Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 34
Filtrar
1.
Cell Mol Life Sci ; 81(1): 179, 2024 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-38602536

RESUMO

Extracellular vesicles (EVs) have recently received increasing attention as essential mediators of communication between tumor cells and their microenvironments. Tumor-associated macrophages (TAMs) play a proangiogenic role in various tumors, especially head and neck squamous cell carcinoma (HNSCC), and angiogenesis is closely related to tumor growth and metastasis. This research focused on exploring the mechanisms by which EVs derived from TAMs modulate tumor angiogenesis in HNSCC. Our results indicated that TAMs infiltration correlated positively with microvascular density in HNSCC. Then we collected and identified EVs from TAMs. In the microfluidic chip, TAMs derived EVs significantly enhanced the angiogenic potential of pHUVECs and successfully induced the formation of perfusable blood vessels. qPCR and immunofluorescence analyses revealed that EVs from TAMs transferred miR-21-5p to endothelial cells (ECs). And targeting miR-21-5p of TAMs could effectively inhibit TAM-EVs induced angiogenesis. Western blot and tube formation assays showed that miR-21-5p from TAM-EVs downregulated LATS1 and VHL levels but upregulated YAP1 and HIF-1α levels, and the inhibitors of YAP1 and HIF-1α could both reduce the miR-21-5p enhanced angiogenesis in HUVECs. The in vivo experiments further proved that miR-21-5p carried by TAM-EVs promoted the process of tumor angiogenesis via YAP1/HIF-1α axis in HNSCC. Conclusively, TAM-derived EVs transferred miR-21-5p to ECs to target the mRNA of LATS1 and VHL, which inhibited YAP1 phosphorylation and subsequently enhanced YAP1-mediated HIF-1α transcription and reduced VHL-mediated HIF-1α ubiquitination, contributing to angiogenesis in HNSCC. These findings present a novel regulatory mechanism of tumor angiogenesis, and miR-21-5p/YAP1/HIF-1α might be a potential therapeutic target for HNSCC.


Assuntos
Exossomos , Neoplasias de Cabeça e Pescoço , MicroRNAs , Carcinoma de Células Escamosas de Cabeça e Pescoço , Microambiente Tumoral , Humanos , Angiogênese , Células Endoteliais , Neoplasias de Cabeça e Pescoço/genética , MicroRNAs/genética , Proteínas Serina-Treonina Quinases , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética , Macrófagos Associados a Tumor , Exossomos/metabolismo , Animais , Camundongos
2.
Ecotoxicol Environ Saf ; 277: 116364, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38657461

RESUMO

The purpose of this study was to investigate the effect of Treg/Th1 imbalance in cadmium-induced lung injury and the potential protective effect of astilbin against cadmium-induced lung injury in chicken. Cadmium exposure significantly decreased T-AOC and GSH-Px levels and SOD activity in the chicken lung tissues. In contrast, it significantly increased the MDA and NO levels. These results indicate that cadmium triggers oxidative stress in lungs. Histopathological analysis revealed that cadmium exposure further induced infiltration of lymphocytes in the chicken lungs, indicating that cadmium causes pulmonary damage. Further analysis revealed that cadmium decreased the expression of IL-4 and IL-10 but increased those of IL-17, Foxp3, TNF-α, and TGF-ß, indicating that the exposure of cadmium induced the imbalance of Treg/Th1. Moreover, cadmium adversely affected chicken lung function by activating the NF-kB pathway and inducing expression of genes downstream to these pathways (COX-2, iNOS), associated with inflammatory injury in the lung tissue. Astilbin reduced cadmium-induced oxidative stress and inflammation in the lungs by increasing antioxidant enzyme activities and restoring Treg/Th1 balance. In conclusion, our results suggest that astilbin treatment alleviated the effects of cadmium-mediated lung injury in chickens by restoring the Treg/Th1 balance.


