Nanocomposite Platform Research Articles

A novel immunosensing platform for serotonin detection in complex real samples based on graphene oxide and chitosan

A novel, simple and versatile nanocomposite platform based on graphene-oxide/chitosan modified screen printed electrode was optimized and used for the development of an immunosensor for the sensitive and highly selective electrochemical detection of serotonin. Graphene oxide has been used for providing carboxylic groups which form covalent bonds with the terminal amine groups from the antibody units, thus ensuring the immobilization of the biocomponent at the electrode surface. The presence of chitosan is necessary to ensure the stability of the nanomaterial film deposited on the electrode’ surface during the modification steps. The platform development protocol was optimized throughout the study by using electrochemical methods (electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry) as well as scanning electron microscopy. The following steps, namely immobilization of the antibody, blocking of the active free sites from graphene template with bovine serum albumin and testing of the immunosensor after immobilization of the analyte molecules at the surface, were optimized based on the differential pulse voltammetry tests following the signal obtained for the electrochemical oxidation of serotonin. The newly customized sensor was found to have a detection range from 10 nM to 100 μM and a limit of detection of 3.2 nM, being used for serotonin detection from human serum, saliva, artificial tears and urine samples as well as in the presence of different interferences, when good recovery rates were obtained.

Hydrogel-Graphene Oxide Nanocomposites as Electrochemical Platform to Simultaneously Determine Dopamine in Presence of Ascorbic Acid Using an Unmodified Glassy Carbon Electrode

The detection of dopamine, an important neurotransmitter in the central nervous system, is relevant because low levels of dopamine can cause brain disorders. Here, a novel electrochemical platform made of a hydrogel–graphene oxide nanocomposite was employed to electrochemically determine simultaneously dopamine (DA) and ascorbic acid (AA). Unlike previous work, where the base electrode is modified, the active material (graphene oxide, GO) was dispersed in the hydrogel matrix, making an active nanocomposite where the electrochemical detection occurs. The GO, hydrogel and nanocomposite synthesis is described. Dynamic Light Scattering, UV-visible and FTIR spectroscopies showed that the synthesized GO nanoparticles present 480 nm of diagonal size and a few sheets in height. Moreover, the polymer swelling, the adsorption capacity and the release kinetic of DA and AA were evaluated. The nanocomposite showed lower swelling capacity, higher DA partition coefficient and faster DA release rate than in the hydrogel. The electrochemical measurement proved that both materials can be employed to determine DA and AA. Additionally, the nanocomposite platform allowed the simultaneous determination of both molecules showing two well separated anodic peaks. This result demonstrates the importance of the incorporation of the nanomaterial inside of the hydrogel and proves that the nanocomposite can be used as a platform in an electrochemical device to determinate DA using an unmodified glassy carbon electrode.

Nanocomposite Platform Based on EDTA Modified Ppy/SWNTs for the Sensing of Pb(II) Ions by Electrochemical Method.

Heavy metal ions are considered as one of the major water pollutants, revealing health hazards as well as threat to the ecosystem. Therefore, investigation of most versatile materials for the sensitive and selective detection of heavy metal ions is need of the hour. Proposed work emphasizes the synthesis of conducting polymer and carbon nanotube nanocomposite modified with chelating ligand for the detection of heavy metal ions. Carbon nanotubes are having well known features such as tuneable conductivity, low density, good charge transport ability, and current carrying capacity. Conducting polymers are the most reliable materials for sensing applications due to their environmental stability and tuning of conductivity by doping and de-doping. Formation of nanocomposite of these two idealistic materials is advantageous over the individual material, which can help to tackle the individual limitations of these materials and can form versatile materials with ideal chemical and electrical properties. Chelating ligands are the most favorable materials due to their ability of complex formation with metal ions. The present work possesses a sensing platform based on conducting polymer and carbon nanotube nanocomposite, which is stable in various aqueous media and possess good charge transfer ability. Chelating ligands played an important role in the increased selectivity toward metal ions. Moreover, in present investigation Ethylenediaminetetraacetic acid (EDTA) functionalized polypyrrole (Ppy) and single walled carbon nanotubes (SWNTs) nanocomposite was successfully synthesized by electrochemical method on stainless steel electrode (SSE). The electrochemical detection of Pb(II) ions using EDTA-Ppy/SWNTs nanocomposite was done from aqueous media. Cyclic voltammetry technique was utilized for the electrochemical synthesis of Ppy/SWNTs nanocomposite. Ppy/SWNTs nanocomposite was further modified with EDTA using dip coating technique at room temperature. The EDTA-Ppy/SWNTs modified stainless steel electrode (SSE) exhibited good sensitivity and selectivity toward heavy metal ions [Pb(II)]. Detection limit achieved for Pb(II) ions was 0.07 μM.

