Quantification of microRNA by gold nanoparticle probes.

MicroRNAs are important posttranscriptional regulators of gene expression in animals and plants. A sensitive and specific detection method is urgently needed for intensive studies on differential expression and regulatory roles of microRNA. Here we present a simple and reliable method for the quantification of microRNA. The hybridization products of target microRNA with capture probe and gold nanoparticle probe are immobilized onto the surface of a streptavidin-coated microplate, and the signal is amplified by silver enhancement. Distribution of miR-122a/miR-128 in mouse brain and liver tissue was detected by this method, and synthetic miRNA122a was quantified. This method allowed a lower detect limit of 10 fM with a linear dynamic range from 10 pM to 10 fM and a high specificity to discriminate one single oligonucleotide mismatch of the target microRNA.

Ultra-sensitive colorimetric method to quantitate hundreds of polynucleotide molecules by gold nanoparticles with silver enhancement.

An ultra-sensitive colorimetric method to quantitate hundreds of polynucleotide molecules by gold nanoparticles with silver enhancement has been developed. The hybridization products from the target polynucleotides with biotin-labeled probes and gold nanoparticle-functioned oligonucleotides were immobilized to microplates via avidin-biotin system, and the absorbance signals of gold nanoparticles were amplified by silver enhance solution. This sandwich colorimetric assay can detect as few as 600 molecules for single-strand oligonucleotides and as few as 6000 molecules for double-strand polynucleotides in a 50 microL reaction system.

[Cohort mortality study of dust exposed miners in iron mine].

OBJECTIVE: To investigate the main diseases jeopardizing the health of the iron miners and to explore the relationship between dust exposure and malignancies as well as other diseases. METHODS: A retrospective study with a cohort of 7,469 workers employed between January 1, 1972 and December 31, 1974 in Daye Iron Ore Mine Co. in Hubei Province was conducted. Standardized mortality ratio (SMR) was calculated for the main causes of death using Chinese national mortality rates for reference. RESULTS: All subjects were followed up through December 31, 2003 with an accumulation of 199, 108.0 person years. A total of 1,752 workers died. The cumulative mortality was 23.5%. The cancers, cerebrovascular diseases, non-malignant respiratory diseases and cardiovascular diseases were main diseases that threatened workers' life span. The SMR for all subjects was a little higher than expected based on the Chinese national mortality rates. The diseases causing the significantly higher death rate were the nasopharynx cancer, liver cancer, lung cancer, pneumoconiosis and accident with SMR 1.84, 1.51, 1.83, 14.94 and 1.25 respectively. Increased mortality was observed among dust-exposed workers in the cohort. The cumulative mortality from all causes such as stomach cancer, lung cancer, nonmalignant respiratory diseases, cardiovascular diseases and accident in dust exposed workers were significantly increased compared with those in non-exposure workers with RR 1.35, 1.83, 1.61, 2.27, 1.34 and 1.69 respectively. CONCLUSION: The risk factors especially dust exposure affect the health and lifespan of the iron mine workers.

Ultrasensitive densitometry detection of cytokines with nanoparticle-modified aptamers.

BACKGROUND: Aptamers mimic properties of antibodies and sometimes turn out to be even better than antibodies as reagents for assays. We describe the establishment of an ultrasensitive densitometry method for cytokine detection by nanoparticle (NP)-modified aptamers. METHODS: The assay simultaneously uses a gold NP-modified aptamer and a biotin-modified aptamer to bind to the target protein, forming a sandwich complex. The absorbance signal generated by the aptamer-protein complex is amplified and detected with a microplate reader. RESULTS: The assay for platelet-derived growth factor B-chain homodimer (PDGF-BB) was linear from 1 fmol/L to 100 pmol/L (R(2) = 0.9869). The analytical detection limit was 83 amol/L. The intraassay and interassay imprecision (CVs) was < or =7.5%. Serum concentrations of PDGF-BB determined with the gold NP-modified aptamer assay and with ELISA were not significantly different. CONCLUSIONS: The gold NP-modified aptamer assay provides a fast, convenient method for cytokine detection and improves the detection range and the detection limit compared with ELISA.