How different are the surfaces of semiconductor Ag2Se quantum dots with various sizes?

The surface of nanocrystals plays a dominant role in many of their physical and chemical properties. However, controllability and tunability of nanocrystal surfaces remain unsolved. Herein, we report that the surface chemistry of nanocrystals, such as near-infrared Ag2Se quantum dots (QDs), is size-dependent and composition-tunable. The Ag2Se QDs tend to form a stable metal complex on the surface to minimize the surface energy, and therefore the surface chemistry can be varied with particle size. Meanwhile, changes in surface inorganic composition lead to reorganization of the surface ligands, and the surface chemistry also varies with composition. Therefore, the surface chemistry of Ag2Se QDs, responsible for the photoluminescence (PL) quantum yield and photostability, can be tuned by changing their size or composition. Accordingly, we demonstrate that the PL intensity of the Ag2Se QDs can be tuned reversely by adjusting the degree of surface Ag+ enrichment via light irradiation or the addition of AgNO3. This work provides insight into the control of QD surface for desired PL properties.

Preclinical efficacy and clinical safety of clinical-grade nebulized allogenic adipose mesenchymal stromal cells-derived extracellular vesicles.

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) turn out to be a promising source of cell-free therapy. Here, we investigated the biodistribution and effect of nebulized human adipose-derived MSC-EVs (haMSC-EVs) in the preclinical lung injury model and explored the safety of nebulized haMSC-EVs in healthy volunteers. DiR-labelled haMSC-EVs were used to explore the distribution of nebulized haMSC-EVs in the murine model. Pseudomonas aeruginosa-induced murine lung injury model was established, and survival rate, as well as WBC counts, histology, IL-6, TNF-α and IL-10 levels in bronchoalveolar lavage fluid (BALF) were measured to explore the optimal therapeutic dose of haMSC-EVs through the nebulized route. Twenty-four healthy volunteers were involved and received the haMSC-EVs once, ranging from 2 × 108 particles to 16 × 108 particles (MEXVT study, NCT04313647). Nebulizing haMSC-EVs improved survival rate to 80% at 96 h in P. aeruginosa-induced murine lung injury model by decreasing lung inflammation and histological severity. All volunteers tolerated the haMSC-EVs nebulization well, and no serious adverse events were observed from starting nebulization to the 7th day after nebulization. These findings suggest that nebulized haMSC-EVs could be a promising therapeutic strategy, offering preliminary evidence to promote the future clinical applications of nebulized haMSC-EVs in lung injury diseases.

Assessing risk factors for SARS-CoV-2 infection in patients presenting with symptoms in Shanghai, China: a multicentre, observational cohort study.

Background: The outbreak of COVID-19 has led to international concern. We aimed to establish an effective screening strategy in Shanghai, China, to aid early identification of patients with COVID-19. Methods: We did a multicentre, observational cohort study in fever clinics of 25 hospitals in 16 districts of Shanghai. All patients visiting the clinics within the study period were included. A strategy for COVID-19 screening was presented and then suspected cases were monitored and analysed until they were confirmed as cases or excluded. Logistic regression was used to determine the risk factors of COVID-19. Findings: We enrolled patients visiting fever clinics from Jan 17 to Feb 16, 2020. Among 53 617 patients visiting fever clinics, 1004 (1·9%) were considered as suspected cases, with 188 (0·4% of all patients, 18·7% of suspected cases) eventually diagnosed as confirmed cases. 154 patients with missing data were excluded from the analysis. Exposure history (odds ratio [OR] 4·16, 95% CI 2·74-6·33; p<0·0001), fatigue (OR 1·56, 1·01-2·41; p=0·043), white blood cell count less than 4 × 109 per L (OR 2·44, 1·28-4·64; p=0·0066), lymphocyte count less than 0·8 × 109 per L (OR 1·82, 1·00-3·31; p=0·049), ground glass opacity (OR 1·95, 1·32-2·89; p=0·0009), and having both lungs affected (OR 1·54, 1·04-2·28; p=0·032) were independent risk factors for confirmed COVID-19. Interpretation: The screening strategy was effective for confirming or excluding COVID-19 during the spread of this contagious disease. Relevant independent risk factors identified in this study might be helpful for early recognition of the disease. Funding: National Natural Science Foundation of China.

