Annual review of analytical chemistry (Palo Alto, Calif.)最新文献

The reduction in ion current as a fine pipette approaches a cell surface allows the cell surface topography to be imaged, with nanoscale resolution, without contact with the delicate cell surface. A variety of different methods have been developed and refined to scan the topography of the dynamic cell surface at high resolution and speed. Measurement of cell topography can be complemented by performing local probing or mapping of the cell surface using the same pipette. This can be done by performing single-channel recording, applying force, delivering agonists, using pipettes fabricated to contain an electrochemical probe, or combining with fluorescence imaging. These methods in combination have great potential to image and map the surface of live cells at the nanoscale.

This article reviews progress in the study of materials using X-ray-based techniques from an electrochemistry perspective. We focus on in situ/in operando surface X-ray scattering, X-ray absorption spectroscopy, and the combination of both methods. The background of these techniques together with key concepts is introduced. Key examples of in situ and in operando investigation of liquid-solid and liquid-liquid interfaces are presented. X-ray scattering and spectroscopy have helped to develop an understanding of the underlying atomic and molecular processes associated with electrocatalysis, electrodeposition, and battery materials. We highlight recent developments, including resonant surface diffraction and time-resolved studies.

Adverse effects of environmental toxicants to human health have traditionally been assayed using in vitro assays. Organ-on-chip (OOC) is a new platform that can bridge the gaps between in vitro assays (or 3D cell culture) and animal tests. Microenvironments, physical and biochemical stimuli, and adequate sensing and biosensing systems can be integrated into OOC devices to better recapitulate the in vivo tissue and organ behavior and metabolism. While OOCs have extensively been studied for drug toxicity screening, their implementation in environmental toxicology assays is minimal and has limitations. In this review, recent attempts of environmental toxicology assays using OOCs, including multiple-organs-on-chip, are summarized and compared with OOC-based drug toxicity screening. Requirements for further improvements are identified and potential solutions are suggested.

Physiological dynamics in living cells and tissues are crucial for maintenance and regulation of their normal activities and functionalities. Tiny fluctuations in physiological microenvironments can leverage significant influences on cell growth, metabolism, differentiation, and apoptosis as well as disease evolution. Fluorescence imaging based on aggregation-induced emission luminogens (AIEgens) exhibits superior advantages in real-time sensing and monitoring of the physiological dynamics in living systems, including its unique properties such as high sensitivity and rapid response, flexible molecular design, and versatile nano- to mesostructural fabrication. The introduction of canonic AIEgens with long-wavelength, near-infrared, or microwave emission, persistent luminescence, and diversified excitation source (e.g., chemo- or bioluminescence) offers researchers a tool to evaluate the resulting molecules with excellent performance in response to subtle fluctuations in bioactivities with broader dimensionalities and deeper hierarchies.

High-resolution mass spectrometry (MS) has advanced the study of metabolism in living systems by allowing many metabolites to be measured in a single experiment. Although improvements in mass detector sensitivity have facilitated the detection of greater numbers of analytes, compound identification strategies, feature reduction software, and data sharing have not kept up with the influx of MS data. Here, we discuss the ongoing challenges with MS-based metabolomics, including de novo metabolite identification from mass spectra, differentiation of metabolites from environmental contamination, chromatographic separation of isomers, and incomplete MS databases. Because of their popularity and sensitive detection of small molecules, this review focuses on the challenges of liquid chromatography-mass spectrometry-based methods. We then highlight important instrumentational, experimental, and computational tools that have been created to address these challenges and how they have enabled the advancement of metabolomics research.

Proteins function as ensembles of interconverting structures. The motions span from picosecond bond rotations to millisecond and longer subunit displacements. Characterization of functional dynamics on all spatial and temporal scales remains challenging experimentally. Two-dimensional infrared spectroscopy (2D IR) is maturing as a powerful approach for investigating proteins and their dynamics. We outline the advantages of IR spectroscopy, describe 2D IR and the information it provides, and introduce vibrational groups for protein analysis. We highlight example studies that illustrate the power and versatility of 2D IR for characterizing protein dynamics and conclude with a brief discussion of the outlook for biomolecular 2D IR.

As one of the major types of biomacromolecules in the cell, glycans play essential functional roles in various biological processes. Compared with proteins and nucleic acids, the analysis of glycans in situ has been more challenging. Herein we review recent advances in the development of methods and strategies for labeling, imaging, and profiling of glycans in cells and in vivo. Cellular glycans can be labeled by affinity-based probes, including lectin and antibody conjugates, direct chemical modification, metabolic glycan labeling, and chemoenzymatic labeling. These methods have been applied to label glycans with fluorophores, which enables the visualization and tracking of glycans in cells, tissues, and living organisms. Alternatively, labeling glycans with affinity tags has enabled the enrichment of glycoproteins for glycoproteomic profiling. Built on the glycan labeling methods, strategies enabling cell-selective and tissue-specific glycan labeling and protein-specific glycan imaging have been developed. With these methods and strategies, researchers are now better poised than ever to dissect the biological function of glycans in physiological or pathological contexts.

Here, the research field of nanoplasmonic sensors is placed under scrutiny, with focus on affinity-based detection using refractive index changes. This review describes how nanostructured plasmonic sensors can deliver unique advantages compared to the established surface plasmon resonance technique, where a planar metal surface is used. At the same time, it shows that these features are actually only useful in quite specific situations. Recent trends in the field are also discussed and some devices that claim extraordinary performance are questioned. It is argued that the most important challenges are related to limited receptor affinity and nonspecific binding rather than instrumental performance. Although some nanoplasmonic sensors may be useful in certain situations, it seems likely that conventional surface plasmon resonance will continue to dominate biomolecular interaction analysis. For detection of analytes in complex samples, plasmonics may be an important tool, but probably not in the form of direct refractometric detection.

Surface chemistry affects the physiochemical properties of nanoparticles in a variety of ways. Therefore, there is great interest in understanding how nanoparticle surfaces evolve under different environmental conditions of pH and temperature. Here, we discuss the use of vibrational spectroscopy as a tool that allows for in situ observations of oxide nanoparticle surfaces and their evolution due to different surface processes. We highlight oxide nanoparticle surface chemistry, either engineered anthropogenic or naturally occurring geochemical nanoparticles, in complex media, with a focus on the impact of (a) pH on adsorption, intermolecular interactions, and conformational changes; (b) surface coatings and coadsorbates on protein adsorption kinetics and protein conformation; (c) surface adsorption on the temperature dependence of protein structure phase changes; and (d) the use of two-dimensional correlation spectroscopy to analyze spectroscopic results for complex systems. An outlook of the field and remaining challenges is also presented.

Three-dimensional (3D) printing has recently emerged as a novel approach in the development of electrochemical sensors. This approach to fabrication has provided a tremendous opportunity to make complex geometries of electrodes at high precision. The most widely used approach for fabrication is fused deposition modeling; however, other approaches facilitate making smaller geometries or expanding the range of materials that can be printed. The generation of complete analytical devices, such as electrochemical flow cells, provides an example of the array of analytical tools that can be developed. This review highlights the fabrication, design, preparation, and applications of 3D printed electrochemical sensors. Such developments have begun to highlight the vast potential that 3D printed electrochemical sensors can have compared to other strategies in sensor development.