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1.
Chem Res Toxicol ; 32(8): 1599-1618, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31315397

RESUMO

The recent emergence of hypervirulent clinical variants of Klebsiella pneumoniae (hvKP) causing community-acquired, invasive, metastatic, life-threatening infections of lungs, pleura, prostate, bones, joints, kidneys, spleen, muscles, soft-tissues, skin, eyes, central nervous system (CNS) including extrahepatic abscesses, and primary bacteremia even in healthy individuals has posed stern challenges before the existing treatment modalities. There is therefore an urgent need to look for specific and effective therapeutic alternatives against the said bacterial infection or recurrence. A new type of MoS2-modified curcumin nanostructure has been developed and evaluated as a potential alternative for the treatment of multidrug-resistant isolates. The curcumin quantum particles have been fabricated with MoS2 via a seed-mediated hydrothermal method, and the resulting MoS2-modified curcumin nanostructures (MQCs) have been subsequently tested for their antibacterial and antibiofilm properties against hypervirulent multidrug-resistant Klebsiella pneumoniae isolates. In the present study, we found MQCs inhibiting the bacterial growth at a minimal concentration of 0.0156 µg/mL, while complete inhibition of bacterial growth was evinced at concentration 0.125 µg/mL. Besides, we also investigated their biocompatibility both in vitro and in vivo. MQCs were found to be nontoxic to the SiHa cells at a dose as high as 1024 µg/mL on the basis of the tested adhesion, spreading of the cells, and also on the various serological, biochemical, and histological investigations of the vital organs and blood of the Charles Foster Rat. These results suggest that MQCs have potent antimicrobial activities against hvKP and other drug resistant isolates and therefore may be used as broad spectrum antibacterial and antibiofilm agents.

2.
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
3.
J Nanosci Nanotechnol ; 19(9): 5674-5686, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-30961724

RESUMO

Recently, there has been growing attention and effort to search for new microbicidal drugs which present different mode of action from those already existing, as an alternative to the global threat of fungal and bacterial multi drug resistance (MDR). Here we propose biological synthesis of SnO2 nanoparticles using mammalian cells as an economic and ecofriendly platform. This presents a novel biogenic method for SnO2 synthesis using metal binding peptides extracted from MCF-7 human cancer cells, which induces the biomineralization of SnO2 nanoparticles. A series of electron donor functional groups and metal binding sites in these peptides reacts with Sn2+ ions and directs the growth of SnO2 nanoparticles without addition of toxic redox and capping agents in the reaction system. Since peptides present reactive sites in aqueous solution at room temperature, a facile reaction environment can be easily achieved. Furthermore, by tuning the reactants' concentration and pH, the size, shape and 3D-structures of SnO2 nanoparticles can be controlled. Peptides also ensure biocompatibility, and SnO2 nanoparticles provide antibacterial properties, which broadens their applications in biomedical fields.

4.
Chemosphere ; 224: 796-804, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30851531

RESUMO

Rapidly expanding nanoparticle industries are predicted to have turnover of ∼$173.95 billion by 2025, indicating an urgency to study their comprehensive toxicological impact(s). Toxic effects of Graphene Oxide (GO) on oxidative stress physiology especially at mitochondrial level and redox modulation in fish in general and in climbing perch Anabas testudineus is absent. Therefore, we have investigated the toxic impacts of sub lethal doses of GO on selected oxidative stress physiology markers, protein and nucleic acid content along with haematological parameters in A. testudineus. Discriminant function and correlation analyses suggest that GO had toxic effects on the fish, as revealed from the studied parameters. Liver and gill tissues had shown strong response to GO than muscle. Augmented gradual accumulation of cellular lipid peroxides, specifically in mitochondria, was noticed. Activity of superoxide dismutase, catalase, and glutathione-S-transferase was augmented in contrast to the lowered level of the reduced glutathione titre. Alleviated total red blood corpuscle count and haemoglobin titre was parallel with an augmentation of white blood corpuscle count under GO administration. The protein level was also alleviated gradually in liver with clear changes in tissue specific nucleic acid levels, which was reduced under GO treatment. Results of the present study indicate that GO induces oxidative stress in cell and mitochondria in fish. Therefore, very careful future practices of use of GO directly, or as cargo in environmental monitoring processes in aquatic models in vitro in general and Pisces model in particular are suggested.


