Free-enzyme and triple-amplified electrochemical sensing of 8-hydroxy-2´-deoxyguanosine by three kinds of short pDNA-driven catalyzed hairpin assembly following with hybridization chain reaction
A sensitive and free-enzyme electrochemical aptasensor was constructed for the testing of 8-hydroxy-2´-deoxyguanosine (8-OH-dG). In the process of constructing the aptasensor, triple signal amplification strategies were introduced to enhance the sensitivity. First, every aptamer/pDNAs complex immobilized on the magnetic beads can release three kinds of pDNAs when 8-OH-dG were introduced, which caused three times magnification of target. Second, the released three kinds of pDNAs initiated the catalyzed hairpin assembly between two hairpin DNAs (HP1 and HP2) on the gold electrode. Meanwhile, three kinds of pDNAs were released again by following strand displacement reaction to perform next catalyzed hairpin assembly. Third, the emerging toehold of HP2 further induced the hybridization chain reaction (HCR) between two hairpin DNAs (HP3 and HP4), forming a long double strand DNA concatamer on the surface of electrode. Finally, [Ru(NH3)6]3+, an electroactive cation, was adsorbed on the long dsDNA concatamer by electrostatic interaction to report electrochemical signal. Under this triple signal amplification, a low detection limit down to 24.34 fM was obtained for 8-OH-dG determination, which is superior to those of most previously methods.