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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. Image 1 • The metal enhanced fluorescence effect can be regulated to generate significant fluorescence enhancement. • Weak background fluorescence can be realized via efficient fluorescence resonance energy transfer. • Telomerase activity down to 7 HeLa cells can be sensitively detected. • The method facilitates cellular imaging, inhibitor screening and drug delivery. [ABSTRACT FROM AUTHOR]

An electrochemical sensor was fabricated for arsenite detection using graphene oxide-assisted generation of prussian blue nanoparticles as enhanced redox signal label. The 5′-thiolate-labeled (GT) 21 -ssDNA was first self-assembled on a gold electrode surface via Au-S bond. Graphene oxide can interact with ssDNA through π-π stacking interaction and facilitate the generation of prussian blue nanoparticles on its surface as an electrochemically active indicator. In the absence of arsenite, plenty of graphene oxide/prussian blue nanoparticles can be adsorbed on the electrode surface to produce a stronger redox signal of prussian blue nanoparticles. While in the presence of arsenite, (GT) 21 -ssDNA can recognize and combine with arsenite via hydrogen bonds to form (GT) 21 -ssDNA/arsenite complex with a frizzy structure. The conformational change of (GT) 21 -ssDNA led to less adsorption of graphene oxide/prussian blue nanoparticles on the electrode surface, resulting in a reduced redox response. The arsenite-induced (GT) 21 -ssDNA structure switching can be used for sensitive detection of arsenite with a linear range from 0.2 to 500 ppb and a detection limit down to 0.058 ppb. Benefiting from (GT) 21 -ssDNA containing arsenite recognition sequence, the proposed sensor exhibited excellent specificity against other heavy metal ions. The applicability of the electrochemical biosensor for arsenite assay in real water samples demonstrated the great potential of this strategy for trace arsenite detection in environment. [ABSTRACT FROM AUTHOR]

Herein, a novel electrochemiluminescence resonance energy transfer (ECL-RET) biosensor using graphene quantum dots (GQDs) as donor and graphene oxide (GO) as acceptor for monitoring the activity of protein kinase was presented for the first time. Anti-phosphoserine antibody conjugated graphene oxide (Ab-GO) nonocomposite could be captured onto the phosphorylated peptide/GQDs modified electrode surface through antibody–antigen interaction in the presence of casein kinase II (CK2) and adenosine 5′-triphosphate (ATP), resulting in ECL from the GQDs quenching by closely contacting GO. This ECL quenching degree was positively correlated with CK2 activity. Therefore, on the basis of ECL-RET between GQDs and GO, the activity of protein kinase can be detected sensitively. This biosensor can also be used for quantitative analysis CK2 activity in serum samples and qualitative screening kinase inhibition, indicating the potential application of the developed method in biochemical fundamental research and clinical diagnosis. [ABSTRACT FROM AUTHOR]