A signal-on magnetic electrochemical immunosensor for ultra-sensitive detection of saxitoxin using palladium-doped graphitic carbon nitride-based non-competitive strategy.

Saxitoxin (STX) has high toxicity, and is water soluble, acid stable and thermostable. Therefore, STX in seawater can be accumulated by marine organism to form bioaccumulation. To ensure the safety of seafood for consumption, it is crucial to accurately determine trace STX in seawater and seafood. We herein developed a novel magnetic electrochemical immunosensor for ultra-sensitive detection of STX in seawater and seafood by using non-competitive strategy. The immunosensor employs STX-specific antibody-functionalized magnetic beads (MBs) for STX recognition, palladium-doped graphitic carbon nitride (g-C3N4-PdNPs) peroxidase mimetic for catalyzing H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate signal. The immunosensor combines the merits of g-C3N4-PdNPs peroxidase mimetic, non-competitive strategy, MBs-based antibody recognition and magnetic gold electrode, and thus has excellent stability, lower cost, no risk of false positive result, high sensitivity and strong ability resist to matrix interference. The proposed immunosensor has been successfully used to detect trace STX in seawater and shellfish samples with a detection limit of 1.2 pg/mL (4.0 × 10-12 M), a recovery of 93-107% and a relative standard deviation (RSD, n = 5) < 5%. The success of this study provided a promising approach for the rapid and on-site detection of trace STX in seawater and seafood.

Exonuclease-assisted multicolor aptasensor for visual detection of ochratoxin A based on G-quadruplex-hemin DNAzyme-mediated etching of gold nanorod.

An exonuclease-assisted multicolor aptasensor was developed for the visual detection of ochratoxin A (OTA). It is based on the etching of gold nanorods (AuNRs) mediated by a G-quadruplex-hemin DNAzyme. A DNA sequence (AG4-OTA) was designed that comprises a hemin aptamer and an OTA aptamer. OTA binds to AG4-OTA to form an antiparallel G-quadruplex, which halts its digestion by exonuclease I (Exo I) from the 3'-end of AG4-OTA. Thus, the retained hemin aptamer can bind to hemin to form a G-quadruplex-hemin DNAzyme. This DNAzyme has peroxidase-like activity that catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce its diimine derivative (TMB2+) in acidic solution. TMB2+ can etch the AuNRs by oxidizing Au(0) into Au(I). This results in the generation of rainbow-like colors and provides a multicolor platform for the visual detection of OTA. The assay is based on the use of a single isolated aptamer and possesses obvious advantages such as multi-color visual inspection, relatively high sensitivity and accuracy. It can be used to detect as little as 30 nM concentrations of OTA by visual observation and even 10 nM concentrations by spectrophotometry. The method was successfully applied to the determination of OTA in spiked beer where it gave recoveries of 101-108%, with a relative standard deviation (RSD, n = 5) of <5%. Graphical abstract Schematic of an exonuclease-assisted multicolor bioassay based on the G-quadruplex-hemin DNAzyme-mediated etching of gold nanorods (AuNRs). It enables visual detection of ochratoxin A (OTA) with a detection limit of 30 nM.

Tumor targeting dual stimuli responsive controllable release nanoplatform based on DNA-conjugated reduced graphene oxide for chemo-photothermal synergetic cancer therapy.

In this research, a novel tumor targeting dual stimuli responsive nanoplatform was fabricated for the controllable delivery and release of a drug to realize chemo-photothermal synergetic cancer therapy by integrating a DNA aptamer with polydopamine reduced graphene oxide (rGO-PDA) nanosheets. The rGO-PDA nanosheets simultaneously acted as a near-infrared radiation (NIR) photothermal agent to generate hyperthermia for photothermal therapy and a nano-carrier for loading doxorubicin (DOX), and the specially designed DNA aptamer served as a supplementary carrier for DOX loading as well as targeting moiety/gatekeeper for specific cellular recognition and controllable release of DOX. The proposed nanoplatform possessed a good targeting ability, remarkable photothermal conversion ability and intelligent drug release with both pH and photothermal heating dual stimuli response. The nanoplatform was successfully used to selectively deliver DOX to protein tyrosine kinase 7 over-expressing cancer cells with a loading capacity of 1.56 mg mg-1 and controllable drug release, which responded to both acidic intracellular environments and NIR irradiation. The combination of the dual stimuli responsive controllable release and the dual nanocarrier for drug loading results in efficient chemo-photothermal synergetic therapy and holds great potential for multimodal cancer therapy.

