A crosslinked submicro-hydrogel formed by DNA circuit-driven protein aggregation amplified fluorescence anisotropy for biomolecules detection

Highly sensitive biosensor for specific miRNA detection based on cascade signal amplification and magnetic electrochemiluminescence nanoparticles

Herein, magnetic electrochemiluminescence (ECL) nanoparticle Fe3O4@PtPd/Ru(bpy)32+ had been synthesized then been coupled with CRISPR/Cas13a system and Zn2+ dependent DNAzyme to design a novel ECL biosensor for specific detection of microRNA-145 (miRNA). The synthesized multifunctional magnetic nanoluminescent materials Fe3O4@PtPd/Ru(bpy)32+ not only load Ru(bpy)32+ to provide ECL signals, but also can quickly achieve separation and enrichment from complex matrices. In addition, ferrocene (Fc) was used as a quencher in the Ru(bpy)32+/tripropylamine (TPA) system. Fc was modified on DNA bound to Fe3O4@PtPd. Benefited from the highly specific recognition ability of CRISPR/Cas13a, the target miRNA induces CRISPR/Cas13a trans-cleavage to trigger the Zn2+-dependent DNAzyme cyclic cleavage to realize the dual signal amplification. DNA modified by Fc was split by target miRNA-induced cleaving, and then magnetic separation was performed to keep Fc away from the surface of the nanoparticles. Thus, the enhanced ECL signal was obtained to detect miRNA-145. Under optimized conditions, the prepared sensor showed a wide linear range (1 fM to 1 nM) and a low limit of detection (LOD) down to 0.41 fM. Furthermore, it shows excellent selectivity and good reproducibility. The proposed ECL platform has huge potential applications in the development of various sensitive sensors for detecting the other miRNA.

CRISPR-Cas12a Coupled with DNA Nanosheet-Amplified Fluorescence Anisotropy for Sensitive Detection of Biomolecules

DNA nanosheets (DNSs) have been utilized effectively as a fluorescence anisotropy (FA) amplifier for biosensing. But, their sensitivity needs to be further improved. Herein, CRISPR-Cas12a with strong trans-cleavage activity was utilized to enhance the FA amplification ability of DNSs for the sensitive detection of miRNA-155 (miR-155) as a proof-of-principle target. In this method, the hybrid of the recognition probe of miR-155 (T1) and a blocker sequence (T2) was immobilized on the surface of magnetic beads (MBs). In the presence of miR-155, T2 was released by a strand displacement reaction, which activated the trans-cleavage activity of CRISPR-Cas12a. The single-stranded DNA (ssDNA) probe modified with a carboxytetramethylrhodamine (TAMRA) fluorophore was cleaved in large quantities and could not bind to the handle chain on DNSs, inducing a low FA value. In contrast, in the absence of miR-155, T2 could not be released and the trans-cleavage activity of CRISPR-Cas12a could not be activated. The TAMRA-modified ssDNA probe remained intact and was complementary to the handle chain on the DNSs, and a high FA value was obtained. Thus, miR-155 was detected through the obviously decreased FA value with a low limit of detection (LOD) of 40 pM. Impressively, the sensitivity of this method was greatly improved about 322 times by CRISPR-Cas12a, confirming the amazing signal amplification ability of CRISPR-Cas12a. At the same time, the SARS-CoV-2 nucleocapsid protein was detected by the strategy successfully, indicating that this method was general. Moreover, this method has been applied in the analysis of miR-155 in human serum and the lysates of cells, which provides a new avenue for the sensitive determination of biomarkers in biochemical research and disease diagnosis.

CSDR Coupling with Exo III for Ultrasensitive Electrochemistry Determination of miR-145

Recently, miRNAs have become a promising biomarker for disease diagnostics. miRNA-145 is closely related to strokes. The accuracy determination of miRNA-145 (miR-145) in stroke patients still remains challenging due to its heterogeneity and low abundance, as well as the complexity of the blood matrix. In this work, we developed a novel electrochemical miRNA-145 biosensor via subtly coupling the cascade strand displacement reaction (CSDR), exonuclease III (Exo III), and magnetic nanoparticles (MNPs). The developed electrochemical biosensor can quantitatively detect miRNA-145 ranging from 1 × 10² to 1 × 10⁶ aM with a detection limit as low down as 100 aM. This biosensor also exhibits excellent specificity to distinguish similar miRNA sequences even with single-base differences. It has been successfully applied to distinguish healthy people from stroke patients. The results of this biosensor are consistent with the results of the reverse transcription quantitative polymerase chain reaction (RT-qPCR). The proposed electrochemical biosensor has great potential applications for biomedical research on and clinical diagnosis of strokes.