Heterologous expression of P9 from Akkermansia muciniphila increases the GLP-1 secretion of intestinal L cells.

Glucagon-like peptide-1(GLP-1) is an incretin hormone secreted primarily from the intestinal L-cells in response to meals. GLP-1 is a key regulator of energy metabolism and food intake. It has been proven that P9 protein from A. muciniphila could increase GLP-1 release and improve glucose homeostasis in HFD-induced mice. To obtain an engineered Lactococcus lactis which produced P9 protein, mature polypeptide chain of P9 was codon-optimized, fused with N-terminal signal peptide Usp45, and expressed in L. lactis NZ9000. Heterologous secretion of P9 by recombinant L. lactis NZP9 were successfully detected by SDS-PAGE and western blotting. Notably, the supernatant of L. lactis NZP9 stimulated GLP-1 production of NCI-H716 cells. The relative expression level of GLP-1 biosynthesis gene GCG and PCSK1 were upregulated by 1.63 and 1.53 folds, respectively. To our knowledge, this is the first report on the secretory expression of carboxyl-terminal processing protease P9 from A. muciniphila in L. lactis. Our results suggest that genetically engineered L. lactis which expressed P9 may have therapeutic potential for the treatment of diabetes, obesity and other metabolic disorders.

Peptide-Based Molecularly Imprinted Polymer: A Visual and Digital Platform for Specific Recognition and Detection of Ethyl Carbamate.

A visual and digital platform was constructed by peptide-based molecularly imprinted polymers (PMIPs) for specific recognition and detection of ethyl carbamate (EC). Here, the optosensing core was creatively constructed by the covalent assembly of dipeptides (H-Phe-Phe-OH) and genipin biomolecules for high fluorescence quantum yield and dual-signal response capability. MIPs were wrapped in the shell of the optosensing core for selectivity of EC from actual samples of alcoholic beverages. The genipin-FF nanoparticles (GFPNs)@PMIPs exhibited dual-band red-blue fluorescence image with a low detection limit of 0.817 and 1.65 µg L-1, respectively, in the optimal linear range of 2-240 µg L-1. The accuracy of this method was verified by the spiked recovery experiment, and a good recovery from 83.97 to 106.75% of the proposed optosensing method was obtained. In addition, a smartphone application was coupled with GFPNs@PMIPs to realize online real-time detection of EC. With the addition of EC, the color change of G and B values was negligible compared with the R value. This work also provides a potential method for on-site visual detection of analytes.

Structural and photoactive properties of self-assembled peptide-based nanostructures and their optical bioapplication in food analysis.

BACKGROUND: Food processing plays an important role in the modern industry because food quality and security directly affect human health, life safety, and social and economic development. Accurate, efficient, and sensitive detection technology is the basis for ensuring food quality and security. Optosensor-based technology with the advantage of fast and visual real-time detection can be used to detect pesticides, metal ions, antibiotics, and nutrients in food. As excellent optical centres, self-assembled peptide-based nanostructures possess attractive advantages, such as simple preparation methods, controllable morphology, tunable functionality, and inherent biocompatibility. AIM OF REVIEW: Self-assembled peptide nanostructures with good fabrication yield, stability, dispersity in a complex sample matrix, biocompatibility, and environmental friendliness are ideal development goals in the future. Owing to its flexible and unique optical properties, some short peptide self-assemblies can possibly be used to achieve the purpose of rapid and sensitive detection of composition in food, agriculture, and the environment, expanding the understanding and application of peptide-based optics in analytical chemistry. KEY SCIENTIFIC CONCEPT OF REVIEW: The self-assembly process of peptides is driven by noncovalent interactions, including hydrogen bonding, electrostatic interactions, hydrophobic interactions, and π-π stacking, which are the key factors for obtaining stable self-assembled peptide nanostructures with peptides serving as assembly units. Controllable morphology of self-assembled peptide nanostructures can be achieved through adjustment in the type, concentration, and pH of organic solvents and peptides. The highly ordered nanostructures formed by the self-assembly of peptides have been proven to be novel biological structures and can be used for the construction of optosensing platforms in biological or other systems. Optosensing platforms make use of signal changes, including optical signals and electrical signals caused by specific reactions between analytes and active substances, to determine the content or concentration of an analyte.

Molecularly imprinted bulk and solgel optosensing based on biomass carbon dots derived from watermelon peel for detection of ethyl carbamate in alcoholic beverages.

Biomass carbon dots synthesized by biological waste conform to the trend of ecological environmental protection and the requirements of green chemistry, which show great application potential in practice. In the study, we used watermelon peels as the raw materials to synthesize a novel blue biomass carbon dots (CDs) by a hydrothermal process with high fluorescence quantum yield of 22.8%. Through bulk polymerization and solgel method, two kinds of core-shell nanospheres were developed as fluorescent probes to recognize and detect ethyl carbamate (EC) rapidly without complex samples pretreatment. The obtained CDs@MIPs integrated the high-performance optical characteristics of CDs with excellent selectivity and adsorption of MIPs, which showed ideal linear relationships in the EC concentration range 1-120 µg L-1 and low LOD of 0.57 µg L-1 and 0.94 µg L-1, respectively. Both CDs@MIPs have a short equilibration time which was around 20 min, and the imprinting factors (IF) are 4.04 and 2.62. The recoveries of the six spiked samples were satisfying, and the RSD precisions were lower than 5.57%. Gas chromatography-mass spectrometry was seen as a parallel analysis to validate the correctness of the results, which indicated the practicability and reliability of the developed method. This proposal strategy of optical sensors provided an effective channel for trace EC recognition, with numerous advantages, involving eco-friendly, low cost, high sensitivity, separation effect, and good selectivity.

Inhibitory Mechanism of Advanced Glycation End-Product Formation by Avenanthramides Derived from Oats through Scavenging the Intermediates.

As a special polyphenolic compound in oats, the physiological function of oat avenanthramides (AVAs) drives a variety of biological activities, and plays an important role in the prevention and treatment of common chronic diseases. In this study, the optimum extraction conditions and structural identification of AVAs from oats was studied. The inhibitory effect of AVAs from oats on advanced glycation end-products (AGEs) in a glucose-casein simulation system was evaluated, and this revealed dose-dependent inhibitory effects. The trapping capacity of AVAs to the α-dicarbonyl compounds of AGE intermediate products was determined by HPLC-MS/MS, and the results indicate that AVA 2c, AVA 2p, and AVA 2f exhibited the ability to capture α-dicarbonyl compounds. More importantly, AVA 2f was found to be more efficient than AVA 2p at inhibiting superoxide anion radical (O2-), hydroxyl radical (OH), and singlet oxygen (1O2) radical generation, which may be the main reason that AVA 2f was more efficient than AVA 2p in AGE inhibition. Thus, this research presents a promising application of AVAs from oats in inhibiting the food-borne AGEs formed in food processing.

Quantum confined peptide assemblies in a visual photoluminescent hydrogel platform and smartphone-assisted sample-to-answer analyzer for detecting trace pyrethroids.

Quantum confinement (QC) effect-related materials have been extensively studied as photoluminescent probes for agricultural, food, and environmental analyses, with the advantage of simple-to-synthesize, reusable, nontoxic, and environmentally friendly. Herein, we propose a strategy to dimerize aromatic cyclo-dipeptides, namely cyclo-ditryptophan (cyclo-WW), cyclo-diphenylalanine (cyclo-FF), and cyclo-dihistidine (cyclo-HH), into quantum dots as basic building blocks for the self-assembly of QC supramolecular structures with excellent photoluminescent properties in aqueous solutions. In particular, through coordination with Zn(II), the bandgap can be tuned to change the photo-absorption and luminescence properties of the cyclo-dipeptide-based QC assemblies. The fluorescence quantum yield of cyclo-WW+Zn(II) was 16.9%. Such a good luminous effect makes it applicable to the detection of LC. A good linear relationship between fluorescence response of cyclo-WW+Zn(II) and LC concentration was observed in the range of 5-350 µg/L, with a low limit of detection of 2.9 µg/L and good spiked recovery of 90.72%-104.3%. A visual platform using the cyclo-WW+Zn(II)-based photoluminescent hydrogel and smartphone-assisted sample-to-answer analyzer were developed, which showed good responsiveness to LC. The developed fluorescence method, validated using traditional HPLC, is a biocompatible alternative for the rapid detection of trace pollutants with the advantages of portability and simple operation.

Fabrication of a fluorescence probe via molecularly imprinted polymers on carbazole-based covalent organic frameworks for optosensing of ethyl carbamate in fermented alcoholic beverages.