Assuntos
Grafite/toxicidade , Peroxidação de Lipídeos/efeitos dos fármacos , Mitocôndrias/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Percas/metabolismo , Animais , Catalase/metabolismo , Monitoramento Ambiental , Brânquias/metabolismo , Glutationa/metabolismo , Glutationa Peroxidase/metabolismo , Glutationa Transferase/metabolismo , Fígado/metabolismo , Nanopartículas/toxicidade , Oxirredução/efeitos dos fármacos , Alimentos Marinhos , Superóxido Dismutase/metabolismo
5.
J Photochem Photobiol B ; 189: 292-297, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30445361

RESUMO

Acetylsalicylic acid commonly termed as aspirin (AS) is a well known antipyretic and anti-inflammatory drug which can also be used to reduce death risks due to heart attack. In addition to this, it also exhibits some adverse effect such as gastrointestinal, tinnitus, Reye's syndrome. The side effects of AS such as gastrointestinal ulcer, tinnitus and Reye's syndrome are caused due to conversion of AS into its active metabolite salicylic acid (SAL). Conversion of AS into SAL has been investigated generally at basic pH. Since the pH of Gastrointestinal tract is on average neutral ranging from 6.5-7.4. Therefore in the present research work, in vitro conversion of AS to SAL was detected at neutral pH in both aqueous medium and human blood serum samples by time series fluorescence measurements and DFT study. The SAL obtained from AS at neutral pH was observed to be stable for ~ 6 and ~ 4 days in aqueous medium and blood serum, respectively. The mechanism of conversion of AS into SAL was investigated using the transition state theory employing density functional theory (DFT). On the basis of DFT calculation the in vitro formation of SAL from AS at neutral pH was found to involve two intermediate transition states.

6.
Front Microbiol ; 9: 423, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29662469

RESUMO

Salinity stress is one of the serious factors, limiting production of major agricultural crops; especially, in sodic soils. A number of approaches are being applied to mitigate the salt-induced adverse effects in agricultural crops through implying different halotolerant microbes. In this aspect, a halotolerant, Exiguobacterium profundum PHM11 was evaluated under eight different salinity regimes; 100, 250, 500, 1000, 1500, 2000, 2500, and 3000 mM to know its inherent salt tolerance limits and salt-induced consequences affecting its natural metabolism. Based on the stoichiometric growth kinetics; 100 and 1500 mM concentrations were selected as optimal and minimal performance limits for PHM11. To know, how salt stress affects the expression profiles of regulatory genes of its key metabolic pathways, and total production of important metabolites; biomass, carotenoids, beta-carotene production, IAA and proline contents, and expression profiles of key genes affecting the protein folding, structural adaptations, transportation across the cell membrane, stress tolerance, carotenoids, IAA and mannitol production in PHM11 were studied under 100 and 1500 mM salinity. E. profundum PHM11 showed maximum and minimum growth, biomass and metabolite production at 100 and 1500 mM salinity respectively. Salt-induced fine-tuning of expression profiles of key genes of stress pathways was determined in halotolerant bacterium PHM11.

7.
J Oral Maxillofac Pathol ; 22(Suppl 1): S65-S68, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29491609

RESUMO

Adenoid cystic carcinomas (ADCCs) are uncommon tumors, comprising < 1% of all head-and-neck cancers and 20%-25% of all salivary cancers. The most common presenting symptom of the lesion is a slowly growing mass followed by pain due to the propensity of these tumors for perineural invasion. The tumor is most often clinically deceptive by its small size and slow growth, which actually overlies its extensive subclinical invasion and marked ability for early metastasis making the prognosis questionable, aptly referred as "wolf in sheep's clothing." Cribriform, tubular and solid are the three recognized histopathological patterns. In ADCC, one of the important prognostic factors is the histological grade determined by the percentage of solid component in the tumor, which in the present study comprise more than 30% of the entire lesion rendering it an unfavorable prognosis.

