View full abstract

In this paper, we describe a simple and highly sensitive fluorescence strategy of mercury ions based on exonuclease III (Exo III)-aided target recycling amplification to ensure sensitivity. With an ultra high sensitivity (1 pM), our strategy has been simple and cost-effective, which does not need any artificial modification fluorescence groups, and can be carried out in a pot. It also shows excellent selectivity. Therefore, our new method provides an effective platform for mercury-ion detection.

View full abstract

Ozone (O₃) gas is widely used as a strong oxidizing agent for many purposes, such as the decomposition/removal of organic contaminants and photoresist, and the deodorization/disinfection of air and water. However, ozone is highly toxic to the human body when the air concentration exceeds about 1 ppm. Therefore, there is increasing demand for simple, sensitive, reliable, and cost-effective techniques for sensing ozone gas. This article describes the features, advantages, and disadvantages of the available, practical techniques for sensing ozone gas in ambient air. The advantages of optical gas sensors as next-generation sensors is specifically introduced. The features of photoluminescent, semiconductor nanoparticles (quantum dots, QDs) as bright phosphors with the potential for various applications is further explored. Lastly, recent research results demonstrating the ozone sensitivity of photoluminescent CdSe-based core-shell quantum dots are presented. These results strongly suggest that optical ozone sensing using photoluminescent quantum dots is a promising technique.

View full abstract

In vivo molecular imaging is a powerful tool to analyze the human body. Precision medicine is receiving high attention these days, and molecular imaging plays an important role as companion diagnostics in precision medicine. Nuclear imaging with PET or SPECT and optical imaging technologies are used for in vivo molecular imaging. Nuclear imaging is superior for quantitative imaging, and whole-body analysis is possible even for humans. Optical imaging is superior due to its ease of use, and highly targeted specific imaging is possible with activatable agents. However, with optical imaging using fluorescence, it is difficult to obtain a signal from deep tissue and quantitation is difficult due to the attenuation and scattering of the fluorescent signal. Recently, to overcome these issues, optoacoustic imaging has been used in in vivo imaging. In this article, we review in vivo molecular imaging with nuclear and optical imaging and discuss their utility for precision medicine.

View full abstract

The complexity of triacylglycerols (TAGs) in edible oils is largely due to the many similar unsaturated TAG compounds, which makes profiling TAGs difficult. In this study, precolumn derivatization with bromine (Br₂) was used to improve the separation and detection sensitivity of TAGs in edible oils by RP-HPLC. Oil samples dissolved in n-hexane and TAGs were derived by reaction with a Br2–CCl₄ (1:1, v/v) solution for 3 h at room temperature. The derivate product solution was stable and was best separated and detected by RP-HPLC using a C18 column, with a mobile phase of methanol–n-hexane (91.5:8.5, v/v) at 25°C. A detection wavelength of 230 nm was used. The results showed that the approach enabled the separation and detection of more similar TAGs by RP-HPLC. The method was applied to profile 20 types of edible oil, and the results presented the differences in the TAG profiles of various edible oils, which may be useful in the identification of edible oils.

View full abstract

Cationic poly-diallyldimethylammonium (PDADMAC), green CdTe quantum dots (QDs) or red CdS coated CdTe QDs, and anionic polyacrylic acid (PAA) were respectively assembled on the nano-carrier SiO₂ to prepare green fluorescence composite nanoparticles (GF-QDs) and red ones (RF-QDs) with the structure SiO₂/PDADMAC/QD/PDADMAC/PAA. The sandwich structure “PDADMAC/QD/PDADMAC” on the nano-carrier not only realized the protection to fluorescence of QDs but also avoided the fluorescence shielding of silica shell for the assembled QDs. In 7 days, the diluent solutions of GF-QD and RF-QD all have a very stable fluorescence. On the contrary, the fluorescence of diluent solutions of red and green QDs reduced by 75.99 and 94.35%, respectively. Indeed, they have not fluorescent shielding and have a very slight fluorescent enhancement. Based on GF-QD and RF-QD, the simultaneous determination of Hepatitis B e antigen and surface antigen has been established. Their determination in buffer and plasma all showed good precision and accuracy.

