Talanta最新文献

Sensitive and accurate detection and imaging of different microRNAs (miRNAs) in cancer cells hold great promise for early disease diagnosis. Herein, a DNA tetrahedral scaffold (DTS)-corbelled autonomous-motion (AM) molecular machine based fluorescent sensing platform was designed for simultaneous detection of two types of miRNAs (miRNA-21 and miRNA-155) in HeLa cells. Locking-strand-silenced DNAzymes (P:L duplex) were firstly grafted at the loop of target-analogue-embedded double-stem hairpin substrates (TDHS) of DTS, making the sensor in a "signal off" state due to the closely distance between modified fluorophores (FAM and Cy5) with the corresponding quenchers (BHQ1 and BHQ2). The detection of miRNA-21 and miRNA-155 was mainly based on the activation of locking-strand-silenced DNAzymes, cleaving hairpin DNA into single-strand DNA segments, accompanying with the release of modified fluorophores and the signal recovery (signal on). Upon the cyclical stimulation of miRNA targets in such AM molecular machine, sensitive detection of miRNA-21 and miRNA-155 was realized in this self-feedback circuit (SFC) with the detection limit down to 38.8 aM and 27.1 aM, respectively. Moreover, the analytical performance was greatly improved for miRNAs imaging in cancer cells with enhanced tumor cell recognition ability, excellent stability in virtue of DTS, indicating a potential analytical tool in early cancer diseases diagnosis.

An idea of using ion-exchanger salt containing optically active cations to prepare ion-selective membranes is proposed. Although the presence of an ion-exchanger in the composition of neutral ionophore based sensors is necessary, the choice of available salts for cation-selective sensors preparation, is usually limited to sodium or potassium compounds. In this work we propose application of an alternative salt, using a cation optically active both in absorption and emission mode as a mobile one. Thus, coloured ion-selective membranes can be obtained. This in turn opens new possibilities of monitoring the state of the receptor layer as well as allows direct analytical application of ion-selective membranes in simple optical mode with all benefits related to eliminating the necessity of using reference electrodes. As a model system Nile blue derivative of tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ion-exchanger was prepared and used to obtain potassium or calcium selective sensors. Selective exchange of ions between the membrane and solution, leading to an increase in optical signal of the solution, can be used to quantify the presence of analyte ions. Thus the sensor pretreatment process is becoming a source of analytical information. The applicability of this approach was verified in determining the presence of potassium ions in the vast majority of interfering ions, e.g. present as impurities in the reagent grade calcium chloride. The resulting potassium ions contents was well comparable with values obtained in course of ICP-MS approach.

Enzyme immobilization techniques are crucial for enhancing enzyme stability and catalytic efficiency. Traditional methods such as physical adsorption and simple covalent binding often fail to maintain enzyme activity and stability. In this study, an innovative multi-level immobilization strategy was proposed to achieve efficient targeted immobilization of nuclease P1 (NP1) by fine-tuning the surface microenvironment. Molecular simulation results revealed that the distinctive electrostatic distribution and the specific placement of basic amino acids, such as lysine, on the NP1 surface caused dopamine to preferentially adsorb on areas away from NP1's active site. This selective adsorption facilitated the directed immobilization of NP1, while the positively charged environment generated by the co-deposited surface further enhanced NP1's adsorption capacity. This multilevel modification was found to significantly optimize the physicochemical environment of the immobilized surface through surface characterization and enzymatic testing. This strategy greatly improves enzyme activity (3590.0 U/mg), stability, and reusability (70 % after 10 cycles). In particular, NP1 on this surface exhibited an optimal Michaelis constant (K_m) of 34.0 mM and a maximum reaction rate of 5.5 mM min^-1, demonstrating the remarkable effect of the modification strategy in enhancing the enzyme catalytic performance. The present study provides an efficient and stable immobilization platform for enzyme catalytic applications by precisely modulating the surface microenvironment and the oriented immobilization strategy, which has an important potential for practical applications. This stable and reusable NP1 platform allows for efficient DNA/RNA cleavage, facilitating its application in industrial biocatalysis, biomedical enzyme-based processes, and biosensors.

