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1.
J Hazard Mater ; 470: 134267, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38608591

RESUMO

Carbonaceous black shale generally contains high concentration of Cd, with weathering leading to Cd release to environment. In this study, the mobility of Cd during weathering was quantified using geochemical assessment on black shale from western Hunan, China. Results suggested that Cd was heterogeneously distributed in shale profiles with concentrations ranging from 0.16 to 109.9 (mg/kg). Cd distribution was heterogeneous resulting from the parent shale inheritance and the mobility of Cd during weathering. Black shales weathered to a moderate degree with Cd mobility characterized by both enrichment in and release from weathered shales. Cd enrichment in weathered shales resulted from the re-enrichment of Cd in secondary minerals formed during the initial stage of carbonate (and phosphorite) dissolution, and the secondary stage of sulfide oxidation. The release of Cd was caused by decomposition of the secondary Cd-bearing minerals. Cadmium was extensively released during pedogenesis, and Cd release mass flux was estimated to range from 1.26 to 9.50 (g/m2) with a mean of 6.60 g/m2. Thus, black shale weathering may lead to the releasing of large amount of Cd resulting in Cd contamination to local environments.

2.
Small ; : e2400238, 2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38385800

RESUMO

The performance of Stimulated Emission Depletion (STED) microscopy depends critically on the fluorescent probe. Ultrasmall Au nanoclusters (Au NCs) exhibit large Stokes shift, and good stimulated emission response, which are potentially useful for STED imaging. However, Au NCs are polydispersed in size, sensitive to the surrounding environment, and difficult to control surface functional group stoichiometry, which results in reduced density and high heterogeneity in the labeling of biological structures. Here, this limitation is overcome by developing a method to encapsulate ultrasmall Au NCs with DNA cages, which yielded monodispersed, and monofunctionalized Au NCs that are long-term stable. Moreover, the DNA-caging also greatly improved the fluorescence quantum yield and photostability of Au NCs. In STED imaging, the DNA-caged Au NCs yielded ≈40 nm spatial resolution and are able to resolve microtubule line shapes with good labeling density and homogeneity. In contrast, without caging, the Au NCs-DNA conjugates only achieved ≈55 nm resolution and yielded spotted, poorly resolved microtubule structures, due to the presence of aggregates. Overall, a method is developed to achieve precise surface functionalization and greatly improve the monodispersity, stability, as well as optical properties of Au NCs, providing a promising class of fluorescent probes for STED imaging.

3.
Anal Chem ; 96(2): 866-875, 2024 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-38164718

RESUMO

Despite extensive efforts, point-of-care testing (POCT) of protein markers with high sensitivity and specificity and at a low cost remains challenging. In this work, we developed an aptamer-CRISPR/Cas12a-regulated liquid crystal sensor (ALICS), which achieved ultrasensitive protein detection using a smartphone-coupled portable device. Specifically, a DNA probe that contained an aptamer sequence for the protein target and an activation sequence for the Cas12a-crRNA complex was prefixed on a substrate and was released in the presence of target. The activation sequence of the DNA probe then bound to the Cas12a-crRNA complex to activate the collateral cleavage reaction, producing a bright-to-dark optical change in a DNA-functionalized liquid crystal interface. The optical image was captured by a smartphone for quantification of the target concentration. For the two model proteins, SARS-CoV-2 nucleocapsid protein (N protein) and carcino-embryonic antigen (CEA), ALICS achieved detection limits of 0.4 and 20 pg/mL, respectively, which are higher than the typical sensitivity of the SARS-CoV-2 test and the clinical CEA test. In the clinical sample tests, ALICS also exhibited superior performances compared to those of the commercial ELISA and lateral flow test kits. Overall, ALICS represents an ultrasensitive and cost-effective platform for POCT, showing a great potential for pathogen detection and disease monitoring under resource-limited conditions.


