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The discovery of reliable biomarkers is essential for early diagnosis, treatment, and prognosis assessment of diseases. Many research studies have shown that circRNA is a potential biomarker for diagnosis and prognosis of diseases. However, in situ monitoring circRNA in live cells is still a challenge at present, which brings a major limitation to the development and verification of circRNA as a disease biomarker. In this study, a catalytic hairpin assembly (CHA) reaction-based DNA octahedral amplifier (DOA) was developed for fluorescence resonance energy transfer (FRET) detection and bioimaging of circRNA in living cells. The DOA was first produced by self-assembling a DNA octahedron with six customized single-stranded DNAs, and two hairpins H1 (Cy3) and H2 (Cy5) were then hybridized to four vertices of the DNA octahedron. Idiopathic pulmonary fibrosis (IPF)-related circHIPK3 was used as the target. Once the CHA reaction from H1 and H2 on DOA was activated by a sequence-specific back-splice junction (BSJ) of circHIPK3, a significant FRET signal can be obtained from Cy3 to Cy5. The circHIPK3 was subsequently released to cause the next CHA reaction. Because the DOA has the advantages of the spatial-confinement effect, resistance to nuclease degradation and easy penetration into cells, rapid and excellent signal amplification FRET detection and bioimaging of endogenous circHIPK3 can be achieved in various cells. This study provides a high-precision assay platform to explore the possibility of using circRNA as a biomarker, and it is valuable for circRNA-related early diagnosis and treatment of diseases. [ABSTRACT FROM AUTHOR]

A single-walled carbon nanohorn (SWCNH) has been used to construct a molecularly imprinted electrochemical sensor for the first time. Kanamycin, a widely used aminoglycoside antibiotic, is used as a representative analyte to test the detection strategy. The kanamycin sensor was constructed by the electropolymerization of a molecularly imprinted poly-o-phenylenediamine film on a SWCNH modified glassy carbon electrode. The sensor was investigated in the presence or absence of kanamycin by cyclic voltammetry to verify the changes in the redox peak currents of K3Fe(CN)6. The sensor exhibits a linear range of 0.1–50 μM with a detection limit of 0.1 μM. It also shows high recognition ability, indicating that the SWCNH-based molecularly imprinted sensor is promising. [ABSTRACT FROM AUTHOR]

Rapid, simultaneous, and sensitive detection of biomolecules has important application prospects in disease diagnosis and biomedical research. However, because the content of intracellular endogenous target biomolecules is usually very low, traditional detection methods can't be used for effective detection and imaging, and to enhance the detection sensitivity, signal amplification strategies are frequently required. The hybridization chain reaction (HCR) has been used to detect many disease biomarkers because of its simple operation, good reproducibility, and no enzyme involvement. Although HCR signal amplification methods have been employed to detect and image intracellular biomolecules, there are still false positive signals. Therefore, a target-triggered enzyme-free amplification system (GHCR system) was developed, as a fluorescent AND-gated sensing platform for intracellular target probing. The false positive signals can be well avoided and the accuracy of detection and imaging can be improved by using the design of the AND gate. Two cancer markers, GSH and miR-1246, were used as two orthogonal inputs for the AND gated probe. The AND-gated probe only works when GSH and miR-1246 are the inputs at the same time, and FRET signals can be the output. In addition to the use of AND-gated imaging, FRET-based high-precision ratiometric fluorescence imaging was employed. FRET-based ratiometric fluorescent probes have a higher ability to resist interference from the intracellular environment, they can avoid false positive signals well, and they are expected to have good specificity. Due to the advantages of HCR, AND-gated, and FRET fluorescent probes, the GHCR system exhibited highly efficient AND-gated FRET bioimaging for intracellular endogenous miRNAs with a lower detection limit of 18 pM, which benefits the applications of ratiometric intracellular biosensing and bioimaging and offers a novel concept for advancing the diagnosis and therapeutic strategies in the field of cancer.

A single-walled carbon nanohorn (SWCNH) has been used to construct a molecularly imprinted electrochemical sensor for the first time. Kanamycin, a widely used aminoglycoside antibiotic, is used as a representative analyte to test the detection strategy. The kanamycin sensor was constructed by the electropolymerization of a molecularly imprinted poly-o-phenylenediamine film on a SWCNH modified glassy carbon electrode. The sensor was investigated in the presence or absence of kanamycin by cyclic voltammetry to verify the changes in the redox peak currents of K 3 Fe(CN) 6 . The sensor exhibits a linear range of 0.1-50 μM with a detection limit of 0.1 μM. It also shows high recognition ability, indicating that the SWCNH-based molecularly imprinted sensor is promising.