A long lifetime ratiometrically luminescent tetracycline nanoprobe based on Ir(III) complex-doped and Eu3+-functionalized silicon nanoparticles.

Different from fluorescent dyes-doped or carbon materials-based ratiometric tetracycline nanoprobes, herein, a new Ir(III) complex-doped and europium(III) ion (Eu3+)-functionalized silicon nanoparticles (Ir(III)@SiNPs-Eu3+) with long luminescent lifetimes was firstly fabricated for selective detection of tetracycline (TC) in complex systems through time-resolved emission spectra (TRES) measurement. In the presence of TC, the red phosphorescence of Eu3+ is greatly enhanced by adsorption energy transfer emission (AETE) of TC, while the strong green luminescence of Ir(III)@SiNPs is quenched by the inner filtration effect (IFE) of TC. Based on these striking emission changes, Ir(III)@SiNPs-Eu3+ can sensitively detect TC in the linear range of 0.01-20 µM with a detection limit of 4.9 × 10-3 µM. Benefitting from the long lifetime of Ir(III)@SiNPs-Eu3+, the nanoprobe demonstrates excellent TC detection performance through TRES in high background system of 5 % human serum. Furthermore, the formed Ir(III)@SiNPs-Eu3+/TC complex can be used to sensitively recognize Hg2+ via a ratiometric luminescence mode. Notably, the cytotoxicity of Ir(III)@SiNPs-Eu3+ is very low and thus the sensitive monitoring the detection of Ir(III)@SiNPs-Eu3+ to TC and Hg2+ also works well in porcine renal cells, demonstrating high application potential in real samples.

A luminescent microRNA nanoprobe based on the target-triggered release of an iridium(III)-solvent complex from mesoporous silica nanoparticles.

A luminescent microRNA nanoprobe based on the target-triggered Ir(III)-solvent complex release has been fabricated. The complex is initially embedded into mesoporous silica nanoparticles (MSNs), and then is capped by single-stranded (ss) DNA. In the presence of the target microRNA, the ssDNA hybridize with the microRNA forming a rigid DNA/RNA heteroduplexes and leaving the surface of MSN. Thus, the capped Ir(III) solvent complex is released and re-coordinated with histidine (His) to form a new luminescent complex. The luminescence intensity of the nascent complex (with excitation/emission maxima at 340/570 nm) is positively correlated with the concentrations of the target microRNA in the range from 0.05 to 2 nM, and the detection limit of microRNA is estimated as 0.2 pM (S/N = 3). The ability of this nanoprobe to detect microRNA in cell extract further demonstrates its potential in practical application. Graphical abstractSchematic of a luminescent microRNA nanoprobe based on the target-triggered release of an Ir(III)-solvent complex from mesoporous silica nanoparticles.

γ-Aminobutyric acid-modified graphene oxide as a highly selective and low-toxic fluorescent nanoprobe for relay recognition of copper(II) and cysteine.

A sensitive and selective graphene oxide (GO)-based fluorescent nanoprobe has been developed for the relay recognition of Cu2+ and cysteine (Cys) by covalently grafting γ-aminobutyric acid (GABA) onto GO. The fluorescence of the probe (with excitation/emission maxima at 360/445 nm) is selectively quenched by Cu2+ via static fluorescence quenching. Fluorescence drops linearly as the concentration of Cu2+ is increased from 50 nM to 1.0 µM, and the detection limit for Cu2+ is calculated as 15 nM. By virtue of the strong interaction between Cys and Cu2+, the GO-GABA/Cu2+ complex can further sensitively recognize Cys in a "switch-on" mode. The linear range for Cys detection is from 50 nM to 1.0 µM, and the detection limit is 38 nM. The probe has low cytotoxicity, and it works well inside living cells, which is verified by the successful application in imaging of LLC-PK1 cells. Graphical abstract Gamma-Aminobutyric Acid (GABA) modified graphene oxide (GO) is a highly selective nanoprobe for the fluorometric relay recognition of Cu2+ and Cys.

A label-free and enzyme-free fluorescent aptasensor for sensitive detection of acetamiprid based on AT-rich dsDNA-templated copper nanoparticles.