Ion-imprinted magnetic nanoparticles for specific separation and concentration of ultra-trace methyl mercury from aqueous sample.

For rapidly and sensitively determining ultra-trace methyl mercury (MeHg) in aqueous environment, we herein synthesized a MeHg ion-imprinted magnetic nanoparticle (MeHg IIMN) to simply and specifically extract/concentrate ultra-trace MeHg from water samples. The MeHg IIMN employed core-shell Fe3O4@SiO2 nanoparticles (Fe3O4@SiO2 NPs) as supporting structure, the complex ion of 1-pyrrolidinecarbodithioic acid and MeHg (PDC-CH3Hg+) as template, methacrylic acid (MAA) as functional monomer and trimethylolpropane trimethacrylate (TMPTM) as cross linker. The MeHg IIMN offered obvious advantages such as low cost, easy manipulation, better specificity and stability, and recycling characteristics. It can be used to separate/concentrate ultra-trace MeHg from natural water sample within 30min with a recovery >95%, an enrichment factor of 250, a relative standard deviation (RSD, n=5) <7%, a 25mg MeHg/g of maximum adsorption capacity, 50 times of recycling, and without obvious interference of other ions. Combining with capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS), it can be used for the accurate detection of ultra-trace methyl mercury in natural water samples with a limit of detection of 0.084pg/mL, a recovery of 92-99% and a RSD (n=5)<8%. The success of this study promises a valuable technique for relatively simple detection of ultra-trace methyl mercury in aqueous environment.

Magnetic beads-based DNA hybridization chain reaction amplification and DNAzyme recognition for colorimetric detection of uranyl ion in seafood.

A novel colorimetric biosensor, which employs DNAzyme-functionalized magnetic beads (MBs) as recognition probe, enzyme-assisted catalytic oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) as signal and DNA hybridization chain reaction as amplification strategy, has been developed for detecting trace uranyl ion (UO22+) in seafood and aqueous environment with high sensitivity and specificity. We demonstrated that UO22+ can specifically cleave DNAzyme immobilized on MBs surface to release a short single-strand DNA (primer), and the released primer trigger DNA hybridization chain reaction to form a long one dimensional DNA concatamer on the MBs surface. The resulting long DNA concatamer could capture a large amount of HRP to generate the one UO22+-to-multiple HRP amplification effect. Upon the addition of TMB-H2O2 solution, the HRP-tagged DNA concatamer-MBs conjugates could catalyze the H2O2-mediated oxidation of TMB, and thus results in a color change from colorless to blue in solution. This provided a sensitive and selective sensing platform for the visual or colorimetric detection of UO22+. The proposed biosensor has high sensitivity and strong anti-interference capability, it can be used to detect as low as 2.5 ppb (9.25 nM) of UO22+ by naked-eye observation and 0.09 ppb (0.33 nM) of UO22+ by UV-visible spectrometry with no interference of other ions and a RSD ≤ 6% (n = 5). With the help of this method, we have successfully determined trace UO22+ in fish muscle and river water with a recovery of 93-106%. High sensitivity and specificity, as well operation convenience, low cost and strong resistibility to the matrix, which makes our method a potential approach for the on-site detection of UO22+ in seafood and aqueous environment.

Capillary electrophoresis inductively coupled plasma mass spectrometry combined with metal tag for ultrasensitively determining trace saxitoxin in seafood.

