 310 to 405 nm, which resulted in the complementary overlap between the absorption of PNP and the excitation of CDs. Because of the competitive absorption, the excitation of CDs was significantly weakened, resulting in the quenching of CDs. The present IFE-based sensing strategy showed a good linear relationship from 0.01 to 25 U/L (R(2) = 0.996) and provided an exciting detection limit of 0.001 U/L (signal-to-noise ratio of 3). The proposed sensing approach was successfully applied to ALP sensing in serum samples, ALP inhibitor investigation and phosphatase cell imaging. The presented IFE-based CDs fluorescence sensing strategy gives new insight on the development of the facile and sensitive optical probe for enzyme activity assay because the surface modification or the linking between the receptor and the fluorophore is no longer required.

Catalyst-free direct arylsulfonylation of N-arylacrylamides with sulfinic acids: a convenient and efficient route to sulfonated oxindoles

A simple, efficient and catalyst-free procedure has been developed for the construction of sulfonated oxindoles via the direct arylsulfonylation of N-arylacrylamides with sulfinic acids. The present protocol, which simply utilizes cheap oxidants, readily-available starting materials, and catalyst-free conditions, provides an alternative and highly attractive approach to a series of sulfonated oxindoles with high atom efficiency and excellent functional group tolerance.

A novel aptamer-functionalized MoS2 nanosheet fluorescent biosensor for sensitive detection of prostate specific antigen

Prostate specific antigen (PSA) is a significant and the most widely used biomarker for the early diagnosis of prostate cancer and its subsequent treatment. A MoS2 nanosheet is a two-dimensional (2D) layered nanomaterial analogous to graphene. However, a MoS2 nanosheet has a higher fluorescence-quenching ability than graphene when applied to a dye-labeled single-stranded DNA probe. In this work, we propose a novel aptamer-functionalized MoS2 nanosheet fluorescent biosensor that detects PSA. The binding of the aptamer to the target PSA induces a rigid aptamer structure which makes the integration with the MoS2 nanosheet very weak. This results in the release of the aptamer probe from the nanosheet surface and restores the quenched fluorescence. This approach has the advantage of simple design and rapid detection of PSA. The biosensor has the merits of high sensitivity and high selectivity with a detection limit for the PSA of 0.2xa0ng/mL. The biosensor was also successfully applied to the detection of PSA in human serum samples with satisfactory results. The foregoing indicates its promising application to real-life biological samples.

Direct difunctionalization of alkynes with sulfinic acids and molecular iodine: a simple and convenient approach to (E)-β-iodovinyl sulfones

A simple and convenient approach for the construction of β-iodovinyl sulfones has been developed via direct difunctionalization of alkynes with sulfinic acids and molecular iodine. The present reaction provides a highly efficient approach to a diverse range of substituted (E)-β-iodovinyl sulfones in moderate to good yields with excellent stereo- and regio-selectivities but no need for any metal catalyst or additives.

A near-infrared fluorescent probe for the detection of hydrogen polysulfides biosynthetic pathways in living cells and in vivo

Hydrogen polysulfides (H2Sn, n > 1), derived from hydrogen sulfide (H2S), have been considered to be involved in cytoprotective processes and redox signaling. The emerging evidences imply that the actual signaling molecule is H2Sn rather than H2S. In this work, we present a near-infrared fluorescent probe BD-ss for the selective detection of H2Sn biosynthetic pathways in living cells and in vivo. The probe is constructed by equipping a bis-electrophilic H2Sn capture group p-nitrofluorobenzoate to a near-infrared fluorophore azo-BODIPY. BD-ss can provide a remarkable turn-on fluorescence response for assessing endogenous H2Sn formation ways in serum, in living cells and in vivo.

Development of a sensitive fluorescent derivatization reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) and its application for determination of amino acids from seeds and bryophyte plants using high-performance liquid chromatography with fluorescence detection and identification with electrospray ionization mass spectrometry.

A pre-column derivatization method for the sensitive determination of amino acids and peptides using the tagging reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) followed by high-performance liquid chromatography with fluorescence detection has been developed. Identification of derivatives was carried out by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS/MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent was replaced by 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing reagent BCEOC. BCEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. The derivatives showed an intense protonated molecular ion corresponding m/z (M+H)(+) under electrospray ionization (ESI) positive-ion mode with an exception being Tyr detected at negative mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 246.2 corresponding to the cleavage of CO bond of BCEOC molecule. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0-10.0. Maximal yields close to 100% are observed with a 3-4-fold molar reagent excess. Derivatives exhibit strong fluorescence and extracted derivatization solution with n-hexane/ethyl acetate (10:1, v/v) allows for the direct injection with no significant interference from the major fluorescent reagent degradation by-products, such as 1,2-benzo-3,4-dihydrocarbazole-9-ethanol (BDC-OH) (a major by-product), mono-1,2-benzo-3,4-dihydrocarbazole-9-ethyl carbonate (BCEOC-OH) and bis-(1,2-benzo-3,4-dihydrocarbazole-9-ethyl) carbonate (BCEOC)(2). In addition, the detection responses for BCEOC derivatives are compared to those obtained with previously synthesized 2-(9-carbazole)-ethyl chloroformate (CEOC) in our laboratory. The ratios AC(BCEOC)/AC(CEOC)=2.05-6.51 for fluorescence responses are observed (here, AC is relative fluorescence response). Separation of the derivatized peptides and amino acids had been optimized on Hypersil BDS C(18) column. Detection limits were calculated from 1.0pmol injection at a signal-to-noise ratio of 3, and were 6.3 (Lys)-177.6 (His) fmol. The mean interday accuracy ranged from 92 to 106% for fluorescence detection with mean %CV<7.5. The mean interday precision for all standards was <10% of the expected concentration. Excellent linear responses were observed with coefficients of >0.9999. Good compositional data could be obtained from the analysis of derivatized protein hydrolysates containing as little as 50.5ng of sample. Therefore, the facile BCEOC derivatization coupled with mass spectrometry allowed the development of a highly sensitive and specific method for the quantitative analysis of trace levels of amino acids and peptides from biological and natural environmental samples.

