Fluorescence enhancement of silver nanocluster at intrastrand of a 12C-loop in presence of methylated region of sept 9 promoter

• Published in: Analytica chimica acta 2018-12, Vol.1038, p.157-165
• Main Authors: Sadeghan, Amir Amiri, Soltaninejad, Hossein, Hosseinkhani, Saman, Hosseini, Morteza, Ganjali, Mohammad Reza, Asadollahi, Mohammad Ali
• Format: Article
• Language: English
• Subjects: Biomarkers; Biosensing Techniques; Colorectal carcinoma; Deoxyribonucleic acid; DNA; DNA Methylation; DNA Probes - chemistry; Epigenetics; Fluorescence; Fluorescent enhancement; Gene expression; Metal Nanoparticles - chemistry; Nanoclusters; Nucleotide sequence; Plasmids; Promoter Regions, Genetic - genetics; Septin9; Septins - genetics; Septins - metabolism; Silver - chemistry; Silver nanoclusters; Spectrometry, Fluorescence; Strands; Turn-on
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2018.07.025

Determining methylation state of a particular DNA sequence is an essential task in many epigenetic investigations. Here a facile method based on silver nanocluster (AgNCs) fluorescence enhancement is presented. Target sequences were selected from Sept9 promoter region that its hypermethylation is demonstrated as a reliable biomarker of colorectal cancer. Probe DNA was complementary to a 25 nucleotide of the target region and possessed twelve additional cytosines in the middle to grant the formation of AgNCs. After probe strands were hybridized with methylated and non-methylated targets separately, AgNCs were synthesized, and their fluorescence intensities were recorded. Fluorescence intensity enhanced when the target strands were methylated and quenched when they were non-methylated. The Linear range of fluorescence enhancement was from 1.0 × 10-7 M to 5.0 × 10-7 M with the detection limit of 7.6 × 10-8 M. Sensor specificity was checked with non-complementary strands with the maximum similarity of 40%. Further experiments explored various characteristics of methylated and non-methylated DNAs carrying AgNC and indicated that structure of methylated and non-methylated DNAs was affected differently by silver ions that could then influence AgNC fluorescence. This effect was strongly sequence-dependent, and either fluorescence enhancement or quenching was observed with two different sequences. Counter diagram of fluorescent excitation and emission of 12C1-NoMet1 (left) and 12C1-4Met1 (right) indicating the similar excitation and emission wavelengths for methylated and non-methylated. [Display omitted] •Detection of methylated DNA by fluorescence turn on is developed.•Target sequence is from Sept9 promoter region.•Detection limit of methylated strand was 7.6 × 10−8 M.•Silver ions affect the structure of methylated and non-methylated DNA.•Trun on in NC fluorescence is depended on methylated DNA sequence.