8.
Biosens Bioelectron ; 105: 173-181, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29412942

RESUMO

Motivation behind the present work is to fabricate a cost effective and scalable biosensing platform for an easy and reliable detection of cancer biomarker Carcinoembryonic antigen (CEA). Here, we report the sensitive and selective detection of CEA using graphene based bio-sensing platform. Large sized (~ 2.5 × 1.0cm2), uniform, continuous, single and few layers graphene films have been grown on copper (Cu) substrate employing chemical vapor deposition (CVD) technique using hexane as a liquid precursor. Functional group has been created over Graphene/Cu substrate through π-π stacking of 1- pyrenebutanoic acid succinimidyl ester (PBSE). Further, to make the sensor specific to CEA, antibody of CEA (anti-CEA) has been covalently immobilized onto PBSE/Graphene/Cu electrode. Selective and sensitive detection of CEA is achieved by anti-CEA/PBSE/Graphene/Cu electrode through electrochemical impedance spectroscopy (EIS) measurements. Under optimal condition, the fabricated sensor shows linear response in the physiological range 1.0-25.0ngmL-1 (normal value ~ 5.0ngmL-1), revealing sensitivity 563.4Ωng-1mLcm-2 with a correlation coefficient of 0.996 and limit of detection (LOD) 0.23ngmL-1. In this way, one step electrode fabrication with high specific surface area provides a light weight, low cost, reliable and scalable novel biosensing platform for sensitive and selective detection of CEA. We believe that this bioelectrode equipped with specific recognition elements could be utilized for detection of other biomolecules too.


Assuntos
Anticorpos Imobilizados/química , Técnicas Biossensoriais/instrumentação , Antígeno Carcinoembrionário/análise , Grafite/química , Animais , Antígeno Carcinoembrionário/sangue , Bovinos , Espectroscopia Dielétrica/instrumentação , Desenho de Equipamento , Humanos , Imunoensaio/instrumentação , Limite de Detecção , Modelos Moleculares , Reprodutibilidade dos Testes , Soroalbumina Bovina/química
9.
Spectrochim Acta A Mol Biomol Spectrosc ; 190: 506-512, 2018 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-28965066

RESUMO

We develop a simple colorimetric method for determination of free cholesterol in aqueous solution based on functionalized gold nanoparticles with cholesterol oxidase. Functionalized gold nanoparticles interact with free cholesterol to produce H2O2 in proportion to the level of cholesterol visually is being detected. The quenching in optical properties and agglomeration of functionalized gold nanoparticles play a key role in cholesterol sensing due to the electron accepting property of H2O2. While the lower ranges of cholesterol (lower detection limit i.e. 0.2mg/dL) can be effectively detected using fluorescence study, the absorption study attests evident visual color change which becomes effective for detection of higher ranges of cholesterol (lower detection limit i.e. 19mg/dL). The shades of red gradually change to blue/purple as the level of cholesterol detected (as evident at 100mg/dL) using unaided eye without the use of expensive instruments. The potential of the proposed method to be applied in the field is shown by the proposed cholesterol measuring color wheel.


Assuntos
Colesterol Oxidase/metabolismo , Colesterol/análise , Colorimetria/métodos , Ouro/química , Nanopartículas Metálicas/química , Técnicas Biossensoriais , Ácidos Graxos/química , Nanopartículas Metálicas/ultraestrutura , Espectrometria de Fluorescência , Espectroscopia de Infravermelho com Transformada de Fourier , Compostos de Sulfidrila/química , Propriedades de Superfície , Fatores de Tempo
10.
Biosens Bioelectron ; 101: 103-109, 2018 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-29054021

RESUMO

Highly fluorescent nitrogen doped carbon quantum dots (NCQDs) were synthesized using microwave assisted green method. It was characterized by Transmission Electron Microscopy (TEM), FTIR, UV-Visible absorption and Photoluminiscence (PL) techniques. The NCQDs were immobilized with an enzyme named quinolinate phoshphoribosyl transferase (QPRTase). The NCQDs immobilized by QPRTase was used as a fluorescent bioprobe for the selective detection of endogenous neurotoxin quinolinic acid (QA) whose elevated level in serum is marker of many neurological disorders such as Alzheimer's, Huntington's and HIV associated dementia (HAD) as well as deficiency of vitamin B6. Steady state PL studies were carried out to measure the PL response of the fabricated fluorescent bioprobe as a function of QA concentrations in human serum samples. This probe was found applicable in linear range [3.22-51µM] with the limit of detection ~ 6.51µM. It has desirable sensitivity ~ (0.02340±0.0001) µM-1, excellent stability for ~ 7 weeks and good reproducibility. The similar response of this fluorescent bioprobe for QA detection in triple distilled water and human serum shows that it is unaffected by variation in media. Hence, this fluorescent bioprobe can be employed for QA detection in serum sample for the early detection of many diseases.


