A new chemiluminescence method for the determination of 8-hydroxyguanine based on l-histidine bound nickel nanoparticles.

A new chemiluminescence aptasensor for sensitive and efficient detection of 8-hydroxyguanine based on the synergistic interaction of Ni NPs@l-histidine@aptamer@MBs has been developed, and it has been applied in the real urine samples of cancer patients.

Label-free and enzyme-free one-step rapid colorimetric detection of DNA methylation based on unmodified gold nanoparticles.

DNA methylation has been identified as one of the important causes of tumorigenesis, so it is important to develop some advanced methods for detecting and quantifying DNA methylation. In this study, a label-free and enzyme-free one-step rapid colorimetric detection of DNA methylation based on unmodified Au nanoparticles(Au NPs)has been proposed. This method can quickly, efficiently, economically and easily colorimetric detect methylated DNA only by the color change of unmodified Au NPs solution without the covalent modification of Au NPs in advance or complicated instruments for implementation with practical limitations or expensive biological enzymes or traditional organic dyes during the reaction. The strategy employed the difference in electrostatic attraction of single-stranded DNA and double-stranded DNA against salt-induced aggregation of Au NPs. The method has a DNA methylated detection limit of 8.47 nM and it is distinctly visible to detect methylated DNA with the naked eye as low as 20 nM. Furthermore, the strategy has an ability to detect methylated DNA in the presence of abundant unmethylated DNA with the detection limit of 0.13% and as low as 1% methylated DNA can be distinguished in heterogeneous samples with the naked eye. Also, the stratagem provides a convenient and rapid platform for methylated DNA detection of human serum samples in one step, which displays a huge potential for clinical diagnosis and treatment of oncological diseases.

Colorimetric determination of the activity of methyltransferase based on nicking enzyme amplification and the use of gold nanoparticles conjugated to graphene oxide.

A method is described for the colorimetric determination of the activity of CpG methyltransferase (M.SssI). It is based on (a) the crosslinking effect between dsDNA-modified gold nanoparticles (AuNPs) and graphene oxide (GO), and (b) an amplification reaction with the aid of a nicking enzyme. To avoid the aggregation of AuNPs (which would produce false signals), a hairpin DNA was connected to the AuNPs. Thus, the red color of the solution (measured at 530 nm) increases linearly with the activity of M.SssI from 0.2 to 60 U·mL-1, and the limit of detection is 67 U·mL-1. This is superior to some reported strategies. The method was successfully applied to analyze spiked serum samples. Conceivably, it represents a powerful tool for use in drug development and diagnosis. Graphical abstracts A method based on the conjugated cross-linking effect between dsDNA modified Au NPs and GO coupled with an amplification reaction of nicking enzyme has been developed for colorimetric detection of the activity of CpG methyltransferase (M.SssI).

Fluorescence-based Polymerase Amplification for the Sensitive Detection of DNA Methyltransferase Activity.

DNA methyltransferase (MTase) is related to transcriptional repressor activity in biological functions. It is an essential for cancer diagnosis and therapeutics to detect DNA MTase activity sensitively. Here, a fluorescent system based on polymerase amplification has been developed to detect DNA adenine MTase (Dam) activity sensitively. The amplification is triggered by the probe DNA regions a, which are the primes of a polymerase-induced replicated reaction. They come from methylation and a digestion reaction of DNA S1-S1, including a 5'-GATC-3' sequence recognized by Dam MTase and methylation sensitive restriction endonuclease Dpn I. The intensities of fluorescence are dependent on the Dam MTase activity. The method shows fine sensitivity with a detection limit of 3.2 × 10-4 U mL-1 and specificity for Dam MTase. In human serum samples, the method has been successfully applied, and it has also been used to screen the inhibitors, which means that the developed method can be a powerful and potential tool for drug development and clinical diagnosis in the future.

Amplification strategy for sensitive detection of methyltransferase activity based on surface plasma resonance techniques.

In this work, a newly developed surface plasma resonance (SPR) system for the sensitive detection of M.SssI activity has been designed based on double signal amplification with DNA chain cyclic reactions and AuNPs. In the absence of M.SssI, hairpin DNA 1 (HP1) can be cleaved into s1 fragments catalyzed by HpaII. The s1 fragments can then trigger a recycling process of hairpin DNA 2 (HP2) hybridization and subsequently release massive s2 and s3 in the solution of Nt.AlwI and HPII. AuNPs-DNA can be captured on gold film by the released s2 and s3 to produce a strong SPR signal. Whereas in the presence of M.SssI, methylated HP1 cannot be cleaved by HpaII, thus produce a weak SPR signal. The SPR signals are dependent on the M.SssI concentration in the range from 0.5 to 50 U/mL. The successful detection of M.SssI activity in clinical serum samples and inhibition of M.SssI using 5-Aza and 5-Aza-dC indicate a great potential of this strategy for building new monitoring platform in bioanalysis and clinical biomedicine.

Label-free colorimetric detection of biothiols utilizing SAM and unmodified Au nanoparticles.

Herein, a sensitive and selective sensor for biothiols based on colorimetric assay is reported. S-adenosyl-L-methionine (SAM) could induce the selective aggregation of unmodified gold nanoparticles (AuNPs) by electrostatic interaction. In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), AuNPs prefer to react with thiols of biothiols rather than SAM due to the formation of Au-S bond. Thus, the AuNPs turn from the aggregation to the dispersion state, and the corresponding color variation in the process of anti-aggregation of AuNPs can be used for the quantitative screening of biothiols through UV-vis spectroscopy or by the naked eye. Under optimized conditions, a good linear relationship in the range of 0.4-1.2 µM is obtained for Cys, 0.2-0.9 µM for GSH, and 0.6-3.0 µM for Hcys. The detection limits of this assay for GSH, Cys and Hcys are 35.8 nM, 21.7 nM, and 62.4 nM, respectively. This colorimetric assay exhibits rapid operation (within 5 min), high selectivity and sensitivity towards biothiols with tunable dynamic ranges.

Label-free colorimetric assay for DNA methylation based on unmodified Au nanorods as a signal sensing probe coupled with enzyme-linkage reactions.

Using unmodified Au nanorods with enzyme-linkage reaction, a label-free colorimetric method for simple and convenient assay of DNA methylation is presented.