As one of paralytic shellfish toxins, the saxitoxin (STX) in the aqueous environment can be accumulated by most shellfish, and thus harms human health through the food chain. Therefore, it is crucial to determine trace STX in seafood samples in order to ensure the safety of seafood consumption. In this study, we developed a novel indirect method for ultrasensitively determining trace STX in seafood by using CE-ICP-MS together with Eu3+ chelate labeling. We demonstrated that diethylenetriamine-N,N,N',N″,N″-pentaacetic acid (DTPA) can couple with STX and simultaneously chelate with Eu3+ to realize metallic labeling of STX, and thus realize the ultrasensitive quantification of trace STX with CE-ICP-MS. The proposed method has strong antiinterference ability, good stability, and extremely high sensitivity. It could be used to determine trace STX in seafood samples with an extremely low detection limit of 0.38 fmol (3.8×10-9 M, 100 nL sample injection) and a relative standard deviation (RSD, n = 5) <7%. The success of this study provides an alternative to precise quantification of ultra-trace STX in seafood samples, and further expands the application of ICP-MS.

Species characteristics of lead in sea foods collected from coastal water of Fujian, Southeastern of China.

Various sea foods including fish, shellfish and shrimp were collected from different coastal areas of Fujian in China, and their Pb species characteristics were investigated in detail. The results indicated that there are two different species characteristics of Pb existing in sea food samples. About half of samples were detected to have only Pb(2+), and another half of samples were detected to have both Pb(2+) and trimethyl lead (TML). The results also revealed that Pb species characteristics in the sea foods rather depend on the species of sea food than the sampling area. In comparison with shellfish/shrimp samples, fish samples have higher concentrations of TML and Pb(2+). Especially, the average concentration of TML in the TML-detected fish samples is about 3 times of that in the TML-detected shellfish/shrimp samples, indicating that fish has stronger ability to uptake and accumulate TML. The concentrations of total lead in all samples are lower than the maximum allowable limit of national standard, suggesting that the sea foods collected from Fujian are safe for consumption. By considering that TAL has more toxicity than Pb(2+), the effect of TML in sea foods on the human health should be paid more attention in the future.

Ultra-sensitive speciation analysis of mercury by CE-ICP-MS together with field-amplified sample stacking injection and dispersive solid-phase extraction.

A simple dispersive solid-phase extraction (DSPE) used to extract and preconcentrate ultra-trace MeHg, EtHg and Hg(2+) from water sample, and a sensitive method for the simultaneous analysis of MeHg, EtHg and Hg(2+) by using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) with field-amplified sample stacking injection (FASI) were first reported in this study. The DSPE used thiol cotton particles as adsorbent, and is simple and effective. It can be used to extract and preconcentrate ultra-trace mercury compounds in water samples within 30 min with a satisfied recovery and no mercury species alteration during the process. The FASI enhanced the sensitivity of CE-ICP-MS with 25-fold, 29-fold and 27-fold for MeHg, EtHg and Hg(2+) , respectively. Using FASI-CE-ICP-MS together with DSPE, we have successfully determined ultra-trace MeHg, EtHg and Hg(2+) in tap water with a limits of quantification (LOQs) of 0.26-0.45 pg/mL, an RSD (n = 3) < 6% and a recovery of 92-108%. Ultra-high sensitivity, as well as much less sample and reagent consumption and low operating cost, make our method a valuable technique to the speciation analysis of ultra-trace mercury.

Phosphatidylserine-functionalized Fe3O4@SiO2 nanoparticles combined with enzyme-encapsulated liposomes for the visual detection of Cu2.

