Magnetic beads-based DNAzyme recognition and AuNPs-based enzymatic catalysis amplification for visual detection of trace uranyl ion in aqueous environment.

We herein developed a novel biosensor for the visual detection of trace uranyl ion (UO2(2+)) in aqueous environment with high sensitivity and specificity by using DNAzyme-functionalized magnetic beads (MBs) for UO2(2+) recognition and gold nano-particles (AuNPs)-based enzymatic catalysis oxidation of TMB (3,3',5,5'-tetramethylbenzidine sulfate) for signal generation. The utilization of MBs facilitates the magnetic separation and collection of sensing system from complex sample solution, which leads to more convenient experimental operation and more strong resistibility of the biosensor to the matrix of sample, and the utilization of AuNPs-based enzymatic catalysis amplification greatly improved the sensitivity of the biosensor. Compared with the previous DNAzyme-based UO2(2+) sensors, the proposed biosensor has outstanding advantages such as relative high sensitivity and specificity, operation convenience, low cost and more strong resistibility to the matrix of sample. It can be used to detect as low as 0.02 ppb (74 pM) of UO2(2+) in aqueous environment by only naked-eye observation and 1.89 ppt (7.0 pM) of UO2(2+) by UV-visible spectrophotometer with a recovery of 93-99% and a RSD ≤ 5.0% (n=6) within 3h. Especially, the visual detection limit of 0.02 ppb (74 pM) is much lower than the maximum allowable level of UO2(2+) (130 nM) in the drinking water defined by the U.S. Environmental Protection Agency (EPA), indicating that our method meets the requirement of rapid and on-site detection of UO2(2+) in the aqueous environment by only naked-eye observation.

A turn-off fluorescent biosensor for the rapid and sensitive detection of uranyl ion based on molybdenum disulfide nanosheets and specific DNAzyme.

A novel fluorescent biosensor for detecting uranyl ion (UO2(2+)) in aqueous environment has been developed based on the specific recognition of DNAzyme and the fluorescence quenching ability of molybdenum disulfide (MoS2) nanosheets. The DNAzyme contains a DNA enzyme strand and a 6-carboxylfluorescein (FAM)-labeled DNA substrate strand. We demonstrated that MoS2 nanosheets have low affinity to the substrate-enzyme complex DNAzyme. Whereas, in the presence of UO2(2+), UO2(2+) can specifically cleave DNAzyme to release FAM-labeled single-strand DNA and the released FAM-labeled single-strand DNA can be firmly adsorbed on the surface of MoS2 nanosheets, which resulted in an obvious decrease of fluorescence intensity. This provided a sensing platform for the rapid, simple and sensitive fluorescent detection of UO2(2+). By using the sensing platform, a sensitive and selective fluorescent method for the rapid detection of UO2(2+) has been developed. In comparison with previous biosensor, the proposed method has obvious analytical advantage such as relatively high sensitivity and good stability, short analytical time and low cost. It can be used to detect as low as 2.14 nM of UO2(2+) in aqueous environment with a recovery of 96-102% and a RSD<5% (n=6). The success of this study provides a promising alternative for the rapid and on-site detection of UO2(2+) in environmental monitoring.

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.

Ultra-sensitive quantification of lysozyme based on element chelate labeling and capillary electrophoresis-inductively coupled plasma mass spectrometry.

In this study, an ultra-sensitive method for the quantification of lysozyme based on the Gd(3+) diethylenetriamine-N,N,N',N″,N″-pentaacetic acid labeling and capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) was described. The Gd(3+)-tagged lysozyme was effectively separated by capillary electrophoresis (CE) and sensitively determined by inductively coupled plasma mass spectrometry (ICP-MS). Based on the gadolinium-tagging and CE-ICP-MS, the lysozyme was determined within 12 min with an extremely low detection limit of 3.89 attomole (3.89×10(-11) mol L(-1) for 100 nL of sample injection) and a RSD<6% (n=5). The proposed method has been successfully used to detect lysozyme in saliva samples with a recovery of 91-106%, suggesting that our method is sensitive and reliable. The success of the present method provides a new potential for the biological assays and sensitive detection of low-abundant proteins.

Speciation analysis of lead in marine animals by using capillary electrophoresis couple online with inductively coupled plasma mass spectrometry.

We herein reported a environment-friendly microwave-assisted extraction used to extract trace lead compounds from marine animals and a ultrasensitive method for the analysis of Pb²âº, trimethyl lead chloride (TML) and triethyl lead chloride (TEL) by using CE-ICP-MS. The extraction method is simple and has a high extracting efficiency. It can be used to completely extract both inorganic lead and organolead in marine animal samples without altering its species. The analytical method has a detection limit as low as 0.012-0.084 ng Pb/mL for Pb²âº, TML, and TEL, and can be used to determine ultratrace Pb²âº, TML, and TEL in marine animals directly without any preconcentration. With the help of above methods, we have successfully determined Pb²âº, TML, and TEL in clam and oyster tissue within 20 min with a RSD (n = 6) < 5% and a recovery of 91-104%. Our results showed that Pb²âº was the main species of lead in clam and oyster, and organolead (TML) was only found in oyster. The proposed method provides a realistic approach for the accurate evaluation of lead pollution in seafood.