Ethyl carbamate (EC), which is a group 2A carcinogen, is a byproduct formed in the alcohol fermentation process that can accumulate with heating, transportation, and storage. In this study, molecularly imprinted polymers (MIPs) on carbazole-based covalent organic frameworks (COFs) were prepared as a fluorescence probe for the optosensing of EC in fermented alcoholic beverages. The excellent optical properties of carbazole-based COFs coupled with the good adsorption and selectivity of MIPs provided fast and efficient recognition of EC. MIPs on carbazole-based COFs exhibited advantages of high efficiency, a good separation effect, fluorescence dependence, and reproducibility. A good linear relationship was obtained over the concentration range of 1-200 µg L-1, with a low limit of detection (LOD) of 0.607 µg L-1. The RSD precision and five-cycle reproducibility were lower than 4.91% and 6.38%, respectively, and the recoveries were 85.30%-109.49%. This optosensor was applied to quantify EC contents in several fermented alcoholic beverages, all of which were less than LOD. The results of the optosensors based on MIPs on carbazole-based COFs were then validated using standard gas chromatography-mass spectrometry (GC-MS), which gave results consistent with the proposed method.

A smartphone-based ratiometric fluorescent sensing system for on-site detection of pyrethroids by using blue-green dual-emission carbon dots.

Exploring the high-performance fluorescence strategy for on-site monitoring of pyrethroids is of great significance to the protection of the ecological environment and human health. Aiming at attaining precise onsite analysis, blue-green dual-emission carbon dots (CDs) were used as well-resolved optosensing centers, and an innovative ratiometric fluorescence core-shell nanosphere was constructed using molecular imprinting in this study. The ratiometric fluorescent signal of the CDs was used by the nanospheres to realize on-site quantitative detection of pyrethroids with excellent selectivity. The detection range of this ratiometric sensing platform was 1-150 µg/L and the limit of detection (LOD) was obtained, as low as 0.048 µg/L. Importantly, the core-shell nanospheres exhibited fluorescence changes on exposure to pyrethroids under UV irradiation. A smartphone application was used to output the color channel values of the captured images. The smartphone-based ratiometric sensing system was used for the quantitative detection of pyrethroid with a sensitive LOD of 0.61 µg/L, which could meet the needs of real analytical samples. This sensing platform showed great application potential for the on-site detection of pesticide residues in agriculture food and pollution control in resource-limited environments.

A smartphone-integrated optosensing platform based on red-emission carbon dots for real-time detection of pyrethroids.

This report described the development of an optosensing platform based on red-emission carbon dots (RCDs) integrated with a smartphone application that, together, can detect pyrethroids in real time. Based on the high stability and selectivity of molecular imprinting technology, RCDs-based optosensing imprinted polymers was obtained by using a one-pot inverse microemulsion surface imprinting method. Lambda-cyhalothrin (LC), which is a pyrethroid pesticide, can interact with the widely distributed -NH2 groups on the surface of the RCD-based optosensing nanomaterials to achieve fixed-point adsorption. The quantitative detection of pyrethroids in a wide concentration range (1-120 µg/L) could be achieved, and the limit of detection (LOD) was 0.89 µg/L. Furthermore, a portable UV light box combined with a smartphone was used to convert the change in fluorescence of the RCDs-based optosensing nanomaterials into specific values upon adding pyrethroids, and the LOD by using smartphone was 6.66 µg/L. The developed platform has numerous advantages, including low cost, simple operation, high sensitivity, and good specificity, among others, and it achieves on-site visualization and rapid detection.

Highland Barley and Its By-Products Enriched with Phenolic Compounds for Inhibition of Pyrraline Formation by Scavenging α-Dicarbonyl Compounds.

Pyrraline, a typical kind of advanced glycation end product, has been found to contribute to the development of pathologies associated with ageing and diabetes mellitus. In the study, phenolic compounds extracted from highland barley whole grain (HBWG) and vinasse (HBVN) were used to inhibit pyrraline formation in a simulated food. The optimal extraction condition for HBWG and HBVN was using 8 mL of 50% acetone solution at 50 °C for 60 min. The extraction and identification of phenolic compounds from HBWG and HBVN were performed by UPLC-PAD-MS/MS. The inhibitory effects of pyrraline in the simulated food were 52.03% and 49.22% by HBVN and HBWG, respectively. The diphenyl picrylhydrazyl radical- and ferric-reducing ability of plasma assays was used to evaluate the antioxidant activity of the extracts. The main inhibition pathways and molecular mechanism of phenolic compounds on pyrraline regulation were explored by scavenging α-dicarbonyl compounds. The study demonstrated that highland barley and its by-products can potentially be used as a functional food to regulate pyrraline formation during food processing.