Cross‐linking gold nanoparticles aggregation method based on localised surface plasmon resonance for quantitative detection of miR‐155

MiR‐155 plays a critical role in the formation of cancers and other diseases. In this study, the authors aimed to design and fabricate a biosensor based on cross‐linking gold nanoparticles (AuNPs) aggregation for the detection and quantification of miR‐155. Also, they intended to compare this method with SYBR Green real‐time polymerase chain reaction (PCR). Primers for real‐time PCR, and two thiolated capture probes for biosensor, complementary with miR‐155, were designed. Citrate capped AuNPs (18.7 ± 3.6 nm) were synthesised and thiolated capture probes immobilised to AuNPs. The various concentrations of synthetic miR‐155 were measured by this biosensor and real‐time PCR method. Colorimetric changes were studied, and the calibration curves were plotted. Results showed the detection limit of 10 nM for the fabricated biosensor and real‐time PCR. Also, eye detection using colour showed the weaker detection limit (1 µM), for this biosensor. MiR‐133b as the non‐complementary target could not cause a change in both colour and UV–visible spectrum. The increase in hydrodynamic diameter and negative zeta potential of AuNPs after the addition of probes verified the biosensor accurately fabricated. This fabricated biosensor could detect miR‐155 simpler and faster than previous methods.Inspec keywords: RNA, molecular biophysics, biochemistry, cancer, nanoparticles, gold, aggregation, surface plasmon resonance, molecular configurations, nanosensors, enzymes, calibration, ultraviolet spectra, visible spectra, eye, hydrodynamics, electrokinetic effects, biosensors, nanofabricationOther keywords: cross‐linking gold nanoparticles aggregation method, localised surface plasmon resonance, quantitative detection, cancers, diseases, biosensor, miR‐155 detection, miR‐155 quantification, SYBR green real‐time polymerase chain reaction, thiolated capture probes, citrate capped AuNPs, synthetic miR‐155, real‐time PCR method, colorimetric changes, calibration curves, eye detection, colour, detection limit, MiR‐133b, noncomplementary target, UV‐visible spectrum, hydrodynamic diameter, negative zeta potential, Au     

Nano‐biosensor based on reduced graphene oxide and gold nanoparticles,for detection of phenylketonuria‐associated DNA mutation

Phenylketonuria (PKU)‐associated DNA mutation in newborn children can be harmful to his health and early detection is the best way to inhibit consequences. A novel electrochemical nano‐biosensor was developed for PKU detection, based on signal amplification using nanomaterials, e.g. gold nanoparticles (AuNPs) decorated on the reduced graphene oxide sheet on the screen‐printed carbon electrode. The fabrication steps were checked by field emission scanning electron microscope imaging as well as cyclic voltammetry analysis. The specific alkanethiol single‐stranded DNA probes were attached by self‐assembly methodology on the AuNPs surface and Oracet blue was used as an intercalating electrochemical label. The results showed the detection limit of 21.3 fM and the dynamic range of 80–1200 fM. Moreover, the selectivity results represented a great specificity of the nano‐biosensor for its specific target DNA oligo versus other non‐specific sequences. The real sample simulation was performed successfully with almost no difference than a synthetic buffer solution environment.Inspec keywords: biosensors, nanosensors, nanoparticles, graphene compounds, gold, nanomedicine, DNA, molecular biophysics, biomedical equipment, electrochemical sensors, electrochemical electrodes, field emission scanning electron microscopy, voltammetry (chemical analysis), self‐assembly, biochemistryOther keywords: reduced graphene oxide, gold nanoparticles, phenylketonuria‐associated DNA mutation, newborn children, electrochemical nanobiosensor, signal amplification, nanomaterials, reduced graphene oxide sheet, screen‐printed carbon electrode, field emission scanning electron microscopy imaging, cyclic voltammetry, alkanethiol single‐stranded DNA probes, self‐assembly methodology, Oracet blue, intercalating electrochemical label, Au‐CO     

Dual‐energy CT imaging of nasopharyngeal cancer cells using multifunctional gold nanoparticles

