Modulation of designer biomimetic matrices for optimized differentiated intestinal epithelial cultures.

The field of intestinal biology is thirstily searching for different culture methods that complement the limitations of organoids, particularly the lack of a differentiated intestinal compartment. While being recognized as an important milestone for basic and translational biological studies, many primary cultures of intestinal epithelium (IE) rely on empirical trials using hydrogels of various stiffness, whose mechanical impact on epithelial organization remains vague until now. Here, we report the development of hydrogel scaffolds with a range of elasticities and their influence on IE expansion, organization, and differentiation. On stiff substrates (>5 kPa), mouse IE cells adopt a flat cell shape and detach in the short-term. In contrast, on soft substrates (80-500 Pa), they sustain for a long-term, pack into high density, develop columnar shape with improved apical-basal polarity and differentiation marker expression, a phenotype reminiscent of features in vivo mouse IE. We then developed a soft gel molding process to produce 3D Matrigel scaffolds of close-to-nature stiffness, which support and maintain a culture of mouse IE into crypt-villus architecture. Thus, the present work is up-to-date informative for the design of biomaterials for ex vivo intestinal models, offering self-renewal in vitro culture that emulates the mouse IE.

Potential metal-related strategies for prevention and treatment of COVID-19.

Abstract: The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed severe threats to human health, public safety, and the global economy. Metal nutrient elements can directly or indirectly take part in human immune responses, and metal-related drugs have served as antiviral drugs and/or enzyme inhibitors for many years, providing potential solutions to the prevention and treatment of COVID-19. Metal-based drugs are currently under a variety of chemical structures and exhibit wide-range bioactivities, demonstrating irreplaceable advantages in pharmacology. This review is an intention to summarize recent progress in the prevention and treatment strategies against COVID-19 from the perspective of metal pharmacology. The current and potential utilization of metal-based drugs is briefly introduced. Specifically, metallohydrogels that have been shown to present superior antiviral activities are stressed in the paper as potential drugs for the treatment of COVID-19.

Author Correction: Directed self-assembly of herbal small molecules into sustained release hydrogels for treating neural inflammation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Giant Phospholipid Folds on Air-Water Surface: Structure Details, Formation Pathway, and Possible Recycle Mechanism.

In vitro mimics recognized that the propensity of a negatively charged phospholipid, DPPS, monolayers to self-aggregate to three-dimensional (3D) giant folds under overcompression at an air-water interface. Time elapsing microscopical observations confirmed that such giant folds were able to float stably on the air-water interface for weeks or even longer. Ex situ atomic force microscopy (AFM) and transmission electronic microscopy (TEM) characterizations pointed out that such giant folds were composed of compactly stacked lipid layers. Phospholipase A2 (PLA2), a principal bactericide in human and animal tear secretion, was chosen to drive the in situ lipid giant folds disassembly on water and supported substrate surfaces, respectively. Our experimental results confirmed the layer-by-layer structures of the giant folds. It is noteworthy that the defect-rich areas of the giant lipid folds were eliminated quickly by PLA2 while defect-free lipid zones were left untouched, suggesting that PLA2 may serve as a highly effective and selective regenerator/cleaner of lipid aggregates in the physiological circumstance of certain organs.

Directed self-assembly of herbal small molecules into sustained release hydrogels for treating neural inflammation.

Self-assembling natural drug hydrogels formed without structural modification and able to act as carriers are of interest for biomedical applications. A lack of knowledge about natural drug gels limits there current application. Here, we report on rhein, a herbal natural product, which is directly self-assembled into hydrogels through noncovalent interactions. This hydrogel shows excellent stability, sustained release and reversible stimuli-responses. The hydrogel consists of a three-dimensional nanofiber network that prevents premature degradation. Moreover, it easily enters cells and binds to toll-like receptor 4. This enables rhein hydrogels to significantly dephosphorylate IκBα, inhibiting the nuclear translocation of p65 at the NFκB signalling pathway in lipopolysaccharide-induced BV2 microglia. Subsequently, rhein hydrogels alleviate neuroinflammation with a long-lasting effect and little cytotoxicity compared to the equivalent free-drug in vitro. This study highlights a direct self-assembly hydrogel from natural small molecule as a promising neuroinflammatory therapy.

Metallogels: Availability, Applicability, and Advanceability.

Introducing metal components into gel matrices provides an effective strategy to develop soft materials with advantageous properties such as: optical activity, conductivity, magnetic response activity, self-healing activity, catalytic activity, etc. In this context, a thorough overview of application-oriented metallogels is provided. Considering that many well-established metallogels start from serendipitous discoveries, insights into the structure-gelation relationship will offer a profound impact on the development of metallogels. Initially, design strategies for discovering new metallogels are discussed, then the advanced applications of metallogels are summarized. Finally, perspectives regarding the design of metallogels, the potential applications of metallogels and their derivative materials are briefly proposed.

Hybrid Catalyst of a Metal-Organic Framework, Metal Nanoparticles, and Oxide That Enables Strong Steric Constraint and Metal-Support Interaction for the Highly Effective and Selective Hydrogenation of Cinnamaldehyde.

In this work, we designed a hybrid catalyst composed of a metal-organic framework (MOF), Pt nanoparticles (NPs), and ferric oxide, namely, Co-MOF-74@(Pt@Fe2O3), which enables not only high turnover frequencies of up to 245.7 h-1 but also ultrahigh 100% selectivity toward cinnamyl alcohol in the hydrogenation of cinnamaldehyde under mild conditions. This excellent performance is attributed to the fact that such a hybrid catalyst enables not only strong steric constraint to provide the favored C═O adsorption of cinnamaldehyde but also strong metal-support interaction to lower the electron density of Pt NPs.

In Situ Fabrication of Defective CoNx Single Clusters on Reduced Graphene Oxide Sheets with Excellent Electrocatalytic Activity for Oxygen Reduction.

A facile one-step strategy for anchoring defective CoNx single clusters on partly reduced graphene oxide (RGO) is constructed to significantly improve the catalytic performance of non-noble metal complexes toward oxygen reduction reaction (ORR). Sequent loading with trace amounts of metal-free porphyrin and Co2+ in RGO can dramatically enhance both the half-wave potential and the peak current density. Intriguingly, the RGO/P/2Co single cluster exhibits the best ORR catalytic performance with the half-wave potential of 0.834 V, extremely approaching that of commercial Pt/C (0.836 V). This half-wave potential surpasses most of the reported half-wave potentials of RGO supported non-noble metal ORR catalysts through low-temperature synthesis. Furthermore, the as-prepared RGO/P/2Co delivers a peak current density of 1.3 times higher than that of Pt/C at the same loading, together with a high mass activity of 2.76 A mgCo-1. During the durability test, a cathodic current loss less than 10% is recorded after 8000 continuous potential cycles. Insights into this successful example will be conducive to the development of elegant routes for constructing metal nitrogen (MN)-based ORR catalysts with high efficiency, outstanding stability, and excellent selectivity.

In situ hybridization of CoOX nanoparticles on N-doped graphene through one step mineralization of co-responsive hydrogels.

The in situ hydrothermal mineralization for a mixture of graphene oxide (GO) and Co-responsive supramolecular hydrogels led to a hybrid graphene aerogel, doped with Co and N elements. The as-prepared aerogels exhibited a competitive half-wave potential (0.840 V, versus RHE) and peak current density (2.35 mA cm-2) to that of Pt/C (0.836 V, 2.23 mA cm-2, respectively). Furthermore, they demonstrated a significantly perfect catalytic efficiency (nearly 100% of 4e- ORR) toward the oxygen reduction reaction (ORR). Insight into the structural details of the hybrid aerogels indicates that the CoOX active sites anchored on the graphene matrix play a central role in the upgrading of the catalytic performance of graphene aerogels.

Designing isometrical gel precursors to identify the gelation pathway for nickel-selective metallohydrogels.

Two novel multi-responsive metallohydrogels, namely, 2-PF-Ni and 3-PF-Ni, were successfully constructed from phenylalanine derivatives. The 2-PF gelator shows specific responses to Ni2+; particularly, 2-PF-Ni is lavender colored, which has been rarely reported among hydrogels triggered by Ni2+. 3-PF-Ni is light green and exhibits perfect thixotropy. This paper provides insights into the gelation mechanisms of these two metallogels.

Cation Tuning toward the Inference of the Gelation Behavior of Supramolecular Gels.

We serendipitously discovered that the tripeptide Asp-Phe-Phe trifluoroacetic acid salt (hereafter abbreviated as ß-AspFF) formed a reversible thermotropic gel in chloroform solution (at temperatures higher than the boiling point of chloroform), and a stable gel in toluene solution (at equal to or lower than the room temperature). Experimental results indicate that doping metal ions into ß-AspFF toluene gels can trigger morphological variations in the gel skeleton, thereby increasing gel volume and inducing the collapse of organogels. Investigation on the cation-tuned gelation behavior of ß-AspFF can be used to elucidate heating-induced gel collapse (of normal gel) or reverse thermotropic gelation as well as select carbamide and acetamide as activators of ß-AspFF gels in chloroform solution at room temperature.

Correction: A Co(2+)-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton.

Correction for 'A Co(2+)-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton' by Xiaojuan Wang et al., Nanoscale, 2016, DOI: 10.1039/c6nr00822d.

A Co²âº-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton.

This paper introduces a new metallohydrogel precursor that offers a peculiar gelation response to Co(2+) at pH 7-8. It is notable that the stability of this metallohydrogel is significantly dependent on its enantiomeric purity. In addition to the expected multi-stimuli responsive properties, including thixotropy, as well as re-assembly properties on adding HCl, this metallohydrogel possesses excellent self-healing behavior, which is uncommon in low-molecular-weight gelators. Electron microscopy (EM) studies revealed that the cryodried remains of this gel presented as well an organized three dimensional (3D) network of fibrils. This interesting metallohydrogel shows potential for developing new soft materials with drug delivery and catalysis properties.