A novel fluorescent aptasensor for ultrasensitive detection of Helicobacter pylori in stool samples based on catalytic hairpin assembly cascade hybridization chain reaction

In this work, a fluorescent aptasensor based on enzyme-free catalytic hairpin assembly cascade hybridization chain reaction (CHA-HCR) was established for rapid and sensitive detection of Helicobacter pylori (H. pylori) in stool samples. Four single-stranded DNA hairpins (HP1, HP2, HP3 and HP4), an aptamer and one trigger strand (T strand) were designed, and the stem of HP3 hairpin was modified with a fluorophore (Cy3) and a quencher (BHQ2), respectively. When H. pylori specifically bonded to the aptamer, the T strand was released from aptamer strand. Consequently, the free T strand triggered the CHA-HCR system, and HP2-HP1-[HP3-HP4]n long double strand complex was produced, resulting in the significant fluorescent enhancement. The proposed aptasensor can detect H. pylori in a wide concentration range (20 cfu/mL~ 1000 cfu/mL) with the detection limit as low as 5 cfu/mL. What’s more, the fluorescent aptasensor was implemented to detect H. pylori in 102 stool samples and the results were highly consistent with those of 13C urea breath test (13C-UBT), which demonstrated that the fluorescent aptasensor possessed enormous potential to rapid screening of H. pylori among the whole population and showed novel perspectives in the analysis of other biomarkers, clinical diagnostics, and biomedical applications. •An enzyme-free fluorescent aptasensor was constructed for determination of H. pylori in stool within 30 min.•Aptamer-based CHA-HCR system was designed to enhance the specificity and sensitivity of H. pylori analysis.•The assay can effectively meet the requirements of point-of-care diagnosis and large-scale screening studies of H. pylori.