Gold nanocrystal arrays as a macroscopic platform for molecular junction thermoelectrics

The thermoelectric properties of gold nanocrystal arrays with thiol-terminated ligands are compared to molecular junction experiments.

Enhancement of the sensitivity of a capillary electrophoresis immunoassay for estradiol with laser-induced fluorescence based on a fluorescein-labeled secondary antibody

A competitive immunoassay for estradiol (E2) based on capillary electrophoresis was established. This method was based on the competitive reaction of complete antigen and E2 with a limited amount of monoclonal antibody, with fluorescein isothiocyanate (FITC)-labeled secondary antibody as a fluorescence probe. The addition of the thermally reversible hydrogel, poly-N-isopropylacrylamide (pNIPA) in the buffer as a replaceable packing material improved reproducibility and resolution of the method. This capillary electrophoresis immunoassay with laser-induced fluorescence can be applied to determine E2 with good precision at concentrations as low as 9 pg/mL. Details of typical separations of immunological complex and free reactants are presented.

Molecularly imprinted polymer using-p-hydroxybenzoic acid, p-hydroxyphenylacetic acid and p-hydroxyphenylpropionic acid as templates

Molecularly imprinted polymers (MIPs) using p-hydroxybenzoic acid (p-HB), p-hydroxyphenylacetic acid (p-HPA) and p-hydroxyphenylpropionic acid (p-HPPA) as templates were synthesized. The performance of the templates and their analogues on polymer-based high performance liquid chromatography (HPLC) columns was studied. The imprinting effect of the MIP using p-HB as template is more obvious than that of MIP using either p-HPA or p-HPPA as template, and the mixture of p-HB and p-HPA can be well separated on the MIP using p-HB as template, but not on the blank. Interestingly, the recognition of MIP (p-HB as the template) to p-HB showed a synergistic effect. The retention factor of p-HB is not the sum of those of phenol and benzoic acid. We also found that the imprinting effect decreased when increasing the concentration of acetic acid in mobile phase. The possible reason is that acetic acid molecules occupied the binding sites of the polymer, thereby decreasing the concentration of binding sites. Furthermore, polymers, which showed specificity to 3,4-dihydroxybenzoic acid, can be prepared with p-HB as template. It is thus possible to synthesize a specific polymer for a compound that is either expensive or unstable by using a structurally similar compound as template.

Molecularly imprinted polymers from nicotinamide and its positional isomers

Imprinted polymers were prepared for nicotinamide and its positional isomers. The influence of porogenic solvent and functional monomer on recognition properties of the polymer was compared. The results indicated that two functional groups, the heterocyclic nitrogen and the amide group, in the nicotinamide or isonicotinamide molecule have a synergistic effect in binding to the polymer. The polymers prepared with nicotinamide and isonicotinamide can be used as HPLC stationary phase for the separation of positional isomers of nicotinamide or isonicotinamide, while the polymer prepared with picolinamide showed no specificity toward the template. The mechanisms for the differences in recognition are discussed. In addition to the retention of polymers to their templates the polymers also displayed excellent retention to nicotinic acid and isonicotinic acid, compounds structurally similar to the template. This dual recognition property of the polymer may be useful in circumstances where the preparation of a polymer for a specific template may be problematic because of poor stability or solubility.

Determination of morphine by capillary electrophoresis immunoassay in thermally reversible hydrogel-modified buffer and laser-induced fluorescence detection

In this paper thermally reversible hydrogel used as a replaceable packed material for capillary electrophoresis was examined. A simple and rapid method of detecting morphine was developed, which demonstrated the potential of strong affinity antibodies as a selector for immunologically-based separations in serum by capillary electrophoresis. Polyclonal antibodies were linked to hydrogel and applied to the separation of free fluorescein isothiocyanate (FITC)-labeled antigen and bound FITC antigen. The separation was monitored with laser-induced fluorescence detection. Different separation conditions were studied. The results indicated that poly-N-isopropylacrylamide hydrogel (PNIPA) is a kind of steady, replaceable gel. The specific determination of morphine did not require a long incubation time and PNIPA hydrogel-modified antibodies can be stockpiled at 4 degrees C before assay. It can be used to determine morphine with good precision and a detection limit lower than 8.5 ng/ml. Details of the preparation of hydrogel cross-linked polyclonal antibody and of typical separations of bound and free antigen are presented.

