Organoids/organs-on-a-chip: new frontiers of intestinal pathophysiological models.

Organoids/organs-on-a-chip open up new frontiers for basic and clinical research of intestinal diseases. Species-specific differences hinder research on animal models, while organoids are emerging as powerful tools due to self-organization from stem cells and the reproduction of the functional properties in vivo. Organs-on-a-chip is also accelerating the process of faithfully mimicking the intestinal microenvironment. And by combining organoids and organ-on-a-chip technologies, they further are expected to serve as innovative preclinical tools and could outperform traditional cell culture models or animal models in the future. Above all, organoids/organs-on-a-chip with other strategies like genome editing, 3D printing, and organoid biobanks contribute to modeling intestinal homeostasis and disease. Here, the current challenges and future trends in intestinal pathophysiological models will be summarized.

Metal-Polyphenol Network-Mediated Protein Encapsulation Strategy Facilitating the Separation of Proteins and Metabolites in Biospecimens.

Access to both protein and metabolite biomarker information in biospecimens from trace samples remains a significant challenge, and it is necessary to separate proteins and metabolites before analysis. In this work, the Fe3O4@SiO2@Proteins@Metal-polyphenol network (MPN) was successfully constructed and applied to separate metabolites and proteins. Tannic acid (TA) and Cu2+ were involved in the synthesis of MPN because of rapid degradation and maintaining the assay performance of proteins. There are a variety of interactions between TA and proteins, including hydrogen-bonding, hydrophobic, and ionic interactions. Moreover, benefiting from the small molecule permeability and surface adherence of MPN, proteins were encapsulated and immobilized on the surface of substrates with the growth of MPN. At the same time, endogenous metabolites remained dispersed in the supernatant. In the model sample and real biospecimen cases, the protein biomarkers (e.g., carcinoembryonic antigen and alanine aminotransferase) were encapsulated on the surface of Fe3O4@SiO2, which allowed the isolation of proteins from the original matrix, as well as release and analysis in a short time. Meanwhile, the metabolites in the produced supernatant were analyzed by LC-MS/MS. By the self-assembly and disassembly of MPN, the group differences of proteins and metabolites between physiological and pathological biospecimens are correctly characterized without multisampling. Overall, an MPN-mediated separation strategy of biomarkers was proposed, and MPN facilitated a "two birds with one stone" approach, where the proteins were encapsulated and immobilized in the precipitation while endogenous metabolites distributed in the produced supernatant, opening a new chapter in the application of MPNs.

Kinetically Orthogonal Probe for Simultaneous Measurement of H2S and Nitroreductase: A Refined Method to Predict the Invasiveness of Tumor Cells.

The concentrations of nitroreductase and H2S have been widely used to predict the invasiveness of tumors. However, the above two substrates always interfere with the measurement of each other as both substrates react with the typical nitroaromatic probe with the same process. Moreover, the above interferences may lead to the misjudgment of the tumor invasiveness. We used a strategy combining kinetical distinguishing and signal amplification to construct a kinetically orthogonal probe labeled KOP. The above strategy expanded the gap between the reactivity of KOP to H2S and nitroreductase with an acceptable reactivity and could determine the concentration of coexisting nitroreductase and H2S on a kinetic curve with a breakpoint. KOP could also indicate the correct invasiveness tendency in the cellular model with a complex H2S generation pathway, while the traditional kinetically nonorthogonal probe could not indicate invasiveness correctly.

Characterization of alkaloids in radix Sophora tonkinensis by UPLC-Q-TOF-MS/MS and its application in the comparison of two different habitats.

Sophora tonkinensis is widely used as traditional Chinese medicine for treating the swelling of the gums and tongue and mouth sores due to flame stomach fire. It is mainly origin from Guangxi, Sichuan provinces of China. Alkaloids are considered as the major bioactive components. A method was established for identifying alkaloids in S. tonkinensis root by UPLC-Q-TOF-MS/MS and was applied in characterizing alkaloids in S. tonkinensis root of two different habitats. Consequently, twenty-four alkaloids including six new compounds were identified in S. tonkinensis root. Additionally, the difference of alkaloids in S. tonkinensis from Guozhou, Sichuan province was investigated. In the present study, we firstly characterize total alkaloids in S. tonkinensis root by UPLC-Q-TOF-MS/MS and firstly established the characteristic fragmentation pathway of alkaloids with hydroxy in S. tonkinensis root.

Nitrite-responsive hydrogel for long-term and smart control of cyanobacteria bloom.