We herein reported on novel phosphatidylserine-functionalized Fe3O4@SiO2 NPs (nanoparticles) and enzyme-encapsulated liposomes for the visual detection of Cu2+ by employing phosphatidylserine for Cu2+ recognition and the enzymatic catalysis/oxidation of 3,3',5,5'-tetramethylbenzidine sulfate (TMB) as a signal generator. Phosphatidylserine (1,2-dioleoyl-sn-glycero-3-phospho-l-serine, DOPS) was covalently assembled on the Fe3O4@SiO2 NP surface to obtain DOPS-functionalized Fe3O4@SiO2 NPs, and was used to encapsulate horseradish peroxidase (HRP) to form HRP-encapsulated DOPS liposomes. It was demonstrated that DOPS-functionalized Fe3O4@SiO2 NPs can specifically bind HRP-encapsulated DOPS liposomes in the presence of Cu2+ at basic pH. The HRP-encapsulated DOPS liposome bound on the DOPS-functionalized Fe3O4@SiO2 NPs was then separated from solution with a magnet. Upon the addition of TMB-H2O2 solution, the HRP-encapsulated DOPS liposome bound on the DOPS-functionalized Fe3O4@SiO2 NPs was broken to release HRP, and the released HRP catalyzes the H2O2-mediated oxidation of TMB, which gives rise to a change from colourless to blue in solution colour and a new absorption peak at 652 nm. This provided a sensing platform for the sensitive, specific and field-portable colorimetric detection of Cu2+. By using the sensing platform, a selective and sensitive visual sensor for the detection of Cu2+ was developed. The proposed method has outstanding advantages including adequate sensitivity (the sensitivity can be improved by using a greater volume of the water sample), shorter analysis time, relatively low cost, operation at room temperature and stronger resistibility to the matrix. It can be used to detect as little as 0.1-0.5 µM of Cu2+ in river water using naked-eye observation and 0.05 µM of Cu2+ in river water using UV-visible spectrophotometry when 2 mL of the water sample was used for detection, within 15 min and with a recovery of 95-101% and a RSD < 5% (n = 5). A visual detection limit of 0.1-0.5 µM is much lower than the maximum allowable level of Cu2+ (∼20 µM) in drinking water defined by the USA EPA. The above features make our sensor a promising approach for the rapid and on-site detection of trace free copper ions in aqueous environments by only naked-eye observation.

A "turn-on" and label-free fluorescent assay for the rapid detection of exonuclease III activity based on Tb(3+)-induced G-quadruplex conjugates.

A "turn-on" and label-free fluorescent assay for the specific, rapid, and sensitive detection of 3' → 5' exonuclease III activity is reported in this study. The assay is based on the Tb(3+)-promoted G-quadruplex, which lead to the enhancement of Tb(3+) fluorescence due to the energy transfer from guanines. The proposed assay is highly simple, rapid, and cost-effective, and does not require sophisticated experimental techniques such as gel-based equipment or radioactive labels. It can be used for the rapid detection of exonuclease III activity with a detection limit of 0.8 U and a RSD (n = 6) <5 %. Notably, no dye was covalently conjugated to the DNA strands, which offers the advantages of low-cost and being interference-free.

Rolling circle amplification combined with gold nanoparticles-tag for ultra sensitive and specific quantification of DNA by inductively coupled plasma mass spectrometry.

A novel method for the ultra specific and sensitive detection of DNA in biological samples was described in this paper based on magnetic beads (MBs)-based rolling circle amplification combined with gold nano-particles (AuNPs)-aptamer labeling technique and inductively coupled plasma mass spectrometry (ICP-MS) detection. The proposed assay has an ultra-high sensitivity and stability, excellent specificity and more robust resistibility to the complex matrix due to the utilization of MBs-based rolling circle amplification, AuNPs-aptamer labeling technique and ICP-MS detection. It can be used to determine DNA or single nucleotide polymorphisms (SNP) with an extremely low detection limit of 0.1fM (1.0×10(-16)M) and a discrimination factor for single-base mismatch of 27. The proposed assay has been successfully used to detect DNA in serum sample with a recovery of 91-106% and a relative standard deviation (RSD) <6% (n=6), suggesting that our method is sensitive and reliable. The ultra-high sensitivity and specificity, easiness of fabrication, operational convenience, short analysis time, better stability and robust resistibility to the complex matrix, make the assay a promising alternative for the detection of various DNA sequence in the clinical diagnosis.

