Identifying 5-Hydroxymethylcytosine without Sequence Specificity Using MOF-Derived MnO x S y Nanoflowers for Boosting Electrochemiluminescence.

It is universally recognized that the quantification of DNA hydroxymethylation at random gene sequences still remains challenging. Herein, the highly sensitive identifying strategy of 5-hydroxymethylcytosine (5-hmC) without sequence specificity was achieved with a novel electrochemiluminescence (ECL) biosensor, which deftly integrated metal-organic framework (MOF)-derived amorphous MnO x S y nanoflowers (MnO x S y NFs) as a bifunctional co-reaction accelerator and cross-shaped DNA tracks as a well-regulated signal switch. Specifically, the target recognition process of 5-hmC was performed through specific chemical modification, where the hydroxymethyl sites were first aminated and then labeled with a 5'-carboxyl-functioned DNA walker, thus forming the target labeled DNA walker (5-ghmC-walker). Subsequently, the cross-shaped DNA tracks were ingeniously designed to endow the 5-ghmC-walker with continuous mechanical motion due to the long periodic linear alignment structure and well-regulated highly ordered interfaces. Furthermore, as a bifunctional co-reaction accelerator synthesized by in situ Mn-MOF template-sacrificing strategy, the MnO x S y NFs could promote the reduction of both dissolved O 2 and S 2 O 8 2- , remarkably boosting the ECL intensity of a peroxydisulfate (S 2 O 8 2- ) solution by 5.2 times compared to the pure S 2 O 8 2- solution. Benefiting from specific target recognition and a dual-pathway strategy for boosting ECL, the proposed ECL platform can quantify 5-hmC with a wide linear range of 1 fM-1 nM and a low detection limit of 0.29 fM. This simple, highly sensitive strategy without sequence specificity provides a powerful platform for 5-hmC detection in the epigenetic study and disease pathogenesis.