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1.
Int J Mol Sci ; 24(6)2023 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-36982979

RESUMO

Gut microbes are closely associated with disease onset and improvement. However, the effects of gut microbes on the occurrence, prevention, and treatment of benign prostatic hyperplasia (BPH) are still unclear. We investigated the alteration of gut microbiota with implications for the diagnosis, prevention, and treatment of BPH and identified correlations among various indicators, including hormone indicators, apoptosis markers in BPH, and finasteride treatment models. BPH induction altered the abundance of Lactobacillus, Flavonifractor, Acetatifactor, Oscillibacter, Pseudoflavonifractor, Intestinimonas, and Butyricimonas genera, which are related to BPH indicators. Among these, the altered abundance of Lactobacillus and Acetatifactor was associated with the promotion and inhibition of prostate apoptosis, respectively. Finasteride treatment altered the abundance of Barnesiella, Acetatifactor, Butyricimonas, Desulfovibrio, Anaerobacterium, and Robinsoniella genera, which are related to BPH indicators. Among these, altered abundances of Desulfovibrio and Acetatifactor were associated with the promotion and inhibition of prostate apoptosis, respectively. In addition, the abundances of Lactobacillus and Acetatifactor were normalized after finasteride treatment. In conclusion, the association between apoptosis and altered abundances of Lactobacillus and Acetatifactor, among other gut microbes, suggests their potential utility in the diagnosis, prevention, and treatment of BPH.


Assuntos
Microbioma Gastrointestinal , Hiperplasia Prostática , Masculino , Humanos , Finasterida/farmacologia , Finasterida/uso terapêutico , Hiperplasia Prostática/tratamento farmacológico , Próstata , Apoptose
2.
Biosci Biotechnol Biochem ; 81(3): 595-603, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27884090

RESUMO

We developed spontaneous diet-induced metabolic disease in mice by feeding them a high-fat diet for 23 weeks and administered Aloe QDM complex for 16 weeks to examine its restorative effect on immune disorders and metabolic syndrome. A series of immune functional assays indicated Aloe QDM complex enhanced lymphocyte proliferation and antigen-specific immunity as determined by the restored functions of cytotoxic T lymphocytes (CTL) and IgG production. The elevated serum TNF-α level was also regulated by Aloe QDM complex treatment, which suggested its complex therapeutic potential. As for metabolic phenotypes, oral administration of Aloe QDM complex significantly improved diabetic symptoms, including high fasting glucose levels and glucose tolerance, and distinctly alleviated lipid accumulation in adipose and hepatic tissue. The simultaneous restoration of Aloe QDM complex on metabolic syndrome and host immune dysfunction, especially on the specific CTL killing was first elucidated in our study.


Assuntos
Aloe/química , Síndrome Metabólica/tratamento farmacológico , Extratos Vegetais/farmacologia , Linfócitos T Citotóxicos/efeitos dos fármacos , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/patologia , Administração Oral , Animais , Glicemia/metabolismo , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Hiperglicemia/tratamento farmacológico , Hiperglicemia/etiologia , Hiperlipidemias/tratamento farmacológico , Hiperlipidemias/etiologia , Imunoglobulina G/sangue , Metabolismo dos Lipídeos/efeitos dos fármacos , Masculino , Síndrome Metabólica/etiologia , Camundongos Endogâmicos C57BL , Extratos Vegetais/química , Plantas Medicinais/química , Linfócitos T Citotóxicos/imunologia , Fator de Necrose Tumoral alfa/sangue
3.
Biochem Biophys Res Commun ; 478(3): 1242-7, 2016 09 23.
Artigo em Inglês | MEDLINE | ID: mdl-27565724