Study on the simultaneous determination of seven benzoylurea pesticides in Oolong tea and their leaching characteristics during infusing process by HPLC-MS/MS.

A method for the simultaneous determination of 7 benzoylurea pesticides (chlorfluazuron, diflubenzuron, fluazuron, flufenoxuron, hexaflumuron, teflubenzuron and triflumuron) in the manufactured Oolong tea leaves and its infusion was described. The method has a LOD of 0.03-1.00ng/mL, a recovery of 90.4-103% for made tea and 90.3-102% for tea-infused liquid, respectively. By using the proposed method, the leaching characteristics of above 7 pesticides during infusing process were investigated. The experimental results revealed that: (1) diflubenzuron can be most easily extracted out during infusing process, followed by triflumuron, teflubenzuron, hexaflumuron, chlorfluazuron, flufenoxuron and fluazuron. (2) The leaching of flufenoxuron and chlorfluazuron during infusing process seems to be controlled by only their solubility, whereas, the leaching of other 5 benzoylurea insecticides was primarily controlled by their partitioning coefficient between made tea and hot water. The results of this study are helpful for the accurate evaluation of the safety of Oolong tea.

A novel phosphatidylserine-functionalized AuNP for the visual detection of free copper ions with high sensitivity and specificity.

In this paper, we have reported on novel phosphatidylserine-functionalized AuNPs (gold nanoparticles) for the visual detection of Cu2+ by employing phosphatidylserine for Cu2+ recognition and AuNPs for signal generation. The phosphatidylserine (1,2-dioleoyl-sn-glycero-3-phospho-l-serine, DOPS) was covalently assembled on the AuNP surface to obtain DOPS-functionalized AuNPs. It was demonstrated that DOPS-functionalized AuNPs could specifically bind Cu2+ and lead to the aggregation of AuNPs, which gave rise to a colour change from wine-red to blue and a new absorption band around 650 nm. This provides a sensing platform for the simple, rapid and field portable colorimetric detection of Cu2+. By using the sensing platform, a selective and sensitive visual biosensor for the detection of Cu2+ was developed. The proposed biosensor has outstanding analytical advantages such as good stability, relatively high sensitivity, low cost and short analysis time. It can be used to detect concentrations of Cu2+ as low as 30 µM in river water by observation with the naked eye and of 1.55 µM Cu2+ in river water by UV-visible spectrophotometry, within 10 min and with a recovery of 98-103% and a relative standard deviation (RSD) < 4% (n = 6). The proposed biosensor is promising for on-site detection of trace Cu2+ in clinical diagnosis or environmental monitoring.

A microfluidic chip-based fluorescent biosensor for the sensitive and specific detection of label-free single-base mismatch via magnetic beads-based "sandwich" hybridization strategy.

A novel microfluidic chip-based fluorescent DNA biosensor, which utilized the electrophoretic driving mode and magnetic beads-based "sandwich" hybridization strategy, was developed for the sensitive and ultra-specific detection of single-base mismatch DNA in this study. In comparison with previous biosensors, the proposed DNA biosensor has much more robust resistibility to the complex matrix of real saliva and serum samples, shorter analysis time, and much higher discrimination ability for the detection of single-base mismatch. These features, as well as its easiness of fabrication, operation convenience, stability, better reusability, and low cost, make it a promising alternative to the SNPs genotyping/detection in clinical diagnosis. By using the biosensor, we have successfully determined oral cancer-related DNA in saliva and serum samples without sample labeling and any preseparation or dilution with a detection limit of 5.6 × 10(-11) M, a RSD (n = 5) < 5% and a discrimination factor of 3.58-4.54 for one-base mismatch.