Identification of driver genes and somatic mutations in cell-free DNA of patients with pulmonary lymphangioleiomyomatosis.

Next-generation sequencing of cell-free circulating DNA (cfDNA) has emerged as promising technique for identifying minimally invasive genomic profiling of tumor cells recently. However, it remains relatively unknown in LAM disease. In our study, paired cfDNA and genomic DNA (gDNA) in blood samples were obtained from 23 LAM patients and seven healthy controls to explore mutations profiles of targeted 70 cancer-related genes. As results, log2-based allele frequencies of mutations in cfDNA were significantly different from those of gDNA. By comparing the mutual mutations identified both in cfDNA and gDNA, a significant correlation was also observed. After removing mutations in gDNA, distinct somatic mutation profiles of cfDNA were observed in LAM patients. Forty of 70 targeted genes had recurrent mutations, of which ATM, BRCA2 and APC showed the highest frequency. Based on the mutation, correlation network constructed of 40 mutated genes, 11 hub genes bearing intensive interactions were highlighted, including BRCA1, BRCA2, RAD50, RB1, NF1, APC, MLH3, ATM, PDGFRA, PALB2 and BLM. Expression of the hub genes showed significant clusters between LAM patients and controls and that RAD50 and BRCA2 had the strongest associations with subject phenotypes. Myogenesis and estrogen response were confirmed to be positively regulated in LAM patients. Collectively, our study provided a landscape of genomic alterations in LAM and discovered several potential driver genes, that is, BRCA2 and RAD50, which shed a substantial light on the clinical application of key molecular markers and potential therapy targets for precision diagnosis and treatment in the future.

Jasmonate promotes artemisinin biosynthesis by activating the TCP14-ORA complex in Artemisia annua.

Artemisia annua produces the valuable medicinal component, artemisinin, which is a sesquiterpene lactone widely used in malaria treatment. AaORA, a homolog of CrORCA3, which is involved in activating terpenoid indole alkaloid biosynthesis in Catharanthus roseus, is a jasmonate (JA)-responsive and trichome-specific APETALA2/ETHYLENE-RESPONSE FACTOR that plays a pivotal role in artemisinin biosynthesis. However, the JA signaling mechanism underlying AaORA-mediated artemisinin biosynthesis remains enigmatic. Here, we report that AaORA forms a transcriptional activator complex with AaTCP14 (TEOSINTE BRANCHED 1/CYCLOIDEA/PROLIFERATING CELL FACTOR 14), which is also predominantly expressed in trichomes. AaORA and AaTCP14 synergistically bind to and activate the promoters of two genes, double bond reductase 2 (DBR2) and aldehyde dehydrogenase 1 (ALDH1), both of which encode enzymes vital for artemisinin biosynthesis. AaJAZ8, a repressor of the JA signaling pathway, interacts with both AaTCP14 and AaORA and represses the ability of the AaTCP14-AaORA complex to activate the DBR2 promoter. JA treatment induces AaJAZ8 degradation, allowing the AaTCP14-AaORA complex to subsequently activate the expression of DBR2, which is essential for artemisinin biosynthesis. These data suggest that JA activation of the AaTCP14-AaORA complex regulates artemisinin biosynthesis. Together, our findings reveal a novel artemisinin biosynthetic pathway regulatory network and provide new insight into how specialized metabolism is modulated by the JA signaling pathway in plants.

Molecular cloning, characterization, and promoter analysis of the isochorismate synthase (AaICS1) gene from Artemisia annua.