Assuntos
Cádmio , Galinhas , Flavonóis , Lesão Pulmonar , Pulmão , Estresse Oxidativo , Transdução de Sinais , Linfócitos T Reguladores , Animais , Cádmio/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Pulmão/patologia , Transdução de Sinais/efeitos dos fármacos , Linfócitos T Reguladores/efeitos dos fármacos , Flavonóis/farmacologia , Lesão Pulmonar/induzido quimicamente , Lesão Pulmonar/tratamento farmacológico
3.
Int J Mol Sci ; 22(3)2021 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-33498664

RESUMO

Male sterility (MS) plays a key role in the hybrid breed production of plants. Researchers have focused on the association between genetic male sterility (GMS) and cytoplasmic male sterility (CMS) in kenaf. In this study, P9BS (a natural GMS mutant of the kenaf line P9B) and male plants of P9B were used as parents in multiple backcross generations to produce P9SA, a CMS line with stable sterility, to explore the molecular mechanisms of the association between GMS and CMS. The anthers of the maintainer (P9B), GMS (P9BS), and CMS (P9SA) lines were compared through phenotypic, cell morphological, physiological, biochemical observations, and transcriptome analysis. Premature degradation of the tapetum was observed at the mononuclear stage in P9BS and P9SA, which also had lower activity of reactive oxygen species (ROS) scavenging enzymes compared with P9B. Many coexpressed differentially expressed genes were related to ROS balance, including ATP synthase, electron chain transfer, and ROS scavenging processes were upregulated in P9B. CMS plants had a higher ROS accumulation than GMS plants. The MDA content in P9SA was 3.2 times that of P9BS, and therefore, a higher degree of abortion occurred in P9SA, which may indicate that the conversion between CMS and GMS is related to intracellular ROS accumulation. Our study adds new insights into the natural transformation of GMS and CMS in plants in general and kenaf in particular.


Assuntos
Hibiscus/fisiologia , Infertilidade das Plantas/fisiologia , Proteínas de Plantas/genética , Pólen/citologia , Espécies Reativas de Oxigênio/metabolismo , Enzimas/genética , Enzimas/metabolismo , Flores/genética , Flores/fisiologia , Regulação da Expressão Gênica de Plantas , Hibiscus/citologia , Hibiscus/genética , Células Vegetais , Infertilidade das Plantas/genética , Proteínas de Plantas/metabolismo , Pólen/genética , Pólen/crescimento & desenvolvimento , Análise de Sequência de RNA , Fatores de Transcrição/genética
4.
Int J Mol Sci ; 20(24)2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31817342

RESUMO

Cytoplasmic male sterility (CMS) is an important agronomic feature and provides an effective tool for heterosis utilization of crops. This study reports the comparative transcriptomic sketches between a novel allohexaploid cotton progeny CMS line LD6A and its maintainer line LD6B using de novo transcriptome sequencing technology at the pollen abortion stage. A total of 128,901 Unigenes were identified, in which 2007 were upregulated and 11,864 were downregulated. The significantly differentially expressed genes (DEGs) in LD6A show a distant and diverse genetic nature due to their distant hybrid hexaploidy progeny. Further analysis revealed that most of the DEGs participated in the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, histone acetyltransferase activity, sepal development, stigma development, cotyledon development and microsporogenesis. A highly differentially expressed toxic protein, Abrin, was identified in the CMS line LD6A, which can catalyze the inactivation of ribosomes and consequently lead to cell death through the mitochondrial pathway in human cells. Twelve DEGs were selected randomly to validate transcriptome data using quantitative reverse-transcribed PCR (qRT-PCR). This study will contribute to new ideas and foundations related to the molecular mechanism of CMS and the innovation of cotton germplasm resources.


Assuntos
Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Gossypium , Infertilidade das Plantas , Proteínas de Plantas , Proteômica , Transcriptoma , Gossypium/genética , Gossypium/metabolismo , Proteínas de Plantas/biossíntese , Proteínas de Plantas/genética
5.
Int J Mol Sci ; 20(21)2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31694312

RESUMO

Cytoplasmic male sterility (CMS) is a maternally inherited trait used for hybrid production in plants, a novel kenaf CMS line 722HA was derived from the thermo-sensitive male-sterile mutant 'HMS' by recurrent backcrossing with 722HB. The line 722HA has great potential for hybrid breeding in kenaf. However, the underlying molecular mechanism that controls pollen abortion in 722HA remains unclear, thus limiting the full utilization of this line. To understand the possible mechanism governing pollen abortion in 722HA, cytological, transcriptomic, and biochemical analyses were carried out to compare the CMS line 722HA and its maintainer line 722HB. Cytological observations of the microspore development revealed premature degradation of the tapetum at the mononuclear stage, which resulted in pollen dysfunction. The k-means clustering analysis of differentially expressed genes (DEGs) revealed that these genes are related to processes associated with the accumulation of reactive oxygen species (ROS), including electron transport chain, F1F0-ATPase proton transport, positive regulation of superoxide dismutase (SOD), hydrogen peroxide catabolic, and oxidation-reduction. Biochemical analysis indicated that ROS-scavenging capability was lower in 722HA than in 722HB, resulting in an accumulation of excess ROS, which is consistent with the transcriptome results. Taken together, these results demonstrate that excessive ROS accumulation may affect the normal development of microspores. Our study provides new insight into the molecular mechanism of pollen abortion in 722HA and will promote further studies of kenaf hybrids.


