Solvent Regulation Induced Cathode Aggregation-Induced Electrochemiluminescence of Tetraphenylethylene Nanoaggregates for Ultrasensitive Zearalenone Analysis.

Zearalenone (ZEN) is an extremely hazardous chemical widely existing in cereals, and its high-sensitivity detection possesses significant significance to human health. Here, the cathodic aggregation-induced electrochemiluminescence (AIECL) performance of tetraphenylethylene nanoaggregates (TPE NAs) was modulated by solvent regulation, based on which an electrochemiluminescence (ECL) aptasensor was constructed for sensitive detection of ZEN. The aggregation state and AIECL of TPE NAs were directly and simply controlled by adjusting the type of organic solvent and the fraction of water, which solved the current shortcomings of low strength and weak stability of the cathode ECL signal for TPE. Impressively, in a tetrahydrofuran-water mixed solution (volume ratio, 6:4), the relative ECL efficiency of TPE NAs reached 16.03%, which was 9.2 times that in pure water conditions, and the maximum ECL spectral wavelength was obviously red-shifted to 617 nm. In addition, "H"-shape DNA structure-mediated dual-catalyzed hairpin self-assembly (H-D-CHA) with higher efficiency by the synergistic effect between the two CHA reactions was utilized to construct a sensitive ECL aptasensor for ZEN analysis with a low detection limit of 0.362 fg/mL. In conclusion, solvent regulation was a simple and efficient method for improving the performance of AIECL materials, and the proposed ECL aptasensor had great potential for ZEN monitoring in food safety.

Construction of an antibacterial low-defect hybrid layer by facile PEI electrostatic assembly promotes dentin bonding.

Dentin bonding is the most common form of human tissue repair among tissue-biomaterial adhesions, concerning billions of people's oral health worldwide. However, insufficient adhesive infiltration in the demineralized dentin matrix (DDM) always produces numerous defects in the bonding interface termed the hybrid layer, which causes high levels of bacteria-related secondary dental diseases, and less than 50% of the bonding lasts more than 5 years. Therefore, it is urgent and vital to construct an antibacterial low-defect hybrid layer to solve the durability-related problems. A DDM with a hydrogel-like surface formed by the hydration of highly-anionic non-collagenous proteins (NCPs) is firstly used as a template to electrostatically assemble polyethyleneimine (PEI). The formation of a stable antibacterial polyelectrolyte complex of PEI/NCPs rapidly eliminates NCP hydration capacity and significantly improves the infiltration of various adhesives. Simultaneously, both the PEI during the assembly and the PEI-assembled DDM can directly destroy a biofilm of S. Mutans on the DDM. Consequently, a long-term antibacterial and low-defect hybrid layer is successfully created, which greatly improves the bonding effectiveness. This helps to improve the clinical treatment of bacteria-based dental diseases and the tooth-restoration repair effect and prevent secondary dental diseases, having significance in clinical dentistry and providing insights for other tissue-biomaterial adhesions.

AICAR transformylase/IMP cyclohydrolase (ATIC) is essential for de novo purine biosynthesis and infection by Cryptococcus neoformans.

The fungal pathogen Cryptococcus neoformans is a leading cause of meningoencephalitis in the immunocompromised. As current antifungal treatments are toxic to the host, costly, limited in their efficacy, and associated with drug resistance, there is an urgent need to identify vulnerabilities in fungal physiology to accelerate antifungal discovery efforts. Rational drug design was pioneered in de novo purine biosynthesis as the end products of the pathway, ATP and GTP, are essential for replication, transcription, and energy metabolism, and the same rationale applies when considering the pathway as an antifungal target. Here, we describe the identification and characterization of C. neoformans 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) transformylase/5'-inosine monophosphate cyclohydrolase (ATIC), a bifunctional enzyme that catalyzes the final two enzymatic steps in the formation of the first purine base inosine monophosphate. We demonstrate that mutants lacking the ATIC-encoding ADE16 gene are adenine and histidine auxotrophs that are unable to establish an infection in a murine model of virulence. In addition, our assays employing recombinantly expressed and purified C. neoformans ATIC enzyme revealed Km values for its substrates AICAR and 5-formyl-AICAR are 8-fold and 20-fold higher, respectively, than in the human ortholog. Subsequently, we performed crystallographic studies that enabled the determination of the first fungal ATIC protein structure, revealing a key serine-to-tyrosine substitution in the active site, which has the potential to assist the design of fungus-specific inhibitors. Overall, our results validate ATIC as a promising antifungal drug target.