Assuntos
Técnicas Biossensoriais , Cristais Líquidos , Sistemas Automatizados de Assistência Junto ao Leito , Sistemas CRISPR-Cas , RNA Guia de Sistemas CRISPR-Cas , Oligonucleotídeos , Sondas de DNA
4.
Nano Lett ; 23(18): 8734-8742, 2023 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-37669506

RESUMO

In order to improve the fluorescence quantum yield (QY) of NIR-II-emitting nanoparticles, D-A-D fluorophores are typically linked to intramolecular rotatable units to reduce aggregation-induced quenching. However, incorporating such units often leads to a twisted molecular backbone, which affects the coupling within the D-A-D unit and, as a result, lowers the absorption. Here, we overcome this limitation by cross-linking the NIR-II fluorophores to form a 2D polymer network, which simultaneously achieves a high QY by well-controlled fluorophore separation and strong absorption by restricting intramolecular distortion. Using the strategy, we developed polymer dots with the highest NIR-II single-particle brightness among reported D-A-D-based nanoparticles and applied them for imaging of hindlimb vasculatures and tumors as well as fluorescence-guided tumor resection. The high brightness of the polymer dots offered exceptional image quality and excellent surgical results, showing a promising performance for these applications.


Assuntos
Nanopartículas , Neoplasias , Pontos Quânticos , Animais , Humanos , Polímeros , Imagem Óptica/métodos , Corantes Fluorescentes
5.
Environ Pollut ; 336: 122384, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37586680

RESUMO

Rare earth elements (REEs) are emerging micropollutants in aquatic environments. In this study, concentrations of REEs and major elements, and mineralogical compositions of sediments from lower reaches of the Xiangjiang River (China) were analyzed using ICP-MS technique. The results suggested that sediments were characterized by terrigenous compositions TiO2, SiO2, Al2O3, K2O, Na2O and P2O, and contained high concentrations of REEs with mean total REE concentrations (∑REE) of 318.7 mg/kg. REEs were moderately enriched in upper river sediments, and slightly or less enriched in downriver sediments. The normalized REE distribution pattern for sediments was characterized by flat shalelike and Eu depleted V-shape REE patterns, which indicated REEs in sediments were lithologically contributed from sedimentary rocks and granites distributed in the watershed respectively. REEs in sediments were hosted mainly in Fe-Mn oxides, and sulfide and organic matters that were characterized by middle REEs (MREE) enrichments relative to light REEs (LREE) and heavy REEs (HREE), and the distribution and differentiation of REEs in sediments were controlled by clays, Fe-Mn oxides, organic matters and finer grains; and also by accessory minerals (e.g., zircon) from granite. The distribution features of REEs in sediments and BCR extraction results suggested that the sediment REE enrichment resulted from additional REE input from anthropogenic sources, including those in discharges from sulfide-ore smelting industries at Zhuzhou city and from phosphate fertilizer plants at Xiangtan city along the river. Thus, sediments were contaminated with REEs in moderate degree in upper river area, and REE contamination was then formed by superimposing anthropogenic REEs on lithological residues. Finally, concentrations of Ce > 100 mg/kg, Gd > 8.12 mg/kg, ∑REE >274.9 mg/kg, ∑LREE >252.3 mg/kg and ∑HREE >28.8 mg/kg here were recommended as the REE contamination levels that represented as REE indices for identifying and rating REE contamination in this mining impacted river.


Assuntos
Metais Terras Raras , Poluentes Químicos da Água , Dióxido de Silício , Rios/química , Poluentes Químicos da Água/análise , Monitoramento Ambiental/métodos , Sedimentos Geológicos/química , Metais Terras Raras/análise , China , Sulfetos
6.
Psychol Res Behav Manag ; 16: 2353-2366, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37396405

RESUMO

Purpose: The prevalence of cyberbullying has increased along with the growth of social media, which has brought about many adverse effects on individual development. The current study aimed to explore the connection between covert narcissism and cyberbullying and to test the roles of hostile attribution bias and self-control in the relationship between covert narcissism and cyberbullying. Materials and Methods: A total of 672 Chinese college students filled up questionnaires measuring covert narcissism, cyberbullying, hostile attribution bias, and self-control. Results: The results indicated that covert narcissism positively and significantly predicted cyberbullying. Hostile attribution bias partially mediated the relationship between covert narcissism and cyberbullying. Additionally, self-control moderated the relationship between covert narcissism and cyberbullying. Specifically, the positive predictive effect of covert narcissism on cyberbullying gradually weakened as self-control improved. Conclusion: This study explored the underlying mechanism of cyberbullying and found that covert narcissism could affect cyberbullying through hostile attribution bias. Self-control moderated the relationship between covert narcissism and cyberbullying. The results have significant implications for the intervention and prevention of cyberbullying and additional evidence for the relationship between covert narcissism and cyberbullying.

