Amperometric glucose biosensor based on a gold nanorods/cellulose acetate composite film as immobilization matrix

We report on the utilization of gold nanorods to create a highly responsive glucose biosensor. The feasibility of an amperometric glucose biosensor based on immobilization of glucose oxidase (GOx) in gold nanorod is investigated. GOx is simply mixed with gold nanorods and cross-linked with a cellulose acetate (CA) medium by glutaraldehyde. The adsorption of GOx on the gold nanorods is confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Circular dichroism (CD) and UV-spectrum results show that the activity of GOx was preserved after conjugating with gold nanorods. The current response of modified electrode is 10 times higher than that of without gold nanorods. Under optimal conditions, the biosensor shows high sensitivity (8.4 μA cm⁻² mM⁻¹), low detection limit (2 × 10⁻⁵ M), good storage stability and high affinity to glucose (). A linear calibration plot is obtained in the wide concentration range from 3 × 10⁻⁵ to 2.2 × 10⁻³ M.     

Development of amperometric glucose biosensor through immobilizing enzyme in a Pt nanoparticles/mesoporous carbon matrix

Pt nanoparticles were deposited on mesoporous carbon material CMK-3. Glucose oxidase (GOx) was immobilized in the resulting Pt nanoparticles/mesoporous carbon (Pt/CMK-3) matrix, and then the mixture was cast on a glassy carbon electrode (GCE) using gelatin as a binder. The glucose biosensor exhibited excellent current response to glucose after cross-linking with glutaraldehyde. At 0.6V (vs. SCE) the response current was linear to glucose concentration in the range of 0.04-12.2mM. The response time (time for achieving 95% of the maximum current) was 15s and the detection limit (S/N=3) was 1 microM. The Michaelis-Menten constant (K(m)(app)) and the maximum current density (i(max)) were 10.8 mM and 908 microAcm(-2), respectively. The activation energy of the enzymatic reaction was estimated to be 22.54 kJ mol(-1). The biosensor showed good stability. It achieved the maximum response current at about 52 degrees C and retained 95.1% of its initial response current after being stored for 30 days. In addition, some fabrication and operation parameters for the biosensor were optimized in this work. The biosensor was used to monitor the glucose levels of serum samples after being covered with an extra Nafion film to improve its anti-interferent ability and satisfied results were obtained.     

A new colorimetric and fluorescent chemosensor based on thiacalix[4]arene for fluoride ions

A new thiacalix[4]arene based fluorescent chemosensor thiacalix[4]arene-N-(quinolin-8-yl)acetamide (TCAN8QA) has been synthesized. TCAN8QA has been found to exhibit highly selective behavior for F⁻ ions among all other anions, that is, Cl⁻, Br⁻, I⁻, PO₄⁻³, OH⁻, H₂PO₄⁻, and CH₃COO⁻ in the absorption spectra as well as in the emission spectra. Red shift and quenching in emission spectra constituting the signature for fluoride detection are due to photoinduced charge transfer (PCT) which can be attributed to deprotonation of acidic NH proton in the presence of fluoride ions.     

F-Induced ‘turn-on’ fluorescent chemosensor based on 1,3-alt thiacalix[4]arene

A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in ‘off-state’ showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to ‘on-state’. The receptor shows pronounced selectivity for fluoride ions. In THF, the presence of F⁻ ions induces the formation of a 1:1 (G:H) complex.     

Determination of Hg(II) ions in water samples by a novel Hg(II) sensor,based on calix[4]arene derivative

A PVC membrane electrode for Hg(II) ions, based on a new cone shaped calix[4]arene (L) as a suitable ionophore was constructed. The sensor exhibits a linear dynamic in the range of 1.0 × 10^?6–1.0 × 10^?1 M, with a Nernstian slope of 29.4 ± 0.4 mV decade^?1, and a detection limit of 4.0 × 10^?7 M. The response time is quick (less than 10 s), it can be used in the pH range of 1.5–4, and the electrode response and selectivity remained almost unchanged for about 2 months. The sensor revealed comparatively good selectivity with respect to most alkali, alkaline earth, and some transition and heavy metal ions. It was successfully employed as an indicator electrode in the potentiometric titration of Hg²⁺ ions with potassium iodide, and the direct determination of mercury content of amalgam alloy and water samples.     

