RNA Condensate as a Versatile Platform for Improving Fluorogenic RNA Aptamer Properties and Cell Imaging.

Fluorogenic RNA aptamers are valuable tools for cell imaging, but they still suffer from shortcomings such as easy degradation, limited photostability, and low fluorescence enhancement. Molecular crowding conditions enable the stabilization of the structure, promotion of folding, and improvement of activity of functional RNA. Based on artificial RNA condensates, here we present a versatile platform to improve fluorogenic RNA aptamer properties and develop sensors for target analyte imaging in living cells. Using the CUG repeat as a general tag to drive phase separation, various fluorogenic aptamer-based RNA condensates (FLARE) were prepared. We show that the molecular crowding of FLARE can improve the enzymatic resistance, thermostability, photostability, and binding affinity of fluorogenic RNA aptamers. Moreover, the FLARE systems can be modularly engineered into sensors (FLARES), which demonstrate enhanced brightness and sensitivity compared to free sensors dispersed in homogeneous solution. This scalable design principle provides new insights into RNA aptamer property regulation and cellular imaging.

A strand displacement signal amplification-assisted fluorescence assay for sensitive detection of microRNA.

MicroRNA is a vital biomarker because of its abnormal expression in the emergence and development of diseases, especially in cancers. Herein, a label-free fluorescent sensing platform is proposed for detecting microRNA-21, coupled with the cascade toehold-mediated strand displacement reaction and magnetic beads. Target microRNA-21 acts as an initiator to trigger the cascade toehold-mediated strand displacement reaction and it outputs double-stranded DNA. After magnetic separation, the double-stranded DNA is intercalated by SYBR Green I, resulting in an amplified fluorescent signal. Under the optimal conditions, a wide linear range (0.5-60 nmol/L) and low limits of detection (0.19 nmol/L) are exhibited. What's more, the biosensor shows great specificity and reliability between microRNA-21 and other microRNAs involved in cancer (microRNA-34a, microRNA-155, microRNA-10b, and let-7a). Owing to the properties of fabulous sensitivity, high selectivity, and simplicity of operator, the proposed method paves a promising way for microRNA-21 detection in cancer diagnosis and biological research.

Catalytic hairpin assembly-assisted dual-signal amplification platform for ultrasensitive detection of tumor markers and intelligent diagnosis of gastric cancer.

Quantification of extracellular tumor markers has shown great promise for non-invasive cancer diagnosis. Combined detection of multiple tumor markers instead of a single one is valuable for accurate diagnosis. Here, we integrate CRISPR-Cas12a with DNA catalytic hairpin assembly (CHA) to doubly amplify the output signal for detecting microRNA-182 (miR-182), which is overexpressed by gastric cancer patients. Additionally, we develop a CHA system with self-replicating capacity (SRCHA) to realize dual-signal amplification for the detection of carcinoembryonic antigen (CEA), a broad-spectrum tumor marker. The proposed cascade amplification strategies enable ultrasensitive detection of miR-182 and CEA with low LODs of 0.063 fM and 4.8 pg mL-1, respectively. Moreover, we design a ternary "AND" logic gate using different concentrations of miR-182 and CEA as inputs, which demonstrates intelligent diagnosis of gastric cancer staging with a high accuracy of 93.3% in a clinical cohort of 30 individuals. Overall, our study expands the application of CRISPR-Cas12a in biosensing and provides a new diagnostic strategy for non-invasive liquid biopsy of gastric cancer before resorting to a traumatic tissue biopsy.

Constructing an acidic microenvironment by sulfonated polymers for photocatalytic reduction of hexavalent chromium under neutral conditions.

Hexavalent chromium (VI) heavy metal contamination is considered a serious threat to human health and the environment. The photocatalytic reduction of Cr(VI) basically occurs in the acidic environment, severely limiting the application of photocatalysts for the reduction of Cr(VI). Therefore, we designed a microenvironment strategy to achieve efficient reduction of Cr (VI) under neutral conditions by introducing sulfonic acid onto the aromatic conjugated skeleton. A series of characterizations and experiments have shown that the sulfonated aromatic ring conjugated polymer (Arcp-SO3H) can efficiently remove Cr(VI) under neutral or even alkaline conditions. In neutral solutions, Arcp-SO3H has a rate constant of 0.054 min-1 within 90 min and has an efficiency of nearly 100 %, which is 16 times faster than before sulfonation (k = 0.0316 min-1). the Arcp-SO3H surpasses all organic polymers and most metal-based photocatalysts in the related field. The capture experiments have proved that •O2- is the main role of reducing Cr(VI), and e- is secondary, which is quite different from the mechanism reported in the previous literature. The efficiency of reducing Cr (VI) in the four-cycle experiment is still 96 %, which also proves that Arcp-SO3H has strong stability and reproducibility. Thus, Arcp-SO3H has great practical application potential in the treatment of wastewater, and microenvironmental strategies also offer new possibilities in the field of environmental remediation.