A portable SERS reader coupled with catalytic hairpin assembly for sensitive microRNA-21 lateral flow sensing.

Nucleic acid lateral flow sensing has drawn great research attention since it has the advantages of being simple, rapid, and cost-effective. However, considering the trace amounts of the nucleic acid targets, its sensitivity is still limited. Although enormous efforts have been devoted to enhancing its sensitivity, developing a simple lateral flow sensing platform with high sensitivity remains challenging. We report a novel lateral flow microRNA-21 biosensing platform based on a portable surface enhanced Raman scattering (SERS) reader coupled with a catalytic hairpin assembly signal amplification strategy. Hairpin DNA probes were anchored on Au@Ag nanotags, and the presence of microRNA-21 triggered the formation of numerous double-stranded DNAs along with the exposure of the biotin groups. By this means, the target was recycled and signal amplification was achieved. The Au@Ag nanoprobes with exposed biotin can be captured on the test line via its interaction with streptavidin. By scanning the strip with a portable SERS reader, the sensitive quantification of microRNA-21 was realized with a detection limit as low as 84 fM. The proposed strategy was employed to detect the target in a serum sample, demonstrating its great potential in amplified point-of-care biosensing for clinical diagnosis.

Catalytic hairpin assembly-assisted lateral flow assay for visual determination of microRNA-21 using gold nanoparticles.

The authors describe an improved lateral flow assay based on (a) the use of catalytic hairpin assembly (CHA), and (b) on signal amplification performed at the interface of gold nanoparticles (AuNPs). The combination of the amplification capability of the CHA reaction and the unique optical properties of AuNPs results in an assay that has a sensitivity that is improved by more than two orders of magnitude. MicroRNA-21 was employed as a model analyte to prove the concept. The presence of microRNA-21 triggers the self-assembly of two hairpin DNAs into double stranded DNA and exposing biotin molecules on the surface of AuNPs. Hence, the target becomes recycled and the signal is strongly amplified. The AuNPs carrying biotin are captured on the test line of the strip to display a red zone. This enables the visual recognition of microRNA without the need for any instrumentation. The fast quantitation of microRNA via the red band intensity is accomplished with the help of software, and the limit of detection is 0.89 pM. The enhanced lateral flow assay was employed to the determination of microRNA-21 in cell extracts and spiked serum samples. Graphical abstract A lateral flow assay for microRNA is described with a detection limit that is improved by two orders of magnitude. It is based on catalytic hairpin assembly (CHA) signal amplification performed at the interface of gold nanoparticles.

Versatile Electrochemiluminescence Assays for PEDV Antibody Based on Rolling Circle Amplification and Ru-DNA Nanotags.

The sensitive and accurate detection methods for PEDV antibody have practical significance for the prevention and treatment of PEDV. In this work, a new multiple pathways signal amplification method was proposed to construct a sensitive electrochemiluminescence (ECL) platform for the detection of PEDV antibody. Using Au NP-modified graphene nanosheet (Au-GN) as the substrate, antibody-antigen reaction as the recognition unit, rolling circle amplification (RCA) for signal enhancement, and assembled cascade Ru-DNA nanotags as signal label, the proposed platform behaved with good specificity and sensitivity. The binding system of biotin-streptavidin, RCA, and Ru(bpy)32+-doped silica nanoparticles (Ru SNPs) showed remarkable amplification efficiency, low background signal, and little nonspecific adsorption. Moreover, the proposed ECL sensor exhibited good analytical performance for PEDV antibody with a wide linear range from 0.1 pg mL-1 to 5000 pg mL-1 with a detection limit of 0.05 pg mL-1 ( S/ N = 3). The proposed strategy exhibited the advantages of excellent stability and sensitivity for determination of the PEDV antibody, which was easy to prepare and had a good application prospect.

From Electrochemistry to Electroluminescence: Development and Application in a Ratiometric Aptasensor for Aflatoxin B1.

