Analytical Chemistry最新文献

Breath particles generated deep within the lung provide noninvasive access to sampling nonvolatiles in peripheral airway lining fluid. However, background contamination, their variable production among subjects, together with a huge unknown dilution when using the common breath condensate method for collection has limited their use for quantitative biomarker analysis. Instead, we first capture and dry the particles in a flexible chamber followed by accurate optical particle characterization during their collection for chemical analysis. By decoupling breathing and aerosol sampling airflows, this sequential approach not only accommodates all types of breathing routines but also enables the use of a variety of aerosol samplers for downstream biomarker analysis. Using ²³Na NMR, we measured 0.66 M Na in dry particles collected on a filter, which suggests that dehydration reduces their volume by a factor of ∼ 5.5 based on known Na levels in lung fluid. ¹H NMR revealed 0.36 and 0.68 M phosphocholine lipids in dried particles collected from two volunteers, presumably enriched to these levels relative to literature values derived from bronchoalveolar lavage fluid due to the film-bursting mechanism that underlies breath particle generation. Decoupling of breath collection and aerosol capture enabled the design of an impactor sampler with 72% efficiency. This impactor minimizes reagent and handling-related contamination associated with traditional filters by collecting dry particles directly in a microreactor for subsequent derivatization and quantification by mass spectrometry. The method is demonstrated by quantifying subnanogram amounts of urea from breath particles, corresponding to lung fluid urea concentrations consistent with literature blood plasma values.

The intracellular delivery toward a specific type of single cell shows great potential in single-cell-specific therapeutic and diagnostic applications. Most of the current methods require high-precision micromanipulators or require multiple steps for motor fabrication, which hinders their practical application. Herein, we for the first time report a method for precise manipulation and selective electroporation of cells using a bipolar electrode. We achieved the precise control of the position of target cells via dielectrophoresis (DEP) at the edge of a bipolar electrode and selective electroporation of specific cells by the local intensified electric field obtained by the gap between the driving electrodes under a direct current (DC) pulse train. Active cell targeting and electroporation of cells are demonstrated using a rotating electric field to drive the cells and a train of pulses to transfect the cells. By harnessing pDEP and twDEP, our device offers the ability to precisely control the movement and placement of specific cells under a rotating electric field and enables the targeted cells to be driven toward regions where the electric field strength is optimized for efficient electroporation. Our method was demonstrated to be applicable across a wide range of cell types, by selective electroporation of different cells including yeast cells, K562 cells, THP-1 cells, 293T cells, and SNU-1 cells. In addition to the injection of fluorescence dye molecules, we also further demonstrated the introduction of plasmids into the SNU-1 cells successfully. This approach is generic and applicable to bacteria and a wide range of cell types, offering an important and novel experimental tool for targeted delivery and single-cell analysis.

The retention mechanisms for polar compounds in HILIC are only qualitatively understood to include hydrophilic partitioning, surface adsorption, and electrostatic interactions if both the analytes and stationary phases are charged. However, the main retention mechanism may be different for different compounds under different chromatographic conditions, and it is difficult to identify the main retention mechanism based on the existing knowledge and methods. We previously developed a methodology to quantitatively determine the retention contributions of hydrophilic partitioning and surface adsorption for nonionized compounds in HILIC. In this study, the methodology has been expanded to include the retention contribution of electrostatic interactions for the ionized compounds on charged stationary phases. When electrostatic interactions are sufficiently shielded at high salt concentrations, the partitioning coefficient of ionized compounds is determined using the same method for nonionized compounds. Then, the retention contributed by partitioning and adsorption is calculated. The retention contribution by electrostatic interactions (both attractive and repulsive) is determined by subtracting the retention contributed by partitioning and adsorption from the observed retention at each salt concentration. This is the first study that evaluated the retention contributions of hydrophilic partitioning, surface adsorption, and electrostatic interactions for ionized compounds. Quantitative information on retention mechanisms will be helpful to better understand selectivity in HILIC and facilitate the development of retention models.