Assuntos
Técnicas Biossensoriais/métodos , Carbono/química , Corantes Fluorescentes/química , Neurotoxinas/sangue , Nitrogênio/química , Pontos Quânticos/química , Ácido Quinolínico/sangue , Técnicas Biossensoriais/instrumentação , Enzimas Imobilizadas/química , Humanos , Limite de Detecção , Neurotoxinas/análise , Pentosiltransferases/química , Ácido Quinolínico/análise , Reprodutibilidade dos Testes
11.
Front Microbiol ; 8: 1517, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28848526

RESUMO

Bacterial biofilm has been reported to be associated with more than 80% of bacterial infections. Curcumin, a hydrophobic polyphenol compound, has anti-quorum sensing activity apart from having antimicrobial action. However, its use is limited by its poor aqueous solubility and rapid degradation. In this study, we attempted to prepare quantum dots of the drug curcumin in order to achieve enhanced solubility and stability and investigated for its antimicrobial and antibiofilm activity. We utilized a newer two-step bottom up wet milling approach to prepare Curcumin Quantum Dots (CurQDs) using acetone as a primary solvent. Minimum inhibitory concentration against select Gram-positive and Gram-negative bacteria was performed. The antibiofilm assay was performed at first using 96-well tissue culture plate and subsequently validated by Confocal Laser Scanning Microscopy. Further, biofilm matrix protein was isolated using formaldehyde sludge and TCA/Acetone precipitation method. Protein extracted was incubated with varying concentration of CurQDs for 4 h and was subjected to SDS-PAGE. Molecular docking study was performed to observe interaction between curcumin and phenol soluble modulins as well as curli proteins. The biophysical evidences obtained from TEM, SEM, UV-VIS, fluorescence, Raman spectroscopy, and zeta potential analysis confirmed the formation of curcumin quantum dots with increased stability and solubility. The MICs of curcumin quantum dots, as observed against both select gram positive and negative bacterial isolates, was observed to be significantly lower than native curcumin particles. On TCP assay, Curcumin observed to be having antibiofilm as well as biofilm degrading activity. Results of SDS-PAGE and molecular docking have shown interaction between biofilm matrix proteins and curcumin. The results indicate that aqueous solubility and stability of Curcumin can be achieved by preparing its quantum dots. The study also demonstrates that by sizing down the particle size has not only enhanced its antimicrobial properties but it has also shown its antibiofilm activities. Further, study is needed to elucidate the exact nature of interaction between curcumin and biofilm matrix proteins.

12.
Biosens Bioelectron ; 90: 224-229, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-27907873

RESUMO

Quinolinic acid (QA) is a metabolite of tryptophan degradation obtained through kynurenine pathway, produced naturally in the mammalian brain as well as in the human cerebrospinal fluid. The presence of QA ~10-40µM is a clear indicator of many neurological disorders as well as deficiency of vitamin B6 in human being. In the present work; rapid, sensitive and cost-effective bio-electrodes were prepared to detect the trace amount of endogenous neurotoxin (QA). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies were carried out to measure the electrochemical response of the fabricated bio-electrodes as a function of QA concentrations. These devices were found to exhibit desirable sensitivity of ~7.86mAµM-1cm-2 in wide concentration range (6.5µM-65mM). The lower detection limit of this device is as low as 6.5µM and it has excellent storage stability of ~30 days. The capability of the proposed electrochemical bio-sensor was also checked to detect QA in the real samples (human serum). These results reveal that the use of this electrochemical bio-sensor may provide a potential platform for the detection of QA in the real samples for the prior detection of many diseases.


Assuntos
Técnicas Biossensoriais/instrumentação , Técnicas Eletroquímicas/instrumentação , Ácido Quinolínico/sangue , Eletrodos , Enzimas Imobilizadas/química , Desenho de Equipamento , Grafite/química , Humanos , Limite de Detecção , Neurotoxinas/análise , Neurotoxinas/sangue , Oxirredução , Pentosiltransferases/química , Ácido Quinolínico/análise
13.
ACS Appl Mater Interfaces ; 8(18): 11698-710, 2016 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-27097308

RESUMO

The microwave-synthesized reduced graphene oxide (MRG), boron-doped reduced graphene oxide (B-MRG), nitrogen-doped reduced graphene oxide (N-MRG), boron-nitrogen-co-doped reduced graphene oxide (B-N-MRG), and TiO2-reinforced B-N-MRG (TiO2-B-N-MRG) nanomaterials have been synthesized and characterized by various state-of-the-art techniques, like Raman spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the tribological properties of prepared nanomaterials as antiwear additives in neutral paraffin oil have been evaluated using a four-ball machine at an optimized additive concentration (0.15% w/v). The tribological parameters, like mean wear scar diameter, coefficient of friction, and wear rates, revealed that these nanomaterials have potential to be developed as environmentally friendly sulfated-ash-, phosphorus-, and sulfur-free antiwear lubricant additives. The friction- and wear-reducing behavior of MRG increased upon successive doping of nitrogen, boron, and both nitrogen and boron. Among these additives, B-N-co-doped MRG shows superior tribological behavior in paraffin base oil. Besides this, the load-carrying properties of B-N-co-doped MRG have significantly improved after its reinforcement with TiO2 nanoparticles. A comparative study of the surface morphology of a lubricated track in the presence of various additives has been assessed by SEM and contact-mode atomic force microscopy. The X-ray photoelectron spectroscopy studies have proved that the excellent lubrication properties of TiO2-B-N-MRG are due to the in situ formation of a tribofilm composed of boron nitride, adsorbed graphene layers, and tribosintered TiO2 nanoparticles during the tribocontact. Being sulfur-, halogen-, and phosphorus-free, these graphene-based nanomaterials act as green antiwear additives, protecting interacting surfaces significantly from wear and tear.

14.
Biosens Bioelectron ; 77: 1008-15, 2016 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-26547427

RESUMO

Charge impurities and polar molecules on the surface of dielectric substrates has long been a critical obstacle to using graphene for its niche applications that involve graphene's high mobility and high sensitivity nature. Self-assembled monolayers (SAMs) have been found to effectively reduce the impact of long-range scatterings induced by the external charges. Yet, demonstrations of scalable device applications using the SAMs technique remains missing due to the difficulties in the device fabrication arising from the strong surface tension of the modified dielectric environment. Here, we use patterned SAM arrays to build graphene electronic devices with transport channels confined on the modified areas. For high-mobility applications, both rigid and flexible radio-frequency graphene field-effect transistors (G-FETs) were demonstrated, with extrinsic cutoff frequency and maximum oscillation frequency enhanced by a factor of ~2 on SiO2/Si substrates. For high sensitivity applications, G-FETs were functionalized by monoclonal antibodies specific to cancer biomarker chondroitin sulfate proteoglycan 4, enabling its detection at a concentration of 0.01 fM, five orders of magnitude lower than that detectable by a conventional colorimetric assay. These devices can be very useful in the early diagnosis and monitoring of a malignant disease.


Assuntos
Anticorpos Monoclonais/química , Proteoglicanas de Sulfatos de Condroitina/análise , Condutometria/instrumentação , Grafite/química , Proteínas de Membrana/análise , Células Neoplásicas Circulantes/química , Transistores Eletrônicos , Biomarcadores Tumorais/análise , Técnicas Biossensoriais/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Imunoensaio/instrumentação , Microquímica/instrumentação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
15.
Talanta ; 144: 745-54, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26452886