Assuntos
Regulação da Expressão Gênica de Plantas , Hibiscus/genética , Infertilidade das Plantas/genética , Pólen/genética , Transcriptoma , Citoplasma/genética , Citoplasma/ultraestrutura , Hibiscus/crescimento & desenvolvimento , Hibiscus/ultraestrutura , Melhoramento Vegetal , Pólen/crescimento & desenvolvimento , Pólen/ultraestrutura , Espécies Reativas de Oxigênio/metabolismo
6.
Int J Mol Sci ; 18(11)2017 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-29068396

RESUMO

In this study, the tetrad stage of microspore development in a new cotton (Gossypium barbadense L.) cytoplasmic male sterility (CMS) line, H276A, was identified using paraffin sections at the abortion stage. To explore the molecular mechanism underlying CMS in cotton, a comparative transcriptome analysis between the CMS line H276A and its maintainer line H276B at the tetrad stage was conducted using an Illumina HiSeq 4000 platform. The comparison of H276A with H276B revealed a total of 64,675 genes, which consisted of 59,255 known and 5420 novel genes. An analysis of the two libraries with a given threshold yielded a total of 3603 differentially expressed genes (DEGs), which included 1363 up- and 2240 down-regulated genes. Gene Ontology (GO) annotation showed that 2171 DEGs were distributed into 38 categories, and a Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that 2683 DEGs were classified into 127 groups. Thirteen DEGs were randomly selected and detected by quantitative reverse-transcribed PCR (qRT-PCR), and the results indicated that the transcriptome sequencing results were reliable. The bioinformatic analysis results in conjunction with previously reported data revealed key DEGs that might be associated with the male sterility features of H276A. Our results provide a comprehensive foundation for understanding anther development and will accelerate the study of the molecular mechanisms of CMS in cotton.


Assuntos
Regulação da Expressão Gênica de Plantas , Ontologia Genética , Gossypium/metabolismo , Infertilidade das Plantas/genética , Transcriptoma , Biologia Computacional , Perfilação da Expressão Gênica , Gossypium/citologia , Gossypium/genética , Gossypium/fisiologia
7.
J Am Chem Soc ; 137(35): 11327-39, 2015 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-26301334

RESUMO

We demonstrate that anatase TiO2 nanocrystals composed of a nanocrystal core and nanorod antennas can be produced via a nonaqueous colloidal seed-mediated growth method. Anatase TiO2 nanocrystals with defined morphologies were first prepared as seeds, and then secondary anatase TiO2 nanorods were grown on the defined facets of the seeds under appropriate conditions. Systematic studies on the growth mechanism reveal that the formation of core-antenna nanocrystals involves an epitaxial growth process with specific orientational preference governed by both thermodynamic and kinetic factors. By manipulating the reaction conditions including the precursor amount and introduction rate, the epitaxial growth behavior can be well controlled. By further varying the morphology of seed nanocrystals, we have also been able to produce core-antenna anatase TiO2 nanocrystals with complex spatial configurations in a highly predictable manner. The high structural configurability and predictability offered by this seed-mediated growth method may provide great opportunities in enhancing the performance of TiO2-based nanostructures in many energy-related applications. As a demonstration, we show by simply manipulating the core-antenna structures that the photocatalytic activity of the anatase nanocrystals can be improved from the relatively less active seed nanocrystals or pure nanorods to the extent that exceeds the activity of the commercial P25 titania.

8.
Nano Lett ; 14(5): 2466-70, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24712540

RESUMO

We report the development of a stress-responsive colorimetric film that can memorize the stress it has experienced. The system is designed by taking advantage of the plasmonic shift associated with the disassembly of one-dimensional gold nanoparticle chains driven by the plastic deformation of the surrounding polymer matrix. By modifying the plasticity of the polymer, we demonstrate that the plasmonic shift and colorimetric change respond to a large range of stresses. This novel pressure indicating film can be used to capture and record the pressure distribution and magnitude between two contacting or impacting surfaces by outputting color information.

9.
Chem Soc Rev ; 42(7): 2610-53, 2013 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-23093173

RESUMO

Templating is one of the most important techniques for the controlled synthesis of nanostructured materials. This powerful tool uses a pre-existing guide with desired nanoscale features to direct the formation of nanomaterials into forms that are otherwise difficult to obtain. As a result, templated synthesis is capable of producing nanostructures with unique structures, morphologies and properties. In this review, we summarize the general principles of templated synthesis and cover recent developments in this area. As a wide variety of synthesis techniques are utilized to produce nanomaterials using template-based methods, the discussion is organized around the various types of common templates. We examine the use of both physical and chemical hard colloidal templates, soft templates, and other non-colloidal templates, followed by our perspective on the state of the field and potential future directions.

10.
Front Vet Sci ; 11: 1357626, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38948669

RESUMO

An 8-year-old castrated male teddy bear dog presented to our clinic with a persistent cough. The sick dog suffered from vehicular trauma 6 months prior to the visit and had imaging and exploratory laparotomy. Imaging and exploratory laparotomy at the time showed no significant damage. We performed contrast radiography (barium gavage) on the sick dog. Based on the results of a complete contrast radiography (barium gavage), tubular shadows in the thoracic cavity were identified as the small intestine and cecum, and delayed traumatic diaphragmatic hernia with hepatothorax and enterothorax was confirmed with radiographs. Accordingly, the sick dog underwent general anesthesia, manual ventilation and diaphragmatic herniorrhaphy by standard ventral midline abdominal approach. Postoperatively, the dog was given analgesia and antibacterial treatment, and the liver biochemical indexes were monitored to prevent endotoxin. Postoperative radiographs revealed clear contours of thoracic and abdominal organs. The dog moved, ate, and urinated normally within 10 days of the surgery. This case provides a reference for a complete barium meal imaging procedure that clearly shows the position of the organs in the thoracoabdominal cavity after the occurrence of a delayed traumatic diaphragmatic hernia. This paper provides a practical reference for the diagnosis of delayed traumatic diaphragmatic hernia with hepatothorax and enterothorax.

11.
Materials (Basel) ; 16(9)2023 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-37176179

RESUMO

This paper presents a finite element model for predicting the performance and failure behaviour of a hybrid joint assembling fibrous composites to a metal part with reinforcement micro pins for enhancing the damage tolerance performance. A unit-strip model using the cohesive elements at the bond interface is employed to simulate the onset and propagation of debonding cracks. Two different traction-separation laws for the interface cohesive elements are employed, representing the fracture toughness properties of the plain adhesive bond and a pin-reinforced interface, respectively. This approach can account for the large-scale crack-bridging effect of the pins. It avoids using concentrated pin forces in the numerical model, thus removing mesh-size dependency, and permitting more accurate and robust computational analysis. Lap joints reinforced with various pin arrays were tested under quasi-static load. Predicted load versus applied displacement relations are in good agreement with the test results, especially for the debonding onset and early stage of crack propagation.

12.
Biomed Chromatogr ; 26(1): 101-8, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21465504

RESUMO

In this work, a liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS) method was developed and validated for quantification of bile acids in fecal materials. Co-eluting matrix impurities in fecal materials have been shown to greatly suppress the ionization of analytes in mass spectrometry, which is known as the matrix effect. To correct large quantitative errors caused by the matrix effect, we developed a scheme that combined the standard addition method with internal standard (SA-IS). The fecal sample pretreatment involved a single step of extraction with ethanol. Bile acids were separated using a Luna C(18) column (150 mm, 2 mm i.d., 5 µm) with gradient elution. The deprotonated analytes were detected in selective ion monitoring mode. Our results showed that, by using this method, the accuracy of quantification was significantly improved in comparison to the conventional internal standard method. The linearity, sensitivity, accuracy and precision of the method were within the range of 0.05-5 µmol/L. This SA-IS method was successfully applied to the analysis of bile acids in the samples collected from patients diagnosed with inflammatory bowel disease.


Assuntos
Ácidos e Sais Biliares/análise , Cromatografia Líquida/métodos , Fezes/química , Espectrometria de Massas por Ionização por Electrospray/métodos , Ácidos e Sais Biliares/química , Ácidos e Sais Biliares/isolamento & purificação , Bolsas Cólicas , Humanos , Modelos Lineares , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
13.
Angew Chem Int Ed Engl ; 51(26): 6373-7, 2012 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-22623318

RESUMO

Charged colloidal gold nanoparticles (AuNPs) can be assembled and disassembled in an aqueous solution in response to temperature change and display reversible thermoresponsive tuning of plasmon coupling. The reversible tuning was made possible by manipulating the electrostatic interaction through the temperature-dependent zeta potential of the charged AuNPs (see the extinction spectra of a typical AuNP dispersion).


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Íons/química
14.
Front Psychol ; 13: 955935, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36312129

RESUMO

This paper investigates whether managers use knowledge transferred from university-industry collaboration when making investment decisions on labor. To establish causality, we use a difference-in-difference method based on the staggered establishment of postdoctoral workstations in Chinese firms. We find that postdoctoral workstations enable managers to improve labor investment efficiency and thus help mitigate over- and under-investment problems in labor, and the higher the operational quality of the workstation, the more significant the increase in investment efficiency. This finding is robust to utilizing the event study approach, placebo test, propensity score matching, instrumental variable, and entropy balancing. Brain gain and knowledge transfer effects between universities and industries are two plausible mechanisms. Furthermore, the main effect is more pronounced for firms located closer to prestigious universities, firms are non-state-owned enterprises, human-capital-intensive, have political connections, and without national fellows' lead. Our findings suggest that brain gain in firms does not merely increase or reduce labor investments Per se, but rather inspires managers to maintain optimal labor levels through knowledge transfer processes.

15.
Chemosphere ; 309(Pt 1): 136813, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36216110

RESUMO

A modified biochar for enhanced denitrification was developed through a facile pyrolysis method using sewage sludge as raw material and melamine as nitrogen source. Through electrochemical analysis, sludge-based pyrolysis biochar (SPBC) has superior electrical conductivity and poor redox activity. SPBC can increase the electron transfer through the geoconductor mechanism. The effect and the mechanism of SPBC on denitrification were studied. The nitrate treatment efficiency increased with the increase of SPBC dosage. From the perspective of molecular biology, the activities of NAR and NIR enzymes, the degradation efficiency of glucose and the ETSA of bacteria were all promoted with the increase of SPBC, thereby promoting the removal of NO3-. In addition, SPBC had a certain screening effect on microbial communities, and biodiversity decreased with the increase of SPBC dosage. Although the biodiversity decreased, the relative abundance of microorganisms conducive to denitrification increased with the increase of SPBC dosage. The transformation strategy of SPBC proposed in this paper provides a technical solution for sludge recycling and application for strengthening denitrification.


Assuntos
Pirólise , Esgotos , Desnitrificação , Nitratos , Carvão Vegetal/química , Nitrogênio/química , Glucose , Reatores Biológicos
16.
Chem Rev ; 114(19): 9853-89, 2014 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-25011918
17.
Materials (Basel) ; 14(22)2021 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-34832387

RESUMO

To meet the high demand for lightweight energy-efficient and safe structures for transport applications, a current state-of-the-art light rail vehicle structure is under development that adopts a multi-material design strategy. This strategy creates the need for advanced multi-material joining technologies. The compatibility of the adhesive with a wide range of material types and the possibility of joining multi-material structures is also a key advantage to its success. In this paper, the feasibility of using either epoxy or polyurethane adhesive joining techniques applied to the multi-material vehicle structure is investigated. Importantly, consideration is given to the effect of variation in bond thickness for both families of structural adhesives. Multi-material adhesively bonded single lap joints with different adhesives of controlled bond thicknesses were manufactured and tested in order to experimentally assess the shear strength and stiffness. The torsional stiffness and natural frequency of the vehicle were modelled using a global two-dimensional finite element model (FEM) with different adhesive properties, and the obtained vehicle performances were further explained by the coupon-level experimental tests. The results showed that the vehicle using polyurethane adhesive with a target bond thickness of 1.0 mm allowed for optimal modal frequency and weight reduction.

18.
Adv Mater ; 33(3): e2006532, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33283355

RESUMO

Precise manipulation of optical properties through the structure-evolution of plasmonic nanoparticles is of great interest in biomedical fields including bioimaging and phototherapy. However, previous success has been limited to fixed assembled structures or visible-NIR-I absorption. Here, an activatable NIR-II plasmonic theranostics system based on silica-encapsulated self-assembled gold nanochains (AuNCs@SiO2 ) for accurate tumor diagnosis and effective treatment is reported. This transformable chain structure breaks through the traditional molecular imaging window, whose absorption can be redshifted from the visible to the NIR-II region owing to the fusion between adjacent gold nanoparticles in the restricted local space of AuNCs@SiO2 triggered by the high H2 O2 level in the tumor microenvironment (TME), leading to the generation of a new string-like structure with strong NIR-II absorption, which is further confirmed by finite-difference-time-domain (FDTD) simulation. With the TME-activated characteristics, AuNCs@SiO2 exhibits excellent properties for photoacoustic imaging and a high photothermal conversion efficiency of 82.2% at 1064 nm leading to severe cell death and remarkable tumor growth inhibition in vivo. These prominent intelligent TME-responsive features of AuNCs@SiO2 may open up a new avenue to explore optical regulated nano-platform for intelligent, accurate, and noninvasive theranostics in NIR-II window.


Assuntos
Raios Infravermelhos , Neoplasias/diagnóstico , Neoplasias/terapia , Técnicas Fotoacústicas/métodos , Fototerapia/métodos , Nanomedicina Teranóstica/métodos , Animais , Humanos , Hipertermia Induzida , Neoplasias/patologia , Dióxido de Silício , Microambiente Tumoral
19.
Nanoscale ; 13(16): 7638-7647, 2021 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-33928960

RESUMO

Herein, we developed a novel strategy for the shape-controlled synthesis of iron oxide nanostructures with superior r2 values through the introduction of fluoride ions as a morphology controlling agent and dopant. The selective adsorption of fluoride ions onto the specified crystal planes of iron oxide nanocrystals leads to the formation of octapod nanoparticles (ONPs) and cubic nanocrystal clusters (CNCs). Both ONPs and CNCs present high r2 values (526.5 and 462.2 mM-1 s-1, respectively) due to the synergistic effect of a larger effective radius, clustering and fluorine doping. The in vivo MRI results show significant enhancement in T2-weighted images of the liver after the intravenous injection of ONPs and CNCs, suggesting their great potential as efficient T2-weighted MRI contrast agents. This new approach of achieving anisotropic fluorine-doped iron oxide nanostructures with high r2 relaxivity provides an alternative strategy for the development of highly sensitive T2 contrast agents for MRI.


Assuntos
Flúor , Nanoestruturas , Meios de Contraste , Compostos Férricos , Fluoretos , Imageamento por Ressonância Magnética
20.
Nanoscale ; 11(46): 22575-22584, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31746903

RESUMO

Anatase TiO2 materials are well-known for their photocatalytic properties and their structure-performance relationship has been intensively studied over the past few decades. In this study, we report a versatile strategy to control the geometric and electronic structure of hierarchical anatase TiO2 nanocrystals via a colloidal synthesis technique in order to optimize their photocatalytic performances. The synthesis is modified from a classical nonaqueous sol-gel approach in which titanium alkoxides and long carbon chain carboxylic acids are used as titanium sources and hydrolysis/capping agents, respectively. By introducing fluoride ions into the reaction as competitive capping agents and controlling other parameters, the geometric structure of TiO2 nanocrystals can be regulated from nanorods and nanobipyramids to their hierarchical assembly structures with controlled dimension and crystallinity. Meanwhile, it is confirmed that the fluoride capping agents also affect the surface structure of TiO2 by fluorine doping, which exerts an additional impact on the electronic structure of TiO2 nanocrystals apart from morphology variation. Further investigation of photocatalytic hydrogen production performances of TiO2 nanocrystals with different structures indicates that the catalytic efficiency is highly dependent on structural factors including hierarchical shape, surface area and doping status. Obvious improvement of photocatalytic performance is observed in the optimized hierarchical TiO2 nanocrystals (2033.6 µmol g-1 h-1) compared to that in commonly prepared TiO2 nanobipyramids (1135.5 µmol g-1 h-1) and other hierarchical TiO2 nanocrystals (1331.9 µmol g-1 h-1 or lower), which demonstrates the effectiveness of material optimization by the strategy developed in this study.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA