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G-quadruplex DNAzyme-based chemiluminescence biosensing strategy for ultrasensitive DNA detection: combination of exonuclease III-assisted signal amplification and carbon nanotubes-assisted background reducing.

Detection of ultralow concentration of specific nucleic acid sequences is important in early diagnosis of gene-related diseases and biodefense application. Herein, we report an amplified chemiluminescence (CL) biosensing platform for ultrasensitive DNA detection. It is based on the exonuclease III-assisted target recycling amplification and catalytic effect of G-quadruplex-hemin DNAzyme to stimulate the generation of CL in the presence of H2O2 and luminol. Moreover, the typical problem of high background induced by excess hemin itself can be effectively addressed through the absorbing of superfluous hemin on the surface of single-walled carbon nanotubes and then removing though centrifugation. Therefore, our proposed biosensing exhibited a high sensitivity toward target DNA with a detection limit of 12 fM, which was about 100-fold lower than that of the DNAzyme-based CL sensor for DNA detection without Exo III-assisted amplification. This sensing platform provides a label-free and cost-effective approach for sensitive detection of DNA.