Mercury (II) ions (Hg²⁺) are a significant source of heavy metal contamination in groundwater, posing a serious threat to human health and the environment. Therefore, there is an urgent need for the development of a new detection technique with high sensitivity for monitoring Hg²⁺ in contaminated groundwater. Here, we developed a signal amplifying MOF-based probe (NXS@ZIF-8) for on-site and ultrasensitive dual-channel portable detection of Hg²⁺ in groundwater. The successful grafting of the fluorescent probe (NXS) onto ZIF-8 effectively enhanced the enrichment of the NXS probe, thereby amplifying the detection signal for Hg²⁺. Upon exposure to Hg²⁺, NXS@ZIF-8 quickly emits fluorescent signals, which can be easily detected using portable laser-induced fluorescence spectrometers (LIFs) with a low detection limit of 0.30 ppb. Importantly, the platform enables on-site detection of Hg²⁺ in groundwater samples and direct on-site and in-situ detection of Hg²⁺ in contaminated groundwater, achieving acceptable results. Furthermore, NXS@ZIF-8 was fabricated as a paper-based sensor and integrated into a portable smartphone device for visual detection of Hg²⁺ in contaminated groundwater. This work presents an approach for on-site, in-situ and highly sensitive portable detection of heavy metals in contaminated groundwater, eliminating the need for access to specialized laboratory equipment.

Detection of airborne chemical threats is an emerging challenge amidst the prevailing tumultuous global milieu. Extensive investigation has showcased the substantial promise of surface-enhanced Raman spectroscopy (SERS) for the on-site identification of hazardous chemicals present in liquid mediums, whether directly from a fluid source or through methodologies such as swab sampling. Nonetheless, exploration into the applicability of SERS for the detection of gas or vapor-phase chemical threats remains severely constrained. In this study, we present the successful realization of sub-parts per million (ppm) detection thresholds via SERS for hydrogen cyanide (HCN) and Tabun (GA) chemical warfare agents, facilitated by a custom-made gas sampling cell integrated with a Peltier cooling mechanism. The cooling regimen, spanning from 20 to -17 °C, verified a 140-fold increase in the SERS signal for 1 ppm HCN, concurrently enabling the detection of HCN and Tabun concentrations as low as 0.25 and 0.5 ppm, respectively. Implementation of temperature modulation and controlled flow routines substantially reduced detection times down to 240 s for HCN, with prospects for further optimization.

Metabolites identification is the major bottleneck in untargeted LC-MS metabolomics, primarily due to the limited availability of MS² information for most detected metabolites in data dependent acquisition (DDA) mode. To solve this problem, we have integrated the iterative, interval, and segmented window acquisition concepts to develop an innovative non-fixed segmented window interval data dependency acquisition (NFSWI-DDA) mode, which achieves comparable MS² coverage to data independent acquisition (DIA) mode. This acquisition strategy harnesses the strengths of both DDA and DIA, which could provide extensive coverage and excellent reproducibility of MS² spectra. Furthermore, utilizing the NFSWI-DDA data, we successfully acquired and identified a large-scale of multiple reaction monitoring (MRM) ion pairs, and transitioned them from high-resolution mass spectrometry (HRMS) to triple quadrupole mass spectrometry (TQ-MS). At last, a large-scale targeted metabolomics method was established practically. This method enables targeted analysis of 475 endogenous metabolites encompassing amino acids, nucleotides, bile acids, fatty acids, and carnitines, which could cover 9 major metabolic pathways as well as 65 secondary metabolic pathways. The established targeted method allows for semi-quantitative assessment of 475 metabolites while enabling quantitative analysis of 327 specific metabolites in biological samples. The method demonstrates immense potential in the detection of various biological samples, offering robust technical support and generating extensive data to advance applications in precision medicine and life sciences.