7.
Nat Commun ; 14(1): 4212, 2023 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-37452037

RESUMO

Kinase inhibitors against Cyclin Dependent Kinase 4 and 6 (CDK4/6i) are promising cancer therapeutic drugs. However, their effects are limited by primary or acquired resistance in virtually all tumor types. Here, we demonstrate that Leucine Rich Pentatricopeptide Repeat Containing (LRPPRC) controls CDK4/6i response in lung cancer by forming a feedback loop with CDK6. LRPPRC binds to CDK6-mRNA, increasing the stability and expression of CDK6. CDK6 and its downstream E2F Transcription Factor 1 (E2F1), bind to the LRPPRC promoter and elevate LRPPRC transcription. The activation of the LRPPRC-CDK6 loop facilitates cell cycle G1/S transition, oxidative phosphorylation, and cancer stem cell generation. Gossypol acetate (GAA), a gynecological medicine that has been repurposed as a degrader of LRPPRC, enhances the CDK4/6i sensitivity in vitro and in vivo. Our study reveals a mechanism responsible for CDK4/6i resistance and provides an enlightening approach to investigating the combinations of CDK4/6 and LRPPRC inhibitors in cancer therapy.


Assuntos
Antineoplásicos , Neoplasias Pulmonares , Humanos , Linhagem Celular Tumoral , Quinase 4 Dependente de Ciclina/metabolismo , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Quinase 6 Dependente de Ciclina/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Inibidores de Proteínas Quinases/uso terapêutico , Proteínas de Neoplasias/genética
8.
Nutrition ; 114: 112127, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37441825

RESUMO

OBJECTIVES: The ketogenic diet (KD) is recommended to improve polycystic ovary syndrome (PCOS); however, its mechanisms of action are unclear. We aimed to study the effects and mechanisms of action of the KD on the gut microbiome and metabolites in PCOS rats and determine whether the sex hormone regulatory effects are related to modulations of the gut microbiota and metabolites. METHODS: PCOS was induced with a high-fat diet and letrozole in the rats. A KD was fed to rats for 8 wk, serum samples were collected for biochemical analysis, and the rats' fecal samples were subjected to 16S ribosomal RNA sequencing and metabolomic analysis. RESULTS: Feeding with a KD for 8 wk suppressed body weight gain, decreased luteinizing hormone and androgen levels, and improved insulin levels. Furthermore, the KD reversed the dysregulation of the gut microbiota in PCOS rats by adjusting the ratio of firmicutes and bacteroidetes. Also, the KD was involved in hormonal metabolic pathways by reducing the levels of some metabolites (such as testosterone and 7α-hydroxytestosterone) that are closely related to gut microbes. CONCLUSIONS: The KD improved the clinical phenotype and insulin resistance in PCOS rats and altered the composition of the gut microbiome and metabolites, which were associated with androgen metabolism, representing a potential mechanism for mediating the effects of the KD on sex hormone metabolism in PCOS. However, our study found contradictory effects of KD on the gut microbiome in PCOS, which need further research.


Assuntos
Dieta Cetogênica , Microbioma Gastrointestinal , Síndrome do Ovário Policístico , Feminino , Humanos , Ratos , Animais , Letrozol/farmacologia , Microbioma Gastrointestinal/fisiologia , Dieta Hiperlipídica/efeitos adversos , Androgênios/farmacologia , Metabolômica , Hormônios Esteroides Gonadais/farmacologia
9.
Drug Des Devel Ther ; 17: 2147-2163, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37521037

