A stable colorimetric biosensor for highly selective detection of malathion residue in food based on aptamer-regulated laccase-mimic activity.

Malathion causes a serious threat to human health due to its widespread use in the environment. Herein, a novel and stable smartphone-integrated colorimetric biosensor for malathion detection is firstly established based on aptamer-enhanced laccase-mimicking activity. The results indicate that the M17-F aptamer can increase the affinity of Ag2O nanoparticles to the substrate 2,4-dichlorophenol and enhance their laccase-mimicking activity. Thus, abundant semiquinone radicals are produced in the catalytic system, which are combined with chromogenic agent to generate dark red products. The corresponding RGB values for the colour change of the solution can be easily obtained using smartphones, which is used for the rapid detection of malathion. The established biosensor for malathion has a limit of detection as low as 5.85 nmol·L-1, and displays good selectivity for other competitive pesticides. Moreover, further studies have verified the applicability of the biosensor in actual samples, indicating that it may have the potential for application in malathion detection in food.

Recent Thymic Emigrants Require RBPJ-Dependent Notch Signaling to Transition into Functionally Mature Naive T Cells.

Recent thymic emigrant (RTE) cells are nascent T cells that continue their post-thymic maturation in the periphery and dominate T cell immune responses in early life and in adults having undergone lymphodepletion regimens. However, the events that govern their maturation and their functionality as they transition to mature naive T cells have not been clearly defined. Using RBPJind mice, we were able to identify different stages of RTE maturation and interrogate their immune function using a T cell transfer model of colitis. As CD45RBlo RTE cells mature, they transition through a CD45RBint immature naive T (INT) cell population that is more immunocompetent but shows a bias toward IL-17 production at the expense of IFN-γ. Additionally, the levels of IFN-γ and IL-17 produced in INT cells are highly dependent on whether Notch signals are received during INT cell maturation or during their effector function. IL-17 production by INT cells showed a total requirement for Notch signaling. Loss of Notch signaling at any stage of INT cells resulted in an impaired colitogenic effect of INT cells. RNA sequencing of INT cells that had matured in the absence of Notch signals showed a reduced inflammatory profile compared with Notch-responsive INT cells. Overall, we have elucidated a previously unknown INT cell stage, revealed its intrinsic bias toward IL-17 production, and demonstrated a role for Notch signaling in INT cell peripheral maturation and effector function in the context of a T cell transfer model of colitis.

DL4-µbeads induce T cell lineage differentiation from stem cells in a stromal cell-free system.

T cells are pivotal effectors of the immune system and can be harnessed as therapeutics for regenerative medicine and cancer immunotherapy. An unmet challenge in the field is the development of a clinically relevant system that is readily scalable to generate large numbers of T-lineage cells from hematopoietic stem/progenitor cells (HSPCs). Here, we report a stromal cell-free, microbead-based approach that supports the efficient in vitro development of both human progenitor T (proT) cells and T-lineage cells from CD34+cells sourced from cord blood, GCSF-mobilized peripheral blood, and pluripotent stem cells (PSCs). DL4-µbeads, along with lymphopoietic cytokines, induce an ordered sequence of differentiation from CD34+ cells to CD34+CD7+CD5+ proT cells to CD3+αß T cells. Single-cell RNA sequencing of human PSC-derived proT cells reveals a transcriptional profile similar to the earliest thymocytes found in the embryonic and fetal thymus. Furthermore, the adoptive transfer of CD34+CD7+ proT cells into immunodeficient mice demonstrates efficient thymic engraftment and functional maturation of peripheral T cells. DL4-µbeads provide a simple and robust platform to both study human T cell development and facilitate the development of engineered T cell therapies from renewable sources.

High-Oxygen Submersion Fetal Thymus Organ Cultures Enable FOXN1-Dependent and -Independent Support of T Lymphopoiesis.

