Automated and ultrasensitive detection of methyl-3-quinoxaline-2-carboxylic acid by using gold nanoparticles probes SIA-rt-PCR.

An ultrasensitive and rapid sequential injection analysis (SIA) based on real-time PCR (SIA-rt-PCR) assay was developed by using different nanoparticles for the detection of small molecule chemicals residues. Gold (Au) nanoparticle, conjugated with goat anti-rabbit IgG and duplex strand DNA (dsDNA), was used as a substitute for chemiluminescent probes in an SIA system. By indirect competitive immunoreactions in the SIA system, the gold nanoparticles were attached to antigens which were immobilized by superparamagnetic nanoparticles (SMNPs). The dsDNA on the gold nanoparticles was dehybridized and then the single-stranded DNA (ssDNA) was collected and quantified with rt-PCR, which showed a rather low linearity range from 2.5 attomol L(-1) (aM) to 250 femtomol L(-1) (fM) and the LOD was 1.4 aM. This method, which is rapid, automated and capable of high-throughput, was used to detect methyl-3-quinoxaline-2-carboxylic acid (MQCA) residues in real samples. The analytical results had a coefficient of variation of less than 15% and the recovery was 89-108%.

A flow-injection chemiluminescence method for the determination of some estrogens by enhancement of luminol-hydrogen peroxide-tetrasulfonated manganese phthalocyanine reaction.

A novel flow-injection chemiluminescence (FI-CL) method for the determination of estrogens is proposed, based upon its enhancing effect on the CL reaction of luminol with hydrogen peroxide catalyzed by tetrasulfonated manganese phthalocyanine (MnTSPc) in alkaline solution. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentration of estrone in the range of 1.0x10(-7) to 1.0x10(-6)mol/l, estradiol in the range of 9.0x10(-8) to 1.0x10(-6)mol/l and estriol in the range of 3.0x10(-7) to 2.0x10(-6)mol/l, respectively. The detection limits were 5.1x10(-8)mol/l for estrone, 7.2x10(-9)mol/l for estradiol and 6.5x10(-8)mol/l for estriol with a relative standard deviation of 2.8% for 5.0x10(-7)mol/l estrone, 2.4% for 1.0x10(-7)mol/l estradiol, and 3.1% for 7.0x10(-7)mol/l estriol (n=11). This method has been applied to the determination of estrogen in pharmaceutical injections and tap water with satisfactory results.

Preparation and application of cysteine-capped ZnS nanoparticles as fluorescence probe in the determination of nucleic acids.

Cysteine-capped ZnS nanometer-sized fluorescent particles were produced by a colloidal aqueous synthesis. The functionalized nanoparticles are water-soluble and suitable for biological application. A synchronous fluorescence method has been developed for the rapid determination of DNA with functionalized nano-ZnS as a fluorescence probe, based on the synchronous fluorescence enhancement of cysteine-capped nano-ZnS in the presence of DNA. When Deltalambda =190 nm, maximum synchronous fluorescence is produced at 267 nm at pH 5.12. Under optimum conditions, the synchronous fluorescence intensity is proportional to the concentration of nucleic acids in the range 0.1-1.2 microg ml(-1) for calf thymus DNA, 0.1-0.6 microg ml(-1) for fish sperm DNA. The corresponding detection limit is 32.9 ng ml(-1) for calf thymus DNA and 24.6 ng ml(-1) for fish sperm DNA. This method is simple, inexpensive, rapid and sensitive. The recovery and relative standard deviation are satisfactory.

Simple and sensitive assay for nucleic acids by use of the resonance light-scattering technique with copper phthalocyanine tetrasulfonic acid in the presence of cetyltrimethylammonium bromide.

On the basis of enhancement of resonance light scattering (RLS) of copper phthalocyanine tetrasulfonic acid (CuTSPc) by nucleic acids and cetyltrimethylammonium bromide (CTMAB) under suitable conditions, a new RLS method for determination of nucleic acids in aqueous solutions has been developed. At pH 9.80-10.95 and ionic strength 0.01 mol L(-1) (NaCl), the interaction of copper phthalocyanine tetrasulfonic acid with nucleic acids in the presence of cetyltrimethylammonium bromide results in enhanced RLS signals at 282.0 nm, 383.6 nm, and 616.2 nm in the enhanced regions. It was found that the enhanced RLS intensity at 383.6 nm was proportional to the concentration of nucleic acids within suitable ranges. The limits of detection were 10.6 ng mL(-1) for fish sperm DNA and 32.4 ng mL(-1) for calf thymus DNA when the concentration of copper phthalocyanine tetrasulfonic acid was 2.0 x 10(-6) mol L(-1). This method is rapid, simple and sensitive. In addition, the reagents used are relatively inexpensive, stable, and easily synthesised. The method can be applied to the determination of nucleic acids in the presence of coexisting substances, and we have applied it to the determination of DNA in synthetic samples, with satisfactory results.

Determination of proteins at nanogram levels by their quenching effect on the chemiluminescence reaction between luminol and hydrogen peroxide with manganese-tetrasulfonatophthalocyanine as a new catalyst.

The manganese-tetrasulfonatophthalocyanine (MnTSPc) catalyzed luminol-hydrogen peroxide chemiluminescence (CL) systems can be quenched in the presence of proteins. A highly sensitive CL quenching method has been developed for the determination of proteins. Under optimum conditions, the linear ranges of the calibration curves were 0.1-20 microg/mL for human serum albumin (HSA), 0.2-20 microg/mL for human gamma-IgG, and 0.5-50 microg/mL for the bovine serum albumin (BSA) with the corresponding detection limits were 1.9 ng/mL, 2.7 ng/mL, and 3.4 ng/mL. The method has been applied to the analysis of total proteins in human serum samples and the results were in good agreement with clinical data provided.