A label-free and enzyme-free aptasensor for sensitive assay of acetamiprid has been established using AT-rich double-stranded (ds) DNA-templated copper nanoparticles (CuNPs) as fluorescent probe. In this work, two hairpin DNA, HP1 and HP2, were elaborately designed with AT-rich DNA sequences in their loops. The aptamer of acetamiprid was located at the 3'-terminal of HP1, which was caged in the stem of HP1. Upon the addition of acetamiprid, the aptamer could combine with acetamiprid to form a target/aptamer complex, and thus its free 5'-terminal was released. Subsequently, the protruded 3'-terminal of HP2 could hybridize with the free 5'-terminal of HP1 to form a stable AT-rich dsDNA. When it interacted with Cu2+ and ascorbic acid (AA), the AT-rich dsDNA/CuNPs were generated with strong fluorescence, offering a "switch-on" detection of acetamiprid. The developed strategy could high selectively detect acetamiprid at the concentration as low as 2.37 nM. Moreover, the possibility of this strategy for the food sample analysis was also investigated. The obtained results demonstrate that the developed strategy has a promising application potential for acetamiprid assay in food safety fields.

A label-free triplex-to-G-qadruplex molecular switch for sensitive fluorescent detection of acetamiprid.

The detection and monitoring of acetamiprid has drawn extensive attentions, due to their potential threat to human health. Herein, a simple, sensitive and label-free fluorescent assay based on triplex-to-G-qadruplex (TTGQ) molecular switch, was developed for the assay of acetamiprid in aqueous solution. In this detection, the proposed TTGQ molecule contained the acetamiprid aptamer sequence at its loop part and the triple-helix structure at its stem part. One single-stranded DNA grafted by two split G-rich DNA sequences at its two ends, participated in the assembly of the triplex part in TTGQ. In the presence of acetamiprid, TTGQ was dissociated, and the split G-rich DNA was released out to result in the fluorescent signal enhancement of a G-quadruplex's probe. By virtue of this TTGQ molecular switch, the proposed assay can sense acetamiprid at the concentration as low as 2.38 nM with excellent selectivity. Furthermore, the detection of acetamiprid in three kinds of foods extract demonstrated the high application potential of the detection platform in the field of food safety. Compared with the other reported strategies for acetamiprid assay, this triplex-to-G-qadruplex-based fluorescent molecular switch was just composed of two DNA probes without the labeling procedure, presenting a really simple and low-cost fluorescent detection for acetamiprid assay.

Label-free and enzyme-free fluorescent isocarbophos aptasensor based on MWCNTs and G-quadruplex.

A novel label-free and enzyme-free detection strategy has been developed for the fluorescent detection of isocarbophos (ICP) using multi-walled carbon nanotubes (MWCNTs) and G-quadruplex as the signal transducers. In this work, the split ICP aptamer were attached to a G-quadruplex motif at their respective terminals. In the presence of ICP, the split aptamers could undergo conformational change into a sandwiched-like ternary complex, which prevent them from adsorbing to the MWCNTs due to the increased steric hindrance. As a result, the fluorescence signal of the G-quadruplex probes N-methyl mesoporphyrin IX (NMM) was enhanced significantly. In the absence of ICP, the split aptamer only existed in the form of single-stranded DNA, which could be easily adsorbed by MWCNTs and resulted in a quenched fluorescence signal of NMM. The proposed strategy could selectively and sensitively detect ICP with a detection limit of 10 nM. Furthermore, we have also demonstrated the capability of this strategy in the detection of ICP in real samples from vegetable extract, indicating the potential application of this strategy in food safety issues.

Complete mitochondrial genome of a cavefish, Sinocyclocheilus anophthalmus (Cypriniformes: Cyprinidae).

In this work, we report the complete mitochondrial genome sequence of a cavefish Sinocyclocheilus anophthalmus. The total length of the mitogenome was 16,574 bp and its overall base composition was estimated to be 31.1% for A, 25.5% for T, 26.9% for C and 16.5% for G, indicating an A-T (56.6%)-rich feature in cavefish mitogenome. It contained the typical structure of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes and a non-coding control region (D-loop region). The arrangement of these genes was the same as that found in other fishes. All the protein initiation codons were ATG, except for COX1 starting with GTG. The complete mitochondrial genome sequence of the cavefish would provide new insight for cavefish's genetic mechanisms.

The complete mitochondrial genome of the Chinese indigenous dog.

In this study, the complete nucleotide sequence of Chinese indigenous dog mitochondrial genome was determined for the first time. Sequence analysis showed that the genome structure was in accordance with other dogs. It contained 22 tRNA genes, 2 ribosomal RNA genes, 13 protein-coding genes and 1 control region (D-loop region). The base composition was A (31.6%), G (14.2%), C (25.5%) and T (28.7%), so the percentage of A and T (60.3%) was higher than that of G and C. The complete mitochondrial genome sequence of the Chinese indigenous dog would shed a new light on further studies in dog domestication.

In vivo investigation of ceftiofur-loaded gelatin and PLGA microspheres in beagle dogs.