RESUMO

This study was designed to characterize the potential therapeutic effects of two statin drugs commonly used to treat dyslipidemia in inflammation-linked metabolic disorders related to type 2 diabetes. Atorvastatin (10 mg/kg/day) and rosuvastatin (3 mg/kg/day) were administered to mice with diet-induced obesity (DIO). The statins lowered serum total and LDL cholesterol levels, and improved the atherogenic index and cardiac risk index. Furthermore, the drugs decreased fasting glucose levels, improved glucose tolerance, and decreased fat tissue weight and adipocyte size; this was accompanied by an overall body weight loss tendency. The statins also improved antigen-specific immunity. The killing activity of cytotoxic T cells and exacerbation of IgG secretion levels were considerably normalized. Most importantly, serum tumor necrosis factor-α and interleukin 6 levels decreased, while their RNA expression levels in fat tissue were regulated by the statins as well. This study is the first to indicate that low doses of atorvastatin and rosuvastatin, the dosing regimen for which has been controversial, could significantly improve diabetes-related metabolic disorders, and could modulate pro-inflammatory cytokines, alleviating inflammation and simultaneously restoring overall humoral and cell-mediated immunity.


Assuntos
Atorvastatina/uso terapêutico , Doenças Metabólicas/tratamento farmacológico , Doenças Metabólicas/imunologia , Rosuvastatina Cálcica/uso terapêutico , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Animais , Atorvastatina/farmacologia , Citocinas/sangue , Dieta Hiperlipídica , Epitopos , Glucose/metabolismo , Homeostase , Imunidade , Mediadores da Inflamação/metabolismo , Metabolismo dos Lipídeos , Masculino , Doenças Metabólicas/sangue , Doenças Metabólicas/fisiopatologia , Camundongos Endogâmicos C57BL , Tamanho do Órgão , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Rosuvastatina Cálcica/farmacologia
4.
PLoS One ; 17(5): e0268695, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35584179

RESUMO

Testosterone undecanoate is a hormone agent with long-acting potential and is used for testosterone replacement therapy for hypogonadism. This study was designed to investigate application of testosterone undecanoate in maintaining high androgen levels for inducing benign prostatic hyperplasia more conveniently than that for testosterone propionate. We conducted two-part studies to determine the optimal dosage and dosing cycle for efficient and stable induction of benign prostatic hyperplasia using testosterone undecanoate. In the injection dosage substudy, single testosterone undecanoate dose (125, 250, 500, 750, or 1000 mg/kg body weight) was administered, and the optimal concentration was determined for 8weeks by measuring changes in testosterone, dihydrotestosterone, and 5-alpha reductase levels. And then, testosterone undecanoate was administered at the optimal dose at intervals of 1, 2, 3, or 4 weeks for 12weeks to induce benign prostatic hyperplasia. The injection dosage substudy showed dose-dependently higher and more stable levels of testosterone in groups administrated testosterone undecanoate than in groups administered testosterone propionate. In the injection cycle substudy, testosterone undecanoate-administered group stably maintained high levels of testosterone, dihydrotestosterone, and 5-alpha reductase compared with testosterone propionate-administered group for the same injection cycle; moreover, the prostate measurements, an important sign of benign prostatic hyperplasia, were significantly increased. Based on these two substudies, we determined the optimal conditions for inducing benign prostatic hyperplasia stably and more conveniently than that for testosterone propionate. This study suggests an extended application of testosterone undecanoate for inducing benign prostatic hyperplasia that can improve research reliability considering the half-life of testosterone as well as injection dosage and concentration.


