Ultrasensitive electrochemiluminescence immunosensor for 5-hydroxymethylcytosine detection based on Fe3O4@SiO2 nanoparticles and PAMAM dendrimers

- Excessive Ru was loaded on PAMAM-avidin to maintain the immunosensor's sensitivity.
- Dual signal amplification strategy was developed for improving sensitivity.
- The assay exhibited excellent stability, reproducibility and selectivity.
- The developed method was employed to detect 5hmC in biological real samples.

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 30 nM with low detection limit of 0.047 nM (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.

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