Bioinspired synthesis of multiple-functional nanocomposite platform showing optically and thermally responsive affinity: Application to environmentally responsive separation membrane

A tremendous effort has been made for the synthesis and multifunction of environmentally responsive and selective separation membranes. With the bioinspired design of polydopamine (pDA)-assisted inorganic film, we proposed a simple, yet efficient, thermo-responsive cell culture substrate. Herein, a Ag/TiO2/pDA-based nanocomposite structure was initially obtained, and the ciprofloxacin-imprinted membranes (MINCMs) with thermo-responsive recognition sites were then synthesized by using NIPAm as backbone monomer. The opto-thermally responsive molecularly imprinted membranes (OT-MIMs) were obtained through in situ reduction of HAuCl4 on membrane surfaces, Au nanoparticles were used as the light-heat converters. The light-switching principle was elaborated as well as the energy conversions that took place in this system. These conformational changes finally allowed the constructions or destructions of ciprofloxacin-imprinted sites. Due to the formation of the opto-thermally responsive ciprofloxacin-imprinted sites, rapid adsorption dynamics and opto-thermally responsive perm-selectivity toward templates were both achieved. Therefore, 58.65 mg/g of adsorption capacity and 4.91 of permselectivity factor from OT-MIMs were successfully obtained. Importantly, the as-designed bioinspired strategy led to a state-of-the-art design that was capable of reversibly controlling the flow rate (J) of ciprofloxacin from 12.10 to 4.93 mg min−1 cm−2 in less than a few minutes using light.

Nanoscale Artificial Plasmonic Lattice in Self-Assembled Vertically Aligned Nitride-Metal Hybrid Metamaterials.

Nanoscale metamaterials exhibit extraordinary optical properties and are proposed for various technological applications. Here, a new class of novel nanoscale two‐phase hybrid metamaterials is achieved by combining two major classes of traditional plasmonic materials, metals (e.g., Au) and transition metal nitrides (e.g., TaN, TiN, and ZrN) in an epitaxial thin film form via the vertically aligned nanocomposite platform. By properly controlling the nucleation of the two phases, the nanoscale artificial plasmonic lattices (APLs) consisting of highly ordered hexagonal close packed Au nanopillars in a TaN matrix are demonstrated. More specifically, uniform Au nanopillars with an average diameter of 3 nm are embedded in epitaxial TaN platform and thus form highly 3D ordered APL nanoscale metamaterials. Novel optical properties include highly anisotropic reflectance, obvious nonlinear optical properties indicating inversion symmetry breaking of the hybrid material, large permittivity tuning and negative permittivity response over a broad wavelength regime, and superior mechanical strength and ductility. The study demonstrates the novelty of the new hybrid plasmonic scheme with great potentials in versatile material selection, and, tunable APL spacing and pillar dimension, all important steps toward future designable hybrid plasmonic materials.

Comparison of Ex-Situ and In-Situ Nano Plasmonic Platforms for Capture and Detection of Exosomes