Comparative study on the transition metal complexes of a novel thiacalix[4]arene derivative

A comparative study on Zn²⁺ and Cu²⁺ complexes of the novel compound 5,11,17,23-tetra-tert-butyl-25,27-bis{[4-(methoxycarbonyl)phenyl]methoxy}-2,8,14,20-tetrathiacalix[4]arene, that possesses potential as a core unit for the construction of molecular receptors, is presented using semiempirical AM1 calculation. The possible structures of each metal complex and their corresponding energetic data are compared with the parent 5,11,17,23-tetra-tert-butyl-2,8,14,20-tetrathiacalix[4]arene. The complexation ability of both thiacalix[4]arenes towards the two metal ions is discussed on the basis of binding energies. Both thiacalix[4]arene 1:1 complexes show higher complexation ability towards Cu²⁺. However, 5,11,17,23-tetra-tert-butyl-25,27-bis{[4-(methoxycarbonyl)phenyl]methoxy}-2,8,14,20-tetrathiacalix[4]arene presents lower complexation ability when compared with the 5,11,17,23-tetra-tert-butyl-2,8,14,20-tetrathiacalix[4]arene. The results of liquid–liquid extraction experiments of the thiacalix[4]arenes are in good agreement with the theoretical calculations.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

新型杯[4]芳烃衍生物的合成及其氨基酸萃取性能

杯[4]-1,3-二乙酸乙酯衍生物(1)与水合肼反应生成杯[4]芳烃酰肼衍生物(2),化合物(2)与异硫氰酸苯酯反应得到含酰胺和硫脲单元的新型杯[4]芳烃衍生物(3).总产率达70%.系列氨基酸萃取实验表明化合物(3)对异亮氨酸有较好的选择性萃取能力.     

Biotinylated alginate immobilization matrix in the construction of an amperometric biosensor: application for the determination of glucose

The use of biotinylated alginate as an immobilization matrix of enzymes on the surface of the amperometric transducer is described herein. The model used is that of the well-established glucose detection. Several types of immobilization protocols were tested. In the exception of one protocol, biotin labeled glucose oxidase was shown to first require conjugation with avidin, before its immobilization onto a biotin-alginate gel matrix. The response of the biosensors to incremental additions of glucose, was measured by potentiostating the modified electrodes at 0.6 V/SCE. The permeability of the modified electrodes was thereafter measured by using rotating disk electrode (RDE) voltammetry with ferrocenemonocarboxylic acid as the electroactive probe.     

Click synthesis and dye extraction properties of novel thiacalix[4]arene derivatives with triazolyl and hydrogen bonding groups

Using a click reaction between alkynylthiacalix[4]arene and ethyl 2-azidoacetate followed by an ammonolysis with ethanolamine,leucinol and hydrazine hydrate,respectively,three novel thiacalix [4]arene derivatives 4,5 and 6 with triazolyl and hydrogen bonding groups(NH and OH) were synthesized in high yields.They exhibited excellent extraction capability for six anionic and cationic dyes.The flexible cavity,π-triazole rings and hydrogen bonding groups all play crucial roles in dye complexation.     

Chromatographic molecular recognition for catechol-related compounds using thiacalix[4]arene as an effective selector

Thiacalix[4]arene (5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxy-2,8,14,20-tetrathiacalix[4]arene) is an amphiphilic molecule comprising four p-tert-butylphenol-like groups ortho-linked by single sulfur atoms. This molecule has a high electron density area owing to the close proximity of the hydroxyl groups and sulfur atoms. We studied the applicability of this interesting compound as a selector for high-performance liquid chromatography (HPLC) thereby presumably exploiting this feature. Firstly, uniformly sized polymer particles were prepared by using a multi-step swelling and polymerization method with ethylene glycol dimethacrylate (EDMA) as a cross-linker. Methacrylic acid (MAA) was introduced onto the surface of the resulting polymer particles through a new modification method. Thiacalix[4]arene was chemically bonded through the MAA group by using 1,4-dibromobutane as a spacer to reduce steric hindrance around the MAA and the polymer particle itself. The performance of the prepared polymer-based thiacalix[4]arene-modified stationary phase was evaluated with HPLC. Specific chromatographic retention behavior was observed for catechol relative to positional isomers of xylene, cresol, and benzene-diol. Catecholamine and catechol showed specific chromatographic retention behavior.     

Bifunctional fluorescent thiacalix[4]arene based chemosensor for Cu and F ions

A new thiacalix[4]arene based fluorescent sensor bearing two dansyl groups has been synthesized in cone conformation. In CH₃CN:CH₂Cl₂ (1:1), the presence of Cu (II) induces the formation of a 1:1 metal:ligand complex, which exhibits increasing emission at 433 nm at the expense of the fluorescent emission of 1 centered at 504 nm. The detection limit of the sensor for Cu²⁺ is 2×10⁻⁷ mol L⁻¹. For anion sensing, 1 shows a high selectivity for fluoride ions over other anions tested.     

Cu and CN-selective fluorogenic sensors based on pyrene-appended thiacalix[4]arenes

Two new fluorescent sensors 1 and 2 based on thiacalix[4]arenes bearing pyrene moieties have been synthesized in cone conformation. The binding abilities of these sensors towards different cations such as lithium, sodium, potassium, nickel, cadmium, copper, zinc, lead, silver, mercury and anions like fluoride, chloride, bromide, iodide, cyanide, acetate, hydrogen sulfate and nitrate have been examined by UV-vis and fluorescence spectroscopies. These receptors show pronounced selectivity for copper and cyanide ions. In CH₂Cl₂/CH₃CN (1:1), the presence of Cu(II) ion induces the formation of 1:1 (H/G) complex with receptor 1 and 1:2 (H/G) complex with receptor 2. The cyanide ions form a 1:1 (H/G) complex with both receptors.     

