Electrogenerated chemiluminescence method for sensitive detection of hydroxylated double-stranded DNA through multifunctional polyadenine probe and hybridization chain reaction
5-Hydroxymethylcytosine (5-hmC), as the sixth base in the mammalian genome, is increasingly regarded as an epigenetic marker with crucial biological functions. Herein, a highly sensitive electrogenerated chemiluminescence (ECL) sensing platform for double-stranded DNA containing 5-hmC (5-hmC-dsDNA) in genome was fabricated, which based on polyadenine-gold interaction combining with signal amplification of hybridization chain reaction (HCR). This biosensing strategy could be executed to detect 5-hmC in the native double-stranded DNA, irrespective of the specific sequences of DNA. Firstly, DNA methyltransferase (M.HhaI) was introduced to chemically modify the hydroxyl of 5-hmC in double-stranded DNA, which converted 5-hmC-dsDNA to amino-derived 5-hmC-dsDNA. Subsequently, DNA sequence containing polyadenine (polyA) was used as an anchor probe to incorporate the derivatized 5-hmC-dsDNA by amide reaction to form compound DNA and then completely assembled onto the gold electrode surface through preferential polyA-gold interaction. Subsequently, two designed DNA hairpin probes which can alternately hybridize with each other were linked to the signal amplification part of multifunctional polyA probes, forming ultra-long nicked double helix structures. Finally, ECL indicator of Ru(phen) 3 2+ molecules were intercalated into the groove of the nicked DNA double helices, resulting greatly increased ECL intensity. Therefore, the quantitatively analysis of 5-hmC-dsDNA could be obtained relied on the relationship between the ECL intensity and 5-hmC-dsDNA content. The detection limit of this method for 5-hmC-dsDNA was 0.0001 % (S/N = 3). Moreover, the biosensing platform was successfully applied to detect 5-hmC-dsDNA in mice tissue samples with satisfactory results, manifesting its great potential application in clinical analysis.
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