[Research progress on preparation and applications of covalent organic framework-based chromatographic stationary phases].

Given continuous developments in industrial and scientific research, the separation and analysis of complex systems with high sensitivity, throughput, and selectivity is facing new challenges. Chromatography plays an irreplaceable role in separation science and is widely applied in environmental monitoring, pharmaceutical analysis, and food safety. Owing to their outstanding advantages, such as high loading capacity, precise quantification, and good reproducibility, chromatographic separation techniques based on various retention mechanisms have been utilized to detect different analytes. The stationary phase is the core material of chromatographic columns and has an extremely important influence on their separation performance. The selectivity and efficiency of separation largely depend on the chromatographic stationary phase. However, traditional stationary phases, such as silicon-based matrices, are characterized by complex preparation processes, poor permeability, large mass transfer resistance, and a narrow pH range. In addition, polymer matrices show poor mechanical stability and susceptibility to swelling, which limit their applications in the field of separation. Therefore, the development of novel stationary phases with the advantages of traditional stationary phases has become a research emphasis in the field of analytical science in efforts to meet separation requirements under different environments. Various stationary phases based on novel porous materials, such as metal organic frameworks (MOFs), porous organic cages (POCs), and covalent organic frameworks (COFs), are used for chromatographic separation. As mesh crystalline porous materials, MOFs have the advantages of a large surface area, adjustable structure, and easy functionalization; thus, they are widely used as chromatographic stationary phases in reverse-phase chromatography, hydrophilic-mode chromatography, mixed-mode chromatography, and other separation modes. However, because the pore size of MOFs is small and most MOFs demonstrate poor chemical stability under acidic or alkaline conditions, their applications in chromatographic separation are greatly limited. COFs are porous, crystalline polymer materials composed of light elements (H, O, C, N, B, and Si) connected via covalent bonds. Their advantages include a low density, large specific surface area, high porosity, good chemical and thermal stability, regular pores, and adjustable pore sizes. Because of their unique structures and properties, COFs are widely used in many fields such as catalysis, enrichment, gas capture, and sensing. COF materials are also suitable for separation analysis and considered ideal materials for novel chromatographic stationary phases. This review summarizes the latest research progress on the preparation and applications of COF-based chromatographic stationary phases over the past five years. First, the preparation of COF-based stationary phases (SiO2@COFs stationary phase, COFs monolithic stationary phase, pure COFs stationary phase and COFs-coated stationary phase) is introduced. The latest applications of COF-based stationary phases in the separation of organic compounds, isomers, and chiral compounds are then described in detail. Finally, the future development trends and challenges of chromatographic stationary phases based on COFs are discussed to provide new ideas for the future design and development of novel chromatographic stationary phases based on COFs.

Fluorescent Turn-On Probes for Visualizing GPx4 Levels in Live Cells and Predicting Drug Sensitivity.

Glutathione peroxidase 4 (GPx4) is the membrane peroxidase in mammals that is essential for protecting cells against oxidative damage and critical for ferroptosis. However, no live cell probe is currently available to specifically label GPx4. Herein, we report both inhibitory and noninhibitory fluorescent turn-on probes for specific labeling of GPx4 in live cells. With these probes, the GPx4 expression levels and degradation kinetics in live cells could be visualized, and their real-time responses to the cellular selenium availability were revealed. These probes could also potentially serve as staining reagents to predict the sensitivity of GPx4-related ferroptosis drugs. In view of these features, these GPx4-selective probes will offer opportunities for a deeper understanding of GPx4 function in natural habitats and hold great promise for biomedical applications.

Engineering surface patterns on nanoparticles: new insights into nano-bio interactions.

The surface properties of nanoparticles affect their fate in biological systems. Based on nanotechnology and its methodology, pioneering studies have explored the effects of chemical surface patterns on the behavior of nanoparticles and provided many new insights into nano-bio interfaces. In this review, we would like to provide a summary of how the nanoparticle surface pattern modulates its biological effects. The relationship between the surface pattern of nanoparticles and the generated interaction with cell membranes, recognition of viruses and adsorption of proteins was discussed. On this basis, we believe that a reasonable design of the surface microstructure will promote the application of artificial nanoparticles in biomedicine and provide a new strategy for improving the design of nano-drug carriers.

