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

An ultrasensitive sandwiched electrochemiluminescence (ECL) immunosensor was developed for 5-hydroxymethylcytosine (5hmC) detection in genomic DNA by using Fe 3 O 4 @SiO 2 core–shell magnetic nanomaterial as a immobilization matrix for anti-5hmC antibody, PAMAM conjugated avidin and Ru(bpy) 2 (phen-5-NH 2 )(PF 6 ) 2 as signal amplification unit. Importantly, Fe 3 O 4 @SiO 2 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.