A novel electrically magnetic-controllable electrochemical biosensor for the ultra sensitive and specific detection of attomolar level oral cancer-related microRNA.

Non-invasive early diagnosis of oral cancer is the most effective means to reduce mortality rate from this disease. In this paper, we described a novel magnetic-controllable electrochemical RNA biosensor for the ultra sensitive and specific detection of oral cancer-related microRNA (miRNA) based on a home-made electrically magnetic-controllable gold electrode. The electrically magnetic-controllable gold electrode combined the merits of heated electrode and magnetic electrode, has notable advantage such as that the strength and direction of the magnetic field and the temperature of the electrode's surface can be easily regulated. The advantage of electrically magnetic-controllable gold electrode, as well as the utilization of "junction-probe" strategy and magnetic beads (MBs)-based enzymatic catalysis amplification, make the biosensor has ultra-high sensitivity and discrimination ability even for the detection of similar miRNAs. It can be used to detect as low as 0.22 aM (2.2 × 10(-19)M) of oral cancer-related miRNA with a recovery of 93-108% and a RSD<6 (n=5). The high sensitivity and selectivity, as well as the easiness of fabrication, operational convenience, short analysis time, good stability and re-usability, make the biosensor a promising alternative for the early point-of-care diagnosis of oral cancer. The success of the biosensor also leads to a great potential in the development of biosensor for the early diagnosis of other diseases.

Field enhancement sample stacking for analysis of organic acids in traditional Chinese medicine by capillary electrophoresis.

A technique known as field enhancement sample stacking (FESS) and capillary electrophoresis (CE) separation has been developed to analyze and detect organic acids in the three traditional Chinese medicines (such as Portulaca oleracea L., Crataegus pinnatifida and Aloe vera L.). In FESS, a reverse electrode polarity-stacking mode (REPSM) was applied as on-line preconcentration strategy. Under the optimized condition, the baseline separation of eight organic acids (linolenic acid, lauric acid, p-coumaric acid, ascorbic acid, benzoic acid, caffeic acid, succinic acid and fumaric acid) could be achieved within 20 min. Validation parameters of this method (such as detection limits, linearity and precision) were also evaluated. The detection limits ranged from 0.4 to 60 ng/mL. The results indicated that the proposed method was effective for the separation of mixtures of organic acids. Satisfactory recoveries were also obtained in the analysis of these organic acids in the above traditional Chinese medicine samples.

Pyrolysis and thermal-oxidation characterization of organic carbon and black carbon aerosols.

In this study, the pyrolytic behaviors and the thermal-oxidation decomposition characteristics of organic carbon (OC), pyrolytically generated elemental carbon (PEC) and black carbon (BC) particles have been studied in inert and air atmosphere respectively, in order to develop a new PEC correction method for the determination of BC by using thermal oxidation method. Our results indicated that: 1) a part of OC can be removed by heating it at 400°C in inert atmosphere and another part of OC was charred to form PEC, whereas, the weight of BC particles approximately keeps no change in the same conditions. 2) PEC and BC began to decompose at a similar temperature in air atmosphere. However, the decomposition rate of PEC is quite different from that of BC in air atmosphere and the difference varied with the temperature. As maximum, the decomposition rate of PEC is 5.64 times faster than that of BC particles at 500°C in air atmosphere. Based on the difference of the decomposition rate between PEC and BC, a new method of PEC correction was developed for the thermal oxidation method. With the help of the new PEC correction method and thermal analyzer, we successfully determined OC and BC concentrations in actual soot sample and artificial soot samples. The results obtained with our PEC correction method are consistent well with the real value or those analyzed with thermal-optical method, suggesting that the novel PEC correction method have a high accuracy.

Separation and determination of ß-casomorphins by using glass microfluidic chip electrophoresis together with laser-induced fluorescence detection.