[Research advances in covalent organic framework materials for sample pretreatment].

Covalent organic frameworks (COFs) are two-dimensional or three-dimensional crystalline porous structures formed by the covalent bonding of organic monomers. As an emerging crystalline porous material, COFs have been widely used in various fields such as gas storage, catalysis, sensing, and drug delivery. In recent years, COFs have shown immense potential in analytical chemistry because of their low density, large surface area, and controllable structure. This paper reviews the application of porous COFs and their composites in sample pretreatment, including dispersive solid-phase extraction, solid phase micro-extraction, and magnetic solid phase extraction.

A selective artificial enzyme inhibitor based on nanoparticle-enzyme interactions and molecular imprinting.

A novel and general strategy is developed to design selective artificial enzyme inhibitor based on nanoparticleenzyme inter actions and molecular imprinting. Due to the creation of specific binding cavities, the resulting artificial inhibitor has high inhibition efficiency for the target enzyme, and shows great target-selectivity over other enzymes of similar function and proteins of compaable mole cular weight.

Preparation and evaluation of a phenylboronate affinity monolith for selective capture of glycoproteins by capillary liquid chromatography.

A phenylboronate affinity monolith was prepared and applied to the selective capture of glycoproteins from unfractionated protein mixtures. The monolith was synthesized in a 100 µm i.d capillary by an in situ polymerization procedure using a pre-polymerization mixture consisting of 4-vinylphenylboronic acid (VPBA) as functional monomer, ethylene dimethacrylate (EDMA) as crosslinker, diethylene glycol and ethylene glycol as binary porogenic solvents, and azobisisobutyronitrile (AIBN) as initiator. The prepared monolith was characterized in terms of the morphology, pore property, and recognition property. The selectivity and dynamic binding capacity were evaluated by using standard glycoproteins and nonglycoproteins as model proteins. The chromatographic results demonstrated that the phenylboronate affinity monolith had higher selectivity and binding capacity for glycoprotein than nonglycoprotein. The resulting phenylboronate affinity monolith was used as the sorbent for in-tube solid phase microextraction (in-tube SPME), and the extraction performance of the monolith was assessed by capture of ovalbumin from egg white sample.

Controllable preferential-etching synthesis of ZnO nanotube arrays on SiO2 substrate for solid-phase microextraction.

An improved route to obtain ZnO nanotube arrays and its first application to headspace solid-phase microextraction (HSSPME) as an adsorptive coating were described. The ZnO nanotube arrays were synthesized by a two-step chemical process including the hydrothermal synthesis of ZnO nanorod arrays on the surface of silica fiber (SiO(2)) in the first step, and the formation of ZnO nanotubes by selectively etching in NH(3)·H(2)O solution in the second step. The influence of NH(3)·H(2)O concentration, etching time, reaction temperature, and aging time in the ZnO nanotubes formation process was investigated, and arrays of ZnO nanotube with tailored dimensions (250 nm external diameters, 70 nm wall thicknesses and 2 µm lengths) could be obtained by varying the conditions. In addition, the feasibility of ZnO nanotube arrays adopted for HSSPME was evaluated by extracting volatile organic compounds (VOCs) by use of benzene, toluene, ethylbenzene, o-, m-and p-xylene (BTEX) as model compounds and the results showed that the coating has good extraction capability. The analytes were linear in the range of 10-600 µg L(-1) (r > 0.9960) and the detection limits were about 0.005-0.01 µg L(-1), lower than that obtained with ZnO nanorod arrays. The relative standard derivations (RSD) for the repeatability of single fiber and fiber-to-fiber were lower than 9.5% and 13.8%, respectively. The prepared coating showed good recoveries in the range of 87%-108% and long lifetime (more than 50 times), implying to be a potential absorbent for the VOCs in water samples.