Over the past few decades, in the field of sensing, the fabrication of the optimal nanostructures for detecting specific bio-entities remained an active area of research. It is well-known that the structure and the plasmonic properties of noble metal nanoparticles can be customized for specific applications such as biosensing, diagnosis, imaging, etc. by tuning the size and shape of the nanoparticles. Thus, by using the plasmonic property of noble metals, the detection at the nano-scale is possible by monitoring the shift of the local resonance band with respect to the changes in refractive index of the surrounding medium. The present study is aimed at comparing the quality and performance of two nano plasmonic platforms for the capture and detection of exosomes. Exosomes are nanoscale heterogeneous vesicles that are released by different cells. These vesicles plays significant role in intercellular communications, transport of proteins, RNA, and other molecular informations. In the last decade, researchers have shown substantial interest in this field as there is a lack of specific methodology to isolate and detect them. Currently, the exact science behind the major standard techniques of isolation of exosomes is not clearly understood. Thus, limitations with low yield and poor quality exosomes compromise further molecular analysis for diagnosis. The ultracentrifugation method of isolation of exosomes is time consuming, laborious, infrastructure intensive and may lack specificity. Therefore, a lot of challenges are existing in this field in order to develop next generation affinity-based technologies to capture the exosomes selectively and use them for further diagnosis at the clinical level. The two different sensing platforms, developed and tested for sensing of exosomes are the ex-situ gold (Au) nano-islands on glass substrates and the in-situ prepared silver (Ag) - polydimethylsiloxane (PDMS) nano-composite. The gold platform is fabricated by depositing colloidal gold on glass by the thermal convection method, followed by morphology tuning of the formed nanoparticles by annealing. The second is the nano-composite platform developed by the in-situ synthesis of silver ions present in the silver nitrate solution and the curing agent present in the PDMS polymer. In both cases, the capture and detection of exosomes is based on the strong affinity of heat shock proteins contained by exosomes and a polypeptide called Vn96, specially synthesized for this purpose. The Vn96 peptide targets canonical heat shock proteins that are present on the surface of exosomes. The Vn96 - based exosomes-capture method is further validated for downstream analyses, clinical compatibility, and liquid biopsy assays (biomarker and mutation detection) and platform-versatility using cell-culture conditioned media and human body fluids as sources of exosomes. Vn96 provides multiple advantages over currently-available methods for exosomes isolation: the scalability, quality, platform versatility, and cost-effectiveness. By using the gold platform, biotinylated Vn96 peptide is bound onto the streptavidin-coated Au nano-islands, and the subsequent steps of binding of nano-sized vesicles (exosomes) are monitored through the localized surface plasmon resonance (LSPR) band of Au. The sensing process was modelled, taking into account the characteristics of the nano-island structure. It is found that the results of the sensing process depend on the two major steps: the molar ratios of streptavidin to biotin-PEG-Vn96 and, the final step, the capture of exosomes by the biotin-PEG-Vn96 complex. The Ag-PDMS platform is used in a similar way and the shift of the Ag LSPR band is monitored after each sensing step. It is found that the bio sensitivity of the ex-situ synthesized gold/glass platform is considerably higher than that of the in-situ synthesized Ag-PDMS nanocomposite and, consequently, this platform is much more performant for the sensing of exosomes. Two principal reasons were identified in order to account for this difference. It is thought that, because of the low temperature of annealing of Ag-PDMS, contrary to the nano-islands of gold, a non-suitable morphology is formed. It has been demonstrated that nano-island structures have a higher sensitivity due to their morphological characteristics. On the other hand, due to the in-situ formation mechanism, a large proportion of the surface Ag particles will diffuse inside the polymer layer, that is, they will not be available anymore for sensing. The morphology of Au nano-islands and Ag-PDMS composite were investigated by SEM and the LSPR techniques are discussed in the paper.

Sensitive detection of pyoverdine with an electrochemical sensor based on electrochemically generated graphene functionalized with gold nanoparticles

The design and development of an electrochemical sensor for the sensitive and selective determination of pyoverdine, a virulence factor secreted by Pseudomonas aeruginosa, bacteria involved in nosocomial infections is presented in this work. The presence of pyoverdine in water and body fluids samples can be directly linked to the presence of the Pseudomonas bacteria, thus being a nontoxic and low cost marker for the detection of water pollution as well as for the biological contamination of other media. The sensor was elaborated using layer-by-layer technique for the deposition of a graphene‑gold nanoparticles composite film on the graphite-based screen printed electrode, from aqueous suspension. Under optimal conditions, the electrochemical signal corresponding to the pyoverdine oxidation process was proportional to its concentration, showing a wide linear range from 1 to 100μmolL−1 and a detection limit of 0.33μmolL−1. This sensor discriminate with satisfactory recoveries the target analyte in different real matrices and also exhibited low response to other interfering species, proving that this technique is promising for medical and environmental applications. In addition, the proposed nanocomposite platform presented good reproducibility, high and long term stability, the sensitivity for pyoverdine remain unchanged after being stored at 4°C for four weeks.

Polyglycolide–montmorillonite as a novel nanocomposite platform for biosensing applications

In catalytic biosensors, the immobilization of biomolecules in a suitable matrix is one of the vital parameters for obtaining improved systems.

Sensitive electrochemical determination of rifampicin using gold nanoparticles/poly-melamine nanocomposite

Green and facile method for fabrication of a conductive polymer–Au nanocomposite platform as a novel electrochemical sensing layer for rifampicin.

Zinc Oxide Nanoflowers Based Graphene Nanocomposite Platform for Catalytic Studies of Febuxostat

Zinc Oxide Nanoflowers Based Graphene Nanocomposite Platform for Catalytic Studies of Febuxostat

Evaluation of Freshness of Fishes Using MWCNT/TiO2 Nanobiocomposites Based Biosensor

In present work, we have developed a highly sensitive biosensor to evaluate the freshness of fishes by determining their xanthine level. This is based on xanthine oxidase (XOx) immobilized on the nanocomposite platform of titanium dioxide nanoparticles and multi-walled carbon nanotubes (TiO2/MWCNT). The biosensor exhibited excellent performances like linear relation in the range from 0.5 to 500 μM, detection limit of 0.5 μM (S/N = 3), and a rapid response time of 30 s. The biosensor showed excellent reproducibility, high selectivity, and long-term stability (60 days). The techniques like dynamic light scattering (DLS), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and X-ray diffraction (XRD) were used to characterize the nanocomposite modified electrode. The current biosensor is very reliable and stable for the determination of the freshness of fishes.

An organic indicator functionalized graphene oxide nanocomposite-based colorimetric assay for the detection of sarcosine.

Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS functionalized GO nanocomposite through π-π stacking has been demonstrated to be useful as a highly efficient catalyst system for the selective and sensitive colorimetric determination of sarcosine by providing a nanocomposite-amplified colorimetric response. Meanwhile, the strategy offered excellent selectivity toward sarcosine species against other amino acids as well as a satisfying detection limit of 0.73 μM. More importantly, by using an electrochemical method, a credible sensing mechanism of GO nanocomposite-based colorimetric platform for a special analyte determination can be easily verified and elucidated, which also provides an attractive alternative to conventional characterization strategies.

Artificial Photosynthesis Device Development for CO2 Photoelectrochemical Conversion.

ABSTRACTDevelopment of a photoelectrochemical conversion device, operated at room temperature and ambient pressure with only ultraviolet radiation as an energy source is presented. We report a nanocomposite platform that combines a photocatalyst and an electrocatalyst capable of reducing gaseous Carbon Dioxide, without using external electricity. The composite catalyst produces Methane from Carbon Dioxide and atmospheric water vapor at an initial high conversion rate of 2596 μL of CH4 per gram of catalyst per hour, which is amongst the highest reported. Our new approach offers a versatile solution to reduce the rising level of atmospheric Carbon Dioxide where a source of light is available.

Doxorubicin loaded nanodiamond-silk spheres for fluorescence tracking and controlled drug release.

Nanoparticle (NP) based technologies have proved to be considerably beneficial for advances in biomedicine especially in the areas of disease detection, drug delivery and bioimaging. Over the last few decades, NPs have garnered interest for their exemplary impacts on the detection, treatment, and prevention of cancer. The full potential of these technologies are yet to be employed for clinical use. The ongoing research and development in this field demands single multifunctional composite materials that can be employed simultaneously for drug delivery and biomedical imaging. In this manuscript, a unique combination of silk fibroin (SF) and nanodiamonds (NDs) in the form of nanospheres are fabricated and investigated. The spheres were loaded with the anthracyline Doxorubicin (DoX) and the drug release kinetics for these ND-SF-DoX (NDSX) spheres were studied. NDs provided the fluorescence modality for imaging while the degradable SF spheres stabilized and released the drug in a controlled manner. The emission and structural properties of the spheres were characterized during drug release. The degradability of SF and the subsequent release of DoX from the spheres were monitored through fluorescence of NDs inside the spheres. This research demonstrates the enormous potential of the ND-SF nanocomposite platforms for diagnostic and therapeutic purposes, which are both important for pharmaceutical research and clinical settings.

PH-Triggered Molecular Alignment for Reproducible SERS Detection via an AuNP/Nanocellulose Platform.

The low affinity of neutral and hydrophobic molecules towards noble metal surfaces hinders their detection by surface-enhanced Raman spectroscopy (SERS). Herein, we present a method to enhance gold nanoparticle (AuNP) surface affinity by lowering the suspension pH below the analyte pKa. We developed an AuNP/bacterial cellulose (BC) nanocomposite platform and applied it to two common pollutants, carbamazepine (CBZ) and atrazine (ATZ) with pKa values of 2.3 and 1.7, respectively. Simple mixing of the analytes with AuNP/BC at pH < pKa resulted in consistent electrostatic alignment of the CBZ and ATZ molecules across the nanocomposite and highly reproducible SERS spectra. Limits of detection of 3 nM and 11 nM for CBZ and ATZ, respectively, were attained. Tests with additional analytes (melamine, 2,4-dichloroaniline, 4-chloroaniline, 3-bromoaniline, and 3-nitroaniline) further illustrate that the AuNP/BC platform provides reproducible analyte detection and quantification while avoiding the uncontrolled aggregation and flocculation of AuNPs that often hinder low pH detection.