A simple, reliable and reproducible method for the separation and determination of five ß-casomorphins (ß-CMs, namely TPGN, PGPI, TPGI, TPGP and TPPG) based on glass microfluidic chip electrophoresis and laser-induced fluorescence detection is first described in here. The microfluidic chip electrophoresis and laser-induced fluorescence detection system consisted of a home-made glass "double-T" microchip and a simple LIF detector with excitation and emission wavelengths of 473 and 525 nm, respectively. Fluorescein isothiocyanate (FITC) was used as the precolumn derivatization reagent to label fluorophore on five ß-CMs, and the optimum conditions of FITC-derivatization reaction and MCE separation were investigated in detail. Under optimum conditions, five ß-CMs were completely separated and detected within 30 min with a detection limit of 18.7-75.1 nmol/L and an RSD (n=5) of 3.0-5.9%, respectively. The proposed method has been successfully used to detect ß-CMs in real cheese sample with a recovery of 89-109%, suggesting that our method is sensitive and reliable. These features, as well as its low cost, operation convenience, stability and reusability, make it a promising alternative to ß-CMs detection methods.

A signal-on electrochemiluminescence aptamer biosensor for the detection of ultratrace thrombin based on junction-probe.

A novel signal-on junction-probe electrogenerated chemiluminescence (ECL) aptamer biosensor has been developed for the detection of ultratrace thrombin based on a structure-switching ECL-quenching mechanism. The ECL aptamer biosensor comprises two main parts: an ECL substrate and an ECL intensity switch. The ECL substrate was made by modifying the complex of Au nanoparticle and ruthenium (II) tris-bipyridine (Ru(bpy)(3)(2+)-AuNPs) on the surface of gold electrode (GE), and the ECL intensity switch contains three probes designed according to the "junction-probe" strategy. The first probe is capture probe (Cp) which was functionalized with a thiol group at one end and covalently attached to Ru(bpy)(3)(2+)-AuNPs modified GE through S-Au bonding. The second probe is aptamer probe (Ap), which containing 15-base anti-thrombin DNA aptamer. The third one is ferrocene-labeled probe (Fp), which was functionalized with ferrocene tag at one end. We demonstrated that, in the absence of thrombin, Cp, Ap and Fp will hybridize to form a ternary "Y" junction structure and resulted in a quenching of ECL of Ru(bpy)(3)(2+). Whereas, in the presence of thrombin, the Ap prefers to form the G-quadruplex aptamer-thrombin complex and lead to an obvious recovery of ECL of Ru(bpy)(3)(2+), which provided a sensing platform for the detection of thrombin. Using this reusable sensing platform, a simple, rapid and selective signal-on ECL aptamer biosensor for the detection of thrombin with a detection limit of 8.0×10(-15) M has been developed. The success in the present biosensor served as a significant step towards the development of monitoring ultratrace thrombin in clinical detection.

Analysis of ultratrace triorganotin compounds in aquatic organisms by using capillary electrophoresis-inductively coupled plasma mass spectrometry.

A microwave-assisted extraction used to extract trace triorganotin from aquatic organisms and a sensitive analytical method for the determination of ultratrace triorganotin (namely trimethyltin, triethyltin, tripropyltin and tributyltin) with capillary electrophoresis-inductively coupled plasma mass spectrometry were firstly described in this study. The extraction method is simple, effective and can be used to extract trace triorganotin in aquatic organisms within several min. The analytical method has a much lower detection limit of 0.2-0.7 ng Sn/mL for triorganotin compounds, and can be used to determine trace triorganotin in aquatic organisms directly without any derivatization and preconcentration. Using above methods, we have successfully determined trimethyltin, triethyltin, tripropyltin and tributyltin in dried Mya arenaria Linnaeus and Corbicula fluminea within 17 min with a recovery of 93-104% and a RSD (relative standard deviation, n=6) of 2-5%. Our results showed that dried M. arenaria Linnaeus contained an extremely high tributyltin of 5.1 microg Sn/g dried weight, indicating that it may be a good biomarker for the organotin pollution in ocean.