Small extracellular–vesicule-associated microRNA (sEV-miRNA) is an important biomarker for cancer diagnosis. However, rapid and sensitive detection of low-abundance sEV-miRNA in clinical samples is challenging. Herein, a simple electrochemical biosensor that uses a DNA nanowire to localize catalytic hairpin assembly (CHA), also called domino-type localized catalytic hairpin assembly (DT-LCHA), has been proposed for sEV-miRNA1246 detection. The DT-LCHA offers triple amplification, (i). CHA system was localized in DNA nanowire, which shorten the distance between hairpin substrate, inducing the high collision efficiency of H1 and H2 and domino effect. Then, larger numbers of CHAs were triggered, capture probe bind DT-LCHA by exposed c sites. (ii) The DNA nanowire can load large number of electroactive substance RuHex as amplified electrochemical signal tags. (iii) multiple DT-LCHA was carried by the DNA nanowire, only one CHA was triggered, the DNA nanowire was trapped by the capture probe, which greatly improve the detection sensitivity, especially when the target concentration is extremely low. Owing to the triple signal amplification in this strategy, sEV-miRNA at a concentration of as low as 24.55 aM can be detected in 20 min with good specificity. The accuracy of the measurements was also confirmed using reverse transcription quantitative polymerase chain reaction. Furthermore, the platform showed good performance in discriminating healthy donors from patients with early gastric cancer (area under the curve [AUC]: 0.96) and was equally able to discriminate between benign gastric tumors and early cancers (AUC: 0.77). Thus, the platform has substantial potential in biosensing and clinical diagnosis. Graphical Abstract

Monitoring tumor biomarkers in a non‐invasive manner for tumor diagnosis has attracted increasing attention. Liquid biopsy mainly includes three types of biomarkers: circulating tumor cells, extracellular vesicles, and circulating nucleic acids. These biomarkers released by tumor cells can travel to other parts of the circulation system. The analysis of circulating tumor markers in the circulation enables early tumor diagnosis, progression evolution, and treatment monitoring, which are important for individualized clinical decisions. In this study, we summarize different DNA nanotechnology strategies that can be used to capture, amplify, and measure circulating biomarkers and discuss the current challenges and outlook.

Circular RNAs in extracellular vesicles (EV‐circRNAs) are gaining recognition as potential biomarkers for the diagnosis of gastric cancer (GC). Most current research is focused on identifying new biomarkers and their functional significance in disease regulation. However, the practical application of EV‐circRNAs in the early diagnosis of GC is yet to be thoroughly explored due to the low accuracy of EV‐circRNAs analysis. In this study, a hybridization chain reaction system based on rectangular DNA framework guidance and constructing a bimodal EV‐circRNA in situ analyzer (BEISA) is developed. The analyzer can provide dual signal outputs in the fluorescence and electrochemical modes, enabling a self‐correcting detection mechanism that significantly improves the accuracy of the assay. It has a broad detection range and an extremely low limit of detection. In a clinical cohort study, the BEISA used four circRNAs as biomarkers, combining them with machine learning for multiparametric analysis, which effectively differentiated between healthy donors and patients with early‐stage GC. It is believed that the BEISA, in conjunction with machine learning technology, provides an efficient, sensitive, and reliable tool for EV‐circRNA analysis, aiding in the early diagnosis of GC.

The profiling of small extracellular vesicle-associated microRNAs (sEV-miRNAs) plays a vital role in cancer diagnosis and monitoring. However, detecting sEV-miRNAs with low expression in clinical samples remains challenging. Herein, we propose a novel electrochemical biosensor using localized DNA tetrahedron-assisted catalytic hairpin assembly (LDT-CHA) for sEV-miRNA determination. The LDT-CHA contained localized DNA tetrahedrons with CHA substrates, leveraging an efficient localized reaction to enable sensitive and rapid sEV-miRNA measurement. Based on the LDT-CHA, the proposed platform can quantitatively detect sEV-miRNA down to 25 aM in 30 min with outstanding specificity. For accurate diagnosis of gastric cancer patients, a combination of LDT-CHA and a panel of four sEV-miRNAs (sEV-miR-1246, sEV-miR-21, sEV-miR-183-5P, and sEV-miR-142-5P) was employed in a gastric cancer cohort. Compared with diagnosis with single sEV-miRNA, the proposed platform demonstrated a higher accuracy of 88.3% for early gastric tumor diagnoses with higher efficiency (AUC: 0.883) and great potential for treatment monitoring. Thus, this study provides a promising method for the bioanalysis and determination of the clinical applications of LDT-CHA. Graphical Abstract