A Multi-signal Fluorescent Probe with Multiple Binding Sites for Simultaneous Sensing of Cysteine, Homocysteine, and Glutathione.

A novel fluorescent probe was developed by integrating chlorinated coumarin and benzothiazolylacetonitrile and exploited for simultaneous detection of cysteine (Cys), homocysteine (Hcy), and glutathione (GSH). Featuring four binding sites and different reaction mechanisms for different biothiols, this probe exhibited rapid fluorescence turn-on for distinguishing Cys, Hcy, and GSH with 108-, 128-, 30-fold fluorescence increases at 457, 559, 529 nm, respectively, across different excitation wavelengths. Furthermore, the probe was successfully applied to the fluorescence imaging of endogenous Cys and GSH and exogenous Cys, Hcy, and GSH in living cells.

A biomimetic colorimetric logic gate system based on multi-functional peptide-mediated gold nanoparticle assembly.

In natural biological systems, proteins exploit various functional peptide motifs to exert target response and activity switch, providing a functional and logic basis for complex cellular activities. Building biomimetic peptide-based bio-logic systems is highly intriguing but remains relatively unexplored due to limited logic recognition elements and complex signal outputs. In this proof-of-principle work, we attempted to address these problems by utilizing multi-functional peptide probes and the peptide-mediated nanoparticle assembly system. Here, the rationally designed peptide probes function as the dual-target responsive element specifically responsive to metal ions and enzymes as well as the mediator regulating the assembly of gold nanoparticles (AuNPs). Taking advantage of Zn2+ ions and chymotrypsin as the model inputs of metal ions and enzymes, respectively, we constructed the peptide logic system computed by the multi-functional peptide probes and outputted by the readable colour change of AuNPs. In this way, the representative binary basic logic gates (AND, OR, INHIBIT, NAND, IMPLICATION) have been achieved by delicately coding the peptide sequence, demonstrating the versatility of our logic system. Additionally, we demonstrated that the three-input combinational logic gate (INHIBIT-OR) could also be successfully integrated and applied as a multi-tasking biosensor for colorimetric detection of dual targets. This nanoparticle-based peptide logic system presents a valid strategy to illustrate peptide information processing and provides a practical platform for executing peptide computing or peptide-related multiplexing sensing, implying that the controllable nanomaterial assembly is a promising and potent methodology for the advancement of biomimetic bio-logic computation.

Molecularly imprinted electrochemical sensor based on amine group modified graphene covalently linked electrode for 4-nonylphenol detection.

In this work, an imprinted electrochemical sensor based on electrochemical reduced graphene covalently modified carbon electrode was developed for the determination of 4-nonylphenol (NP). An amine-terminated functional graphene oxide was covalently modified onto the electrode surface with diazonium salt reactions to improve the stability and reproducibility of the imprinted sensor. The electrochemical properties of each modified electrodes were investigated with differential pulse voltammetry (DPV). The electrochemical characteristic of the imprinted sensor was also investigated using electrochemical impedance spectroscopy (EIS) in detail. The response currents of the imprinted electrode exhibited a linear relationship toward 4-nonylphenol concentration ranging from 1.0 × 10(-11) to 1.0 × 10(-8) gm L(-1) with the detection limit of 3.5 × 10(-12) gm L(-1) (S/N=3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of 4-nonylphenol in rain and lake water samples.

Molecularly imprinted electrochemical sensor based on a reduced graphene modified carbon electrode for tetrabromobisphenol A detection.

A simple strategy for the indirect detection of 3,3',5,5'-tetrabromobisphenol A (TBBPA) was developed with a surface imprinted sensor based on an electrochemical reduced graphene modified carbon electrode. The preparation procedure of imprinted electrode and the response mechanism of the imprinted electrode toward TBBPA are discussed in detail. The electrochemical characteristics of the imprinted sensor were investigated using cyclic voltammetry and their morphologies were characterized using scanning electron microscopy. The indirect detection for TBBPA was successfully implemented by monitoring the peak current of Fe(CN)6(3-/4-)-TBBPA complex. The response currents of the imprinted sensor exhibited a linear relationship toward the TBBPA concentration range from 0.5 to 4.5 nM with a detection limit of 0.23 nM (S/N = 3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of TBBPA in rain and lake water samples using the standard addition method. With the advantages of high sensitivity and simple operation, the determination methodology is a promising candidate for TBBPA detection in real water samples.

Electrochemical determination of L-phenylalanine at polyaniline modified carbon electrode based on ß-cyclodextrin incorporated carbon nanotube composite material and imprinted sol-gel film.

A sensitive and selective electrochemical sensor based on a polyaniline modified carbon electrode for the determination of L-phenylalanine has been proposed by utilizing ß-cyclodextrin (ß-CD) incorporated multi-walled carbon nanotube (MWNT) and imprinted sol-gel film. The electrochemical behavior of the sensor towards L-phenylalanine was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve. The surface morphologies of layer-by-layer assembly electrodes were displayed by scanning electron microscope (SEM). The response mechanism of the imprinted sensor for L-phenylalanine was based on the inclusion interaction of ß-CD and molecular recognition capacity of the imprinted film for L-phenylalanine. A linear calibration plot was obtained covering the concentration range from 5.0 × 10(-7) to 1.0 × 10(-4) mol L(-1) with a detection limit of 1.0 × 10(-9) mol L(-1). With excellent sensitivity, selectivity, stability, reproducibility and recovery, the electrochemical imprinted sensor was used to detect L-phenylalanine in blood plasma samples successfully.

