Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 9.647
Filtrar
1.
J Agric Food Chem ; 67(39): 10977-10983, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31490679

RESUMO

In this study, an analytical method was developed and validated for simultaneous determination of five diamide insecticides (chlorantraniliprole, cyantraniliprole, flubendiamide, cyclaniliprole, and tetrachlorantraniliprole) in food matrices. Determination of the latter two diamide compounds is first reported. Samples were cleaned up by multiplug filters containing carbon nanotubes (CNT) or hydrophilic-lipophilic balanced copolymers (HLB) and classic dispersive solid phase extraction (d-SPE) procedures, respectively. The CNT multiplug filter performed the best in terms of process rapidity and cleanup efficiency; thus, it was finally chosen for sample cleanup. Instrumental analysis was completed in 5 min using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Mean recoveries of the five diamides ranged from 84.3 to 110.0%, with intraday and interday relative standard deviations (RSD) of less than 13.5%. Limits of quantitation (LOQ) of all analytes ranged from 0.005 to 0.01 mg kg-1 in different matrices. The results indicate this method is reliable for monitoring the five diamide insecticides in various foods.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Diamida/química , Filtração/métodos , Contaminação de Alimentos/análise , Inseticidas/química , Resíduos de Praguicidas/química , Espectrometria de Massas em Tandem/métodos , Diamida/isolamento & purificação , Filtração/instrumentação , Inseticidas/isolamento & purificação , Nanotubos de Carbono/química , Resíduos de Praguicidas/isolamento & purificação
2.
Environ Monit Assess ; 191(9): 566, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31418123

RESUMO

Mercury (Hg) is a pollutant that poses a global threat, and it was listed as one of the ten leading 'chemicals of concern' by the World Health Organization in 2017. The review aims to summarize the sources of Hg, its combined effects on the ecosystem, and its remediation in the environment. The flow of Hg from coal to fly ash (FA), soil, and plants has become a serious concern. Hg chemically binds to sulphur-containing components in coal during coal formation. Coal combustion in thermal power plants is the major anthropogenic source of Hg in the environment. Hg is taken up by plant roots from contaminated soil and transferred to the stem and aerial parts. Through bioaccumulation in the plant system, Hg moves into the food chain, resulting in potential health and ecological risks. The world average Hg concentrations reported in coal and FA are 0.01-1 and 0.62 mg/kg, respectively. The mass of Hg accumulated globally in the soil is estimated to be 250-1000 Gg. Several techniques have been applied to remove or minimize elevated levels of Hg from FA, soil, and water (soil washing, selective catalytic reduction, wet flue gas desulphurization, stabilization, adsorption, thermal treatment, electro-remediation, and phytoremediation). Adsorbents such as activated carbon and carbon nanotubes have been used for Hg removal. The application of phytoremediation techniques has been proven as a promising approach in the removal of Hg from contaminated soil. Plant species such as Brassica juncea are potential candidates for Hg removal from soil.


Assuntos
Poluentes Ambientais/análise , Poluentes Ambientais/toxicidade , Recuperação e Remediação Ambiental/métodos , Mercúrio/análise , Mercúrio/toxicidade , Biodegradação Ambiental , Carvão Mineral/análise , Cinza de Carvão/análise , Monitoramento Ambiental/métodos , Mostardeira/crescimento & desenvolvimento , Nanotubos de Carbono/química , Centrais Elétricas , Solo/química
3.
Sci Total Environ ; 685: 997-1005, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31390717

RESUMO

In this study, the morphology, ultrastructure, nutrient removal, metabolite levels, and interaction of an algal-bacterial consortium exposed to different concentrations of carboxylic single-walled carbon nanotubes (C-SWCNT) were investigated. At a C-SWCNT concentration of 0.05 mg·L-1, the removal rates of TN, NH3-N, PO43--P, and COD were 94.7%, 94.8%, 86.4% and 84.3%, respectively. When cells were exposed to 50 mg·L-1 C-SWCNT, its intracellular levels in individual algae and the algal-bacterial consortium were 23.6 µg·g-1 and 12.1 µg·g-1, respectively. C-SWCNT (0.05 mg·L-1) promoted the metabolism of fatty acids, amino acids, small molecules, and acid in the algal-bacterial consortium. The main response to the interaction of C-SWCNT and the consortium was the change in extracellular carbohydrate levels. C-SWCNT also increased chlorophyll a and glycine levels. These findings reveal new insights into our understanding of the biological responses and interactions between C-SWCNT and algal-bacterial consortium.


Assuntos
Consórcios Microbianos , Nanotubos de Carbono/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/microbiologia
4.
Int J Nanomedicine ; 14: 4475-4489, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31354270

RESUMO

Background: Effects of different nanoparticles (NPs) exposure at acutely non-cytotoxic concentrations are particularly worthy to figure out, compare, and elucidate. Objective: To investigate and compare the effect of a small library of NPs at non-cytotoxic concentration on the adherens junction of human umbilical vein endothelial cells (HUVECs), obtaining new insights of NPs safety evaluation. Materials and methods: The HUVECs layer was exposed to NPs including gold (Au), platinum (Pt), silica (SiO2), titanium dioxide (TiO2), ferric oxide (Fe2O3), oxidized multi-walled carbon nanotubes, with different surface chemistry and size distribution. Cellular uptake of NPs was observed by transmission electron microscopy. and the cytotoxicity was determined by Cell Counting Kit-8 assay. The NP-induced variation of intracellular reactive oxygen species (ROS) and catalase (CAT) activity was measured using the probe of 2'7'-dichlorodihydr fluorescein diacetate and a CAT analysis kit, respectively. The level of VE-cadherin of HUVECs was analyzed by Western blot, and the loss of adherens junction was observed with laser confocal microscopy. Results: The acutely non-cytotoxic concentrations of different NPs were determined and applied to HUVECs. The NPs increased the level of intracellular ROS and the activity of CAT to different degrees, depending on the characteristics. At the same time, the HUVECs lost their adherens junction protein VE-cadherin and gaps were formed between the cells. The NP-induced oxidative stress and gap formation could be rescued by the supplementary N-acetylcysteine in the incubation. Conclusion: The increase of intracellular ROS and CAT activity was one common effect of NPs, even at the non-cytotoxic concentration, and the degree was dependent on the composition, surface chemistry, and size distribution of the NP. The effect led to the gap formation between the cells, while could be rescued by the antioxidant. Therefore, the variation of adherens junction between endothelial cells was suggested to evaluate for NPs when used as therapeutics and diagnostics.


Assuntos
Junções Aderentes/metabolismo , Células Endoteliais da Veia Umbilical Humana/metabolismo , Nanopartículas/química , Catalase/metabolismo , Morte Celular , Sobrevivência Celular , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Humanos , Nanopartículas/ultraestrutura , Nanotubos de Carbono/química , Estresse Oxidativo , Tamanho da Partícula , Espécies Reativas de Oxigênio/metabolismo
5.
J Chromatogr A ; 1602: 168-177, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31303311

RESUMO

In this work, we presented the preparation of magnetic carbon nanotubes (MCNTs) functionalized with molecularly imprinted polymers (MIPs) for effective removal of aristolochic acid I (AAI) in traditional Chinese medicine (TCM). MCNTs@AAI-MIPs was obtained via a facile and environmental friendly sol-gel process. Firstly, MCNTs were synthesized by a solvothermal method. Then, the template molecules were self-assembled with the functional monomer phenyltrimethoxysilane (PTMOS) in the presence of ethanol and water. Finally, AAI-MIPs film was coated on the MCNTs to obtain product MCNTs@AAI-MIPs using tetraethyl-orthosilicate (TEOS) as cross-linker. The morphology and structure of prepared MIPs were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen gas adsorption and vibrating sample magnetometer (VSM). The adsorption properties were demonstrated by kinetic, isothermal and selective adsorption experiments. The results showed that the imprinted nanocomposites exhibited fast separation rate (10 s), high adsorption capacity (18.54 µg∙mg-1), short kinetic equilibrium time (15 min), and good selectivity to template molecule with imprinting factor (IF) of 3.17. A regression equation (y=57294x-4734.1) with good linearity was obtained in the concentration range of 0.1-200 µg∙mg-1 for AAI with a correlation coefficient (R2) of 0.9998. The limit of detection (LOD, S/N=3) was 0.034 µg∙mg-1. Moreover, high recoveries ranged from 80% to 110% (RSD=3.27%-8.16%) were received in spiked TCM samples. The results suggested that the proposed MCNTs@AAI-MIPs could efficiently and specifically capture AAI from an actual complex TCM samples.