RESUMO

Purpose: The aim of this study is to examine, using network pharmacology analysis and experimental validation, the pharmacological processes by which Yulin Formula (YLF) reduces cyclophosphamide-induced diminished ovarian reserve (DOR). Methods: First, information about the active components, associated targets, and related genes of YLF and DOR was gathered from open-access databases. The primary targets and pathways of YLF to reduce DOR were predicted using studies of functional enrichment from the Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Protein-Protein Interaction (PPI) networks. Second, we built a cyclophosphamide-induced diminished ovarian reserve (DOR) rat model to verify the primary target proteins implicated in the predicted signaling pathway to explore the mechanism of improve ovarian function of YLF. Results: 98 targets met the targets of the 82 active ingredients in YLF and DOR after searching the intersection of the active ingredient targets and DOR targets. Fourteen targets, including AKT and Caspase-3 among others, were hub targets, according to the PPI network study. The PI3K/AKT pathway was revealed to be enriched by numerous targets by the GO and KEGG enrichment studies, and it was used as a target for in vivo validation. Animal studies showed that YLF administration not only reduced the number of atretic follicles, the proportion of TUNEL-positive ovarian cells, the rate of apoptosis of granulosa cells (GCs) and the proportion of abnormal mitochondria in DOR rats, but also reversed the high expression of Caspase-3, Caspase-9, BAX, cytochrome C, PI3K and P-AKT, improving the ovarian reserve in cyclophosphamide (CTX)-induced DOR rats. Conclusion: Our research results predicted the active ingredients and potential targets of YLF-interfering DOR by an integrated network pharmacology approach, and experimentally validated some key target proteins participated in the predicted signaling pathway. A more comprehensive understanding of the pharmacological mechanism of YLF for DOR treatment was obtained.


Assuntos
Medicamentos de Ervas Chinesas , Doenças Ovarianas , Reserva Ovariana , Feminino , Humanos , Animais , Ratos , Caspase 3 , Farmacologia em Rede , Fosfatidilinositol 3-Quinases , Proteínas Proto-Oncogênicas c-akt , Ciclofosfamida , Simulação de Acoplamento Molecular
10.
J Am Chem Soc ; 145(23): 12861-12869, 2023 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-37276358

RESUMO

Targeted protein degradation (TPD) is an emerging technique for protein regulation. Currently, all TPD developed in eukaryotic cells relies on either ubiquitin-proteasome or lysosomal systems, thus are powerless against target proteins in membrane organelles lacking proteasomes and lysosomes, such as mitochondria. Here, we developed a mitochondrial protease targeting chimera (MtPTAC) to address this issue. MtPTAC is a bifunctional small molecule that can bind to mitochondrial caseinolytic protease P (ClpP) at one end and target protein at the other. Mechanistically, MtPTAC activates the hydrolase activity of ClpP while simultaneously bringing target proteins into proximity with ClpP. Taking mitochondrial RNA polymerase (POLRMT) as a model protein, we have demonstrated the powerful proteolytic ability and antitumor application prospects of MtPTAC, both in vivo and in vitro. This is the first modularly designed TPD that can specifically hydrolyze target proteins inside mitochondria.


Assuntos
Mitocôndrias , Proteínas , Proteólise , Mitocôndrias/metabolismo , Proteínas/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina/metabolismo , Endopeptidases/metabolismo
11.
Adv Healthc Mater ; 12(23): e2300490, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37053081

RESUMO

Nanoenzymes have been widely explored for chemodynamic therapy (CDT) in cancer treatment. However, poor catalytic efficiency of nanoenzymes, especially in the tumor microenvironment with insufficient H2 O2 and mild acidity, limits the effect of CDT. Herein, a new ultrathin RuCu nanosheet (NS) based nanoenzyme which has a large specific surface area and abundant channels and defects is developed. The RuCu NSs show superb catalytic efficiency for the oxidation of peroxidase substrate H2 O2 at a wide range of pH and their catalytic efficiency (kcat /Km = 177.2 m-1  s-1 ) is about 14.9 times higher than that of the single-atom catalyst FeN3 P. Besides being an efficient nanozyme as peroxidase, the RuCu NSs possess other two enzyme activities, not only disproportionating superoxide anion to produce H2 O2 but also consuming glutathione to keep a high concentration of H2 O2 in the tumor microenvironment for Fenton reaction. With these advantages, the RuCu NSs exhibit good performance to kill cancer cells and inhibit tumor growth in mice, demonstrating a promising potential as new CDT reagent.


