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Nucleic acid nanoswitches have a status that cannot be ignored in the field of biosensing due to the excellent biocompatibility and flexibility of design. In our current research, we have constructed a new electrochemical platform based on self-assembled pH-sensitive continuous circular DNA nanoswitch for miRNA-21 detection. We elaborately designed an inside ring probe (IRP) which could form a circle when complemented with an outside ring probe (ORP). Under the weakly acidic condition, IRPs and ORPs are self-assembled into continuous annular DNA, meanwhile, the nanoswitch is activated. However, if it is not a weakly acidic environment with a pH equal to 6, these circles are separated and the nanoswitch cannot be triggered. Therefore, the biosensor doesn’t work. Only when the pH is 6, can the nanoswitch be activated. Consequently, a large number of RuHex will accumulate on the continuous annular DNA, which leads to highly sensitive detection of miRNA-21, with concentration ranged from 10–15 to 10-8 M and limit of detection down to 0.84 fM. More importantly, this nanoswitch-based biosensor can directly detect the target microRNA in human serum without pretreatment. Therefore, the proposed novel electrochemical DNA nanoswitch will have broad application prospects in biomarker detection and clinical diagnosis.

Three new mononuclear copper(II) complexes, [Cu(L2)](2+) (1), [Cu(acac)(L)](+) (2), and [Cu(acac-Cl)(L)](+) (3) (L = 2-(4-pyridine)oxazo[4,5-f]1,10-phenanthroline (4-PDOP); acac = acetylacetone; acac-Cl = 3-chloroacetylacetone), have been synthesized and characterized by elemental analysis, high resolution mass spectrometry (Q-TOF), and IR spectroscopy. Two of the complexes were structurally characterized by single-crystal X-ray diffraction techniques. Their interactions with DNA were studied by UV-vis absorption and emission spectra, viscosity, thermal melting, DNA unwinding assay and CD spectroscopy. The nucleolytic cleavage activity of the compounds was carried out on double stranded pBR322 circular plasmid DNA by using a gel electrophoresis experiment in the presence and absence of an oxidant (H2O2). Active oxygen intermediates such as hydroxyl radicals and hydrogen peroxide generated in the presence of L and complexes 1-3 may act as active species for the DNA scission. The cytotoxicity of the complexes against HepG2 cancer cells was also studied.

The electrogenerated chemiluminescence (ECL) of two water-insoluble iridium(III) complexes (pq)2Ir(acac)(pq = 2-phenyl quinolone anion, acac = acetyl acetonate) and (ppy)2Ir(acac)(ppy = 2-phenylpyridine anion) in carbon nanotube (CNT)/Nafion composite films was investigated at a glassy carbon (GC) electrode. CNT and Nafion play significant roles in the iridium(III) complexes immobilization. The excellent chemical stability and electrical conductivity of CNT promote electron transfer. The experimental conditions, such as potential, pH, concentrations of CNT and various coreactants were investigated. The iridium(III) complexes modified electrode had good stability and reproducibility. In our work, the (pq)2Ir(acac)/DBAE (2-(dibutylamino)ethanol) system was used to detect the codeine, one of the many narcotics, and the detection limit was 0.05 μM (S/N = 3). This method enabled the two water-insoluble iridium(III) complexes to be used for the determination of the analyte in aqueous solution.

The photodynamic activities against Candida albicans have been evaluated for seven silicon (IV) phthalocyanines modified axially by different functional groups. The effects of the axial substituents on the spectroscopic, photochemical, cellular uptake, and photobiological properties of these silicon phthlaocyanines have been revealed. The dicationic compounds 2 and 4 , having two quaternary ammonium groups at the axial positions, exhibit the highest antifungal photocytotoxicity with an IC 90 of 61–66 μM, which can be ascribed to their high singlet oxygen quantum yield, non-aggregation nature, effective cellular uptake, and intracellular distribution pattern (localizing preferentially in the mitochondria). By comparison, compounds 2 and 4 show a higher photodynamic inactivation of C. albicans cells than methylene blue (MB), a known antifungal photosensitizer. The IC 90 values against C. albicans for 2 and 4 are ca. 8 times lower than that for MB. These results indicate that the dicationic silicon phthalocyanines 2 and 4 are interesting candidates as antifungal photosensitizers for future studies.

A sequential extraction procedure followed by HPLC–ICP-MS analysis was developed for the speciation and quantization of arsenic species in dry seafood products (DSPs). The extraction process involved three major steps, which produced respectively three As fractions: non-polar (Asnonpolar), polar (Aspolar) and inorganic arsenic species (Asinorganic). The extraction efficiency (EE%) is in the range of 87–115%. Asnonpolar is 0.6–10.2% of total arsenic in DSPs, which is served as the index of level of arsenolipid. For Aspolar and Asinorganic, a hyphenated HPLC–ICP-MS technique was established for the separation and quantification of six arsenic species including arsenobetaine (AsB), arsenocholine (AsC), arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The results indicate that AsB and AsV are the two dominate species in DSPs, while all other species are present in relatively low concentrations. The recovery efficiency of 77–02.8% could be obtained with spike recovery test in this two-steps extraction.

The effects of direct sampling and three digestion methods were investigated on the determination of arsenic in Chang liver hepatocytes after ultrasonic disintegration were investigated. The results showed that the efficiency of microwave digestion and obturator digestion was better than cold digestion and direct sampling. The day precision (present as RSD) of microwave digestion and obturator digestion were 2.1% and 1.2% the inter-day precision were 1.2% and 2.0%, respectively. The spike recovery for the total As in the sample is 95.7% - 108.1%. The As detection limits with these four sample treatment methods (including direct sampling) were 0.74 - 0.93 mu g/L. In addition, arsenic speciation in Chang liver hepatocytes was also analyzed using the hyphenated technique of high performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry. The experimental results indicated that dimethylarsinic acid (DMA) and an intermediate metabolite of DMA were found lit Chang liver hepatocytes besides inorganic arsenic (As(III) and As(V)).