Assuntos
Hiperplasia Prostática , Propionato de Testosterona , Animais , Colestenona 5 alfa-Redutase , Di-Hidrotestosterona , Humanos , Masculino , Hiperplasia Prostática/tratamento farmacológico , Ratos , Ratos Wistar , Reprodutibilidade dos Testes , Testosterona/análogos & derivados , Testosterona/uso terapêutico
5.
Front Microbiol ; 13: 858192, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35655996

RESUMO

Knowledge of the impact of the gut microbiota on human health has increased, and modulation of the bacterial community is now considered a therapeutic target for various diseases. Certain novel bacterial species have probiotic properties associated with improvement in obesity and related metabolic disorders. The relative abundance of Butyricimonas spp. is correlated with metabolic parameters; however, the physiological role of Butyricimonas in metabolic improvement is unclear. In this study, live and heat-killed Butyricimonas virosa were administered to mice with high-fat diet (HFD)-induced obesity. Both live and heat-killed B. virosa ameliorated HFD-impaired body weight, serum glucose level, insulin resistance, and liver steatosis. Moreover, activation of the glucagon-like peptide-1 receptor (GLP-1R) and peroxisome proliferator-activated receptor α (PPARα) was observed in the liver, and the expression levels of insulin receptor substrate (IRS)-1, IRS-2, Toll-like receptor 5 (TLR5), and zonula occludens-1 (ZO-1) were upregulated in the ileum. Finally, we demonstrated that the effect of B. virosa treatment on glucose regulation may be linked to the upregulation of GLP-1R in the liver and is not a result of colonization of the gut by B. virosa or B. virosa-produced butyrate. Our results provide a rationale for the development of Butyricimonas spp.-based therapeutics and prophylactics for hyperglycemia.

6.
Nano Lett ; 10(11): 4328-34, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-20957985

RESUMO

The fundamental properties of graphene are making it an attractive material for a wide variety of applications. Various techniques have been developed to produce graphene and recently we discovered the synthesis of large area graphene by chemical vapor deposition (CVD) of methane on Cu foils. We also showed that graphene growth on Cu is a surface-mediated process and the films were polycrystalline with domains having an area of tens of square micrometers. In this paper, we report on the effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy. On the basis of the results, we developed a two-step CVD process to synthesize graphene films with domains having an area of hundreds of square micrometers. Scanning electron microscopy and Raman spectroscopy clearly show an increase in domain size by changing the growth parameters. Transmission electron microscopy further shows that the domains are crystallographically rotated with respect to each other with a range of angles from about 13 to nearly 30°. Electrical transport measurements performed on back-gated FETs show that overall films with larger domains tend to have higher carrier mobility up to about 16,000 cm(2) V(-1) s(-1) at room temperature.


Assuntos
Cristalização/métodos , Gases/química , Grafite/química , Membranas Artificiais , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Nanotecnologia/métodos , Tamanho da Partícula , Propriedades de Superfície
7.
J Ethnopharmacol ; 279: 114349, 2021 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-34171398

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Saussurea costus (synonym: Aucklandia lappa Decne) is a medicinal plant distributed in Yunnan, Guangxi, and Sichuan in China. In traditional Korean medicine, the plant parts (especially the root-"radix aucklandiae") is widely used to treat vomiting, diarrhea, and inflammation. However, little has been reported on its effect on benign prostatic hyperplasia (BPH), which is common in middle-aged men. AIM OF THE STUDY: BPH is caused by apoptosis imbalance and inflammation due to aging of the prostate. Therefore, the aim of this was to prove the efficacy of S. costus by analyzing its effect on the biological mechanisms leading to BPH progression. MATERIALS AND METHODS: Wistar rats were injected subcutaneously with a single dose of testosterone (125 mg/kg) to induce BPH, and were later administered with S. costus (20, 40 mg/kg). After 12 weeks, histological changes in the prostate and hormone regulation factors were assessed in all animals. Furthermore, apoptotic protein and apoptotic body values were analyzed to confirm the improvement of apoptosis imbalance, and inflammatory cytokines were analyzed to confirm the anti-inflammatory efficacy of S. costus. RESULTS: In the serum and tissue of S. costus-treated BPH rats, a significant reduction in prostate weight, prostate index, and hormone regulation factors was observed. S. costus also increased the levels of apoptosis marker proteins and reduced the levels of inflammatory cytokines. It also decreased the expression of B-cell lymphoma 2 (BCL-2) and increased the expression of BCL-2 associated X protein (BAX) in the prostate. Histological changes such as epithelial thickness significantly increased in BPH induced group but significantly decreased in the S. costus-treated groups (p < 0.001). CONCLUSIONS: S. costus may prevent and treat BPH occurrence by modulating inflammation and apoptosis imbalance.