[The role of semaphorin 4D in the mechanism of bisphosphonate-related osteonecrosis of the jaw in rats].

PURPOSE: To study the expression level of semaphorin 4D (Sema4D) in bisphosphonate-related osteonecrosis of the jaw (BRONJ) and to explore its possible role in the occurrence of BRONJ. METHODS: BRONJ-like rat model was established by intraperitoneal injection of zoledronic acid assisted with tooth extraction. The maxillary specimens were extracted for imaging and histological examination, and bone marrow mononuclear cells(BMMs) and bone marrow mesenchymal stem cells(BMSCs) of each group were obtained in vitro for co-culture. Trap staining and counting were performed on monocytes after osteoclast induction. RAW264.7 cells were induced by osteoclast orientation under bisphosphonates(BPs) environment, and Sema4D expression was detected. Similarly, MC3T3-E1 cells and BMSCs were induced to osteogenic orientation in vitro, and the expression level of osteogenic and osteoclastic related genes ALP, Runx2, and RANKL was detected under the intervention of BPs, Sema4D and Sema4D antibody. Statistical analysis of the data was performed using GraphPad Prism 8.0 software. RESULTS: BRONJ-like rat model was successfully constructed. Two weeks after tooth extraction, the healing of the tooth extraction wound in the experimental group was significantly limited, and the tooth extraction wound was exposed. H-E staining results showed that regeneration of new bone in the extraction socket of the experimental group was significantly restricted, dead bone was formed, and the healing of the soft tissue was limited. The results of trap staining showed that the number of osteoclasts in the experimental group was significantly less than that in the control group. Micro-CT results showed that bone mineral density and bone volume fraction in the extraction socket of the experimental group were significantly lower than those of the control group. Immunohistochemical results showed that compared with the control group, the expression level of Sema4D in the experimental group was significantly increased. In vitro studies showed that compared with the control group, the osteoclast induction of BMMs in the experimental group was significantly lower than that in the control group. BMSCs in the experimental group significantly reduced the induction of osteoclasts. Osteoclastic induction experiments revealed that bisphosphonates could effectively inhibit the formation of osteoclasts, and the expression of Sema4D was significantly reduced. Osteogenic induction experiment found that Sema4D significantly reduced the expression of Runx2 and RANKL genes in osteoblasts, while the expression of ALP gene decreased and the expression of RANKL up-regulated after adding Sema4D antibody. CONCLUSIONS: BPs can interfere with normal bone healing time by up-regulating the expression of Sema4D in tissues, leading to coupling disorder between osteoclasts and osteoblasts with inhibition of the maturation of osteoclasts, thereby inhibiting the growth of osteoblasts. Differentiation and expression of related osteogenic factors mediate the development of BRONJ.

Structural Evolution of TIR-Domain Signalosomes.

TIR (Toll/interleukin-1 receptor/resistance protein) domains are cytoplasmic domains widely found in animals and plants, where they are essential components of the innate immune system. A key feature of TIR-domain function in signaling is weak and transient self-association and association with other TIR domains. An additional new role of TIR domains as catalytic enzymes has been established with the recent discovery of NAD+-nucleosidase activity by several TIR domains, mostly involved in cell-death pathways. Although self-association of TIR domains is necessary in both cases, the functional specificity of TIR domains is related in part to the nature of the TIR : TIR interactions in the respective signalosomes. Here, we review the well-studied TIR domain-containing proteins involved in eukaryotic immunity, focusing on the structures, interactions and their corresponding functional roles. Structurally, the signalosomes fall into two separate groups, the scaffold and enzyme TIR-domain assemblies, both of which feature open-ended complexes with two strands of TIR domains, but differ in the orientation of the two strands. We compare and contrast how TIR domains assemble and signal through distinct scaffolding and enzymatic roles, ultimately leading to distinct cellular innate-immunity and cell-death outcomes.