Electrodeposition of CdSe quantum dots and its application to an electrochemiluminescence immunoassay for α-fetoprotein

We report on the first label-free electrochemiluminescence (ECL) immunosensor for α-fetoprotein (AFP). It is based on the use of CdSe quantum dots that were electrodeposited directly on a gold electrode from an electrolyte (containing cadmium sulfate, EDTA and selenium dioxide) by cycling the potential between 0 and -1.2?V (vs. SCE) for 60?s. The electrodeposited dots were characterized by scanning electron microscopy and energy dispersive spectroscopy. Under optimal conditions, the specific immunoreaction between AFP and anti-AFP resulted in a decrease of the ECL signal because of the steric hindrance and the transfer inhibition by peroxodisulfate. The quenching effect of the immunoreaction on the intensity of the ECL was used to establish a calibration plot which is linear in the range from 0.05 to 200?ng?mL^?1. The detection limit is 2?pg?mL^?1. The assay is highly sensitive and satisfactorily reproducible. In our opinion it opens new avenues to apply ECL in label-free biological assays.

Flow injection chemiluminescence immunoassay for 17β-estradiol using an immunoaffinity column

A new flow injection chemiluminescent immunoassay was developed for the detection of 17β-estradiol (E₂). The method uses p–iodophenol (PIP) as enhancer and is based on a solid-phase immunoassay format in which an E₂–OVA immobilized immunoaffinity column inserted in the flow system is used to trap unbound horseradish peroxidase (HRP)-labeled anti-E₂ antibody after an off-line incubation of E₂ with HRP-labeled anti-E₂ antibody. The trapped enzyme conjugate was detected by injecting substrates to produce an enhanced chemiluminescence (CL) response. The linear range for E₂ was 10.0–1,000.0 ng mL⁻¹ with a correlation coefficient of 0.996 and a detection limit of 3.0 ng mL⁻¹. The sampling and chemiluminescence detection time for one sample was 400 s after a pre-incubation procedure of 30 min. Serum samples detected by this method were in good agreement with the results obtained by EIA with E₂–biotin.      

Solvent effects on the steady state photophysics of estrone and 17β-estradiol

Absorption and emission yields for estrone and 17β-estradiol were measured in a variety of room temperature solvents. Molar extinction coefficients were found to not vary as a function of solvent, while fluorescence yields were found to be significantly affected by the polarity and hydrogen-bond accepting ability of the solvent, with the yield for 17β-estradiol being highest in nonpolar, hydrogen-bond donating solvents, and lowest in the nonpolar, hydrogen-bond accepting solvent ethyl acetate. Estrone's emission yield was found to be a factor of ten smaller than 17β-estradiol's. Strong solvent and excitation wavelength dependences were found for the relative amounts of emission between estrone's two emission bands, with increased relative emission occurring in nonpolar aprotic solvents, and under higher excitation energies. These results are interpreted with the aid of vertical excitation energies from time-dependent density functional calculations using both explicit and implicit solvation models.     

LapRLSR for NIR spectral modeling and its application to online monitoring of the column separation of Salvianolate

A novel near infrared (NIR) modeling method—Laplacian regularized least squares regression (LapRLSR) was presented, which can take the advantage of many unlabeled spectra to promote the prediction performance of the model even if there are only few calibration samples. Using LapRLSR modeling, NIR spectral analysis was applied to the online monitoring of the concentration of salvia acid B in the column separation of Salvianolate. The results demonstrated that LapRLSR outperformed partial least squares (PLS) significantly, and NIR online analysis was applicable.     

Stereoselective allylation of α-hydroxy aldimines and its application to the formal synthesis of (−)-β-conhydrine

Stereoselective allylation of N-p-methoxyphenyl (PMP)-substituted α-hydroxy aldimines is described. Several Lewis acids (BF₃·OEt₂, SnCl₄, TiCl₄, ZnCl₂, and MgBr₂·OEt₂) were employed to mediate the allylation reactions. The addition of the allyl group generates a new stereocenter and affords the syn vicinal amino alcohol. Formal synthesis of (?)-β-conhydrine (1) was accomplished via syn-selective allyl addition to N-PMP-substituted α-hydroxy aldimine.     

