Label free electrochemiluminescence protocol for sensitive DNA detection with a tris(2,2′-bipyridyl)ruthenium(II) modified electrode based on nucleic acid oxidation

Label free electrochemiluminescence (ECL) DNA detection based on catalytic guanine and adenine bases oxidation using tris  (2,2′-bipyridyl)ruthenium(II) [Ru(bpy)32+] modified glassy carbon (GC) electrode was demonstrated in this work. The modified GC electrode was prepared by casting carbon nanotubes (CNT)/Nafion/Ru(bpy)32+ composite film on the electrode surface. ECL signals of double-stranded DNA and their thermally denatured counterparts can be distinctly discriminated using cyclic voltammetry (CV) with a low concentration (3.04 × 10−8 mol/L for Salmon Testes-DNA). Most importantly, sensitive single-base mismatch detection of p53 gene sequence segment was realized with 3.93 × 10−10 mol/L employing CV stimulation (ECL signal of C/A mismatched DNA oligonucleotides was 1.5-fold higher than that of fully base-paired DNA oligonucleotides). Label free, high sensitivity and simplicity for single-base mismatch discrimination were the main advantages of the present ECL technique for DNA detection over the traditional DNA sensors.