Assuntos
Apoptose/efeitos dos fármacos , Extratos Vegetais/farmacologia , Hiperplasia Prostática/tratamento farmacológico , Saussurea/química , Animais , Anti-Inflamatórios/administração & dosagem , Anti-Inflamatórios/isolamento & purificação , Anti-Inflamatórios/farmacologia , Modelos Animais de Doenças , Progressão da Doença , Relação Dose-Resposta a Droga , Inflamação/tratamento farmacológico , Inflamação/patologia , Masculino , Extratos Vegetais/administração & dosagem , Hiperplasia Prostática/patologia , Ratos , Ratos Wistar
8.
World J Mens Health ; 39(2): 315-323, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31749336

RESUMO

PURPOSE: Sesquiterpene lactones, which are found in plants of the Asteraceae family, contain costunolide (CO) and dehydrocostus lactone (DCL) as indicator material. CO, in particular, has been reported to possess varied pharmacological activity, including anti-inflammatory, antibacterial, and antioxidant effects. This study was designed to characterize the effects of CO and DCL on benign prostate hyperplasia (BPH). MATERIALS AND METHODS: Rats were injected subcutaneously daily for 8 weeks with 5 mg/kg testosterone to induce prostatic hyperplasia. Wistar rats were randomly divided into 5 groups of 10 animals each and received the following treatment: I. Normal control group; II. BPH-induced group; III. CO group (0.075 mg/kg); IV. DCL group (0.075 mg/kg); and V. Finasteride group (0.8 mg/kg). After treatment, changes in prostate weight and serum biochemical indices, serum dihydrotestosterone level, and mRNA levels of BCL2 were measured and histological examinations performed. RESULTS: Absolute and relative prostate weight in the indicator material treated groups, as well as prostate volume, decreased compared to those in the disease-induced group. Epithelial cell thickness increased significantly in the disease-induced group, with a significant decrease being observed in the CO group. The level of the anti-apoptotic protein BCL2 (B-cell lymphoma 2) tended to decrease to a greater extent in the DCL group than in the disease-induced group. CONCLUSIONS: In this study, we confirmed that the indicator materials (CO and DCL) can help suppress the development of BPH.

9.
Immune Netw ; 21(2): e15, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33996171

RESUMO

Abnormal inflammatory responses are closely associated with intestinal microbial dysbiosis. Oral administration of Qmatrix-diabetes-mellitus complex (QDMC), an Aloe gel-based formula, has been reported to improve inflammation in type 2 diabetic mice; however, the role of the gut microbiota in ameliorating efficacy of QDMC remains unclear. We investigated the effect of QDMC on the gut microbiota in a type 2 diabetic aged mouse model that was administered a high-fat diet. Proinflammatory (TNF-α and IL-6) and anti-inflammatory (IL-4 and IL-10) cytokine levels in the fat were normalized via oral administration of QDMC, and relative abundances of Bacteroides, Butyricimonas, Ruminococcus, and Mucispirillum were simultaneously significantly increased. The abundance of these bacteria was correlated to the expression levels of cytokines. Our findings suggest that the immunomodulatory activity of QDMC is partly mediated by the altered gut microbiota composition.

10.
Macromol Rapid Commun ; 31(3): 281-8, 2010 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-21590903

RESUMO

A method for growing polymers directly from the surface of graphene oxide is demonstrated. The technique involves the covalent attachment of an initiator followed by the polymerization of styrene, methyl methacrylate, or butyl acrylate using atom transfer radical polymerization (ATRP). The resulting materials were characterized using a range of techniques and were found to significantly improve the solubility properties of graphene oxide. The surface-grown polymers were saponified from the surface and also characterized. Based on these results, the ATRP reactions were determined to proceed in a controlled manner and were found to leave the structure of the graphene oxide largely intact.