Drug delivery systems based on polymer microspheres have received considerable attention. Ceftiofur sodium and ceftiofur hydrochloride is widely used for the treatment of bacterial diseases in animals but the delivery in vivo has not been reported. In this paper, we report the synthesis of microspheres from gelatin and PLGA, two kinds of typical natural and artificial materials, for loading ceftiofur and the in vivo investigation of the pharmacokinetics in beagle dogs. By controlling the synthesis parameters, gelatin and PLGA microspheres with diameter between 5 and 35 microns were obtained. Assay procedures based on high performance liquid chromatography were evaluated and confirmed. The dogs were randomly divided into three groups, i.e., control group, gelatin group, and PLGA group and administrated via intravenous injection. Plasma concentrations of ceftiofur over time were measured and analyzed. Results indicate that the main kinetic parameters do not show significant difference for the gelatin group and control group, but the area under the curve, plasma half-life, apparent volume of distribution, and clearance ratio of PLGA group show significant difference from the gelatin group and the control group. The PLGA microspheres show a low area under the curve but long time release.

Preparation and characterization of lung-targeting ceftiofur-loaded gelatin microspheres.

BACKGROUND: Ceftiofur is an effective antibiotic against respiratory infections in livestock. However, ceftiofur concentration that is found in lungs after intravenous injection is not effective. Fortunately, ceftiofur-loaded gelatin microsphere (Cef-MS) enjoys advantages of lung-targeting and can achieve an effective concentration. However, no study has been reported on this modality of drug delivery. OBJECTIVE: We investigated the properties of this delivery modality--lung targeting ceftiofur-Cef-MSs. METHODS: We prepared Cef-MS and investigated drug loading, stability and release characteristics in vitro and studied tissue distribution patterns and potential lung injury in mice. RESULTS: Results showed that the average size and span value are 21.26 µm and 1.07, respectively. Drug loading and loading efficiency were 15.31 and 76.55%, respectively. Cef-MSs were stable in light, heat and humidity, except that agglutinative phenomenon was observed in 90% humidity after 10 days. Cef-MS presented a slower in vitro release pattern compared to ceftiofur. Cef-MS mainly concentrates in lungs after intravenous administration. Furthermore, histopathological studies showed that Cef-MS only induces mild and reversible lung injury and is biologically safe. CONCLUSION: Cef-MS is a promising alternative form with high lung-targeting properties for the treatment of respiratory infections.

Investigation of relations between absorption band positions and crystalline environment in Pb2+-doped alkali halides.

The relationships between sp energy levels (A, B and C bands) as well as the charge transfer band (D band) of Pb(2+)-doped alkali halides and the crystalline environment were thoroughly investigated by means of dielectric theory of chemical bonds for complex crystals. It is found that the coordination number of the central ion, the bond volume polarizability, and the fractional covalence of the chemical bond between the central ion and the nearest anion are the major factors influencing the positions of A, B, C and D bands of Pb(2+). Our model has successfully built links between the E(A), E(B), E(C) and E(D) of Pb(2+) and the environmental factor h. Results indicated that the energies of sp levels and the charge transfer band of Pb(2+) all decrease with increase of h. The h has a linear relationship with the sp energy levels, and an exponential relationship with the charge transfer band. The model calculation results are in good agreement with experimental data. The current model can serve as a prediction tool and can be applied to assign and reassign the A, B, C and D band positions of Pb(2+). The model predicts the positions of B, C and D bands of NaF:Pb(2+) at 7.516, 8.688 and 12.796 eV, respectively; the D band of CsCl:Pb(2+), CsBr:Pb(2+) and CsI:Pb(2+) at 6.633, 6.389 and 5.275 eV, respectively. We reassign the C band of Pb(2+) in NaBr as 5.276 eV but not the reported 5.636 eV, which is more reasonable to be ascribed to the charge transfer band.

2-[(2,6-Dichloro-benz-yl)amino]-N-(4-methyl-thia-zol-2-yl)acetamide.

In the title compound, C(13)H(13)Cl(2)N(3)OS, the thia-zole and benzene rings are roughly parallel to one another in two layers [dihedral angle = 5.08 (2)°] because the N-C-C-N-C chain that links the two rings is folded [N-C-C-N torsion angle = 12.0 (2)°] rather than fully extended. An intra-molecular N-H⋯N inter-action occurs. In the crystal, weak inter-molecular N-H⋯N and C-H⋯O inter-actions are present and π-π inter-actions are indicated by the short distances [3.507 (3)-3.665 (2) Å] between the centroids of the thia-zole and benzene rings.