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Herein, a fluorescence turn off-on nanosensor has been successfully developed using functionalized N-doped carbon dots (N-CDs) as the label-free sensing probe for the ultrasensitive detection of Cu 2+ ions first and then ciprofloxacin (CIP), one of the most commonly used antibiotics for disease control, in the presence of bipyridine. The homogeneous and narrowly distributed N-CDs with a mean size of 5.7 nm and a high quantum yield of 84% are fabricated via the hydrothermal method in the presence of citric acid and ethylenediamine as the carbon and nitrogen sources, respectively. The Cu 2+ ions serve as both analyte and fluorescence quenchers in the sensing platform of N-CDs, and a good linear response to Cu 2+ in the range of 0.01-0.35 μM with a limit of detection (LOD) of 0.076 nM is observed. Then, 0.35 μM Cu 2+ is used as the fluorescence quencher of N-CDs to build up the fluorescence turn off-on sensing probe for the detection of CIP using bipyridine (bipy) as the linker for CIP and Cu 2+ ions. The addition of CIP to the bipy-Cu@N-CD composites triggers the formation of CIP-bipy-Cu conjugate as well as the release of N-CDs, resulting in the recovery of fluorescence intensity after 6 min of incubation. The sensing probe exhibits a two-phase linear response to CIP in the concentration range of 0.05-1 and 1-50 μM with a LOD of 0.4 nM. In addition, the bipy-Cu@N-CD probe shows high sensitivity toward CIP over the 19 other interferences. Good recovery of 96-110% is also observed when 0.1-0.9 μM CIP is spiked into the real samples. Results obtained in this study clearly demonstrate a newly developed sensing platform with rapid detection of metal ions and antibiotics, which can open an avenue to develop highly efficient and robust sensing probes for the detection of metal ions, organic metabolites, and biomarkers in biological applications.

Monitoring toxic chlorine (Cl2) at the parts-per-billion (ppb) level is crucial for safe usage of this gas. Herein, ZnO, WO3, and SnO2 nanowire sensors were fabricated using an on-chip growth technique with chemical vapor deposition. The Cl2 gas-sensing characteristics of the fabricated sensors were systematically investigated. Results demonstrated that SnO2 nanowires exhibited higher sensitivity to Cl2 gas than ZnO and WO3 nanowires. The response (RCl2/Rair) of the SnO2 nanowire sensor to 50 ppb Cl2 at 50 °C was about 57. Hence, SnO2 nanowires can be an excellent sensing material for detecting Cl2 gas at the ppb level under low temperatures. Abnormal sensing characteristics were observed in the WO3 and SnO2 nanowire sensors at certain temperatures; in particular, the response level of these sensors to 5 ppm of Cl2 was lower than that to 2.5 ppm of Cl2. The sensing mechanism of the SnO2 nanowire sensor was also elucidated by determining Cl2 responses under N2 and dry air as carrier gases. We proved that the Cl2 molecule was first directly adsorbed on the metal oxide surface and was then substituted for pre-adsorbed oxygen, followed by lattice oxygen.

Cranberry ( Vaccinium macrocarpon ) is known to have a beneficial effect on several aspects of human health. Proanthocyanidins (PACs), the most abundant flavonoids extracted from red cranberry fruits, have been reported to possess antimicrobial, antiadhesion, antioxidant, and anti-inflammatory properties. Recent in vitro studies have shown that cranberry PACs may be potential therapeutic agents for the prevention and management of periodontitis, an inflammatory disease of bacterial origin affecting tooth-supporting tissues. After presenting an overview of cranberry phytochemicals and their potential for human health benefits, this review will focus on the effects of cranberry PACs on connective tissue breakdown and alveolar bone destruction, as well as their potential for controlling periodontal diseases. Possible mechanisms of action of cranberry PACs include the inhibition of (i) bacterial and host-derived proteolytic enzymes, (ii) host inflammatory response, and (iii) osteoclast differentiation and activity. Given that cranberry PACs have shown interesting properties in in vitro studies, clinical trials are warranted to better evaluate the potential of these molecules for controlling periodontal diseases.

The enantiomeric composition of chiral PCB congeners was determined in Twelvemile Creek (Clemson, SC) to examine potential mechanisms of biotransformation in a stream food web. We measured enantiomeric fractions (EFs) of six PCB atropisomers (PCBs 84, 91, 95, 136, 149, and 174) in surface sediment, fine benthic organic matter (FBOM), coarse particulate organic matter (CPOM), periphyton, Asian clam, mayflies, yellowfin shiner, and semipermeable membrane devices (SPMDs) using gas chromatography (GC-ECD). Nonracemic EFs of PCBs 91, 95, 136, and 149 were measured in almost all samples. Enantiomeric compositions of PCBs 84 and 174 were infrequently detected with racemic EFs measured in samples except for a nonracemic EF of PCB 84 in clams. Nonracemic EFs of PCBs 91, 136, and 149 in SPMDs may be due to desorption of nonracemic residues from FBOM. EFs for some atropisomers were significantly different among FBOM, CPOM, and periphyton, suggesting that their microbial communities have different biotransformation processes. Nonracemic EFs in clams and fish suggest both in vivo biotransformation and uptake of nonracemic residues from their food sources. Longitudinal variability in EFs was generally low among congeners observed in matrices.