The purpose of this study is to measure the concentration of gold nanoparticles (AuNPs) attached to folic acid through cysteamin as the linker (FA‐Cys‐AuNPs) and AuNPs in KB human nasopharyngeal cancer cells using dual‐energy CT (DECT). In this study, nanoparticles with a size of ∼15 nm were synthesized and characterised using UV‐Vis, TEM, FTIR and ICP‐OES analyses. The non‐toxicity of nanoparticles was confirmed by MTT assay under various concentrations (40– 100 µg/ml) and incubation times (6, 12 and 24 h). To develop an algorithm for revealing different concentrations of AuNPs in cells, a corresponding physical phantom filled with 0.5 ml vials containing FA‐Cys‐AuNPs was used. The CT scan was performed at two energy levels (80 and 140 kVp). One feature of DECT is material decomposition, which allows separation and identification of different elements. The values obtained from the DECT algorithm were compared with values quantitatively measured by ICP‐OES. Cells were also incubated with AuNPs and FA‐Cys‐AuNPs at different concentrations and incubation times. Subsequently, by increasing the incubation time in the presence of FA‐Cys‐AuNPs, in comparison with AuNPs, DECT pixels were increased. Thus, FA‐Cys‐AuNPs could be a suitable candidate for targeted contrast agent in DECT molecular imaging of nasopharyngeal cancer cells.Inspec keywords: biomedical materials, phantoms, nanoparticles, computerised tomography, nanomedicine, cancer, toxicology, nanofabrication, gold, cellular biophysics, ultraviolet spectra, visible spectra, transmission electron microscopy, Fourier transform infrared spectraOther keywords: Au, time 24.0 hour, time 12.0 hour, time 6.0 hour, head cancer cells, DECT molecular imaging, DECT algorithm, material decomposition, physical phantom, MTT assay, ICP‐OES analyses, FTIR spectra, TEM, UV‐vis spectrophotometry, cysteamin, folic acid, gold nanoparticle concentration, nasopharyngeal cancer cells, dual‐energy CT imaging, neck cancer cells, KB human nasopharyngeal cancer cells, multifunctional gold nanoparticles     

Cu‐induced assembly of methanobactin‐modified gold nanoparticles and its peroxidase mimic activity

Methanobactin (Mb) is a small copper‐chelating molecule that functions as an agent for copper acquisition, uptake and copper‐containing methane monooxygenase catalysis in methane‐oxidising bacteria. The UV–visible spectral and fluorescence spectral suggested that Mb/Cu coordination complex as a monomer (Mb‐Cu), dimmer (Mb₂ ‐Cu) and tetramer (Mb₄ ‐Cu) could be obtained at different ratios of Mb to Cu (II). The kinetics of the oxidation of hydroquinone with hydrogen peroxide catalysed by the different Mb/Cu coordination complex were investigated. The results suggested that Mb₂ ‐Cu coordination form has highest catalytic capacity. Further, Mb‐modified gold nanoparticles (AuNPs) were obtained by ligand exchange and assembled into two‐ and three‐D nanocluster structure by metal‐organic coordination as driving force. It has been found that AuNPs increased the catalytic activity of Mb₂ ‐Cu on AuNPs. The more significant catalytic activity was exhibited by the nanocluster assembly with multi‐catalytic centres. This may be attributed to the multivalent collaborative characteristics of the catalytic active centres in the nanocluster network assembly. The assembly of Mb‐modified AuNPs can act as excellent nanoenzyme models for imitating peroxidase.Inspec keywords: nanoparticles, catalysis, oxidation, enzymes, microorganisms, nanobiotechnology, gold, organic compounds, reduction (chemical), visible spectra, molecular biophysics, ultraviolet spectra, biochemistry, copper, nanofabrication, fluorescenceOther keywords: Mb‐modified gold nanoparticles, catalytic active centres, Mb‐modified AuNPs, Cu‐induced assembly, methanobactin‐modified gold nanoparticles, peroxidase mimic activity, copper‐chelating molecule, copper‐containing methane monooxygenase catalysis, methane‐oxidising bacteria, fluorescence, Mb/Cu coordination complex, catalytic activity, UV–visible spectra, nanocluster assembly, Cu, Au     

Signal amplification strategy using gold/N ‐trimethyl chitosan/iron oxide magnetic composite nanoparticles as a tracer tag for high‐sensitive electrochemical detection