Fabrication of robust M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures for improved visible-light photocatalysis

M/Ag3PO4 (M = Pt, Pd, Au) Schottky-type heterostructures were successfully fabricated by a chemical deposition route using NaBH4 as a reduction agent. The structure and optical properties of the as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and electrochemical techniques. The photocatalytic activity was evaluated by the decomposition of dyes (methyl orange, methylene blue, and rhodamine B) under visible light irradiation (λ > 420 nm). These noble metals as nanoparticles were highly dispersed on the surface of Ag3PO4 polyhedrons. The light absorption of Ag3PO4 in both the UV and visible regions was extensively increased upon noble metal deposition. The photocurrent response over M/Ag3PO4 electrodes was much higher than that of pure Ag3PO4 and followed the decreased order of Pt > Pd > Au. The metallic nanoparticles deposited on Ag3PO4 could promote the transfer of photo-generated electrons, which not only inhibited the recombination of electrons and holes effectively, but also suppressed the photocorrosion of Ag3PO4, leading to a significant increase in photocatalytic activity and stability. On the basis of radical-trapping experiments and the PL technique, h+ and ˙O2− were well-established to correspond to the quick photo-degradation of dyes and a possible mechanism was proposed.

Signal amplification strategy for sensitive immunoassay of prostate specific antigen (PSA) based on ferrocene incorporated polystyrene spheres.

A new kind of signal amplification strategy based on ferrocene (Fc) incorporated polystyrene spheres (PS-Fc) was proposed. The synthesized PS-Fc displayed narrow size distribution and good stability. PS-Fc was applied as label to develop immunosensors for prostate specific antigen (PSA) after the typical sandwich immunoreaction by linking anti-PSA antibody (Ab2) onto PS-Fc. After the fabrication of the immunosensor, tetrahydrofuran (THF) was dropped to dissolve PS and release the contained Fc for the following stripping voltammetric detection. PS-Fc as a new electrochemical label prevented the leakage of Fc and greatly amplified the immunosensor signal. In addition, the good biocompatibility of PS could maintain the bioactivity of the antibodies. The response current was linear to the logarithm of PSA concentration in the range from 0.01 ng mL(-1) to 20 ng mL(-1) with a detection limit of 1 pg mL(-1). The immunosensor results were validated through the detection of PSA in serum samples with satisfactory results.

Speciation analysis of mercury in water samples by dispersive liquid–liquid microextraction coupled to capillary electrophoresis

In this study, a method of pretreatment and speciation analysis of mercury by dispersive liquid–liquid microextraction along with CE was developed. The method was based on the fact that mercury species including methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and Hg(II) were complexed with 1‐(2‐pyridylazo)‐2‐naphthol to form hydrophobic chelates and l‐cysteine could displace 1‐(2‐pyridylazo)‐2‐naphthol to form hydrophilic chelates with the four mercury species. Factors affecting complex formation and extraction efficiency, such as pH value, type, and volume of extractive solvent and disperser solvent, concentration of the chelating agent, ultrasonic time, and buffer solution were investigated. Under the optimal conditions, the enrichment factors were 102, 118, 547, and 46, and the LODs were 1.79, 1.62, 0.23, and 1.50 μg/L for MeHg, EtHg, PhHg, and Hg(II), respectively. Method precisions (RSD, n = 5) were in the range of 0.29–0.54% for migration time, and 3.08–7.80% for peak area. Satisfactory recoveries ranging from 82.38 to 98.76% were obtained with seawater, lake, and tap water samples spiked at three concentration levels, respectively, with RSD (n = 5) of 1.98–7.18%. This method was demonstrated to be simple, convenient, rapid, cost‐effective, and environmentally benign, and could be used as an ideal alternative to existing methods for analyzing trace residues of mercury species in water samples.

Adsorptive stripping voltammetric determination of antimony.

A new method is described for the determination of antimony based on the cathodic adsorptive stripping of Sb(III) complexed with 2,3,4,5,7-pentahydroxyflavone(morin) at a static mercury drop electrode (SMDE). The reduction current of the adsorbed antimony complex was measured by 1.5th-order derivative linear-sweep adsorption voltammetry. The peak potential is at -0.51 V (vs. SCE). The effects of various parameters on the response are discussed. The optimized analytical conditions were found to be: supporting electrolyte, chloroacetic acid (0.04 mol/l, pH 2.3); concentration of morin, 5x10(-6) mol/l; accumulation potential, -0.25 V (vs. SCE); scan rate, 100 mV/s. The limit of detection and the linear range were 7x10(-10) mol/l and 1.0x10(-9) approximately 3.0x10(-7) mol/l Sb(III) for a 2-min accumulation time, respectively. This method has been applied to the determination of Sb(III) in steel and brass samples and satisfactory results were obtained. The adsorptive voltammetric characteristics and composition of the Sb(III)-morin complex were studied.