Assuntos
Ácidos Aristolóquicos/isolamento & purificação , Magnetismo , Impressão Molecular/métodos , Nanotubos de Carbono/química , Polímeros/química , Adsorção , Cinética , Nanotubos de Carbono/ultraestrutura , Nitrogênio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura Ambiente , Difração de Raios X
6.
Biomater Sci ; 7(9): 3906-3917, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31322163

RESUMO

Cardiovascular diseases represent a major socio-economic burden. In recent years, considerable effort has been invested in optimizing cell delivery strategies to advance cell transplantation therapies to restore heart function for example after an infarct. A particular issue is that the implantation of cells using a non-electroconductive matrix potentially causes arrhythmia. Here, we demonstrate that our hydrazide-functionalized nanotubes-pericardial matrix-derived electroconductive biohybrid hydrogel provides a suitable environment for maturation of human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes. hiPSC-derived cardiomyocytes exhibited an improved contraction amplitude (>500%) on conductive hydrogels compared to cells cultured on Matrigel®. This was accompanied by increased cellular alignment, enhanced connexin 43 expression, and improved sarcomere organization suggesting maturation of the hiPSC-derived cardiomyocytes. Sarcomeric length of these cells increased from 1.3 to 1.7 µm. Moreover, 3D cell-laden engineered tissues exhibited enhanced calcium handling as well as positive response to external electrical and pharmaceutical stimulation. Collectively, our data indicate that our biohybrid hydrogels consisting of solubilized nanostructured pericardial matrix and electroconductive positively charged hydrazide-conjugated carbon nanotubes provide a promising material for stem cell-based cardiac tissue engineering.


Assuntos
Materiais Biocompatíveis/química , Hidrogéis/química , Células-Tronco Pluripotentes Induzidas/citologia , Miócitos Cardíacos/citologia , Nanotubos de Carbono/química , Pericárdio/química , Tecidos Suporte/química , Biomarcadores/metabolismo , Cálcio/metabolismo , Diferenciação Celular , Proliferação de Células , Sobrevivência Celular , Colágeno/química , Conexina 43/metabolismo , Combinação de Medicamentos , Condutividade Elétrica , Humanos , Laminina/química , Células-Tronco Mesenquimais/citologia , Tamanho da Partícula , Proteoglicanas/química
7.
Food Chem ; 300: 125179, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325751

RESUMO

In this work, a disposable and portable aptasensor for the fast and sensitive detection of oxytetracycline (OTC) using gold nanoparticles (AuNPs)/carboxylated multi-walled carbon nanotubes (cMWCNTs)@thionine connecting complementary strand of aptamer (cDNA) as signal tags was constructed. The substrate electrode of the aptasensor was thin film gold electrode (TFGE), which have the advantages of portable and uniform performance. In the presence of OTC, OTC competed with cDNA to combine with aptamer. The bioconjugate (AuNPs/cMWCNTs/cDNA@thionine) was released from the TFGE. Thus, the electrochemical signal declined. Under optimized conditions, the aptasensor exhibited good stability, high selectivity and high sensitivity. Furthermore, the developed electrochemical aptamer-based TFGE had a wide dynamic range of 1 × 10-13-1 × 10-5 g mL-1 for target OTC with a low detection limit of 3.1 × 10-14 g mL-1 and was successfully used for the determination of OTC in chicken sample.


Assuntos
Técnicas Eletroquímicas/métodos , Eletrodos , Contaminação de Alimentos/análise , Oxitetraciclina/análise , Produtos Avícolas/análise , Animais , Antibacterianos/análise , Aptâmeros de Nucleotídeos , Galinhas , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Ouro/química , Limite de Detecção , Nanopartículas Metálicas/química , Nanotubos de Carbono/química , Sensibilidade e Especificidade
8.
Food Chem ; 298: 124981, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260993