Preparation of PLL-PEG-PLL and its application to DNA encapsulation

With the successful sequencing of Human Genome, it would be possible to cure all diseases by gene ther- apy in the near future. However, one of the major problems in gene therapy is the development of gene vectors. To date, there are two kinds of gene vectors, namely, viral and non-viral gene vectors. Viruses are widely used as vectors in gene therapy, with the trans- fection efficiency being relatively high, but they have the safety problems such as immunogenicity, non- biocompatibility and …     

Hypersensitivity and its application to structural analysis of lanthanide complexes

Hypersensitivity of the ternary complexes Ln(β-dik)4HMQ(where Ln=Nd, Ho, Er,β-dik=acetylacetonate(AA), dibenzoylmethanate(DBM) and MQ=4-methylquinoline) in acetone solution is studied based on the dynamic coupling model. The structures of these complexes in solution are deduced. Their coordination polyhedrons are all distorted square antiprism. Neodymium complexes have D2 symmetry, while holmium and erbium complexes have exact D2d symmetry.     

Development of Magnetic Particle-based Chemiluminescence Enzyme Immunoassay for the Detection of 17β-estradiol in Environmental Water

In the present work, a simple, fast, and highly sensitive chemiluminescence enzyme immunoassay for 17β-estradiol (E2) in environmental water samples was developed, using magnetic particles (MPs) labeled with secondary antibody as both the immobilization matrix and the separation tools. The specific anti-E2 polyclonal antibody (PcAb) was produced against a conjugate of estradiol–bovine serum albumin. The specificity of the anti-E2 antibody was studied. The results showed that the antibody did not cross-react with the structurally related endocrine-disrupting compounds, including estrone, ethinyl E2, estriol, E2-17-glucuronide, E2-3-sulfate-17-glucuronide, androstenedione, and dihydrotestosterone. The water samples were pretreated with solid-phase extraction using C₁₈ cartridges for the removal of matrix effects. Several physicochemical parameters including the dilution ratios of E2-6–horseradish peroxidase conjugate and anti-E2 PcAb, immunoreaction time, volume of chemiluminescent substrate and MPs, chemiluminescence reaction time, and pH of assay solution were studied and optimized. At optimal experimental conditions, it was found that the proposed method exhibited high performance with detection limit of 2.0 pg/mL, linear range of 20–1,200 pg/mL, and total assay time of 45 min. Both inter- and intra-assay coefficient of variation were less than 10%. The average recoveries of three different spiked concentration samples ranged from 86.3% to 108%. The method was successfully applied to the determination of E2 in river, waste, and tap water, and showed a good correlation with the commercially available radioimmunoassay kit.     

Laccase-mediated oxidation of the steroid hormone 17β-estradiol in organic solvents

Laccase-mediated oxidation of the steroid hormone 17β-estradiol 1 in organic solvents or in a biphasic system allowed the isolation of the C–C and C–O dimers 1a–d. Concerning the C–C dimers, the relative ratio of the symmetric 4-4′ 1c and asymmetric 4-2′ 1d products was influenced by the catalyst used. Both 1c and 1d were formed as an equimolar mixture of diastereomeric atropisomers.     

Development of an information-intensive structure–activity relationship model and its application to human respiratory chemical sensitizers

Structure–activity relationship (SAR) models are recognized as powerful tools to predict the toxicologic potential of new or untested chemicals and also provide insight into possible mechanisms of toxicity. Models have been based on physicochemical attributes and structural features of chemicals. We describe herein the development of a new SAR modeling algorithm called cat-SAR that is capable of analyzing and predicting chemical activity from divergent biological response data. The cat-SAR program develops chemical fragment-based SAR models from categorical biological response data (e.g. toxicologically active and inactive compounds). The database selected for model development was a published set of chemicals documented to cause respiratory hypersensitivity in humans. Two models were generated that differed only in that one model included explicate hydrogen containing fragments. The predictive abilities of the models were tested using leave-one-out cross-validation tests. One model had a sensitivity of 0.94 and specificity of 0.87 yielding an overall correct prediction of 91%. The second model had a sensitivity of 0.89, specificity of 0.95 and overall correct prediction of 92%. The demonstrated predictive capabilities of the cat-SAR approach, together with its modeling flexibility and design transparency, suggest the potential for its widespread applicability to toxicity prediction and for deriving mechanistic insight into toxicologic effects.     

Characterization of 17α-hydroxysteroid dehydrogenase activity (17α-HSD) and its involvement in the biosynthesis of epitestosterone

Background  

Epi-testosterone (epiT) is the 17α-epimer of testosterone. It has been found at similar level as testosterone in human biological fluids. This steroid has thus been used as a natural internal standard for assessing testosterone abuse in sports. EpiT has been also shown to accumulate in mammary cyst fluid and in human prostate. It was found to possess antiandrogenic activity as well as neuroprotective effects. So far, the exact pathway leading to the formation of epiT has not been elucidated.     