This study presents a novel signal amplification method for high‐sensitive electrochemical immunosensing. Gold (Au)/N ‐trimethyl chitosan (TMC)/iron oxide (Fe₃ O₄) (shell/shell/core) nanocomposite was used as a tracing tag to label antibody. The tag was shown to be capable of amplifying the recognition signal by high‐density assembly of Au nanoparticles (NPs) on TMC/Fe₃ O₄ particles. The remarkable conductivity of AuNPs provides a feasible pathway for electron transfer. The method was found to be simple, reliable and capable of high‐sensitive detection of human serum albumin as a model, down to 0.2 pg/ml in the range of 0.25–1000 pg/ml. Findings of the present study would create new opportunities for sensitive and rapid detection of various analytes.Inspec keywords: gold, filled polymers, conducting polymers, iron compounds, magnetic particles, nanoparticles, nanocomposites, nanosensors, electrochemical sensors, proteins, molecular biophysics, biomagnetism, biosensorsOther keywords: signal amplification strategy, gold‐N‐trimethyl chitosan‐iron oxide magnetic composite nanoparticles, tracer tag, high‐sensitive electrochemical detection, high‐sensitive electrochemical immunosensing, antibody, high‐density assembly, AuNP conductivity, electron transfer, human serum albumin, FeO‐Au     

Surface stress‐induced membrane biosensor based on double‐layer stable gold nanostructures for E. coli detection

The surface stress‐based biosensor has been applied in fast and sensitive identification of Escherichia coli (E. coli)with significance for public health, food, and water safety. However, the stable sensitive element of flexible biosensor based on surface stress is still crucial and challengeable. Here, the authors reported surface stress‐induced biosensors based on double‐layer stable gold nanostructures (D‐AuNS‐SSMB) for E. coli O157:H7 detection. Bacterial detection demonstrates the high stability of the biosensor. The resistance change of biosensor is linear to the logarithmic value of the E. coli O157:H7 concentrations ranging from 10³  to 10⁷  CFU/mL with a limit of detection (LOD) of 43 CFU/mL. The captured signals of D‐AuNS‐SSMB comes from surface stress generated by antigen–antibody binding. In addition, the biosensor exhibits good stability, reproducibility and specificity in detection of E. coli O157:H7 as well. This study provides a new preparation method of stable sensitive element for the E. coli detection.Inspec keywords: microorganisms, biosensors, gold, membranes, stress measurement, nanostructured materials, nanosensorsOther keywords: double‐layer stable gold nanostructures, D‐AuNS‐SSMB, bacterial detection, surface stress‐induced membrane biosensor, escherichia coli detection, water safety, stability, E. coli O157:H7 concentration detection, antigen–antibody binding, Au     

On‐chip label‐free impedance‐based detection of antibiotic permeation

Biosensors are analytical tools used for the analysis of biomaterial samples and provide an understanding about the biocomposition, structure, and function of biomolecules and/or biomechanisms by converting the biological response into an electrical and/or optical signal. In particular, with the rise in antibiotic resistance amongst pathogenic bacteria, the study of antibiotic activity and transport across cell membranes in the field of biosensors has been gaining widespread importance. Herein, for the rapid and label‐free detection of antibiotic permeation across a membrane, a microelectrode integrated microfluidic device is presented. The integrated chip consists of polydimethylsiloxane based microfluidic channels bonded onto microelectrodes on‐glass and enables us to recognize the antibiotic permeation across a membrane into the model membranes based on electrical impedance measurement, while also allowing optical monitoring. Impedance testing is label free and therefore allows the detection of both fluorescent and non‐fluorescent antibiotics. As a model membrane, Giant Unilamellar Vesicles (GUVs) are used and impedance measurements were performed by a precision inductance, capacitance, and resistance metre. The measured signal recorded from the device was used to determine the change in concentration inside and outside of the GUVs. We have found that permeation of antibiotic molecules can be easily monitored over time using the proposed integrated device. The results also show a clear difference between bilayer permeation that occurs through the lipidic bilayer and porin‐mediated permeation through the porin channels inserted in the lipid bilayer.     