RESUMO

Development of an effective sensor for sensing glucose in commercially available "sugar free" food products is important as people are becoming diabetic health conscious. Although multi-walled carbon nanotubes (MWCNTs) possess interesting electrical properties, their hydrophobic nature limits their applications. Their hydrophilicity can be improved through modification. In the present study, Inulin, that was isolated from Allium sativum L. using hot water diffusion and incorporated with titanium dioxide (TiO2), was used for the modification of MWCNTs. The as-synthesized MWCNT-Inulin-TiO2 bio-nanocomposite immobilized with glucose oxidase (GOx) was incorporated into the carbon paste matrix and was utilized for the sensing of glucose in food products. Differential pulse voltammetric studies revealed that the fabricated electrode demonstrated good linear range (1.6 nM to 1 µM) and was sensitive to nanomolar concentrations of glucose with a very low limit of detection up to 0.82 nM and exhibited a long term stability of 150 days.


Assuntos
Eletrodos , Análise de Alimentos/métodos , Glucose Oxidase/química , Glucose/análise , Nanocompostos/química , Enzimas Imobilizadas/química , Análise de Alimentos/instrumentação , Alho/química , Glucose/química , Inulina/química , Limite de Detecção , Nanotubos de Carbono/química , Sensibilidade e Especificidade , Titânio/química
9.
Chemphyschem ; 20(16): 2082-2092, 2019 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-31233266

RESUMO

The studied enzyme-based biocatalytic system mimics NXOR Boolean logic gate, which is a logical operator that corresponds to equality in Boolean algebra. It gives the functional value true (1) if both functional arguments (input signals) have the same logical value (0,0 or 1,1), and false (0) if they are different (0,1 or 1,0). The output signal producing reaction is catalyzed by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH), which is inhibited at acidic and basic pH values. Two other reactions catalyzed by esterase and urease produce acetic acid and ammonium hydroxide, respectively, shifting solution pH from the optimum pH for PQQ-GDH to acidic and basic values (1,0 and 0,1 input combinations, respectively), thus switching the enzyme activity off (output 0). When the input signals are not applied (0,0 combination) or both applied compensating each other (1,1 combination) the optimum pH is preserved, thus keeping PQQ-GDH running at the high rate (output 1). The biocatalytic cascade mimicking the NXOR gate was characterized optically and electrochemically. In the electrochemical experiments the PQQ-GDH enzyme communicated electronically with a conducting electrode support, thus resulting in the electrocatalytic current when signal combinations 0,0 and 1,1 were applied. The logic gate operation, when it was realized electrochemically, was also extended to the biomolecular release controlled by the gate. The release system included two electrodes, one performing the NXOR gate and another one activated for the release upon electrochemically stimulated alginate hydrogel dissolution. The studied system represents a general approach to the biocatalytic realization of the NXOR logic gate, which can be included in different catalytic cascades mimicking operation of concatenated gates in sophisticated logic circuitries.


Assuntos
Computadores Moleculares , Esterases/química , Glucose Desidrogenase/química , Lógica , Urease/química , Acetatos/química , Alginatos/química , Animais , Canavalia/enzimologia , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Fluoresceína-5-Isotiocianato/química , Corantes Fluorescentes/química , Concentração de Íons de Hidrogênio , Ferro/química , Nanotubos de Carbono/química , Suínos , Ureia/química
10.
Environ Pollut ; 251: 921-929, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31234258

RESUMO

The fast-growing production and application of carbon nanotube (CNT) materials in a variety of industrial products inevitably lead to their release to wastewater and surface water. CNT would experience oxidization in wastewater treatment plant due to the presence of large amount of disinfectants, such as H2O2 and O3, which in turn affects the environmental fates and risks of CNT. In this study, oxidized CNT materials (O-CNTs) were prepared by treating CNT with H2O2/UV and O3 (denoting as H2O2-CNT and O3-CNT, respectively). A variety of characterizations indicated that oxygen containing groups were generated on CNT surface upon the oxidation, and the O/C ratio increased in the order of pristine CNT < H2O2-CNT < O3-CNT. In the presence of Na+, K+ and Mg2+, the O-CNTs displayed better colloidal stability than the pristine CNT, and the stability increased with the oxidation degree (indicated by O/C ratio). This could be explained by the more negative surface charge and stronger hydrophilicity of the O-CNTs. Unexpectedly, in the presence of Ca2+, the most oxidized O3-CNT exhibited the poorest colloidal stability. The abundant carboxyl groups in O3-CNT provided effective binding sites for cation bridging effect through Ca2+ and led to stronger aggregation. Increasing pH was more favorable to disperse CNTs (both O-CNT and pristine CNT) in the presence of Na+, but much less effective in inhibiting the aggregation of O3-CNT in presence of Ca2+. This could be explained by the stronger cation bridging effect due to enhanced deprotonation the -COOH groups at higher pH conditions. The calculated Hamaker constants of the CNTs decreased with the oxidation degree, implying that there was lower van der Waals force between the O-CNTs. The Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation confirmed that O-CNTs had to overcome higher energy barrier and thus showed better colloidal stability than the pristine CNT in the presence of Na+.


Assuntos
Coloides/química , Peróxido de Hidrogênio/química , Nanotubos de Carbono/química , Ozônio/química , Interações Hidrofóbicas e Hidrofílicas , Magnésio/química , Oxirredução , Potássio/química , Sódio/química , Águas Residuárias/química , Água/química
11.
Environ Pollut ; 251: 945-951, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31234261

RESUMO

The removals of arsenic and selenium pollutants are always urgent desires for the water security. In this study, both sorption and catalysis strategies were combined for the effective removals of As(V) and Se(VI) over magnetic graphene oxide sheets (GOs)-oxidized carbon nanotubes (OCNTs) hydrogels. The sorption behavior facilitated the operation of catalysis reactions, meanwhile, the catalytic reduction promoted the release of occupied sorption sites and then restarted a new sorption-catalysis cycle. The synergic effect of sorption and catalysis realized 258.2 mg g-1 for As(V) enrichment capacity on MPG2T1, and ultra-fast sorption and catalysis equilibriums were identified within 9 min. In the case of Se(VI), a moderate enrichment performance was observed to be 46.2 mg g-1. Similarly, the ultra-fast sorption and reduction of Se(VI) were realized within 2 min. In the competition experiments, only SO42-, SO32-, and HPO42- showed interference for As(V) and Se(VI) removals. These results testified the superiority of the synergy effect of sorption and catalysis, and the feasibility of 3D magnetic GOs-OCNTs hydrogel in practical implementations.


Assuntos
Arsênico/química , Grafite/química , Nanotubos de Carbono/química , Selênio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Catálise , Hidrogéis/química
12.
Food Chem ; 297: 125005, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253325

RESUMO

Multiwalled carbon nanotubes molybdenum disulfide 3D nanocomposite (MWCNT-MoS2 NC) was successfully synthesized via eco-friendly hydrothermal method. The microstructural characterization of synthesized nanocomposite was carried out using different spectroscopic and microscopic techniques. Nanocomposite was activated using glutaraldehyde chemistry and used as a platform to immobilize Lens culinaris ß-galactosidase (Lsbgal) which resulted in 93% of immobilization efficiency. Attachment of Lsbgal onto nanocomposite was confirmed by AFM, FE-SEM, FTIR, and CLSM. The nanobiocatalyst showed broadening in operational pH and temperature working range. Remarkable increase in thermal stability was observed as compared to soluble enzyme. Nanobiocatalyst showed outstanding increase in storage stability, retained 92% of residual activity over a period of 8 months. This offers good reusability as it retained ∼50% residual activity up to 21 reuses and exhibited higher rate of lactose hydrolysis in whey. MWCNT-MoS2 NC conjugated to biomolecules can serve as a potential platform for fabrication of lactose biosensor.


Assuntos
Lactose/metabolismo , Lens (Planta)/enzimologia , Nanocompostos/química , Soro do Leite/metabolismo , beta-Galactosidase/metabolismo , Biocatálise , Dissulfetos/química , Estabilidade Enzimática , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Concentração de Íons de Hidrogênio , Molibdênio/química , Nanotubos de Carbono/química , Temperatura Ambiente , beta-Galactosidase/química
13.
Food Chem ; 297: 125035, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253330

RESUMO

In this study, an electrochemical system was established to detect the branched-chain amino acid aminotransferase (BCAT) activity in lactic acid bacteria (LAB). A nanocomposite of chitosan (CS) with multi-walled carbon nanotubes (MWCNTs) was synthesized, and the composite solution were uniformly spread over the glassy carbon electrode (GCE) surface by drop-casting to fabricate an electrochemical biosensor. The composite was characterized by scanning electron microscopy (SEM) and cyclic voltammetry (TEM). Results indicated that the MWCNTs-CS/GCE electrode exhibited higher stability and sensitivity, compared with the GCE electrode. The linear response for nicotinamide adenine dinucleotide (NADH) was 1.0-9.0 µM and the response limit was 0.12 µM. The system effectively and sensitively detected the BCAT activity by NADH concentration in the LAB culture, comparing with the optical method. The culture condition of LAB was optimized by using this system, evidencing that established method was available to detect the BCAT activity of LAB.