11.
Nano Lett ; 9(4): 1593-7, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19265429

RESUMO

We report that homogeneous colloidal suspensions of chemically modified graphene sheets were readily produced in a wide variety of organic solvent systems. Two different sets of solubility parameters are used to rationalize when stable colloidal suspensions of graphene oxide sheets and, separately, of reduced graphene oxide sheets in a given solvent type are possible and when they are not. As an example of the utility of such colloidal suspensions, "paperlike" materials generated by very simple filtration of the reduced graphene oxide sheets had electrical conductivity values as high as 16,000 S/m.

12.
Front Microbiol ; 10: 1947, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31551944

RESUMO

Dysbiosis of the gut microbiota is a contributing factor for obesity-related metabolic diseases such as hyperglycemia and hyperlipidemia. Pharmacotherapy for metabolic diseases involves the modulation of gut microbiota, which is suggested to be a potential therapeutic target. In this study, the modulation of gut microbiota by statins (cholesterol-lowering drugs: atorvastatin and rosuvastatin) was investigated in an aged mouse model of high-fat diet-induced obesity, and the association between gut microbiota and immune responses was described. Atorvastatin and rosuvastatin significantly increased the abundance of the genera Bacteroides, Butyricimonas, and Mucispirillum. Moreover, the abundance of these genera was correlated with the inflammatory response, including levels of IL-1ß and TGFß1 in the ileum. In addition, oral fecal microbiota transplantation with fecal material collected from rosuvastatin-treated mouse groups improved hyperglycemia. From these results, the effect of statins on metabolic improvements could be explained by altered gut microbiota. Our findings suggest that the modulation of gut microbiota by statins has an important role in the therapeutic actions of these drugs.

13.
Immune Netw ; 19(4): e28, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31501716

RESUMO

IL-18 is a crucial pro-inflammatory cytokine that mediates chronic intestinal inflammation. Metformin, an anti-diabetic drug, was reported to have ameliorative effects on inflammatory bowel disease. Recently, the mechanism of action of metformin was explained as a modulation of gut microbiota. In this study, fecal microbiota transplantation (FMT) using fecal material from metformin-treated mice was found to upregulate the expression of GLP-1 and pattern-recognition receptors TLR1 and TLR4 for the improvement in hyperglycemia caused by a high-fat diet. Further, FMT downregulated the expression of the inflammatory cytokine IL-18. Within the genera Akkermansia, Bacteroides, and Butyricimonas, which were promoted by metformin therapy, Butyricimonas was found to be consistently abundant following FMT. Our findings suggest that modulation of gut microbiota is a key factor for the anti-inflammatory effects of metformin which is used for the treatment of hyperglycemia.

14.
Gut Microbes ; 9(2): 155-165, 2018 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-29157127

RESUMO

The gut microbiota is a contributing factor in obesity-related metabolic disorders. The effect of metformin on the gut microbiota has been reported; however, the relationship between the gut microbiota and the mechanism of action of metformin in elderly individuals is unclear. In this study, the effect of metformin on the gut microbiota was investigated in aged obese mice. The abundance of the genera Akkermansia, Bacteroides, Butyricimonas, and Parabacteroides was significantly increased by metformin in mice fed a high-fat diet. Metformin treatment decreased the expression of IL-1ß and IL-6 in epididymal fat, which was correlated with the abundance of various bacterial genera. In addition, both fecal microbiota transplantation from metformin-treated mice and extracellular vesicles of Akkermansia muciniphila improved the body weight and lipid profiles of the mice. Our findings suggest that modulation of the gut microbiota by metformin results in metabolic improvements in aged mice, and that these effects are associated with inflammatory immune responses.


