MXene Boosted Ultrasensitive Electrochemical Detection of 5-Hydroxymethylcytosine in Genomic DNA from Complex Backgrounds

5-Hydroxymethylcytosine in genomic DNA (5hmC-DNA), a predominant epigenetic mark, plays key roles in a broad range of bioprocesses such as cancer progression. However, efficient detection of 5hmC-DNA, especially from highly complex biological specimens, remains a harsh challenge due to its low abundance as well as the serious disturbance of non-targets. Leveraging MXene as the signal booster, an electrochemical biosensing technique is presented here for ultrasensitive detection of 5hmC-DNA from complex biological samples. The developed technique integrates enzyme-catalyzed transform of the hydroxyl group of 5hmC, sequence-specific recognition of the 5hmC-DNA targets, and facile electrochemical reaction. Remarkably, nanosized Ti 3 C 2 T x MXene is introduced as a highly conductive agent, managing to greatly boost the signals. Exhibiting outstanding consistency and robustness, the technique not only achieves excellent linear responses in a broad range of 5hmC-DNA (1.0 × 10 −13 –1.0 × 10 −9 m ) with the lowest detection limit of 59 fM but also possesses excellent selectivity against 5hmC analogs of including cytosine (C)- and 5-methylcytosine (5mC). More importantly, a proof-of-concept validation demonstrates the extraordinary ability of this technique for directly detecting 5hmC-DNA from complex backgrounds including cellular genomic extracts and serum of irradiated or non-irradiated mice, suggesting its highly promising potential for diverse applications such as early cancer screening.