RESUMO

The present work proposes partially reduced graphene oxide-gold nanorods supported by chitosan (CH-prGO-AuNRs) as a potential bioelectrode material for enhanced glucose sensing. Developed on ITO substrate by immobilizing glucose oxidase on CH-prGO-AuNRs composite, these CH-prGO-AuNRs/ITO bioelectrodes demonstrate high sensitivity of 3.2 µA/(mg/dL)/cm(2) and linear range of 25-200 mg/dL with an ability to detect as low as 14.5 mg/dL. Further, these CH-prGO-AuNRs/ITO based electrodes attest synergistiacally enhanced sensing properties when compared to simple graphene oxide based CH-GO/ITO electrode. This is evident from one order higher electron transfer rate constant (Ks) value in case of CH-prGO-AuNRs modified electrode (12.4×10(-2) cm/s), in contrast to CH-GO/ITO electrode (6×10(-3) cm/s). Additionally, very low Km value [15.4 mg/dL(0.85 mM)] ensures better binding affinity of enzyme to substrate which is desirable for good biosensor stability and resistance to environmental interferences. Hence, with better loading capacity, kinetics and stability, the proposed CH-prGO-AuNRs composite shows tremendous potential to detect several bio-analytes in the coming future.


Assuntos
Técnicas Biossensoriais/métodos , Ouro/química , Grafite/química , Óxidos/química , Técnicas Biossensoriais/instrumentação , Quitosana/química , Eletroquímica , Eletrodos , Glucose/análise , Glucose Oxidase/química , Glucose Oxidase/metabolismo , Nanotubos/química , Oxirredução , Compostos de Estanho/química
16.
ACS Appl Mater Interfaces ; 7(35): 19831-42, 2015 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-26287816

RESUMO

The electromagnetic interference (EMI) shielding of reduced graphene oxide (MRG), B-doped MRG (B-MRG), N-doped MRG (N-MRG), and B-N co-doped MRG (B-N-MRG) have been studied in the Ku-band frequency range (12.8-18 GHz). We have developed a green, fast, and cost-effective microwave assisted route for synthesis of doped MRG. B-N-MRG shows high electrical conductivity in comparison to MRG, B-MRG and N-MRG, which results better electromagnetic interference (EMI) shielding ability. The co-doping of B and N significantly enhances the electrical conductivity of MRG from 21.4 to 124.4 Sm(-1) because N introduces electrons and B provides holes in the system and may form a nanojunction inside the material. Their temperature-dependent electrical conductivity follows 2D-variable range hopping (2D-VRH) and Efros-Shklovskii-VRH (ES-VRH) conduction model in a low temperature range (T<50 K). The spatial configuration of MRG after doping of B and N enhances the space charge polarization, natural resonance, dielectric polarization, and trapping of EM waves by internal reflection leading to a high EMI shielding of -42 dB (∼99.99% attenuation) compared to undoped MRG (-28 dB) at a critical thickness of 1.2 mm. Results suggest that the B-N-MRG has great potential as a candidate for a new type of EMI shielding material useful in aircraft, defense industries, communication systems, and stealth technology.

17.
Biosens Bioelectron ; 74: 207-13, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26143460

RESUMO

In the present study, we manifest that traditionally used gold nanoparticles when supported on molybdenum disulfide nanoribbons matrix (MoS2 NRs-Au NPs) show synergistically enhanced intrinsic peroxidase like catalytic activity and can catalyze the oxidation of 3,3',5,5' tetramethyl benzidine by H2O2 to produce a highly sensitive blue shade product depending on level of free cholesterol, when tested on complex system of human serum. Further the system attests appreciable kinetics, owing to Km value as low as 0.015 mM and better loading capacity (Vmax=6.7×10(-6) M s(-1)). Additionally, the proposed system is stable for weeks with ability to perform appreciably in wide pH (3-6) and temperature range (25-60 °C). Utilizing this potential, the present work proposes a cholesterol detection color wheel which is used along with cost effective cholesterol detection strips fabricated out of proposed MoS2 NRs-Au NPs system for quick and reliable detection of free cholesterol using unaided eye.