Assuntos
Dieta Hiperlipídica/efeitos adversos , Epididimo/imunologia , Microbioma Gastrointestinal/efeitos dos fármacos , Metformina/farmacologia , Obesidade/metabolismo , Obesidade/microbiologia , Fatores Etários , Animais , Bactérias/classificação , Bactérias/efeitos dos fármacos , Glicemia/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Modelos Animais de Doenças , Epididimo/efeitos dos fármacos , Fezes/microbiologia , Microbioma Gastrointestinal/fisiologia , Regulação da Expressão Gênica/imunologia , Interleucina-1beta/genética , Interleucina-6/genética , Metabolismo dos Lipídeos/efeitos dos fármacos , Masculino , Metformina/uso terapêutico , Camundongos , Camundongos Endogâmicos C57BL , Obesidade/tratamento farmacológico , Obesidade/imunologia
15.
Nutrients ; 10(12)2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-30513715

RESUMO

Metabolic syndrome is characterized by a combination of several metabolic disorders, including obesity, hyperglycemia, and hyperlipidemia. A simultaneous occurrence is one of the most crucial features of metabolic syndrome; therefore, we selected an animal model in which this would be reflected. We fed C57BL/6N mice a high-fat diet for 23 weeks to develop metabolic syndrome and examined the efficacy of Rubus occidentalis (RO) for hyperglycemia and hypercholesterolemia. Oral administration of RO for 16 weeks improved hyperglycemia as indicated by significantly decreased fasting glucose levels and a glucose tolerance test. Improvements were also observed in hypercholesterolemia, in which significant decreases in serum total cholesterol, non-high-density lipoprotein (non-HDL) cholesterol, apolipoprotein A-1, and apolipoprotein B levels were observed. The time comparison of major biomarkers, observed at the initiation and termination of the experimental period, consistently supported the beneficial effects of RO on each metabolic phenotype. In addition, RO treatment attenuated the excessive fat accumulation in hepatic and adipose tissue by decreasing the size and number of lipid droplets. These results suggested that RO simultaneously exerted antihyperglycemic and antihyperlipidemic effects in mice with diet-induced metabolic syndrome.


Assuntos
Glicemia/metabolismo , Dieta Hiperlipídica , Metabolismo dos Lipídeos/efeitos dos fármacos , Síndrome Metabólica/tratamento farmacológico , Fitoterapia , Extratos Vegetais/uso terapêutico , Rubus , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Colesterol/sangue , Teste de Tolerância a Glucose , Hipercolesterolemia/tratamento farmacológico , Hipercolesterolemia/metabolismo , Hiperglicemia/tratamento farmacológico , Hiperglicemia/metabolismo , Hipoglicemiantes/farmacologia , Hipoglicemiantes/uso terapêutico , Hipolipemiantes/farmacologia , Hipolipemiantes/uso terapêutico , Lipoproteínas/sangue , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Síndrome Metabólica/metabolismo , Síndrome Metabólica/patologia , Camundongos Endogâmicos C57BL , Extratos Vegetais/farmacologia
16.
Biomol Ther (Seoul) ; 25(2): 140-148, 2017 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-27737523

RESUMO

Hyperlipidemia, which is closely associated with a fatty diet and aging, is commonly observed in the western and aged society. Therefore, a novel therapeutic approach for this disease is critical, and an immunological view has been suggested as a novel strategy, because hyperlipidemia is closely associated with inflammation and immune dysfunction. In this study, the effects of an aqueous extract of Rubus occidentalis (RO) in obese mice were investigated using immunological indexes. The mice were fed a high-fat diet (HFD) to induce hyperlipidemia, which was confirmed by biochemical analysis and examination of the mouse physiology. Two different doses of RO and rosuvastatin, a cholesterol synthesis inhibitor used as a control, were orally administered. Disturbances in immune cellularity as well as lymphocyte proliferation and cytokine production were significantly normalized by oral administration of RO, which also decreased the elevated serum tumor necrosis factor (TNF)-α level and total cholesterol. The specific immune-related actions of RO comprised considerable improvement in cytotoxic T cell killing functions and regulation of antibody production to within the normal range. The immunological evidence confirms the significant cholesterol-lowering effect of RO, suggesting its potential as a novel therapeutic agent for hyperlipidemia and associated immune decline.

17.
Small ; 6(2): 210-2, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19924742
18.
ACS Nano ; 5(4): 2433-9, 2011 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-21361332

RESUMO

Understanding and engineering the domain boundaries in chemically vapor deposited monolayer graphene will be critical for improving its properties. In this study, a combination of transmission electron microscopy (TEM) techniques including selected area electron diffraction, high resolution transmission electron microscopy (HR-TEM), and dark field (DF) TEM was used to study the boundary orientation angle distribution and the nature of the carbon bonds at the domain boundaries. This report provides an important first step toward a fundamental understanding of these domain boundaries. The results show that, for the graphene grown in this study, the 46 measured misorientation angles are all between 11° and 30° (with the exception of one at 7°). HR-TEM images show the presence of adsorbates in almost all of the boundary areas. When a boundary was imaged, defects were seen (dangling bonds) at the boundaries that likely contribute to adsorbates binding at these boundaries. DF-TEM images also showed the presence of a "twinlike" boundary.

19.
ACS Nano ; 5(9): 6916-24, 2011 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-21894965

RESUMO

Reproducible dry and wet transfer techniques were developed to improve the transfer of large-area monolayer graphene grown on copper foils by chemical vapor deposition (CVD). The techniques reported here allow transfer onto three different classes of substrates: substrates covered with shallow depressions, perforated substrates, and flat substrates. A novel dry transfer technique was used to make graphene-sealed microchambers without trapping liquid inside. The dry transfer technique utilizes a polydimethylsiloxane frame that attaches to the poly(methyl methacrylate) spun over the graphene film, and the monolayer graphene was transferred onto shallow depressions with 300 nm depth. The improved wet transfer onto perforated substrates with 2.7 µm diameter holes yields 98% coverage of holes covered with continuous films, allowing the ready use of Raman spectroscopy and transmission electron microscopy to study the intrinsic properties of CVD-grown monolayer graphene. Additionally, monolayer graphene transferred onto flat substrates has fewer cracks and tears, as well as lower sheet resistance than previous transfer techniques. Monolayer graphene films transferred onto glass had a sheet resistance of ∼980 Ω/sq and a transmittance of 97.6%. These transfer techniques open up possibilities for the fabrication of various graphene devices with unique configurations and enhanced performance.

20.
ACS Nano ; 5(1): 321-8, 2011 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-21162551

RESUMO

Using micro-Raman spectroscopy, the thermal conductivity of a graphene monolayer grown by chemical vapor deposition and suspended over holes with different diameters ranging from 2.9 to 9.7 µm was measured in vacuum, thereby eliminating errors caused by heat loss to the surrounding gas. The obtained thermal conductivity values of the suspended graphene range from (2.6 ± 0.9) to (3.1 ± 1.0) × 10(3) Wm(-1)K(-1) near 350 K without showing the sample size dependence predicted for suspended, clean, and flat graphene crystal. The lack of sample size dependence is attributed to the relatively large measurement uncertainty as well as grain boundaries, wrinkles, defects, or polymeric residue that are possibly present in the measured samples. Moreover, from Raman measurements performed in air and CO(2) gas environments near atmospheric pressure, the heat transfer coefficient for air and CO(2) was determined and found to be (2.9 +5.1/-2.9) and (1.5 +4.2/-1.5) × 10(4) Wm(-2)K(-1), respectively, when the graphene temperature was heated by the Raman laser to about 510 K.

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