Smart Target-Initiated Catalytic DNA Junction Circuit Amplification Strategy for the Ultrasensitive Electrochemiluminescence Detection of MicroRNA.

One of the highly attractive research directions in the electrochemiluminescence (ECL) field is how to regulate and improve ECL efficiency. Quantum dots (QDs) are highly promising ECL materials due to their adjustable luminescence size and strong luminous efficiency. MoS2 NSs@QDs, an ECL emitter, is synthesized via hydrothermal methods, and its ECL mechanism is investigated using cyclic voltammetry and ECL-potential curves. Then, a stable and vertical attachment of a triplex DNA (tsDNA) probe to the MoS2 nanosheets (NSs) is applied to the electrode. Next, an innovative ECL sensor is courageously empoldered for precise and ultrasensitive detection of target miRNA-199a through the agency of ECL-resonance energy transfer (RET) strategy and a dextrous target-initiated catalytic three-arm DNA junction assembly (CTDJA) based on a toehold strand displacement reaction (TSDR) signal amplification approach. Impressively, the ingenious system not only precisely regulates the distance between energy donor-acceptor pairs leave energy less loss and more ECL-RET efficiency, but also simplifies the operational procedure and verifies the feasibility of this self-assembly process without human intervention. This study can expand MoS2 NSs@QDs utilization in ECL biosensing applications, and the proposed nucleic acid amplification strategy can become a miracle cure for ultrasensitive detecting diverse biomarkers, which helps researchers to better study the tumor mechanism, thereby unambiguously increasing cancer cure rates and reducing the risk of recurrence.

Quantitative determination of erythromycylamine in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study of dirithromycin.

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of erythromycylamine in human plasma was developed and validated. Erythromycylamine in plasma (0.2 mL) was extracted with ethyl acetate, the organic phase was transferred to another clear 1.5 mL Eppendorf tube and evaporated to dryness under gentle nitrogen stream at 45 degrees C, and the residue was dissolved in 100 microL of mobile phase. The samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150 mm x 2.1 mm I.D., 5 microm). A mobile phase containing 10 mM of ammonium acetate (pH = 6.4)-acetonitrile-methanol (50:10:40, v/v/v) was used isocratically eluting at a flow rate of 0.2 mL/min. Erythromycylamine and its internal standard (IS), midecamycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 4.5 to 720 ng/mL with r = 0.9997. The limit of quantification for erythromycylamine in plasma was 4.5 ng/mL with good accuracy and precision. The mean extraction recovery of the method was higher than 75.1% and 72.7% for erythromycylamine and IS, respectively. The intra-day and inter-day precision ranged from 5.2% to 6.4% and 5.6-9.3% (relative standard deviation, RSD), respectively. The established method has been successfully applied to a bioequivalence study of two dirithromycin formulations for 18 healthy volunteers.

[Evaluation of Performance of an Aminated Rosin-based Resin for Adsorption of Norfloxacin from Aqueous Solutions].

An aminated rosin-based resin (ARBR) was synthesized as a novel environmentally-friendly adsorbent for removal of Norfloxacin (NOR) from aqueous solutions. Its features were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and surface area measurements (BET). The effects of resin dosage, pH, and ionic strength on the ARBR adsorption properties of NOR were investigated by batch experiments. Results showed that the NOR adsorption amounts increased with pH in the range from 2.0 to 6.0, but decreased at higher pH (8-10). The adsorption process of NOR followed a pseudo-second rate model and could be fitted to the Langmuir isotherm, with calculated maximum monolayer adsorption capacity of 30.29 mg·g-1 at pH 6.0 and 20℃. Thermodynamic calculations showed that the adsorption of NOR was a spontaneous and endothermic process and could be attributed to a combination of electrostatic interactions and hydrogen bonding. Furthermore, the adsorbed NOR on ARBR could be efficiently desorbed by 0.1 mol·L-1 HCl to regenerate the resin. After five adsorption-desorption recycles, ARBR had a stable adsorption performance and could be recycled. The adsorption performance is better than that of various commercial resins, and these research results contribute to the development of applications of rosin derivatives and their utilization in the environmental control of micro pollutants.

Ru(bpy)32+-Silica@Poly-L-lysine-Au as labels for electrochemiluminescence lysozyme aptasensor based on 3D graphene.

In this work, the feasibility of a novel sensitive electrochemiluminescence aptasensor for the detection of lysozyme using Ru(bpy)32+-Silica@Poly-L-lysine-Au (RuSiNPs@PLL-Au) nanocomposites labeling as an indicator was demonstrated. The substrate electrode of the aptasensor was prepared by depositing gold nanoparticles (AuNPs) on 3D graphene-modified electrode. The lysozyme binding aptamer (LBA) was attached to the 3D graphene/AuNPs electrode through gold-thiol affinity, hybridized with a complementary single-strand DNA (CDNA) of the lysozyme aptamer labeled by RuSiNPs@PLL-Au as an electrochemiluminescence intensity amplifier. Thanks to the synergistic amplification of the 3D graphene, the AuNPs and RuSiNPs@PLL-Au NPs linked to Ru(bpy)32+-ECL further enhanced the ECL intensity of the aptasensor. In presence of lysozyme, the CDNA segment of the self-assembled duplex was displaced by the lysozyme, resulting in decreased electrochemiluminescence signal. Under the optimized conditions, the decrease in electrochemiluminescence intensity varied proportionally with the logarithmic concentration of the lysozyme from 2.25 × 10-12 to 5.0 × 10-8 mol L-1, and the detection limit was estimated to 7.5 × 10-13 mol L-1. The aptasensor was further tested in real samples and found reliable for the detection of lysozyme, thus holding great potential application in food safety researches and bioassay analysis.

Quantitative determination of azithromycin in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study.

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2mL) was extracted with methyl tert-butyl ether-hexane (50:50, v/v), organic phase was transferred to another clear 1.5mL Eppendorf tube and evaporated to dryness at 40 degrees C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150mmx2.1mm i.d., 5microm), together with a mobile phase containing of 20mM ammonium acetate (pH 5.2)-acetonitrile-methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000ng/mL with r=0.9977. The limit of quantification for azithromycin in plasma was 2ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.

[Kinetics of monochloramine decay in disinfection of drinking water].

The model of second-order reaction kinetics has been used to fit the monochloramine decay in water samples by nonlinear imitation. Several factors were investigated, including pH, temperature, carbonate, bromide, iodide concentrations and natural organic matters in this system. The results showed that pH value was an important factor on the monochloramine decay rate, especially when pH was below 7.0. Temperature and carbonate levels also had obvious effect on the monochloramine decay. Co-existence of bromide anions had different impact under different pH values. At pH 6.60, monochloramine decay rate tended to decrease dramatically with the increment of bromide levels. However, when pH was above 7.60, 0.1 mg/L of bromide hardly affected the decay rate of mononchloramine. Co-existence of iodide showed stronger effect on the decline rate of monochloramine than that of bromide. It was demonstrated that the second-order kinetic model could fit well the experimental results of monochloramine decay reaction under the conditions of bromide or iodide co-existence. The results of this study will be of benefit to the theory and technology of drinking water disinfection, especially for the reduction of DBPs and the control of disinfectant dosages in the area of coastland and estuary.