[Determination of lipase activity by gas chromatography].

A rapid gas chromatography method was developed for determination of lipase activity using tributyrin as substrate. The standard curves of butyric acid hydrolyzed from tributyrin were linear in the range of 0.11-11.35 mmol L(-1). The recoveries of low, moderate and high concentrations of tributyrin were 90.3%, 104.6%, 89.4% with RSD of 3.01%, 4.50%, 6.64%, respectively. The incubation time was only 5 minutes which was less than with the half time of the conventional titrimetry and spectrophotometry. The optimum pH value was 7.5 and the optimum temperature was 32 degrees C. Based on the Lineweaver-Burk plots, the Michaelis-Menten constant was 0.25 mmol mL(-1). The effect of orlistat on the enzyme inhibiting activity was studied to prove the accuracy of this method. It was found that the half-inhibition concentration (IC50) of orlistat was 0.0485 mg mL(-1). The small total reaction volume, the simple treating procedures, the high accuracy and precision present the advantages of the new method.

Quality control of medicinal herbs Fructus gardeniae, Common Andrographis Herb and their preparations for their active constituents by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry.

Dehydroandrographolide, andrographolide and geniposide are the main active constituents of many herbal medicines, e.g., Fructus gardeniae, Common Andrographis Herb. They are used as the markers to control the quality of such herbal medicines and their herbal preparations. In this paper, a simple and sensitive high-performance liquid chromatographic (HPLC) method coupled with photodiode array detection (DAD) and electrospray mass spectrometry (ESI/MS) were developed to determine the three compounds simultaneously in extracts of medicinal herbs and herbal preparations produced by different companies. The extracts were separated on a C(18) reversed phase HPLC column, with a gradient solvent system, the time for the separation of the three target analytes was 1 0min. The abundance ions were recorded using selected ion monitoring (SIM) mode with m/z 297.3, 297.3 and 411.1 for dehydroandrographolide, andrographolide and geniposide, respectively. The limit of detection for dehydroandrographolide, andrographolide and geniposide were 20, 30 and 150 ng mL(-1), respectively. The proposed method was successfully applied to the determination of the contents of the compounds in related to medicinal herbs and preparations.

Rapid determination of protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata by microwave-assisted solvent extraction and HPLC-ESI/MS.

An isocratic high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed to determine protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata. The sample was extracted with hydrochloric acid aqueous solution using microwave-assisted extraction method. The extracts were separated on a C8 reversed-phase HPLC column with acetonitrile:acetate buffer as mobile phase, and full elution of all analytes was realized isocratically within 10 min. The abundance of pseudomolecule ions was recorded using selected ion recording at m/z 354.4, 370.1, 332.5, 348.5 and 338.5 for protopine, allocryptopine, sanguinarine, chelerythrine and the internal standard, jatrorrhizine, respectively. Internal standard curves were used for the quantification of protopine, allocryptopine, sanguinarine and chelerythrine, which showed a linear range of 0.745-74.5, 0.610-61.0, 0.525-105 and 0.375-75 microg/mL, respectively, with correlation coefficients of 0.9995, 0.9992, 0.9993 and 0.9989, and limits of detection of 3.73, 3.05, 1.60 and 1.11 ng/mL, respectively.

[Determination of orlistat in health food for controlling body weight by high performance liquid chromatography/electrospray spectrometry].

OBJECTIVE: To establish a method of determining orlistat in health food by on line HPLC-UV-ESI/MS. METHODS: The separation was completed on an analytical Spherigel C8 column (5 microm, 200 mm x 4.6 mm) with acetonitrile (0.1% formic acid) : water (0.1% formic acid) = 80 : 20 as mobile phase, the detection wavelength was 2003 mm. RESULTS: Good linearity between peak areas and concentrations was obtained during rag of 0.3 - 0.6 mg/ml. CONCLUSION: The method is simple and can be used to determine orlistat in the health food for controlling body weight accurately.

Simultaneous analysis of caffeic acid derivatives and alkamides in roots and extracts of Echinacea purpurea by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry.

High-performance liquid chromatography (HPLC) coupled with UV photodiode-array detection and electrospray ionization mass spectrometry was developed for the simultaneous analysis of caffeic acid derivatives and alkamides in the roots and extracts of Echinacea purpurea. Caffeic acid derivatives and alkamides produced very abundant peaks in the total ion current chromatogram during negative and positive cone voltage switching. Cichoric acid and the isomer pair, dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamide, were used as a standard for quantification of caffeic acid derivatives and alkamides in E. purpurea. This novel method surpasses previously published ones in product quality control and providing the HPLC chromatographic fingerprints of biological active components in E. purpurea.