Assuntos
Neoplasias , Peroxidase , Animais , Camundongos , Peroxidases , Catálise , Glutationa , Superóxidos , Microambiente Tumoral , Peróxido de Hidrogênio , Linhagem Celular Tumoral , Neoplasias/tratamento farmacológico
12.
Adv Mater ; 35(24): e2211332, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36971342

RESUMO

The tumor-associated macrophages (TAMs) in intratumoral hypoxic regions are key drivers of immune escape. Reprogramming the hypoxic TAMs to antitumor phenotype holds great therapeutic benefits but remains challenging for current drugs. Here, an in situ activated nanoglycocluster is reported to realize effective tumor penetration and potent repolarization of hypoxic TAMs. Triggered by the hypoxia-upregulated matrix metalloproteinase-2 (MMP-2), the nanoglycocluster is self-assembled from the administered mannose-containing precursor glycopeptides and presents densely-arrayed mannoses to multivalently engage with mannose receptors on M2-like TAMs for efficient phenotype switch. By virtue of the high diffusivity of precursor glycopeptides due to their low molecular mass and weak affinity with TAMs in perivascular regions, the nanoglycoclusters are capable of substantially accumulating in hypoxic areas to strongly interact with local TAMs. This enables the efficient repolarization of overall TAMs with a higher rate than the small-molecule drug R848 and CD40 antibody, and beneficial therapeutic effects in mouse tumor models especially when combining with PD-1 antibody. This on-demand activated immunoagent is endowed with tumor-penetrating properties and inspires the design of diverse intelligent nanomedicines for hypoxia-related cancer immunotherapy.


Assuntos
Neoplasias , Macrófagos Associados a Tumor , Animais , Camundongos , Metaloproteinase 2 da Matriz , Macrófagos , Imunoterapia , Neoplasias/terapia , Neoplasias/patologia , Hipóxia , Glicopeptídeos/farmacologia , Microambiente Tumoral
13.
ACS Appl Mater Interfaces ; 15(10): 12822-12830, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36856721

RESUMO

The strategy of enhancing molecular recognition by improving the binding affinity of drug molecules against targets has generated a lot of successful therapeutic applications. However, one critical consequence of such affinity improvement, generally called "on-target, off-tumor" toxicity, emerged as a major obstacle limiting their clinical usage. Herein, we provide a modular assembly strategy that affords affinity-tunable DNA nanostructures allowing for immobilizing multiple aptamers that bind to the example antigen of EpCAM with different affinities. We develop a theoretical model proving that the apparent affinity of aptamer assemblies to target cells varies with antigen density as well as aptamer valency. More importantly, we demonstrate experimentally that the theoretical model can be used to predict the least valency required for discrimination between EpCAMhigh and EpCAMlow cells in vitro and in vivo. We believe that our strategy will have broad applications in an engineering nucleic acid-based delivery platform for targeted and cell therapy.


Assuntos
Aptâmeros de Nucleotídeos , Nanoestruturas , Molécula de Adesão da Célula Epitelial/metabolismo , Aptâmeros de Nucleotídeos/química , DNA , Membrana Celular/metabolismo
14.
Int J Mol Sci ; 25(1)2023 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-38203545

RESUMO

G protein-coupled receptors (GPCRs) represent promising therapeutic targets due to their involvement in numerous physiological processes mediated by downstream G protein- and ß-arrestin-mediated signal transduction cascades. Although the precise control of GPCR signaling pathways is therapeutically valuable, the molecular details for governing biased GPCR signaling remain elusive. The Angiotensin II type 1 receptor (AT1R), a prototypical class A GPCR with profound implications for cardiovascular functions, has become a focal point for biased ligand-based clinical interventions. Herein, we used single-molecule live-cell imaging techniques to evaluate the changes in stoichiometry and dynamics of AT1R with distinct biased ligand stimulations in real time. It was revealed that AT1R existed predominantly in monomers and dimers and underwent oligomerization upon ligand stimulation. Notably, ß-arrestin-biased ligands induced the formation of higher-order aggregates, resulting in a slower diffusion profile for AT1R compared to G protein-biased ligands. Furthermore, we demonstrated that the augmented aggregation of AT1R, triggered by activation from each biased ligand, was completely abrogated in ß-arrestin knockout cells. These findings furnish novel insights into the intricate relationship between GPCR aggregation states and biased signaling, underscoring the pivotal role of molecular behaviors in guiding the development of selective therapeutic agents.