Assuntos
Colesterol/sangue , Dissulfetos/química , Ouro/química , Nanopartículas Metálicas/química , Molibdênio/química , Benzidinas/química , Técnicas Biossensoriais , Catálise , Colorimetria , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Nanopartículas Metálicas/ultraestrutura , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Oxirredução
18.
Appl Biochem Biotechnol ; 176(2): 480-92, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25809996

RESUMO

We report a surfactant-free synthesis of monodispersed gold nanoparticles (AuNPs) with average size of 15 nm. An approach for visual and fluorescent sensing of urea in aqueous solution based on shift in surface plasmon band (SPB) maxima as well as quench in fluorescence intensity. To enable the urea detection, we functionalized the thiol-capped gold nanoparticles with urease, the enzyme specific to urea using carbodiimide chemistry. The visible color changed of the gold colloidal solution from red to blue (or purple); this was evident from quenching in absorbance and fluorescence intensity, is the principle applied here for the sensing of urea. The solution turns blue when the urea concentration exceeds 8 mg/dL which reveals visual lower detection limit. The lower detection limits governed by the fluorescence quenching were found 5 mg/dL (R(2) = 0.99) which is highly sensitive and selective compared to shift in SPB maxima. The approach depicted here seems to be important in clinical diagnosis.


Assuntos
Fluorescência , Ouro/química , Nanopartículas Metálicas/química , Ureia/análise , Urease/química , Enzimas Imobilizadas/química
19.
Appl Biochem Biotechnol ; 174(3): 960-70, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24916804

RESUMO

We report results of the studies relating to the fabrication of a highly sensitive label free biosensor based on graphene oxide (GO) platform for the detection of aflatoxin B1 (AFB1) which is most toxic and predominant food toxin, using electrochemical impedance spectroscopy. The structural and optical characterization of GO/Au and anti-AFB1/GO/Au has been done by electron microscopy, Raman, X-ray diffraction (XRD), UV-vis and electrochemical impedance spectroscopy (EIS). The impedimetric sensing response of immunoelectrode as a function of AFB1 concentration reveals wider linear detection range (0.5-5 ng/ml), high sensitivity (639 Ω ng(-1) ml), improved detection limit (0.23 ng ml(-1)) and good stability (5 weeks) for the label-free detection. Association constant (k a) for antigen-antibody interaction obtained as 0.46 ng ml(-1) indicates high affinity.


Assuntos
Aflatoxina B1/isolamento & purificação , Anticorpos/química , Técnicas Biossensoriais , Grafite/química , Aflatoxina B1/imunologia , Anticorpos/imunologia , Espectroscopia Dielétrica , Análise de Alimentos , Ouro/química , Humanos , Óxidos/química , Difração de Raios X
20.
Biosens Bioelectron ; 60: 201-9, 2014 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-24813908

RESUMO

Surface plasmon resonance (SPR) screening of monoclonal and polyclonal antibodies of Plasmodium falciparum (MoabPf and PoabPf) for recombinant Histidine rich protein-II antigen (Ag) of Pf (rHRP-II Ag) was conducted in a real-time and label-free manner to select an appropriate antibody (Ab) for biosensor applications. In this study 4-mercaptobenzoic acid (4-MBA) modified gold SPR chip was used for immobilizing the Ag and then Ab was interacted. SEM image showed modification of SPR chip with 4-MBA and EDAX confirmed the presence of 4-MBA on the SPR chip. Equilibrium constant (KD) and maximum binding capacity of analyte (Bmax) values for the interaction of MoabPf or PoabPf with the immobilized rHRP-II Ag were calculated and found to be 0.517 nM and 48.61 m° for MoabPf and 2.288 nM and 46.80 m° for PoabPf, respectively. In addition, thermodynamic parameters such as ΔG, ΔH and ΔS were determined for the interaction between rHRP-II Ag and MoabPf or PoabPf and the values revealed that the interaction is spontaneous, exothermic and driven by entropy. The kinetics and thermodymanic results of this study revealed that the interaction between MoabPf and rHRP-II Ag is more effective than that of PoabPf due to the fact that MoabPf was derived from a single epitope (single clone) whereas the PoabPf was from the mixture of a number of epitopes (polyclones). Finally, SPR methodology was developed for the sensing of malarial antibodies. The limit of detection was found to be 5.6 pg with MoabPf which was found to be the best in our study.


Assuntos
Anticorpos Monoclonais/imunologia , Imunoensaio/métodos , Malária Falciparum/imunologia , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Ressonância de Plasmônio de Superfície/métodos , Técnicas Biossensoriais/métodos , Humanos , Malária Falciparum/diagnóstico , Plasmodium falciparum/isolamento & purificação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
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