Aflatoxin B1 (AFB1), one of the most toxic chemical carcinogens, has been widely studied. It remains challenging to develop simple, accurate, and sensitive analytical methods for the detection of AFB1 in food matrixes. In this work, on the basis of a dual-signaling strategy, a ratiometric aptasensor was designed and verified for the accurate and sensitive detection of AFB1. The electrochemical method was first used as a model to verify the specific interaction between AFB1 and the aptamer, in which ferrocene (Fc)-anchored and methylene blue (MB)-anchored DNA sequences acted as dual signals. Consequently, the specific interaction between AFB1 and its aptamer was demonstrated by the "signal-on" mode of Fc and the "signal-off" mode of MB. Due to the simple dual-signaling mode, the electrochemical sensor was further extended to the construction of an electrochemiluminoscence (ECL) aptasensor. In the ECL system, dual ECL signals were produced from CdTe/CdS/ZnS quantum dots (QDs) and luminol. Horseradish peroxidase-modified gold nanorods (HRP/Au NRs) acted as the quencher/enhancer and as such quenched the ECL signal of the QDs by ECL energy transfer and simultaneously catalyzed H2O2 to enhance the ECL of luminol. Owing to the self-calibration by the internal reference, both of the ratiometric aptasensors exhibited accurate and sensitive analytical performance for AFB1 with a good linear range from 5.0 pM to 10 nM and detection limits of 0.43 and 0.12 pM (S/N = 3), respectively. The aptasensors also exhibited good selectivity, reproducibility, and stability, revealing potential applications in food safety monitoring and environmental analysis.

Cellular hnRNP A1 Interacts with Nucleocapsid Protein of Porcine Epidemic Diarrhea Virus and Impairs Viral Replication.

The nucleocapsid (N) protein is a major structural component of porcine epidemic diarrhea virus (PEDV), which is predicted to be a multifunctional protein in viral replication. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a cellular protein participating in the splicing of pre-mRNA in the nucleus and translation regulation in the cytoplasm. According to our previous proteomic study about PEDV infection in vivo, hnRNP A1 was thought to be a cellular factor influencing PEDV replication. In this report, PEDV N protein was discovered to colocalize with cellular hnRNP A1 in perinuclear region of PEDV infected cells. Co-immunoprecipitation (CO-IP) results clearly demonstrated that PEDV N protein could bind to human hnRNP A1. Replication of PEDV was inhibited by silencing the expression of hnRNP A1 in CCL-81 cells, suggesting the positive effect of hnRNP A1 on PEDV infection.

Target-triggered signal-on ratiometric electrochemiluminescence sensing of PSA based on MOF/Au/G-quadruplex.

Signal-amplified ratiometric electrochemiluminescence (Sa-RECL) provides an attractive approach to maximize signal-to-noise ratio through enhancing signals and eliminate interferences. In this work, we prepared a novel metal-organic framework (MOF)/Au/G-quadruplex as both quenchers and enhancers to fabricate a target-triggered ratiometric ECL sensor for high sensitive and accurate detection of prostatic specific antigen (PSA). The ratiometric ECL sensor using the dual-potential-dependent ECL emitters (quantum dots (QDs) and luminol) and MOF/Au/G-quadruplex not only achieved signal self-calibration but also realized cooperative amplification. After the sequential hybridization among of complementary DNA-QDs, PSA aptamer and pDNA-Au-Hemin-MIL-DNAzyme and the further competition of PSA, the pDNA-Au-Hemin-MIL-DNAzyme probe would keep away from the electrode surface, causing a switchover of their ECL signals from "off-on" state to "on-off" state. The ratiometric ECL aptasensor exhibits high-sensitive and accurate analytical performance toward PSA with a linear detection range from 0.5 to 500 ng mL-1 and a detection limit of 0.058 ng mL-1 (S/N = 3). The novel ratiometric ECL biosensor has been successfully applied to determine different serum samples of PSA, indicating its potential application in the clinical diagnosis.