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An ultrasensitive sandwiched electrochemiluminescence (ECL) immunosensor was developed for 5-hydroxymethylcytosine (5hmC) detection in genomic DNA by using Fe3O4@SiO2 core-shell magnetic nanomaterial as a immobilization matrix for anti-5hmC antibody, PAMAM conjugated avidin and Ru(bpy)2(phen-5-NH2)(PF6)2 as signal amplification unit. Importantly, Fe3O4@SiO2 nanoparticles were verified to not only possess enormous surface for loading antibody by amido link, but also exhibit excellent bioactivity. With the dual signal amplification strategy, the ECL immunosensor showed wide detection range from 0.1 to 30nM with low detection limit of 0.047nM (S/N = 3). Based on the specific immunoreaction, the developed method also illustrated excellent detection selectivity. The fabricated immunosensor was also applied to detect the 5hmC in genomic DNA of cancer tissue, which indicated that the immunosensor possess potential applications in clinical detection.

A novel, simple and sensitive photoelectrochemical (PEC) immunosensing platform was constructed for detecting N6-methyladenosine (m6A) based on the carboxylated CN and avidin functionalized Ru@SiO2 (ARS) nanocomposite. Herein, the N6-methyladenosine-5'-triphosphate (m6ATP) was selected as the detection target molecule, m6A antibody was used as recognition unit for m6A, the carboxylated g-C3N4 (CN) was not only used as the photoactive substance, but the substrate for the m6A antibody immobilization, ARS was synthesized and used as signal amplification unit to improve the photocurrent of CN, Phos-tag-biotin was employed as bridge of m6ATP and Ru@SiO2 through the specific interaction between phosphate group of m6ATP and Phos-tag, biotin and avidin, respectively. Under the optimal condition, the fabricated PEC biosensor showed a linear range of 0.01-10nM and high detection sensitivity with low detection limit of 3.23pM for m6ATP. Besides, the developed strategy was also successfully applied to evaluate the content of m6A in human serum samples.

N6-methyladenosine (m6A) is an enigmatic and abundant internal modification in eukaryotic messenger RNA (mRNA), which could affect various aspects of RNA metabolism and mRNA translation. Herein, a novel photoelectrochemical (PEC) immunosensor was constructed for m6A detection based on the inhibition of Cu2+ to the photoactivity of g-C3N4/CdS quantum dots (g-C3N4/CdS) heterojunction, where g-C3N4/CdS heterojunction was used as photoactive material, anti-m6A antibody as recognition unit for m6A-containing RNA, Phos-tag-biotin as link unit and avidin functionalized CuO as PEC signal indicator. When CuO was captured on electrode through biotin-avidin affinity reaction and then treated with HCl, Cu2+ could be released and CuxS would be formed based on the selective interaction between CdS and Cu2+, leading the photocurrent obviously decreased. Under the optimal detection conditions, the PEC biosensor displayed a linear range of 0.01-10nM and a low detection limit of 3.53 pM for methylated RNA determination. Furthermore, the developed method could also be used to detect the expression level of m6A methylated RNA in serum samples of breast cancer patient before and after operative treatment. The proposed assay strategy has a great potential for detecting the expression methylation level of RNA in real sample.

N6-methyladenosine (m6A), a kind of RNA methylation form and important epigenetic event, plays crucial roles in many biological progresses. Thus it is essential to quantitatively detect m6A in complicated biological samples. Herein, a simple and sensitive electrochemical method was developed for m6A detection using N6-methyladenosine-5′-triphosphate (m6ATP) as detection target molecule. In this detection strategy, anti-m6A antibody was selected as m6A recognition and capture reagent, silver nanoparticles and amine-PEG3-biotin functionalized SiO2 nanospheres (Ag@SiO2) was prepared and used as signal amplification label, and phos-tag-biotin played a vital role of “bridge” to link m6ATP and Ag@SiO2 through the two forms of specific interaction between phosphate group of m6ATP and phos-tag, biotin and streptavidin, respectively. Under the optimal experimental conditions, the immunosensor presented a wide linear range from 0.2 to 500 nM and a low detection limit of 0.078 nM (S/N=3). The reproducibility and specificity were acceptable. Moreover, the developed method was also validated for detect m6A content in human cell lines. Importantly, this detection strategy provides a promising immunodetection platform for ribonucleotides and deoxyribonucleotides with the advantages of simplicity, low-costing, specificity and sensitivity.