Frequent cyanobacteria bloom has caused serious environmental consequences and economic loss, especially in aquaculture. Direct algaecide addition, the most commonly used method, suffered from the poor control and overdose of algaecide. In this manuscript, we designed a smart nitrite-responsive hydrogel (DHPG) loading algaecide (BZK@DHPG) based on selective crosslinker: a kind of dihydropyridine derivatives termed DHPL. The network of the polymer could be decomposed by the nitrite-induced cleavage of DHPL. Compared to the traditional method, BZK@DHPG can adjust releasing speed according to the concentration of NO2-, the marker of cyanobacteria bloom level, and elongate the releasing time. Furthermore, BZK@DHPG could shift the effective dose of algaecide much ahead of the safety threshold, thus reducing deterioration of water quality caused by the overdose of algaecide.

Composable microfluidic spinning platforms for facile production of biomimetic perfusable hydrogel microtubes.

Microtissues with specific structures and integrated vessels play a key role in maintaining organ functions. To recapitulate the in vivo environment for tissue engineering and organ-on-a-chip purposes, it is essential to develop perfusable biomimetic microscaffolds. We developed facile all-aqueous microfluidic approaches for producing perfusable hydrogel microtubes with diverse biomimetic sizes and shapes. Here, we provide a detailed protocol describing the construction of the microtube spinning platforms, the assembly of microfluidic devices, and the fabrication and characterization of various perfusable hydrogel microtubes. The hydrogel microtubes can be continuously generated from microfluidic devices due to the crosslinking of alginate by calcium in the coaxial flows and collecting bath. Owing to the mild all-aqueous spinning process, cells can be loaded into the alginate prepolymer for microtube spinning, which enables the direct production of cell-laden hydrogel microtubes. By manipulating the fluid dynamics at the microscale, the composable microfluidic devices and platforms can be used for the facile generation of six types of biomimetic perfusable microtubes. The microfluidic platforms and devices can be set up within 3 h from commonly available and inexpensive materials. After 10-20 min required to adjust the platform and fluids, perfusable hydrogel microtubes can be generated continuously. We describe how to characterize the microtubes using scanning electron or confocal microscopy. As an example application, we describe how the microtubes can be used for the preparation of a vascular lumen and how to perform barrier permeability tests of the vascular lumen.

Nitrite-Responsive Hydrogel: Smart Drug Release Depending on the Severity of the Nitric Oxide-Related Disease.

Nitric oxide (NO) is known as one of the most important biomarkers of many diseases. However, the development of NO-triggered drug releasing platforms is challenging due to the low concentration and short lifetime of NO in vivo. In this work, a novel nitrite (NO2-)-responsive hydrogel (DHPL-GEL), which can be used for smart drug release depending on the severity of the NO-related disease, is demonstrated. A dihydropyridine cross-linking agent is designed to construct DHPL-GEL to enable the responsive degradation of the hydrogel triggered by NO2-. On-demand release of the drug loaded in DHPL-GEL was observed under the stimulation of various concentrations of NO2- at the physiological level both in vitro and in vivo. In the inflammatory arthritis rat model, the DHPL-GEL drug delivery system showed a better therapeutic effect and less side effects than the traditional therapy and nonresponsive hydrogel drug delivery system, demonstrating the promising application of the NO2--responsive hydrogel for the treatment of NO-related diseases.

Microfluidics for Biosynthesizing: from Droplets and Vesicles to Artificial Cells.

Fabrication of artificial biomimetic materials has attracted abundant attention. As one of the subcategories of biomimetic materials, artificial cells are highly significant for multiple disciplines and their synthesis has been intensively pursued. In order to manufacture robust "alive" artificial cells with high throughput, easy operation, and precise control, flexible microfluidic techniques are widely utilized. Herein, recent advances in microfluidic-based methods for the synthesis of droplets, vesicles, and artificial cells are summarized. First, the advances of droplet fabrication and manipulation on the T-junction, flow-focusing, and coflowing microfluidic devices are discussed. Then, the formation of unicompartmental and multicompartmental vesicles based on microfluidics are summarized. Furthermore, the engineering of droplet-based and vesicle-based artificial cells by microfluidics is also reviewed. Moreover, the artificial cells applied for imitating cell behavior and acting as bioreactors for synthetic biology are highlighted. Finally, the current challenges and future trends in microfluidic-based artificial cells are discussed. This review should be helpful for researchers in the fields of microfluidics, biomaterial fabrication, and synthetic biology.