Polymeric membrane sodium-selective electrodes based on calix[4]arene ionophores

Six kinds of tetra alkylester type calix[4]arene derivatives, (R₁=R₂=CH₃1, C₂H₅2, C₃H₇3,n-C₄H₉4,t-C₄H₉5,n-C₁₀H₂₁6), a diethyl-didecyl mixed ester type (R₁=C₂H₅, R₂ =C₁₀H₂₁7), and three kinds of lower rim bridged types (R₁=C₂H₅, R₂–R₂=(CH₂)₁₀8, (CH₂)₁₂9, (CH₂)₂(OCH₂CH₂)₃10) were characterized by electrochemical measurement to elucidate the effect of the length of the alkyl group of alkoxycarbonyl substituents on Na⁺ selectivity. To obtain excellent Na⁺ selective ionophores, introduction of short chain alkyl groups rather than long chain ones, such as a decyl group, and maintenance of sufficient solubility of the calix[4]arene derivatives in the membrane solvent are required concurrently. Among the calix[4]arenes tested, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcalix[4]arene2, and the diethyl-didecyl mixed ester type derivative7 are the best ionophores for a Na⁺ selective electrode. On the other hand, sodium selectivity of the bridged type derivative9 is comparable or even superior to that of the known bis(12-crown-4).This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Synthesis and evaluation of a novel pyrenyl-appended triazole-based thiacalix[4]arene as a fluorescent sensor for Ag ion

New fluorescent chemosensors 1,3-alternate-1 and 2 with pyrenyl-appended triazole-based on thiacalix[4]arene were synthesized. The fluorescence spectra changes suggested that chemosensors 1 and 2 are highly selective for Ag⁺ over other metal ions by enhancing the monomer emission of pyrene in neutral solution. However, other heavy metal ions, such as Cu²⁺, and Hg²⁺ quench both the monomer and excimer emission of pyrene acutely. The ¹H NMR results indicated that Ag⁺ can be selectively recognized by the triazole moieties on the receptors 1 and 2 together with the ionophoricity cavity formed by the two inverted benzene rings and sulfur atoms of the thiacalix[4]arene.     

25,26,27,28-羟乙氧基-杯[4]芳烃的合成

以对叔丁基苯酚为原料,经4步反应合成了新的杯[4]芳烃衍生物--25,26,27,28-羟乙氧基-杯[4]芳烃,其结构经~1H NMR和MS表征.     

Highly selective fluorescent chemosensor for Na~+ based on pyrene-modified calix[4]arene derivative

A novel calix[4]arene derivative with pyrene fluorophores at the upper rim and tetraester ionophores at the lower rim was synthesized in six steps,and its structure was proved by NMR and ESI-MS spectro-scopies. Furthermore,the chemosensing behavior of the host compound for alkali and alkaline earth metal ions was investigated by fluorescence spectroscopy. The obtained results show that the calix-arene host can selectively bind sodium ion with the complexation stability constant of 2190 mol-1.L. The complexa...     

Phase behaviour,structural properties and intermolecular interactions of systems based on substituted thiacalix[4]arene and nonionic surfactants

Supramolecular organised materials were prepared from nonionic surfactants and the following macrocyclic ionic liquids: n-tert-butylthiacalix[4]arenes containing quaternary ammonium fragments with amino acid substituents. Tetraethylene glycol monododecyl ether and decadiethylene glycol monododecyl ether were used as nonionic surfactants. They form lamellar and hexagonal mesophases in aqueous media, respectively. Liquid crystal and structural properties of these systems were studied. Intermolecular interactions of system components leading to formation of lyomesophases were estimated. Molecular structure of thiacalixarene contributes to the formation of a hydrogen bonding with surfactants. This process, in turn, initiates formation of a denser packed hexagonal structure.     

Structure elucidation of phenoxathiin-based thiacalix[4]arene conformations using NOE and RDC data

Phenoxathiin-based thiacalix[4]arene, obtained by the acid-catalysed rearrangement of the corresponding spirodienone derivative, was immobilized using the alkylation with chloroacetonitrile to yield three (out of four theoretically possible) stereoisomers. As the conformational outcome of the reaction could not be unambiguously assigned using standard NMR techniques, the method of Residual Dipolar Coupling constants (RDCs) was applied. The measuring of an anisotropic through-space dipole-dipole interactions in the lyotropic liquid crystalline alignment medium (PELG, poly-γ-ethyl-l-glutamate, and PBLG, poly-γ-benzyl-l-glutamate) enabled the assignment of the individual conformers. The usefulness of this approach was finally confirmed by the X-ray crystallography data.     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.