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Equipment Studying Guided Activity regarding Multinary Chevrel Stage Chalcogenides.
MicroRNAs (miRNAs), considered as therapeutic targets and biomarkers, play important roles in biological processes. Herein, an enzyme-free surface plasmon resonance imaging (SPRi) biosensing method has been developed for miRNA detection based on catalytic hairpin assembly and spherical nucleic acid. The hairpin H1 tethered on the surface of the sensor chip is unfolded by miRNA, and then the hybridized miRNA is released through the displacement of the hairpin H2 for the successive hybridization and assembly process. The emerging DNA fragments on the sensor chip surface after hairpins assembly are further used to hybridize with spherical nucleic acid, inducing a remarkably amplified SPR signal. This biosensing method is highly sensitive to miRNA with a detection limit of 53.7 fM and a linear range of 4 orders of magnitude. Moreover, the biosensor demonstrates good specificity and has the ability to distinguish members of homologous miRNA family even with single base differences. Thus, the SPRi biosensing method may hold a great promise for further application in early clinical diagnosis. Polymerase chain reaction (PCR) is an extremely important tool for molecular diagnosis, as it can specifically amplify nucleic acid templates for sensitive detection. As another division of PCR, free convective PCR was invented in 2001, which can be performed in a capillary tube pseudo-isothermally within a significantly short time. Convective PCR thermal cycling is implemented by inducing thermal convection inside the capillary tube, which stratifies the reaction into spatially separate and stable melting, annealing, and extension zones created by the temperature gradient. Convective PCR is a promising tool that can be used for nucleic acid diagnosis as a point-of-care test (POCT) due to the significantly simplified heating strategy, reduced cost, and shortened detection time without sacrificing sensitivity and accuracy. Here, we review the history of free convective PCR from its invention to development and its commercial applications. In recent years, paper-based Surface-enhanced Raman spectroscopy (SERS) substrates have received extensive attention in the field of rapid analysis. However, obtaining quantitative SERS results is still challenging because of the inferior uniformity originating from the irregular morphology of the filter paper. In this work, a novel paper-fluidic SERS sensor was developed and its in-depth applications in the real-word quantitative analysis of contaminants in complex matrices were demonstrated. In particular, the Au@Ag core-shell nanospheres were labeled with an internal standard molecule to successfully normalize the fluctuation of the SERS signal caused by the microstructure of the filter paper, which could significantly improve the detection accuracy and accomplish the SERS quantitative analysis. In addition, a facile and robust strategy for the fabrication of a paper-based SERS sensor, which uses a dropper and mask to transfer the nanoparticle monolayers, was developed. This convenient and flexible approach effectively achieved a precise patterned assembly of nanoparticles on the filter paper. Furthermore, the paper-fluidic SERS sensor was fabricated by cutting and packaging for two detection modes, i.e., lateral-flow and vertical-flow, which generates the functionalization of the paper-based SERS substrate. Both detection modes integrated sample pretreatment and sample enrichment with SERS detection were applied to accurately detect the pesticide thiram in a complex sample of orange juice with pulp. In summary, this paper-fluidic SERS sensor with a simple preparation process and integrated functions is an ideal candidate for real sample analysis without pretreatment. Herein, a simple enzyme-free method based on the seesaw-gate-driven isothermal signal amplification strategy was developed for nucleic acid detection. In this method, a partially complementary double-stranded beacon was designed, after the addition of ssDNA or RNA of target sequence, the fluorescence signal was restored through a toehold-mediated strand displacement process, followed by a seesaw-like reaction with the aid of an auxiliary strand with the same length of the toehold domain. Liberation of the target would initiate the next round of seesaw reaction to achieve recycling amplification of the fluorescence signal. The method has the advantages of simple sequence design and free of any enzyme, which can realize rapid detection of the target at 25 °C with a detection limit of 9.8 pM for DNA and 83 pM for RNA. The potential applicability of the proposed method was also demonstrated, indicating that it can provide a fundamental strategy for the development of nucleic acid sensors. In this study, direct detection of fluazinam was realized using a fluorescent sensor using disulfide quantum dots (MoS2 QDs) via inner filter effect (IFE). The maximum excitation of as-prepared MoS2 QDs presented a complementary spectral-overlap with the maximum absorption of fluazinam. Thus the occurrence of inner filter effect led to the significant fluorescence quenching of MoS2 QDs. Additionally, fluorescent quenching efficiency of MoS2 QDs could be enhanced by the effects of π-π stacking, hydrogen bond and electrostatic interaction between fluazinam and MoS2 QDs, and these non-chemical bond responses also promoted the selectivity for fluazinam detection. Under the optimum conditions, the IFE-based fluorescent sensor exhibited a relative wide linear range from 50 nM to 25 μM with the LOD of 2.53 nM (S/N = 3). In addition, a paper-based sensor was established by cross-linking the MoS2 QDs into cellulose membrane for naked-eyed detection and digital analysis of fluazinam. The paper-based sensor presented a liner range from 10 μM to 800 μM for fluazinam detection with the LOD of 2.26 μM. Additionally, the acceptable recoveries were obtained for fluazinam detection in the spiked samples of tomato, potato and cucumber, indicating that the proposed method provided an effective sensing platform for real applications of fluazinam detection in food safety. Tofacitinib mouse
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