Quantification of MicroRNA in a Single Living Cell via Ionic Current Rectification-Based Nanopore for Triple Negative Breast Cancer Diagnosis.

Accurate analysis of microRNAs (miRNAs) at the single-cell level is extremely important for deeply understanding their multiple and intricate biological functions. Despite some advancements in analyzing single-cell miRNAs, challenges such as intracellular interferences and insufficient detection limits still remain. In this work, an ultrasensitive nanopore sensor for quantitative single-cell miRNA-155 detection is constructed based on ionic current rectification (ICR) coupled with enzyme-free catalytic hairpin assembly (CHA). Benefiting from the enzyme-free CHA amplification strategy, the detection limit of the nanopore sensor for miRNA-155 reaches 10 fM and the nanopore sensor is more adaptable to complex intracellular environments. With the nanopore sensor, the concentration of miRNA-155 in living single cells is quantified to realize the early diagnosis of triple-negative breast cancer (TNBC). Furthermore, the nanopore sensor can be applied in screening anticancer drugs by tracking the expression level of miRNA-155. This work provides an adaptive and universal method for quantitatively analyzing intracellular miRNAs, which will greatly improve our understanding of cell heterogeneity and provide a more reliable scientific basis for exploring major diseases at the single-cell level.

Molecular Recognition-Triggered Aptazyme Sensor Using a Co-MOF@MCA Hybrid Nanostructure as Signal Labels for Adenosine Triphosphate Detection in Food Samples.

Developing rapid detection technology for adenosine triphosphate (ATP) is crucial in quality supervision and food safety. Herein, an electrochemical aptasensor based on an aptazyme-catalyzed signal amplification strategy is constructed for ATP detection using polyethyleneimine-functionalized molybdenum disulfide (PEI-MoS2)/Au@PtPd nanobipyramids (MoS2/Au@PtPd NBPs) as a modification material. Additionally, a novel kind of nitrogen-rich covalent organic framework (COF) is prepared using melamine and cyanuric acid (MCA). We synthesize MCA and the Co-based metal organic framework (Co-MOF) as the signal label. Due to the fact that π-π stacking interactions of Co-MOF@MCA can expand the load efficiency and surface concentration of the signal label, the signal response is an order of magnitude higher than that of Co-MOF or MCA as the signal label. Target ATP changes the conformation of the aptazyme, and it becomes activated. With the assistance of metal ions, the signal label is circularly cleaved, causing an amplification of the signal. Among them, MoS2/Au@PtPd NBPs have a large specific surface area and good electrical conductivity and can carry substantial DNA strands and amplify the redox signal of methylene blue (MB). Under optimal conditions, the aptasensor can detect ATP from 10 pM to 100 µM with a low limit of detection of 7.37 × 10-10 µM. Therefore, the novel aptasensor has extensive application prospects in quality supervision and food safety.