Highly-sensitive and homogenous detection of 8-oxoguanine based DNA oxidative damage by a CRISPR-enhanced structure-switching aptamer assay.

8-oxoguanine (8-oxoG) based DNA damage is the most common type of DNA damage which greatly affect gene expression. Therefore, accurate quantification of 8-oxoG based DNA damage is of high clinical significance. However, current methods for 8-oxoG detection struggle to balance convenience, low cost, and sensitivity. Herein, we have proposed and investigated the shortened crRNA mode of CRISPR-Cas12a system and greatly enhanced its signal-to-noise ratio. Taking advantages of the shortened crRNA mode, we further developed a CRISPR-enhanced structure-switching aptamer assay (CESA) for 8-oxoG. The analytical performance of CESA was thoroughly investigated via detecting free 8-oxoG and 8-oxoG on gDNA. The CESA displayed impressive sensitivity for free 8-oxoG, with detection and quantification limits of 32.3 pM and 0.107 nM. These limits modestly rose to 64.5 pM and 0.215 nM when examining 8-oxoG on gDNA. To demonstrate the clinical practicability and significance of the CESA system, we further applied it to measuring 8-oxoG levels in 7 plasma samples (Cervical carcinoma, 11.87 ± 0.69 nM VS. Healthy control, 2.66 ± 0.42 nM), 24 seminal plasma samples (Asthenospermia, 22.29 ± 7.48 nM VS. Normal sperm, 9.75 ± 3.59 nM), 10 breast-tissue gDNA samples (Breast cancer, 2.77 ± 0.63 nM/μg VS. Healthy control, 0.41 ± 0.09 nM/μg), and 24 sperm gDNA samples (Asthenospermia, 28.62 ± 4.84 VS. Normal sperm, 16.67 ± 3.31). This work not only proposes a novel design paradigm of shortened crRNA for developing CRISPR-Cas12a based biosensors but also offers a powerful tool for detecting 8-oxoG based DNA damage.