Visual detection of trace copper ions based on copper-catalyzed reaction of ascorbic acid with oxygen.

A visual detection method for trace Cu(2+) in aqueous solutions using triangular silver nanoplates (abbreviated as TAgNPs) as the probe was developed. The method is based on that TAgNPs could be corroded in sodium thiosulfate (Na2S2O3) solutions. The absorption spectrum of TAgNPs solution changed when it is corroded by Na2S2O3. The reaction of oxygen with ascorbic acid (Vc) in the presence of a low concentration of Cu(2+) generates hydrogen peroxide that reacts with Na2S2O3, which leads the concentration of Na2S2O3 in the solution to be decreased. Therefore, the reaction between TAgNPs and the reacted mixture of Na2S2O3/Vc/Cu(2+) was prevented efficiently. When the Na2S2O3 concentration and reaction time are constant, the decrease in the concentration of Na2S2O3 is directly proportional to the Cu(2+) concentration. Thus, morphology, color, and maximum absorption wavelength of TAgNPs changed with the change of Cu(2+) concentration. The changed maximum absorption wavelength of TAgNPs (Δλ) is proportional to Cu(2+) concentration in the range from 7.5×10(-9) to 5.0×10(-7) M with a correlation coefficient of r=0.9956. Moreover, color change of TAgNP solution was observed clearly over a Cu(2+) concentration range from 7.5×10(-8) to 5.0×10(-7) M. This method has been used to detect the Cu(2+) content of a human hair sample, and the result is in agreement with that obtained by the atomic absorption spectroscopy (AAS) method.

Chitosan Influences the Expression of P-gp and Metabolism of Norfloxacin in Grass Carp.

The aim of this study was to investigate the relationship between the administration of chitosan (CTS), expression of permeability glycoprotein (P-gp), and the metabolism of norfloxacin (NOR) in Grass Carp Ctenopharyngodon idella. Fish were administrated with a single dose of either NOR, CTS, 1:5 NOR-CTS or 1:10 NOR-CTS. The P-gp expression was analyzed by immunohistochemistry and real time-PCR. The concentration of NOR was determined using HPLC. The mRNA and protein expression of P-gp in the fish intestine was significantly enhanced following a single dosage of 40 mg/kg NOR, and peak expression occurred at 3 h after drug administration (P < 0.05). A single dosage of both 1:5 NOR-CTS and 1:10 NOR-CTS reduced the intestinal P-gp expression to levels significantly lower than that from NOR alone (P < 0.05), but significantly higher than that from the control (P < 0.05). Interestingly, CTS alone also led to a slight decrease in P-gp expression. In addition, pharmacokinetic assays revealed a marked increase in area under the curve (AUC) of NOR with 1:5 and 1:10 NOR-CTS, by approximately 1.5-fold and threefold, respectively. Finally, the relative bioavailability of NOR after a single oral dosage of 1:5 and 1:10 NOR-CTS was enhanced to 148.02% and 304.98%, respectively. In this study, we demonstrated that the transmembrane glycoprotein P-gp regulates NOR metabolism in the intestine of Grass Carp, suggesting that NOR may be a direct substrate of P-gp. More importantly, we showed that CTS can inhibit P-gp expression in a dose-dependent manner and improve the relative bioavailability of NOR in this species.