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

Avoiding the growth of SiO_x has been an enduring task for the use of silicon as an electrode material in dynamic electrochemistry. This is because electrochemical assays become unstable when the SiO_x levels change during measurements. Moreover, the silicon electrode can be completely passivated for electron transfer if a thick layer of insulating SiO_x grows on the surface. As such, the field of silicon electrochemistry was mainly developed by electron-transfer studies in nonaqueous electrolytes and by applications employing SiO_x-passivated silicon-electrodes where no DC currents are required to cross the electrode/electrolyte interface. A solution to this challenge began by functionalizing Si-H electrodes with monolayers based on Si-O-Si linkages. These monolayers have proven very efficient to avoid SiO_x formation but are not stable for a long-term operation in aqueous electrolytes due to hydrolysis. It was only with the development of self-assembled monolayers based on Si-C linkages that a reliable protection against SiO_x formation was achieved, particularly with monolayers based on α,ω-dialkynes. This review discusses in detail how this surface chemistry achieves such protection, the electron-transfer behavior of these monolayer-modified silicon surfaces, and the new opportunities for electrochemical applications in aqueous solution.

Organs-on-chips (OOC) are widely seen as being the next generation in vitro models able to accurately recreate the biochemical-physical cues of the cellular microenvironment found in vivo. In addition, they make it possible to examine tissue-scale functional properties of multicellular systems dynamically and in a highly controlled manner. Here we summarize some of the most remarkable examples of OOC technology's ability to extract clinically relevant tissue-level information. The review is organized around the types of OOC outputs that can be measured from the cultured tissues and transferred to clinically meaningful information. First, the creation of functional tissues-on-chip is discussed, followed by the presentation of tissue-level readouts specific to OOC, such as morphological changes, vessel formation and function, tissue properties, and metabolic functions. In each case, the clinical relevance of the extracted information is highlighted.

Measurement of humoral factors secreted from cells has served as an indispensable method to monitor the states of a cell ensemble because humoral factors play crucial roles in cell-cell interaction and aptly reflect the states of individual cells. Although a cell ensemble consisting of a large number of cells has conventionally been the object of such measurements, recent advances in microfluidic technology together with highly sensitive immunoassays have enabled us to quantify secreted humoral factors even from individual cells in either a population or a temporal context. Many groups have reported various miniaturized platforms for immunoassays of proteins secreted from single cells. This review focuses on the current status of time-resolved assay platforms for protein secretion with single-cell resolution. We also discuss future perspectives of time-resolved immunoassays from the viewpoint of systems biology.

Technological advances in mass spectrometry have enabled the extensive identification, characterization, and quantification of proteins in any biological system. In disease processes proteins are often altered in response to external stimuli; therefore, proteomics, the large-scale study of proteins and their functions, represents an invaluable tool for understanding the molecular basis of disease. This review highlights the use of mass spectrometry-based proteomics to study the pathogenesis, etiology, and pathology of several neglected tropical diseases (NTDs), a diverse group of disabling diseases primarily associated with poverty in tropical and subtropical regions of the world. While numerous NTDs have been the subject of proteomic studies, this review focuses on Buruli ulcer, dengue, leishmaniasis, and snakebite envenoming. The proteomic studies highlighted provide substantial information on the pathogenic mechanisms driving these diseases; they also identify molecular targets for drug discovery and development and uncover promising biomarkers that can assist in early diagnosis.

Traditional microfabrication techniques suffer from several disadvantages, including the inability to create truly three-dimensional (3D) architectures, expensive and time-consuming processes when changing device designs, and difficulty in transitioning from prototyping fabrication to bulk manufacturing. 3D printing is an emerging technique that could overcome these disadvantages. While most 3D printed fluidic devices and features to date have been on the millifluidic size scale, some truly microfluidic devices have been shown. Currently, stereolithography is the most promising approach for routine creation of microfluidic structures, but several approaches under development also have potential. Microfluidic 3D printing is still in an early stage, similar to where polydimethylsiloxane was two decades ago. With additional work to advance printer hardware and software control, expand and improve resin and printing material selections, and realize additional applications for 3D printed devices, we foresee 3D printing becoming the dominant microfluidic fabrication method.

High-resolution SIMS analysis can be used to explore a wide range of problems in material science and engineering materials, especially when chemical imaging with good spatial resolution (50-100 nm) can be combined with efficient detection of light elements and precise separation of isotopes and isobaric species. Here, applications of the NanoSIMS instrument in the analysis of inorganic materials are reviewed, focusing on areas of current interest in the development of new materials and degradation mechanisms under service conditions. We have chosen examples illustrating NanoSIMS analysis of grain boundary segregation, chemical processes in cracking, and corrosion of nuclear components. An area where NanoSIMS analysis shows potential is in the localization of light elements, in particular, hydrogen and deuterium. Hydrogen embrittlement is a serious problem for industries where safety is critical, including aerospace, nuclear, and oil/gas, so it is imperative to know where in the microstructure hydrogen is located. By charging the metal with deuterium, to avoid uncertainty in the origin of the hydrogen, the microstructural features that can trap hydrogenic species, such as precipitates and grain and phase boundaries, can be determined by NanoSIMS analysis on a microstructurally relevant scale.

The detailed molecular characterization of petroleum-related samples by mass spectrometry, often referred to as petroleomics, continues to present significant analytical challenges. As a result, petroleomics continues to be a driving force for the development of new ultrahigh resolution instrumentation, experimental methods, and data analysis procedures. Recent advances in ionization, resolving power, mass accuracy, and the use of separation methods, have allowed for record levels of compositional detail to be obtained for petroleum-related samples. To address the growing size and complexity of the data generated, vital software tools for data processing, analysis, and visualization continue to be developed. The insights gained impact upon the fields of energy and environmental science and the petrochemical industry, among others. In addition to advancing the understanding of one of nature's most complex mixtures, advances in petroleomics methodologies are being adapted for the study of other sample types, resulting in direct benefits to other fields.

Lipids are an important class of biomolecules with many roles within cells and tissue. As targets for study, they present several challenges. They are difficult to label, as many labels lack the specificity to the many different lipid species or the labels maybe larger than the lipids themselves, thus severely perturbing the natural chemical environment. Mass spectrometry provides exceptional specificity and is often used to examine lipid extracts from different samples. However, spatial information is lost during extraction. Of the different imaging mass spectrometry methods available, secondary ion mass spectrometry (SIMS) is unique in its ability to analyze very small features, with probe sizes <50 nm available. It also offers high surface sensitivity and 3D imaging capability on a subcellular scale. This article reviews the current capabilities and some remaining challenges associated with imaging the diverse lipids present in cell and tissue samples. We show how the technique has moved beyond show-and-tell, proof-of-principle analysis and is now being used to address real biological challenges. These include imaging the microenvironment of cancer tumors, probing the pathophysiology of traumatic brain injury, or tracking the lipid composition through bacterial membranes.

The electrochemical behavior of platinum single crystal surfaces can be taken as a model response for the interpretation of the activity of heterogeneous electrodes. The cyclic voltammogram of a given platinum electrode can be considered a fingerprint characteristic of the distribution of sites on its surface. We start this review by providing some simple mathematical descriptions of the voltammetric response in the presence of adsorption processes. We then describe the voltammogram of platinum basal planes, followed by the response of stepped surfaces. The voltammogram of polycrystalline materials can be understood as a composition of the response of the different basal contributions. Further resolution in the discrimination of different surface sites can be achieved with the aid of surface modification using adatoms such as bismuth or germanium. The application of these ideas is exemplified with the consideration of real catalysts composed of platinum nanoparticles with preferential shapes.