Isochorismate synthase (ICS) is a crucial enzyme in the salicylic acid (SA) synthesis pathway. The full-length complementary DNA (cDNA) sequence of the ICS gene was isolated from Artemisia annua L. The gene, named AaICS1, contained a 1710-bp open reading frame, which encoded a protein with 570 amino acids. Bioinformatics and comparative study revealed that the polypeptide protein of AaICS1 had high homology with ICSs from other plant species. Southern blot analysis suggested that AaICS1 might be a single-copy gene. Analysis of the 1470-bp promoter of AaICS1 identified distinct cis-acting regulatory elements, including TC-rich repeats, MYB binding site (MBS), and TCA-elements. An analysis of AaICS1 transcript levels in multifarious tissues of A. annua using quantitative real-time polymerase chain reaction (qRT-PCR) showed that old leaves had the highest transcription levels. AaICS1 was up-regulated under wounding, drought, salinity, and SA treatments. This was corroborated by the presence of the predicted cis-acting elements in the promoter region of AaICS1. Overexpressing transgenic plants and RNA interference transgenic lines of AaICS1 were generated and their expression was compared. High-performance liquid chromatography (HPLC) results from leaf tissue of transgenic A. annua showed an increase in artemisinin content in the overexpressing plants. These results confirm that AaICS1 is involved in the isochorismate pathway.

Fluorescence-Converging Carbon Nanodots-Hybridized Silica Nanosphere.

Ultrabright carbon nanodots-hybridized silica nanospheres (CSNs) are synthesized through the Stöber process of silane functionalized C-dots. The fluorescence of carbon nanodots is converged intensely. A CSN is about 3800 times brighter than a single-carbon nanodot. Along with their high brightness and low cytotoxicity, CSNs also indicate their potential application in cellular labeling.

Ultrasmall Magnetically Engineered Ag2Se Quantum Dots for Instant Efficient Labeling and Whole-Body High-Resolution Multimodal Real-Time Tracking of Cell-Derived Microvesicles.

Cell-derived microvesicles (MVs) are natural carriers that can transport biological molecules between cells, which are expected to be promising delivery vehicles for therapeutic purposes. Strategies to label MVs are very important for investigation and application of MVs. Herein, ultrasmall Mn-magnetofunctionalized Ag2Se quantum dots (Ag2Se@Mn QDs) integrated with excellent near-infrared (NIR) fluorescence and magnetic resonance (MR) imaging capabilities have been developed for instant efficient labeling of MVs for their in vivo high-resolution dual-mode tracking. The Ag2Se@Mn QDs were fabricated by controlling the reaction of Mn(2+) with the Ag2Se nanocrystals having been pretreated in 80 °C NaOH solution, with an ultrasmall size of ca. 1.8 nm, water dispersibility, high NIR fluorescence quantum yield of 13.2%, and high longitudinal relaxivity of 12.87 mM(-1) s(-1) (almost four times that of the commercial contrast agent Gd-DTPA). The ultrasmall size of the Ag2Se@Mn QDs enables them to be directly and efficiently loaded into MVs by electroporation, instantly and reliably conferring both NIR fluorescence and MR traceability on MVs. Our method for labeling MVs of different origins is universal and free of unfavorable influence on intrinsic behaviors of MVs. The complementary imaging capabilities of the Ag2Se@Mn QDs have made the long-term noninvasive whole-body high-resolution dual-mode tracking of MVs in vivo realized, by which the dynamic biodistribution of MVs has been revealed in a real-time and in situ quantitative manner. This work not only opens a new window for labeling with QDs, but also facilitates greatly the investigation and application of MVs.

Cytotoxicity of nucleus-targeting fluorescent gold nanoclusters.

Gold nanoclusters (AuNCs) with ultra small sizes and unique fluorescence properties have shown promising potential for imaging the nuclei of living cells. However, little is known regarding the potential cytotoxicity of AuNCs after they enter the cell nucleus. The aim of this study is to investigate whether and how nucleus-targeting AuNCs affect the normal functioning of cells. Highly stable, water-soluble and bright fluorescent Au25NCs (the core of each nanocluster is composed of 25 gold atoms) were synthesized. Specific targeting of Au25NCs to the cell nucleus was achieved by conjugating the TAT peptide to the Au25NCs. Cell viability, cell morphology, cell apoptosis/necrosis, reactive oxygen species (ROS) level and mitochondrial membrane potential examinations were performed on different cell lines exposed to the nucleus-targeting Au25NCs. We found that the nucleus-targeting Au25NCs caused cell apoptosis in a dose-dependent manner. A possible mechanism for the cytotoxicity of the nucleus-targeting Au25NCs was proposed as follows: the nucleus-targeting Au25NCs induce the production of ROS, resulting in the oxidative degradation of mitochondrial components, in turn leading to apoptosis via a mitochondrial damage pathway. This work facilitates a better understanding of the toxicity of AuNCs, especially nucleus-targeting AuNCs.

Revealing carbon nanodots as coreactants of the anodic electrochemiluminescence of Ru(bpy)3²âº.

Recently, research on carbon nanodots (C-dots), a new type of luminescent nanoparticles with superior optical properties, biocompatibility, and low cost, has been focused on exploring novel properties and structure-related mechanisms to extend their scope. Herein, electrochemiluminescence, a surface-sensitive tool, is used to probe the unrevealed property of carbon nanodots which is characterized by surface oxygen-containing groups. Together with chemiluminescence, carbon nanodots as the coreactants for the anodic electrochemiluminescence of Ru(bpy)3(2+) are demonstrated for the first time. During the anodic scan, the benzylic alcohol units on the C-dots surface are oxidized "homogeneously" by electrogenerated-Ru(bpy)3(3+) to form reductive radical intermediate, which further reduce Ru(bpy)3(3+) into Ru(bpy)3(2+)* that produces a strong ECL emission. This work has provided an insight into the ECL mechanism of the C-dots-involved system, which will be beneficial for in-depth understanding of some peculiar phenomena of C-dots, such as photocatalytic activity and redox properties. Moreover, because of the features of C-dots, the ECL system of Ru(bpy)3(2+)/C-dots is more promising in the bioanalysis.

Enzyme-induced metallization as a signal amplification strategy for highly sensitive colorimetric detection of avian influenza virus particles.

A novel colorimetric assay method based on enzyme-induced metallization has been proposed for detection of alkaline phosphatase (ALP), and it was further applied to highly sensitive detection of avian influenza virus particles coupled with immunomagnetic separation. The enzyme-induced metallization-based color change strategy combined the amplification of the enzymatic reaction with the unique optical properties of metal nanoparticles (NPs), which could lead to a great enhancement in optical signal. The detection limit for ALP detection was 0.6 amol/50 µL which was 4-6 orders of magnitude more sensitive than other metal NP-based colorimetric methods. Moreover, this technique was successfully employed to a colorimetric viral immunosensor, which could be applied to complex samples without complicated sample pretreatment and sophisticated instruments, and a detection limit as low as 17.5 pg mL(-1) was achieved. This work not only provides a simple and sensitive sensing approach for ALP and virus detection but also offers an effective signal enhancement strategy for development of a highly sensitive nonaggregation metal NP-based colorimetric assay method.

Near-infrared electrogenerated chemiluminescence of ultrasmall Ag2Se quantum dots for the detection of dopamine.

The near-infrared (NIR) electrogenerated chemiluminescence (ECL) of water-dispersed Ag(2)Se quantum dots (QDs) with ultrasmall size was presented for the first time. The Ag(2)Se QDs have shown a strong and efficient cathodic ECL signal with K(2)S(2)O(8) as coreactant on the glassy carbon electrode (GCE) in aqueous solution. The ECL spectrum exhibited a peak at 695 nm, consistent with the peak in photoluminescence (PL) spectrum of the Ag(2)Se QDs solution, indicating that the Ag(2)Se QDs had no deep surface traps. Dopamine was chosen as a model analyte to study the potential of Ag(2)Se QDs in the ECL analytical application. The ECL signal of Ag(2)Se QDs can also be used for the detection of the dopamine concentration in the practical drug (dopamine hydrochloride injection) containing several adjuvants such as edetate disodium, sodium bisulfite, sodium chloride and so on. The Ag(2)Se QDs could be a promising candidate emitter of ECL biosensors in the future due to their fantastic features, such as ultrasmall size, low toxicity, good water solubility, and near infrared (NIR) fluorescent emission.