View full abstract

Dual-template magnetic molecularly imprinted polymer nanoparticles were synthesized and used for the solid-phase extraction of acetaminophen and codeine before simultaneous determination by corona discharge ion mobility spectrometry. The magnetic molecularly imprinted polymer nanoparticles were prepared using silica-coated magnetic nanoparticles as supporters, acetaminophen and codeine as template molecules, 3-aminopropyltriethoxysilane and phenyltriethoxysilane as functional monomers, and tetraethoxysilane as a cross-linker. The obtained molecularly imprinted polymer was characterized by transmission electron microscopy, x-ray diffraction and Fourier-transform infrared spectroscopy. The adsorption performance of the imprinted polymers was studied by a series of experiments, indicating a satisfactory recognition ability of products for acetaminophen and codeine. The detection limits of 0.05 and 0.12 μg mL⁻¹, and the dynamic range of 0.20 – 2.0 and 0.40 – 3.0 μg mL⁻¹ were achieved for acetaminophen and codeine, respectively. The proposed method was used for simultaneous determinations of acetaminophen and codeine in urine samples, and the corresponding recoveries were calculated in the range of 87 – 94%. These satisfactory results revealed the ability of the method for a routine analysis of acetaminophen and codeine, simultaneously.

View full abstract

A method capable of accurately and selectively measuring Cr³⁺ in water is required and was therefore studied. The precision and reproducibility of chlorophosphonazo I color reaction spectrophotometry (CCRS) for the selective determination of Cr³⁺ was improved to be acceptable standards. The CCRS established is therefore an accurate, reproducible and inexpensive method. It also has reasonably good sensitivity and selectivity, and a high sample output. This method should be readily adapted for the routine and selective determination of Cr³⁺ in bottled mineral drinking water with (or without) the supplementation of Cr³⁺ or in natural water such as mineral or pipe water with the presence of Cr⁶⁺.

View full abstract

This research was to prepare the titanium dioxide nanotube arrays (TiNT arrays) and deposit the Au nanoparticles on its surface using the pulse electrodeposition technique. The Au nanoparticles-TiNT arrays (AuNP-TiNT arrays) were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction, and cyclic voltammetry. The results showed that the Au nanoparticles were uniformly dispersed on the TiNT array surface. The size and loading of Au nanoparticles can be controlled by deposition time, deposition potential, and concentration of HAuCl₄. The AuNP-TiNT arrays were then used as a working electrode for hydrogen peroxide (H₂O₂) detection. Compared with the pure TiNT array electrode, the AuNP-TiNT array electrode had higher sensitivity for the detection of H₂O₂ and thus provided a simple, promising, and cost-effective sensing platform for the development of enzyme-based biosensors.

View full abstract

Here, we report a sol-gel integrated affinity microarray for on-chip matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) that enables capture and identification of prostate?specific antigen (PSA) in samples. An anti-PSA antibody (H117) was mixed with a sol?gel, and the mixture was spotted onto a porous silicon (pSi) surface without additional surface modifications. The antibody easily penetrates the sol-gel macropore fluidic network structure, making possible high affinities. To assess the capture affinity of the platform, we performed a direct assay using fluorescein isothiocyanate-labeled PSA. Pure PSA was subjected to on-chip MALDI-TOF-MS analysis, yielding three clear mass peptide peaks (m/z = 1272, 1407, and 1872). The sol-gel microarray platform enables dual readout of PSA both fluorometric and MALDI-TOF MS analysis in biological samples. Here we report a useful method for a means for discovery of biomarkers in complex body fluids.

View full abstract

We have developed a novel bioassay method for the detection of snake venom based on the permeability of endothelial cell monolayers cultured in Transwell cell culture inserts. This assay relies on the proteolytic degradation of capillary basement membrane proteins, a pathophysiological event that occurs due to snakebites in vivo. Transwell permeability assays with fluorescence measurements are advantageous with regard to ethical considerations for the use of animals. The assay time was reduced from 24 h for animal tests to 2 h, and many samples could be assayed easily.

View full abstract

A fluorescent probe, 7-(diethylamino)-2-oxo-2H-chromene-4-carbaldehyde (probe 1), was designed and synthesized for the sensitive detection of hydrazine. The addition of N₂H₄ caused the fluorescence intensity of probe 1 to decrease. The probe’s fluorescence was turn-off after adding N₂H₄, which could be observed under UV light at 365 nm. Moreover, once treated with different concentrations N₂H₄ solutions, the solution color change could be distinguished, which indicates that probe 1 could be used as a visual sensor for hydrazine. Moreover, probe 1 can be used as a signal tool to determine hydrazine levels in solutions, such as red wine and water.