Assuntos
Proteínas de Bactérias/metabolismo , Técnicas Eletroquímicas/métodos , Lactobacillales/enzimologia , Transaminases/metabolismo , Técnicas Biossensoriais/métodos , Quitosana/química , Eletrodos , Proteínas Musculares/metabolismo , NAD/química , NAD/metabolismo , Nanotubos de Carbono/química
14.
Int J Nanomedicine ; 14: 3861-3874, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31213806

RESUMO

Purpose: Infections associated with medical devices that are caused by biofilms remain a considerable challenge for health care systems owing to their multidrug resistance patterns. Biofilms of Pseudomonas aeruginosa and Staphylococcus aureus can result in life-threatening situations which are tough to eliminate by traditional methods. Antimicrobial photodynamic inactivation (aPDT) constitutes an alternative method of killing deadly pathogens and their biofilms using reactive oxygen species (ROS). This study investigated the efficacy of enhanced in vitro aPDT of P. aeruginosa and S. aureus using malachite green conjugated to carboxyl-functionalized multi-walled carbon nanotubes (MGCNT). Both the planktonic cells and biofilms of test bacteria were demonstrated to be susceptible to the MGCNT conjugate. These MGCNT conjugates may thus be employed as a facile strategy for designing antibacterial and anti-biofilm coatings to prevent the infections associated with medical devices. Methods: Conjugation of the cationic dye malachite green to carbon nanotube was studied by UV-visible spectroscopy, high-resolution transmission electron microscopy, and Fourier transform infrared spectrometry. P. aeruginosa and S. aureus photodestruction were studied using MGCNT conjugate irradiated for 3 mins with a red laser of wavelength 660 nm and radiant exposure of 58.49 J cm-2. Results: Upon MGCNT treatment, S. aureus and P. aeruginosa were reduced by 5.16 and 5.55 log10 , respectively. Compared to free dye, treatment with MGCNT afforded improved phototoxicity against test bacteria, concomitant with greater ROS production. The results revealed improved biofilm inhibition, exopolysaccharide inhibition, and reduced cell viability in test bacteria treated with MGCNT conjugate. P. aeruginosa and S. aureus biofilms were considerably reduced to 60.20±2.48% and 67.59±3.53%, respectively. Enhanced relative MGCNT phototoxicity in test bacteria was confirmed using confocal laser scanning microscopy. Conclusion: The findings indicated that MGCNT conjugate could be useful to eliminate the biofilms formed on medical devices by S. aureus and P. aeruginosa.


Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Nanotubos de Carbono/química , Fotoquimioterapia , Plâncton/citologia , Plâncton/efeitos dos fármacos , Pseudomonas aeruginosa/fisiologia , Corantes de Rosanilina/farmacologia , Staphylococcus aureus/fisiologia , Cinética , Peroxidação de Lipídeos/efeitos dos fármacos , Viabilidade Microbiana/efeitos dos fármacos , Nanotubos de Carbono/ultraestrutura , Pseudomonas aeruginosa/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/efeitos dos fármacos
15.
Bioelectrochemistry ; 129: 211-217, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31200251

RESUMO

In this paper, we constructed MIL-53 (AlOHbdc, bdc = benzene-1,4-dicarboxylate) /CNTs and Prussian blue (PB) as the double sensitization material of the sensing platform, in which the MIL-53/CNTs hybrid can not only increase the specific surface area but also increase the conductivity of the sensor and PB can play a role in amplifying electrical signals and accelerating electron transmission. Pyrrole was used as monomer and E2 was used as template for electropolymerization to form conductive film. Moreover, the overoxidation/dedoping elution method were used to simplify the experimental process. Under optimal conditions, the MIECS exhibited an excellent sensitivity and high selectivity with a wide linear response range between 10-14 to 10-9 mol L-1 and an estimated detection limit of 6.19 × 10-15 mol L-1.