Induction and flow cytometry identification of tetraploids from seed-derived explants through colchicine treatments in Catharanthus roseus (L.) G. Don.

The tetraploid plants of Catharanthus roseus (L.) G. Don was obtained by colchicine induction from seeds explants, and the ploidy of the plants was identified by flow cytometry. The optimal treatment is 0.2% colchicine solution treated for 24 hours, and the induction rate reaches up to 30%. Comparing with morphological characteristics and growth habits between tetraploids and the control, we found that tetraploids of C. roseus had larger stoma and more branches and leaves. HPLC analysis showed tetraploidization could increase the contents of terpenoid indole alkaloids in C. roseus. Thus, tetraploidization could be used to produce higher alkaloids lines for commercial use. QRT-PCR results showed that the expression of enzymes involved in terpenoid indole alkaloids biosynthesis pathway had increased in the tetraploid plants. To our knowledge, this was the first paper to explore the secondary metabolism in autotetraploid C. roseus induced by colchicine.

Over-expression GbERF2 transcription factor in tobacco enhances brown spots disease resistance by activating expression of downstream genes.

ERF transcription factors can bind GCC boxes or non-GCC cis elements to regulate biotic and abiotic stress responses. Here, we report that an ERF transcription factor gene (GbERF2) was cloned by suppression subtraction hybridization from sea-island cotton after Verticillium dahliae attack. The GbERF2 cDNA has a total length of 1143 bp with an open reading frame of 597 bp. The genomic sequence of GbERF2 contains an intron of 515 bp. The gene encodes a predicated polypeptide of 198 amino acids with a molecular weight of 22.5 kDa and a calculated pI of 9.82. The GbERF2 protein has a highly conserved ERF domain while the nucleotide and amino acid sequences have low homology with other ERF plant proteins. An RNA blot revealed that GbERF2 is constitutively expressed in different tissues, but is higher in the leaves. High levels of GbERF2 transcripts rapidly accumulated when the plants were exposed to exogenous ethylene treatment and V. dahliae infection, while there was only a slight accumulation in response to salt, cold, drought and water stresses. In contrast, GbERF2 transcripts declined in response to exogenous abscisic acid (ABA) treatment. GbERF2 transgenic tobacco plants constitutively accumulated higher levels of pathogenesis-related gene transcripts, such as PR-1b, PR2 and PR4. The resistance of transgenic tobacco to fungal infection by Alternaria longipes was enhanced. However, the resistance to bacterial infection by Pseudomonas syringae pv. tabaci was not improved. These results show that GbERF2 plays an important role in response to ethylene stress and fungal attack in cotton.

Functional analysis of the SGNP I in the pupal diapause of the oriental tobacco budworm, Helicoverpa assulta (Lepidoptera: Noctuidae).

Helicoverpa assulta suboesophageal ganglion neuropeptide I (Has-SGNP I) is a 24-amino acids peptide amide, which shows 62.5% similarity with the diapause hormone of Bombyx mori (Bom-DH). It has been demonstrated that embryonic diapause is induced by DH in B. mori. Injection of synthetic amidated Has-SGNP I terminated pupal diapause in a dose-dependent manner. Therefore, Has-SGNP I might be referred to a "diapause termination hormone" in H. assulta (Has-DTH). The maximal dose of Has-DTH for diapause termination was 1.0 microg and the half-maximal dose 0.4 microg. The time required for diapause termination of Has-DTH was 2-3 days longer than that of 20-hydroxyecdysone. During the pupal stage, DTH mRNA content in the SGs of nondiapausing pupae was always higher than in diapausing pupae using the combined method of quantitative RT-PCR and Southern blot. DTH gene also expressed at a low level while diapausing pupae were chilled at 4 degrees C, but increased rapidly and largely after being transferred to 25 degrees C. Using a competitive ELISA, Has-DTH-like immunoreactivity in the haemolymph showed the same pattern as that of Has-DTH gene expression. Those results indicated that Has-DTH gene expression was related to diapause development and could be activated by low temperature. Has-DTH might be useful to elucidate the mechanism of diapause termination in pupal diapause species.