View full abstract

Quinones are a class of compounds having substantial toxicity and pharmacological function. This work has produced a derivatization method for quinone detection with high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC-ESI-MS/MS). Through introducing tags (methoxy) to the quinone structures, the ionization efficiencies of five quinones (p-benzoquinone (BQ), methyl-p-benzoquinone (MBQ), 1,4-naphthoquinone (1,4-NQ), 1,2-naphthoquinone (1,2-NQ), and 1,4-anthraquinones (AQ)) were greatly improved during ESI. The limit of detections (LODs) for quinone determination could be flexibly adjusted by changing the reaction time or the solvent composition. While lower LODs (<0.02 – 2.06 pg for five quinones) were achieved with methanol as the derivatization reagent, the reaction time was substantially shortened (from 27 to 3 h or 11 h) with methanol/water (v/v, 1:1) as the derivatization reagent. Finally, the proposed method was successfully used for quinone determination in airborne particulates.

View full abstract

The ability to directly detect alkaline phosphatase (ALP) activity in undiluted serum samples is of great importance for clinical diagnosis. In this work, we report the use of the distinctive metal-to-ligand charge-transfer (MLCT) absorption properties of the Cu(BCA)₂⁺ (BCA = bicinchoninic acid) reporter for the visual detection of ALP activity. In the presence of ALP, the substrate ascorbic acid 2-phosphate (AAP) can be enzymatically hydrolyzed to release ascorbic acid (AA), which in turn reduces Cu²⁺ to Cu⁺. Subsequently, the complexation of Cu⁺ with the BCA ligand generates the chromogenic Cu(BCA)₂⁺ reporter, accompanied by a color change of colorless-to-purple of the solution with a sharp absorption band at 562 nm. The underlying MLCT-based mechanism has been demonstrated on the basis of density functional theory (DFT) calculations. Needless of any sequential multistep operations and elaborately designed colorimetric probe, the proposed MLCT-based method allows for a fast and sensitive visual detection of ALP activity within a broad linear range of 20 – 200 mU mL⁻¹ (R² = 0.999), with a detection limit of 1.25 mU mL⁻¹. The results also indicate that it is highly selective and has great potential for the screening of ALP inhibitors in drug discovery. More importantly, it shows a good analytical performance for the direct detection of the endogenous ALP levels of undiluted human serum samples. Owing to the prominent simplicity and practicability, it is reasonable to conclude that the proposed MLCT-based method has a high application prospect in clinical diagnosis.

View full abstract

For caffeine and its seven major metabolites (i.e., theobromine, theophylline, paraxanthine, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, and xanthine), an optimized analytical method using liquid chromatography–tandem mass spectrometry (LC-MS/MS) for their detection in wastewater samples was developed in this study. Extraction of these compounds (recoveries ranged from 60.3 to 83.2%) was made possible by combining universal polymeric reversed-phase cartridge and polymeric strong cation exchange cartridge. This method was applied to the determination of caffeine and its metabolites in the influent and effluent of an anaerobic–anoxic–oxic (A2O) process. In the A2O influent, caffeine and its metabolites (except xanthine) ranged from 1.39 to 5.45 μg/L, and their concentrations in the A2O effluent ranged from 10.2 to 171.3 ng/L. The mass load of caffeine was 14.9 g/day/1000 inhabitants, considering the population served by the target wastewater treatment plant (WWTP). The concentration of caffeine derivatives in wastewater influent is a tool for estimating the population size in the area served by WWTPs.

View full abstract

An innovative electrochemical interface for quantitation of L-proline (L-Pro) based on ternary amplification strategy was fabricated. In this work, gold nanoparticles prepared by soft template methodology were immobilized onto green and biocompatible nanocomposite containing poly as a conductive matrix and graphene quantum dots as the amplification element. Therefore, a novel multilayer film based on poly-L-cysteine, graphene quantum dots (GQDs), and gold nanoparticles (GNPs) was exploited to develop a highly sensitive electrochemical sensor for the detection of L-Pro. Fully electrochemical methodology was used to prepare a new transducer on a glassy carbon electrode, which provided a high surface area towards sensitive detection of L-Pro. The prepared electrode was employed for the detection of L-Pro. Under optimized conditions, the calibration curve for L-Pro concentration was linear in 0.5 nM – 10 mM with a low limit of quantification of 0.1 nM. The practical analytical utility of the modified electrode was illustrated by determination of L-Pro in unprocessed human plasma samples.