Determination of doping methyltestosterone by capillary electrophoresis immunological analysis with thermally reversible hydrogel and laser-induced fluorescence

In this paper thermally reversible hydrogel used as a replaceable packed material for capillary electrophoresis was examined. A simple and rapid method of detecting doping methyltestosterone (MTS) was developed, which demonstrated the potential of strong affinity antibodies (k(d) = 10(9)) as a selector for immunologically based separations in serum, not in urine, by capillary electrophoresis. Polyclonal antibodies (Ab) were polymerized on the hydrogel and applied in the separation of fluorescein isothiocyanate (FITC)-labeled antigen and free antigen with laser-induced fluorescence detector (LIF). The results indicated that N-isopropylacrylamide (PNIPA) hydrogel is a steady, replaceable gel. The specific determination of MTS did not require reaching equilibrium of immunological reaction and the PNIPA hydrogel including antibodies can be stockpiled at 4 degrees C, in preparation for determining MTS at any time. It can be used to determine MTS with good precision with a sensitivity lower than 50 ng/mL. The theoretical plate numbers obtained could reach 168,449 for free-antigen. Details of the preparation of hydrogel cross-linked polyclonal antibody and of typical separations of bound and free antigen are presented.

Detection of the organophosphorus nerve agent sarin by a competitive inhibition enzyme immunoassay

Two artificial antigens, NalphaNepsilon-di(O,O-diisopropyl) phosphoryl L-lysine (DIP)- bovine serum albumin (BSA) conjugate (DIP-BSA) and DIP-KLH (keyhole limpet hemocyanin), were synthesized. Antibodies against sarin (O-isopropyl methylphosphonofluoridate) were obtained after immunization of rabbits with DIP-KLH conjugate. A competitive inhibition enzyme immunoassay (CIEIA) was developed to detect the organophosphorus nerve agent sarin. The antibody solutions could be inhibited by sarin as low as 10(-6) mol/l, and the standard curve was linear over 3 orders of magnitude. The coefficients of intraassay and interassay variation of this method were 5.4-6.2% (n = 11) and 8.0-9.5% (n = 6) at a sarin concentration range of 10(-3)-10(-6) mol/l, respectively. The recovery of sarin in water samples at the concentration of 5 x 10(-5) mol/l was in the range of 96.8-102.5%. The specificity of the antiserum was assessed by comparing the inhibition induced by sarin with soman, Vx, isopropyl alcohol and isopropyl methyl phosphonic acid. The results showed that less than 5 mmol/l soman, 2 mmol/l Vx, 16 mmol/l isopropyl alcohol and 8 mmol/l isopropyl methyl phosphonic acid did not influence the determination of sarin in water samples.

Production, characterization and application of monoclonal antibodies against the organophosphorus nerve agent Vx

Two monoclonal antibodies (Vx-BB8 and Vx-EA11) to the chemical warfare agent Vx were produced and characterized. A competitive inhibition enzyme immunoassay was developed to detect Vx concentrations as low as 3.7 x 10(-7) - 3.7 x 10(-6) mol/l in biological samples. Vx-BB8 400 micrograms given intravenously immediately before 1 x LD95 Vx or 400 micrograms Vx-BB8 intraperitoneally 1.5 h-3 days before 1 x LD95 Vx could protect all the tested mice from death.

Fluorescence labelling with europium chelate of beta-diketones and application in time-resolved fluoroimmunoassays (TR-FIA)

Five beta-diketone derivatives were studied for multiple labelling of proteins. The labelled proteins were characterized by absorption and fluorescence measurements. It was found that proteins labelled with chlorosulfonyl-thenoyltrifluoroacetone (CTTA) were able to form highly fluorescent complexes with Eu3+ which exhibited prolonged fluorescence whereas the Eu3+ complex of hydrolyzed CTTA exhibited almost no fluorescence, and so unreacted ligand gave no background signal in immunoassays even if it was not removed from the labelled reagent. The effect of labelling on the biological activity of albumin and polyclonal antibody was studied and it was also shown that the new probe could be used in time-resolved fluorescence immunoassays.

Spectrofluorimetric determination of tetracycline and anhydrotetracycline in serum and urine

A spectrofluorimetric method, involving alkaline degradation and formation of a magnesium complex, is described for the determination of tetracycline (TC) and anhydrotetracycline (ATC) in their mixed solution. Tetracycline is degraded and determined in alkaline solution. This treatment of ATC produces almost no fluorescence, but a fluorescent magnesium complex forms at pH 7.5. Several synthetic samples of TC and ATC, with TC:ATC ratios ranging from 50:1 to 1:50, were analysed. The recoveries of TC and ATC are about 71-76 and 61-63% in serum, respectively, and are all about 100% in urine.