Target proteins-regulated DNA nanomachine-electroactive substance complexes enable separation-free electrochemical detection of clinical exosome

Simple and reliable profiling of tumor-derived exosomes (TDEs) holds significant promise for the early detection of cancer. Nonetheless, this remains challenging owing to the substantial heterogeneity and low concentration of TDEs. Herein, we devised an accurate and highly sensitive electrochemical sensing strategy for TDEs via simultaneously targeting exosomal mucin 1 (MUC1) and programmed cell death ligand 1 (PD-L1). This approach employs high-affinity aptamers as specific recognition elements, utilizes rolling circle amplification and DNA nanospheres as effective bridges and signal amplifiers, and leverages methylene blue (MB) and doxorubicin (DOX) as robust signal reporters. The crux of this separation- and label-free method is the specific response of MB and DOX to G-quadruplex structures and DNA nanospheres, respectively. Quantifying TDEs using this strategy enabled precise discrimination of lung cancer patients (n = 25) from healthy donors (n = 12), showing 100% specificity (12/12), 92% sensitivity (23/25), and an overall accuracy of 94.6% (35/37), with an area under the receiver operating characteristic curve (AUC) of 0.97. Furthermore, the assay results strongly correlated with findings from computerized tomography and pathological analyses. Our approach could facilitate the early diagnosis of lung cancer through TDEs-based liquid biopsy.

Accelerated diagnosis: a crosslinking catalytic hairpin assembly system for rapid and sensitive SARS-CoV-2 RNA detection

The COVID-19 pandemic has underscored the urgent need for rapid and reliable strategies for early detection of SARS-CoV-2. In this study, we propose a DNA nanosphere-based crosslinking catalytic hairpin assembly (CCHA) system for the rapid and sensitive SARS-CoV-2 RNA detection. The CCHA system employs two DNA nanospheres functionalized with catalytic hairpin assembly (CHA) hairpins. The presence of target SARS-CoV-2 RNA initiated the crosslinking of DNA nanospheres via CHA process, leading to the amplification of fluorescence signals. As a result, the speed of SARS-CoV-2 diagnosis was enhanced by significantly increasing the local concentration of the reagents in a crosslinked DNA product, leading to a detection limit of 363 fM within 5 min. The robustness of this system has been validated in complex environments, such as fetal bovine serum and saliva. Hence, the proposed CCHA system offers an efficient and simple approach for rapid detection of SARS-CoV-2 RNA, holding substantial promise for enhancing COVID-19 diagnosis.

Biomolecules-mediated electrochemical signals of Cu2+: Y-DNA nanomachines enable homogeneous rapid one-step assay of lung cancer circulating tumor cells

This study presents a straightforward efficient technique for extracting circulating tumor cells (CTCs) and a rapid one-step electrochemical method (45 min) for detecting lung cancer A549 cells based on the specific recognition of mucin 1 using aptamers and the modulation of Cu2+ electrochemical signals by biomolecules. The CTCs separation and enrichment process can be completed within 45 min using lymphocyte separation solution (LSS), erythrocyte lysis solution (ELS), and three centrifugations. Besides, the influence of various biomolecules on Cu2+ electrochemical signals is comprehensively discussed, with DNA nanospheres selected as the medium. Three single-stranded DNA sequences were hybridized to form Y-shaped DNA (Y-DNA), creating DNA nanospheres. Upon specific capture of mucin 1 by the aptamer, most DNA nanospheres could form complexes with Cu2+ (DNA nanosphere-Cu2+), significantly reducing the concentration of free Cu2+. Our approach yielded the limit of detection (LOD) of 2 ag/mL for mucin 1 and 1 cell/mL for A549 cells. 39 clinical blood samples were used for further validation, yielding results closely correlated with pathological, computed tomography (CT) scan findings and folate receptor-polymerase chain reaction (FR-PCR) kits. The receiver operating characteristic (ROC) curve displayed an area under the curve (AUC) value of 0.960, demonstrating 100% specificity and 93.1% sensitivity for the assay. Taken together, our findings indicate that this straightforward and efficient pretreatment and rapid, highly sensitive electrochemical assay holds great promise for liquid biopsy-based tumor detection using CTCs.

Size-Controllable and Self-Assembled DNA Nanosphere for Amplified MicroRNA Imaging through ATP-Fueled Cyclic Dissociation

Visualizing intracellular microRNA (miRNA) is of great importance for revealing its roles in the development of disease. However, cell membrane barrier, complex intracellular environment and low abundance of target miRNA are three main challenges for efficient imaging of intracellular miRNA. Here, we report a size-controllable and self-assembled DNA nanosphere with ATP-fueled dissociation property for amplified miRNA imaging in live cells and mice. The DNA nanosphere was self-assembled from Y-shaped DNA (Y-DNA) monomers through predesigned base pair hybridization, and the size could be easily controlled by varying the concentration of Y-DNA. Once the nanosphere was internalized into cells, the intracellular specific target miRNA would trigger the cyclic dissociation of the DNA nanosphere driven by ATP, resulting in amplified FRET signal. The programmable DNA nanosphere has been proven to work well for detecting the expression of miRNA in cancer cells and in mice, which demonstrates its fairish cell penetration, stability and sensitivity.