View full abstract

Molecular adsorption on a sensing surface involves molecule-substrate and molecule-molecule interactions. Combining optical systems and a quartz crystal microbalance (QCM) on the same sensing surface allows the quantification of such interactions and reveals the physicochemical properties of the adsorbed molecules. However, low sensitivity of the current reflection-based techniques compared to the QCM technique hinders the quantitative analysis of the adsorption events. Here, a layer-by-layer surface modification of a QCM sensor is studied to increase the optical sensitivity. The intermediate layers of organic-inorganic molecules and metal-metal oxide were explored on a gold (Au) surface of a QCM sensor. First, polyhedral oligomeric silsesquioxane-derivatives that served as the organic-inorganic intermediate layer were synthesized and modified on the Au-QCM surface. Meanwhile, titanium oxide, fabricated by anodic oxidation of titanium, was used as a metal-metal oxide intermediate layer on a titanium-coated QCM surface. The developed technique enabled interrogation of the molecular adsorption owing to the enhanced optical sensitivity.

View full abstract

A new analytical methodology for a simple and efficient on-line preconcentration of trace inorganic anions in water and salt samples prior to ion chromatographic determination is proposed. The preconcentration method is based on partition/ion-exclusion chromatographic ion stacking (PIEC ion stacking) with a hydrophilic polymer gel column containing a small amount of fixed anionic charges. The developed on-line PIEC ion stacking–ion chromatography method was validated by recovery experiments for the determination of nitrate in tap water in terms of both accuracy and precision, and the results showed the reliability of the method. The method proposed was also successfully applied to the determination of trace impurity nitrite and nitrate in reagent-grade salts of sodium sulfate. A low background level can be achieved since pure water is used as the eluant for the PIEC ion stacking. It is possible to reach sensitive detection at sub-μg L⁻¹ levels by on-line PIEC ion stacking–ion chromatography.

View full abstract

Humic acid (HA) could become a useful agent for removing trace amounts of Cu(II) from contaminated seawater. This study reports on the use of a thin alginate membrane (TAM) containing immobilized HA as a Cu(II) binding agent for this purpose. The removal efficiency of Cu(II) by a TAM functionalized with HA was significantly increased compared to TAM alone. In this removal method, HA extracted from hardwood bark compost was more effective in removing Cu(II) than that from peat soil.

View full abstract

We have developed a compact disc (CD)-shaped microfluidic device for multiple, rapid enzyme-linked immunosorbent assays (ELISA). The device has a versatile design that can be adapted for the detection of various proteins by selecting the push-in-type reaction parts and appropriate reagents for each target. In this paper, we report the rapid quantification of insulin, adiponectin, and leptin, which can be used for the early diagnosis of diabetes, in human serum in only 16 min with our device.

View full abstract

An optode method for the determination of sulfate ion was developed. The optode membrane is 2-nitrophenyl octyl ether-plasticized poly(vinyl chloride) membrane containing tetrabromophenolphthalein ethyl ester. The method is based on formation of an ion associate between the excess of 2-aminoperimidine hydrobromide (Ap) and sulfate ion in the sample solution, and detection of the concentration of the remaining Ap ion by the optode. Under the optimal conditions, a good linear relationship was found to exist between the absorbance of the optode membrane, and concentrations of sulfate ion in a concentration range from 20 to 400 μM. The developed optode method was applied to the determination of sulfate ion in environmental water samples.

View full abstract

A sequential flow-based analysis system with on-line solid-phase extraction (SPE) columns coupled to microwave plasma atomic emission spectrometry (MP-AES) was developed for strontium and nickel determination. Crown ether chromatographic resin and dimethylglyoxime polymethacrylate resin were used for strontium and nickel retention under acidic and basic conditions, respectively; eluted with a nitric acid solution in both cases followed by MP-AES detection. The calculated detection limits were 0.25 μg L⁻¹ for strontium and 3.56 μg L⁻¹ for nickel.

View full abstract