Assuntos
Técnicas Eletroquímicas , Estradiol/análise , Ferrocianetos/química , Estruturas Metalorgânicas/química , Impressão Molecular , Nanotubos de Carbono/química , Poluentes Químicos da Água/análise , Técnicas Eletroquímicas/métodos , Água Doce/análise , Impressão Molecular/métodos , Polímeros/química , Pirróis/química
16.
Bioelectrochemistry ; 129: 259-269, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31247532

RESUMO

Proton-conducting porous ceramic membranes were synthesized via a polymer-derived ceramic route and probed in a microbial fuel cell (MFC). Their chemical compositions were altered by adding carbon allotropes including graphene oxide (GO) and multiwall carbon nanotubes into a polysiloxane matrix as filler materials. Physical characteristics of the synthesized membranes such as porosity, hydrophilicity, mechanical stability, ion exchange capacity, and oxygen mass transfer coefficient were determined to investigate the best membrane material for further testing in MFCs. The ion exchange capacity of the membrane increased drastically after adding 0.5 wt% of GO at an increment of 9 fold with respect to that of the non-modified ceramic membrane, while the oxygen mass transfer coefficient of the membrane decreased by 52.6%. The MFC operated with this membrane exhibited a maximum power density of 7.23 W m-3 with a coulombic efficiency of 28.8%, which was significantly higher than the value obtained using polymeric Nafion membrane. Hence, out of all membranes tested in this study the GO-modified polysiloxane based ceramic membranes are found to have a potential to replace Nafion membranes in pilot scale MFCs.


Assuntos
Fontes de Energia Bioelétrica , Cerâmica/química , Grafite/química , Membranas Artificiais , Nanotubos de Carbono/química , Siloxanas/química , Fontes de Energia Bioelétrica/microbiologia , Eletricidade , Modelos Moleculares , Porosidade
17.
Int J Nanomedicine ; 14: 3245-3263, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31190792

RESUMO

Background: Bacterial resistance to antibiotics is one of the biggest challenges facing medicine today. Anti-adhesive therapy, using inhibitors of bacterial adhesion to epithelial cells, one of the first stages of infection, is a promising approximation in this area. The size, shape, number of sugar and their placement are variables that have to be taken into account in order to develop multivalent systems able to inhibit the bacterial adhesion based on sugar-lectin interaction. Materials and methods: In the present work we report a modular approach for the synthesis of water-soluble 1D-carbon nanotube-sugar nanoconstructs, with the necessary flexibility to allow an efficient sugar-lectin interaction. The method is based on the reaction of aryl diazonium salts generated in situ from aniline-substituted mannose and lactose derivatives with single wall carbon nanotubes (SWCNTs) sidewalls. Results: Two hybrid nanosystems, I-II, exposing mannose or lactose and having a tetraethylene glycol spacer between the sugar and the nanotube sidewall were rapidly assembled and adequately characterized. The sweet nano-objects were then tested for their ability to agglutinate and selectively inhibit the growth of uropathogenic Escherichia coli. These studies have shown that nanosystem I, exposing mannose on the nanotube surface is able to agglutinate and to inhibit the bacterial growth unlike nano-objects II exposing lactose. Conclusion: The results reported constitute a proof of principle in using mannose-coated 1D-carbon nanotubes as antiadhesive drugs that compete for FimH binding and prevent the uropathogenic bacteria from adhering to the urothelial surface.


Assuntos
Escherichia coli/citologia , Nanotubos de Carbono/química , Aglutinação , Aderência Bacteriana/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Escherichia coli/ultraestrutura , Manose/química , Nanotubos de Carbono/ultraestrutura , Polissacarídeos/síntese química , Polissacarídeos/química , Propriedades de Superfície
18.
Water Sci Technol ; 79(8): 1541-1549, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31169512