Assuntos
Receptor Tipo 1 de Angiotensina , Imagem Individual de Molécula , Ligantes , Transdução de Sinais , beta-Arrestina 1 , Proteínas de Ligação ao GTP
15.
ACS Nano ; 16(12): 21129-21138, 2022 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-36484532

RESUMO

Cytotoxic T cells initiate antitumor effects mainly through direct interactions with tumor cells. As a counter to this, tumor cells can put the brakes on such T-cell activity via specific linkage between programmed death ligand 1 (PDL1) and its receptor programmed cell death protein 1 (PD1). Bispecific inhibitors that enabled synchronous blockade of PD1 and PDL1, thereby releasing the brakes on T-cell antitumor activity, should significantly improve the efficacy of immune checkpoint blockade (ICB) therapy. In this work, we identified a DNA aptamer, Ap3, that could specifically recognize PDL1 on tumor cells and competed with the binding of PD1. By integrating Ap3 with an anti-PD1 aptamer, the bispecific aptamer Ap3-7c was constructed, and it showed promise for improving the T-cell immune response. We further designed a dibenzocyclooctyne (DBCO)-labeled bispecific aptamer, D-Ap3-7c, allowing covalent conjugation of aptamers onto PD1 and PDL1 after specific cell recognition. Our in vivo studies showed that this recognition-then-conjugation strategy could induce a potent immunological effect against tumors. This work is expected to provide clues for antitumor immunotherapy.


Assuntos
Neoplasias , Receptor de Morte Celular Programada 1 , Humanos , Neoplasias/terapia , Antígeno B7-H1 , Imunoterapia
16.
Chem Sci ; 13(41): 11964-11980, 2022 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-36349113

RESUMO

Single-molecule microscopy is advantageous in characterizing heterogeneous dynamics at the molecular level. However, there are several challenges that currently hinder the wide application of single molecule imaging in bio-chemical studies, including how to perform single-molecule measurements efficiently with minimal run-to-run variations, how to analyze weak single-molecule signals efficiently and accurately without the influence of human bias, and how to extract complete information about dynamics of interest from single-molecule data. As a new class of computer algorithms that simulate the human brain to extract data features, deep learning networks excel in task parallelism and model generalization, and are well-suited for handling nonlinear functions and extracting weak features, which provide a promising approach for single-molecule experiment automation and data processing. In this perspective, we will highlight recent advances in the application of deep learning to single-molecule studies, discuss how deep learning has been used to address the challenges in the field as well as the pitfalls of existing applications, and outline the directions for future development.

17.
RSC Adv ; 12(34): 22197-22201, 2022 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-36043103

RESUMO

C60-fullerenes have unique potential in antiviral, drug delivery, photodynamic therapy and other biomedical applications. However, little is known about their effects on macrophage surface morphology and ultrastructure. Here by using contact-free scanning ion conductance microscopy (SICM), we investigated the effects of two water-soluble fullerenes on the surface ultrastructure and function of macrophages. The results showed that these fullerenes would be a promising phagocytosis inhibitor and SICM would be an excellent tool to study the morphological information of adhesive and fragile samples.

18.
Opt Express ; 30(8): 13481-13490, 2022 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-35472959

RESUMO

Stimulated-emission-depletion (STED) nanoscope achieves super-resolution imaging by using a donut-shaped depletion beam to darken the fluorophores around the excitation spot. As an important factor determining the resolution of imaging, the coaxiality between the excitation and the depletion beam is required to be maintained at the nanoscale, which is often degraded by various interference such as ambient vibration and temperatures etc. Here, we propose a specially designed STED illumination module to guarantee the coaxiality between the two beams while modulating the phase of the depletion beam. This STED illumination module can realize phase modulation, polarization adjustment, pulse delay and two beams coaxial at the same time. With the experiments, the module can guarantee the two beams are stably coaxial for a long time. We imaged fluorescence particles with diameter 40 nm and got images of 40 nm full width at half maximum. Adjacent microfilaments at 80 nm being clearly distinguished with our STED nonoscope demonstrates that it could be well applied to biological samples.

19.
Sci Total Environ ; 829: 154394, 2022 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-35276153

RESUMO

This paper reports Pb isotopes in different fractions following the three step BCR and 1 M HCl extractions on river sediments from lower reaches of the Xiangjiang river in China, and highlights the importance of Pb isotopes in heavy metal contamination assessment. Lead concentrations and Pb isotopes in bulk sediments and sediment fractions (leachates and residues) from the river were analysed using ICP-MS techniques. Results showed that sediments were highly enriched with Pb with enrichment factors >5.5, while Pb in sediments was dominated by reducible and residual Pb fractions, residing mainly in Fe-oxide and silicate minerals. Pb isotopes in sediments was characterized by radiogenic Pb produced from the decay of uranium and thorium with 206Pb/207Pb ratios of 1.1744 for less radiogenic Pb and 1.1816 for more radiogenic Pb. The leachates and residues from BCR extraction generally had similar Pb isotope compositions, of which the 206Pb/207Pb ratios were 1.1798 ± 0.002 and 1.1844 ± 0.008 respectively. Differentiation of Pb isotopes between BCR leachates and residues was insignificant. However, differentiation between leachates and residues using 1 M HCl extraction was significant, as shown by average 206Pb/207Pb ratios of 1.1746 ± 0.005 and 1.1858 ± 0.008 for leachates and residues respectively. Pb isotopic tracing suggests that Pb in sediments from Zhuzhou section arose from the mixing of anthropogenic Pb from coal combustion (39%) and mining-smelting for Pb-Zn ores (58%); while Pb in sediments from Xiangtan, Changsha and Xiangyin sections arose from the mixing of anthropogenic Pb from mining-smelting for Pb-Zn ores (54%), and lithologically inherited Pb from granite weathering (35%) with a small amount of contribution from coal combustion (10%). The present study suggests that the BCR extraction scheme was not appropriate for ecological risk assessment of heavy metal contamination in mining-impacted (ore-Pb dominated) river sediments.


Assuntos
Metais Pesados , Urânio , Poluentes Químicos da Água , China , Carvão Mineral/análise , Monitoramento Ambiental/métodos , Sedimentos Geológicos/química , Isótopos/análise , Chumbo/análise , Metais Pesados/análise , Rios/química , Urânio/análise , Poluentes Químicos da Água/análise
20.
Anal Chem ; 94(7): 3056-3064, 2022 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-35142221

RESUMO

Stimulated emission depletion (STED) nanoscopy is an emerging super-resolution imaging platform for the study of the cellular structure. Developing suitable fluorescent probes of small size, good photostability, and easy functionalization is still in demand. Herein, we introduce a new type of surface-engineered gold nanoclusters (Au NCs) that are ultrasmall (1.7 nm) and ultrabright (QY = 60%) for STED bioimaging. A rigid shell formed by l-arginine (l-Arg) and 6-aza-2-thiothymine (ATT) on the Au NC surface enables not only its strong fluorescence in aqueous solution but also its easy chemical modification for specific biomolecule labeling. Au NCs show remarkable performance as STED nanoprobes, including high depletion efficiency, good photobleaching resistance, and low saturation intensity. Super-resolution imaging has been achieved with these Au NCs, and targeted nanoscopic imaging of cellular tubulin has been demonstrated. Moreover, the circular structure of lysosomes in live cells has been revealed. As a Au NC is also an ideal probe for electron microscopy, dual imaging of Aß42 aggregates with the single labeling probe of Au NCs has been realized in correlative light and electron microscopy (CLEM). This work reports, for the first time, the application of Au NCs as a novel probe in STED and CLEM imaging. With their excellent properties, Au NCs show promising potential for nanoscale bioimaging.


Assuntos
Ouro , Nanopartículas Metálicas , Corantes Fluorescentes/química , Ouro/química , Nanopartículas Metálicas/química , Microscopia Eletrônica , Fotodegradação
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