Assembly of Anionic Conjugated Polymer with 6-O-Modified PNP-ß-Galactoside for Fluorescence Logic-signal-based Multiplex Detections of Enzymes.

Anionic conjugated polymer (PFP-SO 3-) was assembled with a novel enzymatic substrate 6-O-modified PNP-ß-galactoside (1) for sensitive multiplex enzyme detections. The PFP-SO 3-/1/lipase/ß-galactosidase system has two chemical input signals which are Input 1 (lipase) and Input 2 (ß-galactosidase), and output optical signals such as fluorescence emission at 416 nm or 450 nm. Four types of logic gates, including YES, INH, NAND and AND, were successfully constructed and utilized for multiplex detections of lipase and ß-galactosidase in one tube.

Chemiluminescent detection of DNA hybridization using gold nanoparticles as labels.

A chemiluminescent (CL) detection method has been developed for DNA hybridization. The assay relies on a sandwich-type DNA hybridization in which gold nanoparticles modified with alkylthiol-capped oligonucleotide strands are used as probes to monitor the presence of the specific target DNA. The AuCl(4)(-), which is the dissolving product of the gold nanoparticles anchored on the DNA hybrids, serves as an analyte in the H(2)O(2)-luminol- AuCl(4)(-) CL reaction for the indirect measurement of the target DNA. The combination of the remarkable sensitivity of the CL analysis with the large number of AuCl(4)(-) released from each DNA hybrid allows a detection limit at levels as low as 0.1 pM of the target DNA. Moreover, with a further silver amplification step, the detection limit will be pushed down to the femtomolar domain.

A chemiluminescent metalloimmunoassay based on silver deposition on colloidal gold labels.

A sensitive chemiluminescent (CL) immunoassay of human immunoglobulin (IgG) which combined the inherent high sensitivity of CL analysis with the dramatic signal amplification of silver precipitation on colloidal gold tags was developed. First, the sandwich-type complex was formed in this protocol by the primary antibody immobilized on the polystyrene wells, the analyte in the sample, and the secondary antibody labeled with colloidal gold. Second, the colloidal gold was treated by an Ag(+) reduction solution, which resulted in the catalytic precipitation of silver on the surface of colloidal gold. Third, a large number of Ag(+) were oxidatively released in HNO(3) solution from the silver metal anchored on the sandwich-type complexes and then the human IgG was indirectly determined by a sensitive combined CL reaction of Ag(+)-K(2)S(2)O(8)-Mn(2+)- H(3)PO(4)-luminol. The chemiluminescence intensity depends linearly on the logarithm of the concentration of human IgG over the range of 0.02-50ngml(-1) and detection limit (3sigma) is 0.005ngml(-1) (i.e., approximately 3x10(-14)M, 3amol in 100-mul sample). This assay has been successfully applied to the determination of human IgG in human serum samples and showed great potential for numerous applications in immunoassay.

Silver nanoparticle-based ultrasensitive chemiluminescent detection of DNA hybridization and single-nucleotide polymorphisms.

A new nanoparticle-based chemiluminescent (CL) method has been developed for the ultrasensitive detection of DNA hybridization. The assay relies on a sandwich-type DNA hybridization in which the DNA targets are first hybridized to the captured oligonucleotide probes immobilized on polystyrene microwells and then the silver nanoparticles modified with alkylthiol-capped oligonucleotides are used as probes to monitor the presence of the specific target DNA. After being anchored on the hybrids, silver nanoparticles are dissolved to Ag+ in HNO3 solution and sensitively determined by a coupling CL reaction system (Ag+-Mn2+-K2S2O8-H3PO4-luminol). The combination of the remarkable sensitivity of the CL method with the large number of Ag+ released from each hybrid allows the detection of specific sequence DNA targets at levels as low as 5 fM. The sensitivity increases 6 orders of magnitude greater than that of the gold nanoparticle-based colorimetric method and is comparable to that of surface-enhanced Raman spectroscopy, which is one of the most sensitive detection approaches available to the nanoparticle-based detection for DNA hybridization. Moreover, the perfectly complementary DNA targets and the single-base mismatched DNA strands can be evidently differentiated through controlling the temperature, which indicates that the proposed CL assay offers great promise for single-nucleotide polymorphism analysis.

Selective determination of cysteine by resonance light scattering technique based on self-assembly of gold nanoparticles.

The interaction between cysteine and gold nanoparticles was studied. Through the covalent combination with the -SH group and the electrostatic binding with the -NH3+ group of cysteine, gold nanoparticles can self-assemble to form a network structure, which results in greatly enhanced resonance light scattering (RLS). The experimental results demonstrate that the RLS technique offers a sensitive tool for investigations of self-assembly of nanoparticles. On the other hand, the RLS method can be applied to selectively determine cysteine with high sensitivity and simple operation. The linear range of determination of cysteine is from 0.01 to 0.25 microg/mL with the detection limit of 2.0 ng/mL (16.5 nM, 3sigma). None of the amino acids found in proteins interferes with the determination.

Study on self-assembly of gold nanoparticles directed by glutathione with resonance light scattering technique and its analytical applications.

In this paper, it has been demonstrated that gold nanoparticles can self-assemble to form network structure in the presence of glutathione, which results in great enhancement of resonance light scattering (RLS). Results from this RLS experiments confirm that RLS is a sensitive and convenient technique for studying the self-assembly of nanoparticles. The principles of the enhanced RLS of nanoparticle assemblies are discussed, and the mechanism of the interaction between gold nanoparticles and glutathione is investigated. The enhanced RLS of gold nanoparticle assemblies directed by glutathione is also successfully applied to sensitive determination of glutathione. Under the optimal conditions, the calibration curve for glutathione determination is linear in concentration range of 0.01-0.1 microg/ml, and the corresponding detection limit is 4.7 ng/ml (3sigma, 15.3 nM).