RESUMO

Batch adsorption and desorption of crystal violet (CV) and basic red 9 (BR9) on multi-walled carbon nanotubes (MWCNTs) were conducted. To investigate the possible mechanisms of adsorption/desorption hysteresis, oxidized MWCNTs (O-MWCNTs) with more oxygen-containing groups were obtained by oxidizing as-purchased MWCNTs (A-MWCNTs) using nitric acid. The adsorption kinetics could be described by the pseudo-second-order model, suggesting that chemical reactions are the rate-limiting steps. The adsorption isotherms were fitted well by the Langmuir model, which suggests that, in addition to π-π interactions, chemical reactions significantly affect the adsorption. The adsorption capacity decreased in the order of CV on A-MWCNTs, BR9 on A-MWCNTs, and BR9 on O-MWCNTs, possibly because the amidation between BR9 and the surface groups of MWCNTs results in steric hindrance, which limits the adsorption of BR9 to inner grooves between CNT bundles. Adsorption/desorption hysteresis was observed for BR9 but not for CV. It was found that the π-π interaction and molecular entrapment were not responsible for the adsorption/desorption hysteresis. The hysteresis might be caused by the irreversible amide bonds between BR9 and MWCNTs. The results indicate that the steric hindrance due to the three-dimensional structure of organic compounds plays an important role in both adsorption/desorption kinetics and equilibria.


Assuntos
Violeta Genciana/química , Modelos Químicos , Nanotubos de Carbono/química , Adsorção , Cinética , Compostos Orgânicos
19.
Anal Chim Acta ; 1074: 108-116, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159930

RESUMO

As an important "food and drug dual-use" product, chrysanthemums are widely used in both botanical medicine and food applications. However, the misuse of pesticides during chrysanthemum cultivation makes pesticide residue monitoring crucial. The aim of the present work was to address this practical demand for the simultaneous determination of multiple pesticide residues in various species of chrysanthemums. Both the sample pre-treatment and instrumental methods were systematically investigated. Seven chrysanthemum samples were extracted using acetonitrile and purified by dispersive solid-phase extraction with amino-modified multi-walled carbon nanotubes (MWCNTs-NH2) and C18 as the cleanup co-adsorbents. After optimizing the amounts of MWCNTs-NH2 and C18, matrix effects could not be avoided during LC-MS/MS analysis of 112 pesticides, although satisfactory recoveries were obtained. The use of SFC-MS/MS was evaluated, which demonstrated the significant positive role of SFC-MS/MS in reducing the matrix effects during pesticide residue analysis. In addition, the use of SFC-MS/MS permitted a shorter run time and afforded greater analytical efficiency. Method validation was further performed to evaluate the linearity, sensitivity, recovery, and precision of the developed method. Good linearity was observed for 92% of the analytes in the concentration range of 2-250 µg L-1 for all seven of the chrysanthemum samples. The LODs of the 112 pesticides ranged from 0.01 to 31.41 µg L-1, depending on the sample, while the mean recoveries of all of the spiked pesticides ranged from 81.8% to 102% for concentrations of 20, 50, and 200 µg kg-1. These results clearly demonstrate the applicability of the developed method for the simultaneous determination of multi-pesticides in various chrysanthemum samples.


Assuntos
Cromatografia com Fluido Supercrítico/métodos , Chrysanthemum/química , Resíduos de Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Acetonitrilos/química , Adsorção , Contaminação de Medicamentos/prevenção & controle , Contaminação de Alimentos/análise , Limite de Detecção , Nanotubos de Carbono/química , Extração em Fase Sólida/métodos
20.
Anal Chim Acta ; 1074: 131-141, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31159933

RESUMO

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s-SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu-s-SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10-10 M to 5 × 10-6 M with a limit of detection (LOD) of 3.75 × 10-11 M. In addition, the BSA/AChE-Glu-s-SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu-s-SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE-s-SWCNTs/GCE, s-SWCNTs/GCE and bare GCE.


Assuntos
Acetilcolinesterase/química , Inseticidas/análise , Metil Paration/análise , Nanocompostos/química , Nanotubos de Carbono/química , Soroalbumina Bovina/química , Animais , Técnicas Biossensoriais/métodos , Carbono , Bovinos , Reagentes para Ligações Cruzadas/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Electrophorus , Enzimas Imobilizadas/química , Contaminação de Alimentos/análise , Fragaria/química , Glutaral/química , Inseticidas/química , Limite de Detecção , Malus/química , Metil Paration/química , Reprodutibilidade dos Testes
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA