A novel approach to assemble an H2O2 amperometric biosensor was introduced. The biosensor was constructed by entrapping horseradish peroxidase (HRP) labeled nano‐scaled particulate gold (nano‐Au) (HRP‐nano‐Au electrostatic composite) in a new silica sol‐gel/alginate hybrid film using glassy carbon electrode as based electrode. This suggested strategy fully merged the merits of sol‐gel derived inorganic‐organic composite film and the nano‐Au intermediator. The silica sol‐gel/alginate hybrid material can improve the properties of conventional sol‐gel material and effectively prevent cracking of film. The entrapment of HRP in the form of HRP‐nano‐Au can not only factually prevent the leaking of enzyme out of the film but also provide a favorable microenvironment for HRP. With hydroquinone as an electron mediator, the proposed HRP electrode exhibited good catalytic activity for the reduction of H2O2. The parameters affecting both the qualities of sol‐gel/alginate hybrid film and the biosensor response were optimized. The biosensor exhibited high sensitivity of 0.40 Al mol−1 cm−2 for H2O2 over a wide linear range of concentration from 1.22×10−5 to 1.46×10−3 mol L−1, rapid response of <5 s and a detection limit of 0.61×10−6 mol L−1. The enzyme electrode has remarkable stability and retained 86% of its initial activity after 45 days of storage in 0.1 mol L−1 Tris‐HCl buffer solutions at pH 7.
A near-infrared fluorescent probe NIR-Hg, for the detection of Hg2+ ion, has been synthesized directly by condensing Changsha dye with 4-Phenyl-3-thiosemicarbazide and the structure has fully characterized by (HNMR)-H-1, (CNMR)-C-13, and ESI-MS. The probe has been designed on the basis of the reaction that Hg2+ ion promotes thiosemicarbazide to oxazole in aqueous media and had been induced to produce turn-on fluorescence via an irreversible spirolactam ring-opening process. The probe NIR-Hg has exhibited fast response (1 min), high sensitivity with 44-fold fluorescence intensity enhancement under six equivalent amounts of Hg2+ added, high selectivity over other related metal ions and a low detection limit of 5.8 x 10(-8) M in the phosphate buffer. The linear response range covers the concentration of Hg2+ from 5 x 10(-7) to 5 x 10(-6) M. In addition, the probe has good cell-membrane permeability, which is suitable for fluorescence imaging for Hg2+ in living cells and in vivo mice.
The interactions of meso-tetraphenylporphyrin (TPP), meso-tetraphenylporphyrin cobalt(ii) (CoTPP) and protein in the presence of a cyclodextrin derivative, heptakis(2,6-di-O-n-octyl)-beta-cyclodextrin (Oc-beta-CD), have been investigated. In the presence of Oc-beta-CD, significant increase of TPP fluorescence was realized, but the increased fluorescence was quenched by CoTPP. To further investigate the fluorescence-quenched system and explore its potential application in bioanalysis, a strategy has been devised to restore the quenching fluorescence of TPP upon interacting with protein. The restoration of TPP fluorescence in the present system is fast and accomplished upon interaction with bovine serum albumin (BSA) or human serum albumin (HSA). On the basis of the spectroscopic measurement and excited state fluorescence lifetime, the mechanism of TPP fluorescence quenching is attributed to formation of a ground-state complex of TPP and CoTPP, and the fluorescence restoration is attributed to the binding of CoTPP with the protein molecule which destroys the aggregate, releasing the free base porphyrin. With optimized conditions, the calibration equations are linear from 0.80 to 75.4 microg mL(-1) BSA and from 3.20 to 93.2 microg mL(-1) HSA. The corresponding detection limits are 0.32 microg mL(-1) for BSA and 1.06 microg mL(-1) for HSA, respectively. The method was used for the direct assay of HSA content in human serum. The result is comparable to that obtained by another method. The recovery from BSA in synthetic sample is also satisfactory.
A novel water-compatible microporous and mesoporous hyper-cross-linked resin modified with phenolic hydroxyl group (named as GQ-03) was synthesized to remove aniline in aqueous solution as compared with XAD-4. The maximum adsorption capacity of GQ-03 emerged at the molecular state for both aniline and p-cresol while the pH dependency trend of aniline adsorbed onto XAD-4 was accordant with the dissociation curve of aniline. The ionic strength influenced the adsorption obviously. The pseudo-first-order rate equation could describe the adsorption process of aniline onto GQ-03 in two stages while this equation could characterize the entire adsorption process of XAD-4. The adsorption isotherms could be correlated to the Freundlich model, higher K-F and n values for GQ-03 than XAD-4. The breakthrough capacity and the total adsorption capacity of GQ-03 and XAD-4 was up to 47.2 mg mL(-1) and 28.3 mg mL(-1), 271.7 mg mL(-1) and 115.6 mg mL(-1), respectively. The size matching between the pore diameter of GQ-03 and the molecular size of aniline, and hydrogen bonding between GQ-03 and aniline resulted in the larger adsorption capacity. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.
Cobalt hexacyanoferrate (CoHCF) film was formed on multiwalled carbon nanotubes (MWNTs) modified gold electrode by electrodeposition from 0.5 M KCl solution containing CoCl2 and K3Fe(CN)6. The electrochemical behavior and the electrocatalytic property of the modified electrode were investigated. Compared with CoHCF/gold electrode, the CoHCF/MWNTs/gold electrode exhibits greatly improved stability and enhanced electrocatalytic activity toward the oxidation of thiosulfate. A linear range from 5.0×10−5 to 6.5×10−3 M (r=0.9990) for thiosulfate detection at the CoHCF/MWNTs/gold electrode was obtained, with a detection limit of 2.0×10−5 M (S/N=3).
[Yang, Ronghua] Hunan Univ, State Key Lab Chemo Biosensing & Chemometr, Changsha 410082, Hunan, Peoples R China.
We report that the hydrogen-bonding pattern in a molecular beacon can be replaced by metal-dependent pairs of Hg(2+) and DNA thymine ( T) bases. A molecular beacon based on T-Hg(2+)-T exhibits a lower background signal and higher thermostability than regular molecular beacons.
Chinese Chemical Letters,2012年23(1):123-126 ISSN：1001-8417
Xiao, Gu Qing
[Long Li Ping; Wang Jiao Liang; Xiao Gu Qing] Hunan City Univ, Coll Chem & Environm Engn, Yiyang 413000, Peoples R China.
[Xiao, Gu Qing] Hunan City Univ, Coll Chem & Environm Engn, Yiyang 413000, Peoples R China.
A novel p-acetaminophen resin (named as GQ-1) was synthesized with chloromethylated polystyrene and p-acetaminophen. It can be used without any wetting process. The objective of this work was to study the adsorption performances for vanillin onto GQ-1 with two kinds of the hydrogen bond site of acetamino group and hydroxyl group. The results showed that the adsorption property of vanillin onto GQ-1 was superior to XAD-4, H103, NDA150, and NDA88. The adsorption capacity of vanillin onto GQ-1 is not greatly discrepant until the solution pH is higher than 5.31. The saturated adsorption quantity of vanillin was up to 141.32 mg/mL (wet resin) according to the dynamic adsorption and desorption experiments at 293 K. The resin could be regenerated by 7 BV ethanol.
Cyanine has been widely utilized as a near infrared (NIR) fluorophore for detection of glutathione (GSH). However, the excitation of most of the reported cyanine-based probes was less than 800 nm, which inevitably induce biological background absorption and lower the sensitivity, limiting their use for detection of GSH in blood samples. To address this issue, here, a heptamethine cyanine probe (DNIR), with a NIR excitation wavelength at 804 nm and a NIR emission wavelength at 832 nm, is employed for the detection of GSH and its oxidized form (GSSG) in blood. The probe displays excellent selectivity for GSH over GSSG and other amino acids, and rapid response to GSH, in particular a good property for indirect detection of GSSG in the presence of enzyme glutathione reductase and the reducing agent nicotinamideadenine dinucleotide phosphate, without further separation prior to fluorescent measurement. To the best of our knowledge, this is the first attempt to explore NIR fluorescent approach for the simultaneous assay of GSH and GSSG in blood. As such, we expect that our fluorescence sensors with both NIR excitation and NIR emission make this strategy suitable for the application in complex physiological systems.