Chip-based scanometric detection of mercuric ion using DNA-functionalized gold nanoparticles

We have developed a chip-based scanometric method for the detection of mercuric ion (Hg (2+)). This method takes advantage of the cooperative binding and catalytic properties of DNA-functionalized gold nanoparticles and the selective binding of a thymine-thymine mismatch for Hg (2+). The limit of detection of this assay in buffer and environmentally relevant samples (lake water) is 10 nM (2 ppb) Hg (2+), which is the U.S. Environmental Protection Agency (EPA) limit of [Hg (2+)] for drinkable water and 1 order of magnitude lower than previous colorimetric assays. This assay is capable of discriminating Hg (2+) from 15 other environmentally relevant metal ions. The method is attractive for potential point-of-use applications due to its high throughput, convenient readout, and portability.     

Nutratherapeutics approach against cancer: tomato‐mediated synthesised gold nanoparticles

In this study, an eco‐friendly biosynthesis of stable gold nanoparticles (T‐GNPs) was carried out using different concentrations of tomato juice (nutraceuticals) as a reducing agent and tetrachloroauric acid as a metal precursor to explore their potential application in cancer therapeutics. The synthesis of T‐GNPs was monitored by UV‐visible absorption spectroscopy, which unveiled their formation by exhibiting the typical surface plasmon absorption maxima at 522 nm. The size of T‐GNPs was found to be 10.86 ± 0.6 nm. T‐GNPs were characterised by dynamic light scattering, zeta potential, transmission electron microscopy analysis and Fourier transform infrared spectroscopy. T‐GNPs were further investigated for their anti‐cancer activity against human lung carcinoma cell line (A ₅₄₉) and human cervical cancer cell line wherein the IC₅₀ values were found to be 0.286 and 0.200 mM, respectively. T‐GNPs inhibited the growth of cancer cells by generating ROS and inducing apoptosis. T‐GNPs were found highly effective by virtue of their size, metallic property and capping molecules. Thus, this study opens up the prospects of using nutraceutical (tomato juice) as nutratherapeutic agent (T‐GNPs) against critical diseases like lung cancer and cervical cancer.Inspec keywords: gold, nanoparticles, particle size, cancer, ultraviolet spectra, visible spectra, electrokinetic effects, transmission electron microscopy, Fourier transform infrared spectra, cellular biophysics, spectrochemical analysis, nanomedicine, nanofabricationOther keywords: tomato‐mediated synthesised gold nanoparticles, tomato juice, reducing agent, tetrachloroauric acid, cancer therapeutics, UV‐visible absorption spectroscopy, surface plasmon absorption, dynamic light scattering, zeta potential, transmission electron microscopy analysis, Fourier transform infrared spectroscopy, human lung carcinoma cell line, anticancer activity, human cervical cancer cell line, nutratherapeutic agent, lung cancer, Au     

Biogenic gold nanoparticles for reduction of 4‐nitrophenol to 4‐aminophenol: an eco‐friendly bioremediation

The present study investigated the synthesis of gold nanoparticles (AuNPs) using mangrove plant extract from Avicennia marina as bioreductant for eco‐friendly bioremediation of 4‐nitrophenol (4‐NP). The AuNPs synthesised were confirmed by UV spectrum, transmission electron microscopy (TEM), X‐ray diffraction, Fourier transmission infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential. The AuNPs were found to be spherical in shape with size ranging from 4 to 13 nm, as evident by TEM and DLS. Further, the AuNPs were encapsulated with sodium alginate in the form of gold nano beads and used as heterogeneous catalyst and degrading agent to reduce 4‐NP. This reduction in 4‐NP into 4‐aminophenol was confirmed by UV and FTIR. The aqueous solution of 4‐NP peaked its absorbance at 320 nm, and shifted to 400 nm, with an intense yellow colour, appeared due to formation of 4‐nitrophenolate ion. After the addition of AuNps, the 4‐NP solution became colourless and peaked at 400 nm and reduced to 290 nm corresponding to the formation of 4‐aminophenol. Hence, the present work suggested the AuNPs as the potent, eco‐friendly bionanocomposite catalyst for bioremediation of 4‐NP.Inspec keywords: gold, nanoparticles, nanobiotechnology, nanofabrication, ultraviolet spectra, transmission electron microscopy, X‐ray diffraction, Fourier transform spectra, infrared spectra, electrokinetic effects, catalysts, nanocomposites, biochemistryOther keywords: biogenic gold nanoparticles, 4‐nitrophenol, 4‐aminophenol, eco‐friendly bioremediation, mangrove plant extract, Avicennia marina, bioreductant, UV spectrum, transmission electron microscopy, TEM, X‐ray diffraction, Fourier transmission infrared spectroscopy, FTIR, dynamic light scattering, DLS, zeta potential, degrading agent, 4‐nitrophenolate, bionanocomposite catalyst, size 4 nm to 13 nm, wavelength 400 nm, wavelength 290 nm, Au     

Anti‐triangle centrality‐based community detection in complex networks

Community detection has been extensively studied in the past decades largely because of the fact that community exists in various networks such as technological, social and biological networks. Most of the available algorithms, however, only focus on the properties of the vertices, ignoring the roles of the edges. To explore the roles of the edges in the networks for community discovery, the authors introduce the novel edge centrality based on its antitriangle property. To investigate how the edge centrality characterises the community structure, they develop an approach based on the edge antitriangle centrality with the isolated vertex handling strategy (EACH) for community detection. EACH first calculates the edge antitriangle centrality scores for all the edges of a given network and removes the edge with the highest score per iteration until the scores of the remaining edges are all zero. Furthermore, EACH is characterised by being free of the parameters and independent of any additional measures to determine the community structure. To demonstrate the effectiveness of EACH, they compare it with the state‐of‐the art algorithms on both the synthetic networks and the real world networks. The experimental results show that EACH is more accurate and has lower complexity in terms of community discovery and especially it can gain quite inherent and consistent communities with a maximal diameter of four jumps.Inspec keywords: biology computing, complex networks, graph theory, social sciences computingOther keywords: antitriangle centrality‐based community detection, complex networks, technological networks, social networks, biological networks, vertex properties, edge roles, community discovery, antitriangle property, community structure, edge antitriangle centrality, isolated vertex handling strategy, EACH, antitriangle centrality scores, synthetic networks, real world networks     

Fast colorimetric detection of copper ions using L-cysteine functionalized gold nanoparticles

This communication reports an efficient visual detection method of Cu2+ by L-cysteine functionalized gold nanoparticles in aqueous solution. Upon exposure to Cu2+, the gold nanoparticle solution changed from red to blue, in response to surface plasmon absorption of dispersed and aggregated nanoparticles. This colorimetric sensor allows a rapid quantitative assay of Cu2+ down to the concentration range of 10(-5) M. Recognition of Cu2+ and formation of the aggregates are proposed to occur via a 2 : 1 sandwich complex between L-cysteine and Cu2+.     

Phyto‐mediated synthesis,biological and catalytic activity studies of gold nanoparticles

In the present study, a phyto‐mediated synthesis of gold nanoparticles (AuNPs) using an isoflavone, Dalspinosin (5,7‐dihydroxy‐6,3′,4′‐trimethoxy isoflavone) isolated from the alcoholic extract of roots of Dalbergia coromandeliana is reported. It is observed that Dalspinosin itself acts both as a reducing and a capping agent in the synthesis of the nanoparticles (NPs). An ultraviolet–visible (UV–Vis) spectral study showed a surface plasmon resonance band at 526 nm confirming the formation of AuNPs. The NPs formed were characterised by UV–Vis spectroscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR‐TEM) with energy‐dispersive x‐ray spectroscopy (EDX) and dynamic light scattering. HR‐TEM analysis showed the synthesised AuNPs were spherical in shape with a size of 7.5 nm. The AuNPs were found to be stable for seven months when tested by in vitro methods showed good antioxidant and anti‐inflammatory activities. They also showed moderate anti‐microbial activities when tested against Gram positive (Staphylococcus aureus and Streptococcus sp), Gram negative bacterial strains (Klebsiella pneumonia and Klebsiella terrigena) and fungal strain (Candida glabrata). The biosynthesised AuNPs showed significant catalytic activity in the reduction of methylene blue with NaBH₄ to leucomethylene blue.Inspec keywords: biomedical materials, catalysis, Fourier transform infrared spectra, gold, light scattering, microorganisms, nanomedicine, nanoparticles, spectrochemical analysis, surface plasmon resonance, transmission electron microscopy, ultraviolet spectra, visible spectra, X‐ray chemical analysis, X‐ray diffractionOther keywords: phyto‐mediated synthesis, biological activity studies, catalytic activity studies, dalspinosin (5,7‐dihydroxy‐6,3′,4′‐trimethoxy isoflavone), alcoholic extract, roots, Dalbergia coromandeliana, ultraviolet‐visible spectral study, surface plasmon resonance band, UV‐Vis spectroscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction, high‐resolution transmission electron microscopy, EDX analysis, dynamic light scattering, HR‐TEM analysis, antioxidant activities, antiinflammatory activities, antimicrobial activities, Gram positive bacterial strains, Staphylococcus aureus, Streptococcus sp, Gram negative bacterial strains, wavelength 526 nm, size 7.5 nm, time 7 month, Au     

