Facile synthesis of fluorescent tungsten oxide quantum dots for telomerase detection based on the inner filter effect.

The traditional detection of telomerase activity is mainly based on the polymerase chain reaction (PCR), which has the disadvantages of being time-consuming and susceptible to interferences; thus, here, we propose a facile method for the fabrication of fluorescent tungsten oxide quantum dots (WOx QDs) and employ them for telomerase activity sensing. It is found that the fluorescence of WOx QDs can be significantly quenched by hemin based on the inner filter effect (IFE). However, in the presence of telomerase, the primer-DNA can be extended to generate repeating units of TTAGGG to form G-quadruplex and thus, hemin can be encapsulated to reduce its absorbance, resulting in decreased IFE and efficient fluorescence recovery of WOx QDs. Based on the fluorescence changes of IFE between hemin and WOx QDs, the telomerase activity within the range of 50-30 000 HeLa cells can be detected and the lowest detection amount can reach 17 cells. The method exhibits good versatility that can also be applied to telomerase detection in A549 and L929 cells. In addition, because of the good biocompatibility of the sensor, it can be used for the real-time monitoring of telomerase activity in living cells, thus showing great potential in tumor diagnosis and inhibitor drug screening.

Cobalt phosphide nanowires for fluorometric detection and in-situ imaging of telomerase activity via hybridization chain reactions.

The authors describe cobalt phosphide (CoP) nanowires for use in sensitive fluorometric determination of the activity of the enzyme telomerase. A hybridization chain reaction (HCR) is applied to amplify the signal and carboxyfluorescein (FAM)-labelled hairpin probes (H1 and H2) are applied to match the telomeric DNA sequence. The CoP nanowires act as both the photoinduced electron transfer (PET) acceptor to induce fluorescence quenching, and also as an efficient probe carrier to facilitate telomerase imaging in living cells. The telomerase-triggered primer extension initiates an alternating hybridization reaction between H1 and H2. These result in the dissociation of FAM-labelled probes from CoP nanowires and thus an enhancement of the green fluorescence. The method is fairly simple and was applied to the detection of three types of cancer cells. The detection limit is as low as 7 cells (in case of HeLa cells). Conceivably, the method has a large potential in terms of inhibitor drug screening. Graphical abstract Schematic presentation of telomerase detection based on cobalt phosphide (CoP) nanowires and hybridization chain reaction (HCR). The telomerase-triggered primer extension can initiate the alternating hybridization reaction between carboxyfluorescein (FAM)-labelled hairpin probes (H1 and H2), and the generated long DNA duplex cannot be adsorbed on the CoP nanowires. This prevents the photoinduced electron transfer (PET) from FAM to CoP nanowires.

A facile graphene oxide-based fluorescent nanosensor for the in situ "turn-on" detection of telomerase activity.

A facile and sensitive method for the quantitative detection of telomerase and in situ imaging of intracellular telomerase is developed by using a graphene oxide (GO)-based fluorescent nanosensor. The nanosensor consists of a fluorescent DNA (P1) adsorbed on the GO surface. Here, GO serves not only as a fluorescence quencher but also as a carrier to successfully transport P1 into cancer cells as a signal reporter. P1 is a dye-labeled single-stranded DNA complementary to the telomeric repeated sequence, and initially the combination of P1 and GO exhibits minimal background fluorescence. When telomerase extends its repeat units of TTAGGG on the 3'-end of the primer-DNA, the fluorescence of P1 is subsequently recovered because the telomeric repeated sequence can hybridize with P1 and liberate it from the GO surface. This method enables the determination of telomerase activity down to 10 cells. For the in situ detection of telomerase, upon endocytosis of the P1/GO combinatorial probe into living cancer cells, the intracellular telomerase extends its primer to produce the telomeric repeated sequence and then turns on the fluorescence of P1, which can be directly monitored by confocal laser scanning microscopy. The feasibility of the assay is further investigated by treating with telomerase-related drugs, and the results demonstrate its potential in antitumor drug screening and cancer therapy evaluation.

Genome-wide scan for familial nasopharyngeal carcinoma reveals evidence of linkage to chromosome 4.

Nasopharyngeal carcinoma (NPC) occurs with high frequency in Asian populations, especially among people of Cantonese ancestry. In areas with high incidence, NPC clusters in families, which suggests that both geography and genetics may influence disease risk. Although the HLA-Bw46 locus is associated with increased risk of NPC, no predisposing genes have been identified so far. Here we report the results of a genome-wide search carried out in families at high risk of NPC from Guangdong Province, China. Parametric analyses provide evidence of linkage to the D4S405 marker on chromosome 4 with a logarithm of odds for linkage (lod) score of 3.06 and a heterogeneity-adjusted lod (hlod) score of 3.21. Fine mapping with additional markers flanking D4S405 resulted in a lod score of 3.54 and hlod score of 3.67 for the region 4p15.1-q12. Multipoint nonparametric linkage analysis gives lod scores of 3.54 at D4S405 (P = 5.4 x 10(-5)) and 4.2 at D4S3002 (P = 1.1 x 10(-5)), which is positioned 4.5 cM away from D4S405. When Epstein Barr virus antibody titer was included as a covariate, the lod scores reached 4.70 (P = 2.0 x 10(-5)) and 5.36 (P = 4.36 x 10(-6)) for D4S405 and D4S3002, respectively. Our findings provide evidence of a major susceptibility locus for NPC on chromosome 4 in a subset of families.

Regulation of multiple energy transfer processes in a simple nano-system for sensitive telomerase detection.

Telomerase, as a potential biomarker for early cancer diagnostics and therapies, has attracted considerable interests concerning its detection and monitoring. Herein, we develop a novel method for sensitive detection of telomerase activity by designing a gold nanoparticles/graphene oxide (AuNPs/GO) probe. The AuNPs were functionalized with a telomerase substrate (TS) primer and a 6-carboxy-fluorescein (FAM)-modified complementary DNA (P1). In the absence of telomerase, P1 exists in the random-coiled conformation, and the fluorescence resonance energy transfer (FRET) from FAM to AuNPs and GO results in efficient fluorescence quenching. In the presence of telomerase, the multiple hybridization between TS extension products and P1 leads to the conformation transition of P1 from single-stranded DNA to double-stranded rigid structure, and thus the FRET process can be prevented with the efficient fluorescence recovery. The metal enhanced fluorescence (MEF) effect between FAM and AuNPs can further effectively enhance the fluorescence of FAM, and thus the sensitivity and specificity of telomerase detection can be remarkably improved. It is worth mentioning that the proposed strategy does not need to design complex hairpin structure and allows the measurement of telomerase activity in three crude cell extracts equivalent to 7 HeLa cells, 8 A549 cells and 8 L929 cells in 1 h. In addition, the present sensing platform can be applied to inhibitor screening, in situ telomerase imaging, and intracellular drug delivery.