A family of four-step trigonometrically-fitted methods and its application to the schrödinger equation

In this article we present a singularly almost P-stable exponentially-fitted four-step method for the approximate solution of the one-dimensional Schrödinger equation. More specifically we present a method that is singularly almost P-stable (a concept later introduced in this article) and also integrates exactly any linear combination of the functions {1, x, exp ( ±I v x) , x exp ( ±I v x) , x ² exp ( ±I v x)}. The numerical experimentation showed that our method is considerably more efficient compared to well known methods used for the approximate solution of resonance problem of the radial Schrödinger equation.     

PANI–TiC nanocomposite film for the direct electron transfer of hemoglobin and its application for biosensing

A novel polyaniline and titanium carbide (PANI–TiC) nanocomposite was synthesized by an in situ chemical oxidative polymerization method, and a hydrogen peroxide (H₂O₂) biosensor was fabricated by PANI–TiC with hemoglobin (Hb)-modified glassy carbon electrode (GCE). Scanning electron microscope and energy dispersive X-ray spectroscopy showed the morphology and ingredient of PANI–TiC. Electrochemical investigation of the biosensor showed a pair of well-defined, quasi-reversible redox peaks with E _pa?=??0.318 V and E _pc?=??0.356 V (vs SCE) in 0.1 M, pH 7.0 sodium phosphate-buffered saline at the scan rate of 150 mV s^?1. Transfer rate constant (k _s) was 2.01 s^?1. The Hb/PANI–TiC/GCE showed a good electrochemical catalytic response for the reduction of H₂O₂ with the linear range from 0.5 to 285.5 μM and the detection limit of 0.2 μM (S/N?=?3). The apparent Michaelis–Menten constant (K _m) was estimated to be 1.21 μM. Therefore, the PANI–TiC as a novel matrix opened up a further possibility for study on the design of enzymatic biosensors with potential applications.     

Surface plasmon resonance biosensor for the detection of VEGFR-1—a protein marker of myelodysplastic syndromes

The surface plasmon resonance (SPR) biosensor system with dispersionless microfluidics for the direct and label-free detection of a soluble vascular endothelial growth factor receptor (sVEGFR-1) is described. The detection approach takes advantage of an affinity interaction between sVEGFR-1 and its ligand, vascular endothelial growth factor (VEGF-A), which is covalently immobilized on the surface of the SPR sensor. The ability of the immobilized VEGF-A to specifically bind the sVEGFR-1 receptor is demonstrated in a buffer. The detection of sVEGFR-1 in 2% human blood plasma is carried out by using the sequential injection approach. The detection limit of 25 ng/mL is achieved. In addition, we demonstrate that the functional surface of the sensor can be regenerated for repeated use.     

C4−H alkoxylation of 6-bromoindole and its application to the synthesis of breitfussin B

Subjecting 6-bromoindole to an iridium-catalysed triborylation-diprotodeborylation sequence followed by Chan-Evans-Lam coupling gives 6-bromo-4-methoxyindole in good overall yield. This indole C4?H alkoxylation process was used in a formal synthesis of the natural product breitfussin B.     

SPE and HPLC monitoring of 17-β-estradiol in Egyptian aquatic ecosysetms

Solid-phase extraction and HPLC methods are described for monitoring of 17-β-estradiol residues in Egyptian aquatic ecosystems (water, fish, mollusks, sediment, and drinking water) at the Nile River, Suez Canal region, and northeast of Egypt. Molecular imprinted polymer was prepared and used in extraction. High performance liquid chromatography (HPLC) columns used were Supelcosil C₁₈ and Nucleosil C₁₈. The mobile phases used were different combinations of water and acetonitrile. The concentration of 17-β-estradiol in water, aquatic animals, and sediment samples were of 265.13–7988.12 µg/L, 0.503–96.167, and 0.775–11.884 µg/kg, respectively. Marine lake was contained with high levels of 17-β-estradiol (P < 0.05). Similarly, the Nile River downstream showed high levels of 17-β-estradiol. The detected concentrations in mollusks were significantly higher than those detected in fish. Tilapia fish did not show 17-β-estradiol. Contrarily, low concentrations were detected in the rivulet streams supplied by the Nile River. Besides, 17-β-estradiol was also detected in the sediments at low levels. Detection of 17-β-estradiol in the Egyptian ecosystems attracted attention toward heavy reliance on some esterogenic medicinal products in Egypt. The monitoring of 17-β-estradiol in other water bodies was recommended. Besides, the development of methodologies of bioremediation to eliminate 17-β-estradiol from the Egyptian and other water resources of the world was also suggested.