Microelectromechanical system‐based biosensor for label‐free detection of human cytomegalovirus

The human cytomegalovirus (HCMV) is an asymptomatic common virus that is typically harmless, but in some cases, it can be life threatening. Thus, there is an urgent need to develop novel diagnostic methods and strengthen the efforts to combat this virus. A microcantilever‐based biosensor functionalised with the UL83‐antibody of HCMV (UL83‐HCMV antibody) has been developed to detect the UL83‐antigen of HCMV (UL83‐HCMV antigen) at different concentrations ranging from 0.3 to 300 ng/ml. The response of the biosensor to the presence of UL83‐HCMV antigen was measured through the shift in resonance frequency before and after antigen–antibody binding. The system shows a low detection limit of 84 pg/ml, which is comparable to traditional sensors, and a detection time of less than 15 min was achieved. The selectivity of the sensor was demonstrated using three different proteins with and without the UL83‐HCMV antigen. The biosensor shows high selectivity for the UL83‐HCMV antigen. Mass loading by the UL83‐HCMV antigen was roughly estimated with a sensitivity of ∼30 fg/Hz. This technique is crucial for the fabrication of portable and low‐cost biosensors that can be used in real‐time monitoring and enables early medical diagnosis.     

Treatment of tumour tissue with radio‐frequency hyperthermia (using antibody‐carrying nanoparticles)

Intelligent inorganic nanoparticles were designed and produced for use in imaging and annihilating tumour cells by radio‐frequency (RF) hyperthermia. Nanoparticles synthesised to provide RF hyperthermia must have magnetite properties. For this purpose, magnetite nanoparticles were first synthesised by the coprecipitation method (10–15 NM). These superparamagnetic nanoparticles were then covered with gold ions without losing their magnetic properties. In this step, gold ions are reduced around the magnetite nanoparticles. Surface modification of the gold‐coated magnetic nanoparticles was performed in the next step. A self‐assembled monolayer was created using cysteamine (2‐aminoethanethiol) molecules, which have two different end groups (SH and NH₂). These molecules react with the gold surface by SH groups. The NH₂ groups give a positive charge to the nanoparticles. After that, a monoclonal antibody (Monoclonal Anti‐N‐CAM Clone NCAM‐OB11) was immobilised by the 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide/N‐hydroxysuccinimide method. Then, the antenna RF system (144.00015 MHz) was created for RF hyperthermia. The antibody‐nanoparticle binding rate and cytotoxicity tests were followed by in vitro and in vivo experiments. As the main result, antibody‐bound gold‐coated magnetic nanoparticles were successfully connected to tumour cells. After RF hyperthermia, the tumour size decreased owing to apoptosis and necrosis of tumour cells.     

Investigation of graphene‐on‐metal substrates for SPR‐based sensor using finite‐difference time domain

In this study, the authors investigated the effects of a single layer graphene as a coating layer on top of metal thin films such as silver, gold, aluminum and copper using finite‐difference time domain method. To enhance the resolution of surface plasmon resonance (SPR) sensor, it is necessary to increase the SPR reflectivity and decrease the full‐width‐half maximum (FWHM) of the SPR curve so that there is minimum uncertainty in the determination of the resonance dip. Numerical data was verified with analytical and experimental data where all the data were in good agreement with resonance angle differing in <10% due to noise present in components such as humidity and temperature. In further analysis, reflectivity and FWHM were compared among four types of metal with various thin film thicknesses where graphene was applied on top of the metal layers, and data was compared against pure conventional metal thin films. A 60 nm‐thick Au thin film results in higher performance with reflectivity of 92.4% and FWHM of 0.88° whereas single layer graphene‐on‐60 nm‐thick Au gave reflectivity of 91.7% and FWHM of 1.32°. However, a graphene‐on‐40 nm‐thick Ag also gave good performance with narrower FWHM of 0.88° and reflection spectra of 89.2%.Inspec keywords: graphene, surface plasmon resonance, finite difference time‐domain analysis, reflectivity, metallic thin films, silver, gold, aluminium, copper, chemical sensors, biological techniquesOther keywords: graphene‐on‐metal substrates, SPR‐based sensor, finite‐difference time domain, metal thin films, surface plasmon resonance sensor, SPR curve, resonance angles, reflectivity, C, Ag, Au, Al, Cu     

Synthesis,characterisation and anti‐tumour activity of biopolymer based platinum nanoparticles and 5‐fluorouracil loaded platinum nanoparticles

A facile and green synthesis of platinum nanoparticles [gum kondagogu platinum nanoparticles (GKPtNP)] using biopolymer‐ gum kondagogu was developed. The formation of GKPtNP was confirmed by ultraviolet (UV)–visible spectroscopy, scanning electron microscopy–energy dispersive X‐ray spectroscopy, transmission electron microscopy, X‐ray diffraction, Zeta potential, Fourier transform infrared, inductively coupled plasma mass spectroscopy. The formed GKPtNP are well dispersed, homogeneous with a size of 2–4 ± 0.50 nm, having a negative zeta potential (−46.1 mV) indicating good stability. 5‐Fluorouracil (5FU) was loaded onto the synthesised GKPtNP, which leads to the development of a new combination of nanomedicine (5FU–GKPtNP). The in vitro drug release studies of 5FU–GKPtNP in pH 7.4 showed a sustained release profile over a period of 120 min. Agrobacterium tumefaciens induced in vitro potato tumour bioassay was employed for screening the anti‐tumour potentials of GKPtNP, 5FU, and 5FU–GKPtNP. The experimental results suggested a complete tumour inhibition by 5FU–GKPtNP at a lower concentration than the GKPtNP and 5FU. Furthermore, the mechanism of anti‐tumour activity was assessed by their interactions with DNA using agarose gel electrophoresis and UV‐spectroscopic analysis. The electrophoresis results revealed that the 5FU–GKPtNP totally diminishes DNA and the UV‐spectroscopic analysis showed a hyperchromic effect with red shift indicating intercalation type of binding with DNA. Over all, the present study revealed that the combined exposure of the nanoformulation resulted in the enhanced anti‐tumour effect. Inspec keywords: nanoparticles, transmission electron microscopy, biomedical materials, tumours, ultraviolet spectra, DNA, drugs, electrophoresis, polymers, platinum, pH, drug delivery systems, biochemistry, X‐ray chemical analysis, microorganisms, molecular biophysics, electrokinetic effects, X‐ray diffraction, scanning electron microscopy, cancer, nanofabrication, visible spectra, nanomedicine, Fourier transform infrared spectra, materials preparationOther keywords: 5FU–GKPtNP, 5‐fluorouracil loaded platinum nanoparticles, gum kondagogu platinum nanoparticles, antitumour activity, scanning electron microscopy‐energy dispersive X‐ray spectroscopy, biopolymer‐based platinum nanoparticles, biopolymer‐based platinum nanoparticles, ultraviolet‐visible spectroscopy, UV‐visible spectroscopy, transmission electron microscopy, X‐ray diffraction, zeta potential, Fourier transform infrared spectroscopy, inductively coupled plasma mass spectroscopy, nanomedicine, in vitro drug release studies, sustained release profile, Agrobacterium tumefaciens, in vitro potato tumour bioassay, tumour inhibition, tumour activity, agarose gel electrophoresis, UV‐spectroscopic analysis, DNA, time 120.0 min, Pt     

Biosynthesis of gold nanoparticles using fungus Trichoderma sp. WL‐Go and their catalysis in degradation of aromatic pollutants

An efficient green method of gold nanoparticles (AuNPs) biosynthesis was achieved by cell‐free extracts of fungus Trichoderma sp. WL‐Go. Based on UV–Vis spectra, AuNPs biosynthesised by cell‐free extracts with 90 mg/l protein exhibited a characteristic absorption band at 556 nm and was stable for 7 days. Transmission electron microscopy images revealed that the as‐synthesised AuNPs were spherical and pseudo‐spherical, and the average size was calculated to be 9.8 nm with a size range of 1–24 nm. The AuNPs illustrated their good catalytic activities for reduction of nitro‐aromatics (2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2‐nitroaniline, 3‐nitroaniline) with catalytic rate constants of 7.4 × 10⁻³ s⁻¹, 10.3 × 10⁻³ s⁻¹, 4.9 × 10⁻³ s⁻¹, 5.8 × 10⁻³ s⁻¹, 15.0 × 10⁻³ s⁻¹, respectively. Meanwhile, the AuNPs also showed excellent catalytic performance in decolourisation of azo dyes with decolourisation efficiency from 82.2 to 97.5%. This study provided a green gentle method for AuNPs synthesis as well as exhibiting efficient catalytic capability for degradation of aromatic pollutants.Inspec keywords: catalysts, dyes, particle size, reduction (chemical), nanobiotechnology, nanofabrication, ultraviolet spectra, gold, transmission electron microscopy, nanoparticles, proteins, catalysis, visible spectra, pollution control, microorganismsOther keywords: nitro‐aromatics, catalytic rate constants, decolourisation efficiency, green gentle method, efficient green method, gold nanoparticles biosynthesis, cell‐free extracts, UV–Vis spectra, characteristic absorption band, transmission electron microscopy images, as‐synthesised AuNPs, catalytic performance, protein, catalytic activities, efficient catalytic capability, fungus Trichoderma sp. WL‐Go, aromatic pollutants degradation, 2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2‐nitroaniline, 3‐nitroaniline, azo dye decolourisation, Au     

Catalytic reduction in 4‐nitrophenol using Actinodaphne madraspatana Bedd leaves‐mediated palladium nanoparticles

There is a growing demand for the development of non‐toxic, cost‐effective, and environmentally benign green synthetic strategy for the production of metal nanoparticles. Herein, the authors have reported Actinodaphne madraspatana Bedd (AMB) leaves as the bioreducing agent for the synthesis of palladium nanoparticles (PdNPs) and its catalytic activity was evaluated for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol with undisruptive effect on human health and environment. The broad and continuous absorbance spectrum obtained in the UV–visible region indicated the formation of PdNPs. The synthesized PdNPs were found to be crystalline, spherical, and quasi‐spherical in shape with an average particle size of 13 nm was confirmed by X‐ray diffractometer and transmission electron microscope. Fourier transform infrared spectra revealed the active photo constituents present in the aqueous extract of AMB involved in the bioreduction of palladium ions to PdNPs. The catalytic activity of biosynthesized PdNPs was demonstrated for the reduction of 4‐NP via electron‐relay process. Also, the influential parameters such as catalyst dosage, concentration of 4‐NP, and sodium borohydride were studied in detail. From the present study, PdNPs were found to be a potential nanocatalyst for nitro compound reduction and also for environmental remediation of wastewater effluents from industries.Inspec keywords: palladium, nanoparticles, particle size, nanofabrication, catalysis, catalysts, reduction (chemical), organic compounds, ultraviolet spectra, visible spectra, X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectraOther keywords: nitro compound reduction, environmental remediation, wastewater effluents, Pd, nanocatalyst, sodium borohydride, 4‐NP concentration, catalyst dosage, electron‐relay process, bioreduction, aqueous extract, Fourier transform infrared spectra, transmission electron microscopy, X‐ray diffractometry, particle size, quasispherical shape, spherical shape, crystalline shape, UV‐visible abosprtion spectra, human environment, human health, 4‐aminophenol, catalytic activity, bioreducing agent, metal nanoparticles, Actinodaphne madraspatana Bedd leaves‐mediated palladium nanoparticles, 4‐nitrophenol, catalytic reduction