T cell development is effectively supported in fetal thymus organ cultures (FTOCs), which places thymus lobes atop an air-liquid interface (ALI) culture system. The direct exposure to air is critical for its success, as fetal thymus lobes placed in low oxygen submersion (LOS)-FTOCs fail to support thymocyte development. However, submersion cultures performed in the presence of high concentration of ambient oxygen (60~80%) allow for normal thymocyte development, but the underlying mechanism for this rescue has remained elusive. Here, we show that FOXN1 expression in thymic epithelial cells (TECs) from LOS-FTOCs was greatly reduced compared to conventional ALI-FTOCs. Consequently, the expression of important FOXN1 target genes, including Dll4 and Ccl25, in TECs was extinguished. The loss of DLL4 and CCL25 interrupted thymocyte differentiation and led to CD4+CD8+ cells exiting the lobes, respectively. High oxygen submersion (HOS)-FTOCs restored the expression of FOXN1 and its target genes, as well as maintained high levels of MHCII expression in TECs. In addition, HOS-FTOCs promoted the self-renewal of CD4-CD8-CD44-CD25+ cells, allowing for the continuous generation of later stage thymocytes. Forced FOXN1 expression in TECs rescued thymocyte developmental progression, but not cellularity, in LOS-FTOCs. Given that oxidative stress has been reported to accelerate the onset of age-associated thymic involution, we postulate that regulation of FOXN1 by oxygen and antioxidants may underpin this biological process.

Application of DNA barcoding and metabarcoding for species identification in salmon products.

Mislabelling is a significant manifestation of food fraud. Traditional Sanger sequencing technology is the gold standard for seafood species identification. However, this method is not suitable for analysing processed samples that may contain more than one species. This study tested the feasibility of next-generation sequencing in identifying mixed salmon products. Salmon samples containing up to eight species were amplified using 16S rRNA mini-barcode primers, and sequenced on an Illumina HiSeq2500 platform. All species were accurately identified, and mixtures as low as 1% (w/w) could be detected. Furthermore, this study conducted a market survey of 32 products labelled as salmon. For pure and mixed fish products, Sanger and next-generation sequencing techniques were respectively used for species identification, and for NGS results, we also used real-time PCR method to cross-validate the mixed products to further verify the accuracy of the DNA metabarcoding technology established in this study. DNA barcoding and metabarcoding of commercial salmon food products revealed the presence of mislabelling in 16 of 32 (50%) samples. The developed DNA barcoding and metabarcoding methods are useful for the identification of salmon species in food and can be used for quality control of various types of salmon products.

A 2020 View of Thymus Stromal Cells in T Cell Development.

The thymus is an intricate primary lymphoid organ, wherein bone marrow-derived lymphoid progenitor cells are induced to develop into functionally competent T cells that express a diverse TCR repertoire, which is selected to allow for the recognition of foreign Ags while avoiding self-reactivity or autoimmunity. Thymus stromal cells, which can include all non-T lineage cells, such as thymic epithelial cells, endothelial cells, mesenchymal/fibroblast cells, dendritic cells, and B cells, provide signals that are essential for thymocyte development as well as for the homeostasis of the thymic stroma itself. In this brief review, we focus on the key roles played by thymic stromal cells during early stages of T cell development, such as promoting the homing of thymic-seeding progenitors, inducing T lineage differentiation, and supporting thymocyte survival and proliferation. We also discuss recent advances on the transcriptional regulation that govern thymic epithelial cell function as well as the cellular and molecular changes that are associated with thymic involution and regeneration.

Rapid Classification and Quantification of Camellia (Camellia oleifera Abel.) Oil Blended with Rapeseed Oil Using FTIR-ATR Spectroscopy.

Currently, the authentication of camellia oil (CAO) has become very important due to the possible adulteration of CAO with cheaper vegetable oils such as rapeseed oil (RSO). Therefore, we report a Fourier transform infrared (FTIR) spectroscopic method for detecting the authenticity of CAO and quantifying the blended levels of RSO. In this study, two characteristic spectral bands (1119 cm-1 and 1096 cm-1) were selected and used for monitoring the purity of CAO. In combination with principal component analysis (PCA), linear discriminant analysis (LDA), and partial least squares regression (PLSR) analysis, qualitative and quantitative methods for the detection of camellia oil adulteration were proposed. The results showed that the calculated I1119/I1096 intensity ratio facilitated an initial check for pure CAO and six other edible oils. PCA was used on the optimized spectral region of 1800-650 cm-1. We observed the classification of CAO and RSO as well as discrimination of CAO with RSO adulterants. LDA was utilized to classify CAO from RSO. We could differentiate and classify RSO adulterants up to 1% v/v. In the quantitative PLSR models, the plots of actual values versus predicted values exhibited high linearity. Root mean square error of calibration (RMSEC) and root mean square error of cross validation (RMSECV) values of the PLSR models were 1.4518%-3.3164% v/v and 1.7196%-3.8136% v/v, respectively. This method was successfully applied in the classification and quantification of CAO adulteration with RSO.

DNA barcoding and mini-barcoding in authenticating processed animal-derived food: A case study involving the Chinese market.

This study used DNA barcoding and DNA mini-barcoding to test a variety of animal-derived food products sold in the Chinese market for potential mislabeling. Samples (52) including meat, poultry, and fish purchased from retail and online sources were examined. Regions of cytochrome C oxidase I (COI) gene (~650 bp) and 16S rRNA (~220 bp) were used as full- and mini-barcode markers, respectively. Approximately 94% (49 of 52) of the samples generated barcode sequences. The failure rate for full COI full-barcodes was 44%, but we obtained the 16S rRNA mini-barcode from 87% of the COI-failed cases. Overall, the survey revealed that 23% (12 of 52) of animal-derived products were mislabeled and, in most cases, contain undeclared species. Thus, regulatory measures and continuous monitoring for mislabeling of animal-derived products should be conducted.

Authentication of Edible Bird's Nest (EBN) and its adulterants by integration of shotgun proteomics and scheduled multiple reaction monitoring (MRM) based on tandem mass spectrometry.

Edible bird's nest (EBN) has been traditionally regarded as a kind of medicinal and healthy food in Asia. However, economically motivated adulteration (EMA) has been an issue in the EBN supply chain. To develop an accurate high-throughput approach for detecting EBN and its adulterants (exemplified by porcine skin, swim bladder, white fungus, and egg white), shotgun proteomics was applied for discovery of specific peptides that were subsequently converted into scheduled multiple reaction monitoring (MRM) transitions. Totally, 28 specific peptides were verified as unique to EBN and its adulterants by tandem mass spectrometry. Subsequently, 9 quantitative MRM-transitions of peptides from adulterants and 2 internal standard references from EBN were screened for the quantitative analysis of the adulterants, which allowed detection of adulterants in EBN matrix in the range of 1-80%. These results suggested that integration of shotgun proteomics and scheduled MRM had potential for the authentication of EBN and its adulterants.

[Effect of High Hydrostatic Pressure Combined with Temperature on the Antigenicity and Conformation of Tropomyosin Purified from Shrimp].

Foodborne shrimp allergy events have occurred in recent years. To illustrate the mechanism of high hydrostatic pressure technology to change the allergenicity of shrimp, the major allergen tropomyosin was separated and purified from Litopenaeus vannamei, and indentified with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). The effect of temperature factor under high hydrostatic pressure was measured with indirect ELISA method, CD and fluorescence spectrum. The results showed that the antigenicity of TM protein had an increase after being heated at 35 or 45 ℃ when treated at 300 MPa for 15 minutes, while the antigenicity decreased at 55, 65, and 75 ℃. With the increase of heat temperature, the secondary structure of TM also changed. The mutual transformation happened between the alpha-helix and beta-sheet, beta-turn, and the random coil. The tertiary structure of TM was observed dynamic changes from the extended state to the folded state, and then re-extended state to re-folded state. These results suggested that high hydrostatic pressure combined with temperature could influence the antigenicity of TM by the change of conformation which would be useful as theoretical guidance on developing new methods or technologies for producing hypoallergenic shrimp products.