We report a mechanistic study of the electrocatalytic response of single Pt nanoparticles (NPs) on a carbon ultramicroelectrode (UME) in a hydrazine (N₂H₄) solution. Using a NP collision approach, our study shows their catalytic response is characterized by a sharp, <50 μs-long current spike followed by a steady step-current signal. Our results suggest that the current spike is due to the quick oxidation of N₂H₄ molecules preadsorbed onto the NP surface, while the step current reflects the continuous catalytic oxidation of protonated hydrazine (N₂H₅⁺), which goes through a deprotonation and adsorption step on Pt. Since each N₂H₅⁺ molecule releases five H⁺ upon complete oxidation, a drastic decrease in local pH can be expected in the vicinity of the NP. This pH shift in turn limits the rate of adsorption and the steady-state oxidation current one can observe from each colliding particle. Our study reveals the key importance of molecular adsorption and the changing local chemical environment (e.g., pH) to the observed catalytic response of single NPs and highlights that steady-state currents in their measurement may be chemically or mass-transport limited.

The spatiotemporal assessment of tissue dynamics after the introduction of disruptive factors is crucial for evaluating their impact and for developing effective countermeasures. Here, we report a 4D-spatiotemporal imaging approach using second harmonic generation (SHG) imaging microscopy, enabling an advanced time-resolved analysis of three-dimensional tissue features. This is of particular interest as topical administration of drugs during spinal surgeries is a standard practice for preventing and treating postoperative complications like infections. Local drug concentrations on tissue are high in these scenarios, and given the dura's role as a protective barrier for the brain and spinal cord, potential drug-induced damage should be evaluated critically. By employing 4D-SHG imaging, we gained detailed insights into changes in dimensional properties of thin section samples, namely, width, height, and volume, as well as into alterations within the hierarchic structure of collagen. The latter thereby allowed us to postulate a mode of action, which we attributed for the herein investigated samples to the pH of the formulation.

A new dual-channel and dual-functional fluorescent probe, DX3-AXI, is developed with the aid of computational chemistry, enabling viscosity and SO₂ detection in separate fluorescence emission channels. The probe DX3-AXI exhibits significant fluorescence changes in the detection, demonstrating excellent interference resistance and a linear response. Through Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) calculations, along with hole-electron molecular analysis, energy level structure, and molecular local attachment energy analysis, the mechanism of the dual-channel response of the DX3-AXI probe is systematically revealed, demonstrating that the regulation of interactions between the rotatable bond and double bond drives the fluorescence changes. Furthermore, a portable sensing platform for on-site sulfite detection in water samples was developed by coupling the probe with a smartphone, enabling the rapid qualitative and semiquantitative detection of sulfite. Significantly, DX3-AXI has demonstrated successful application in detecting changes in the microenvironment of normal and cancer cells while also enabling the visualization of viscosity variations in the liver tissue of mice with liver injury. The DX3-AXI probe has shown significant potential for application in disease diagnostics, drug assessment, and environmental monitoring.

The manufacture of high-performance liquid chromatography (HPLC) medium has long been viewed as an art rather than science; this raised a great challenge in securing separation consistency, method transferability, and scaling-up in purification of biomolecules. Herein, we report a large scale layer-by-layer manufacturing strategy for a high performance chromatography medium utilizing 3D-printing technology. Combining stereolithography 3D printing and porogenic chemistry, the strategy enables parallel production of high-performance separation medium in diverse scales, shapes, and throughput. Between 1,000 printed devices, high performance consistency was demonstrated by column-to-column and batch-to-batch reproducibility (coefficient of variation of retention time, 2.04%). Fast separations of intact proteins were realized in reversed-phase chromatography: within 1 min, resolution > 1.5 was achieved, and nondenatured antibody separation was realized in hydrophobic interaction chromatography. Purification of native proteins was directly amplified by 3 orders of magnitude: 12 mg of hemeproteins was isolated in 8 min at negligible scaling-up cost, supporting liter-scale processing of fermentation within 7 h on one 20 mm i.d. printed column. With advantages in automatic and parallel production capacity, high-fidelity microstructure across dimensions, and highly efficient method transfer and scaling-up, the stereolithographically printed high performance chromatography medium may open a new path to speeding up separation and purification processes from primary analysis to mass-purification of biomolecular entities, as demanded in the biosynthesis and pharmaceutical industries.