A Nicotinamide Adenine Dinucleotide Dispersed Multi-walled Carbon Nanotubes Electrode for Direct and Selective Electrochemical Detection of Uric Acid.

A nanocomposite platform built with multi-walled carbon nanotubes (MWCNTs) and nicotinamide adenine dinucleotide (NAD(+)) via a noncovalent interaction between the large π systems in NAD(+) molecules and MWCNTs on a glassy carbon substrate was successfully developed for the sensitive and selective detection of uric acid (UA) in the presence of ascorbic acid (AA), dopamine (DA). NAD(+) has an adenine subunit and a nicotinamide subunit, which enabled interaction with the purine subunit of UA through a strong π-π interaction to enhance the specificity of UA. Compared with a bare glassy carbon electrode (GCE) and MWCNTs/GCE, the MWCNTs-NAD(+)/GCE showed a low background current and a remarkable enhancement of the oxidation peak current of UA. Using differential pulse voltammetry (DPV), a high sensitivity for the determination of UA was explored for the MWCNTs-NAD(+) modified electrode. A linear relationship between the DPV peak current of UA and its concentration could be obtained in the range of 0.05 - 10 μM with the detection limit as low as 10 nM (S/N = 3). This present strategy provides a novel and promising platform for the detection of UA in human urine and serum samples.

Highly sensitive label free electrochemical detection of VGEF165 tumor marker based on "signal off" and "signal on" strategies using an anti-VEGF165 aptamer immobilized BSA-gold nanoclusters/ionic liquid/glassy carbon electrode.

In this work, a label free electrochemical aptasensor for the detection of ultra-traces of vascular endothelial growth factor (VEGF165) based on "signal off" and "signal on" mechanisms of response was developed. The BSA-gold nanoclusters/ionic liquid (BSA-AuNCs/IL) was used as a suitable nanocomposite platform for immobilization of the aptamer on a glassy carbon electrode. In "signal off" mechanism, the interaction of VEGF165 with its anti-VEGF165 aptamers, resulted in desorption of methylene blue (MB) probe from aptamer and its release into solution. Consequently, the decrease in current intensity of the differential pulse voltammogram of adsorbed MB was monitored and found to be linearly proportional with increasing concentration of VEGF165 in sample solution in the range of 1-120 pM with a limit of detection of 0.32p M. While, in "signal on" mechanism, the interaction of immobilized anti-VEGF165 aptamers on the electrode surface with VEGF165, led to more mass-transfer limiting of the [Fe(CN)6](3-/4-) probe to the electrode surface. Therefore, the charge transfer resistance (Rct) of the probe was increased linearly with increasing concentration of VEGF165 in the range of 2.5-250 pM with a limit of detection of 0.48 pM. The experimental results demonstrated that both of these mechanisms are suitable for determination of low levels of the VEGF165 tumor marker in serum samples.

MagRET Nanoparticles: An Iron Oxide Nanocomposite Platform for Gene Silencing from MicroRNAs to Long Noncoding RNAs.

Silencing of RNA to knock down genes is currently one of the top priorities in gene therapies for cancer. However, to become practical the obstacle of RNA delivery needs to be solved. In this study, we used innovative maghemite (γ-Fe2O3) nanoparticles, termed magnetic reagent for efficient transfection (MagRET), which are composed of a maghemite core that is surface-doped by lanthanide Ce(3/4+) cations using sonochemistry. Thereafter, a polycationic polyethylenimine (PEI) polymer phase is bound to the maghemite core via coordinative chemistry enabled by the [CeL(n)](3/4+)cations/complex. PEI oxidation was used to mitigate the in vivo toxicity. Using this approach, silencing of 80-100% was observed for mRNAs, microRNAs, and lncRNA in a variety of cancer cells. MagRET NPs are advantageous in hard to transfect leukemias. This versatile nanoscale carrier can silence all known types of RNAs and these MagRET NPs with oxidized PEI are not lethal upon injection, thus holding promise for therapeutic applications, as a theranostic tool.

Controllable gold nanoparticle deposition on carbon nanotubes and their application in immunosensing

A CNT–AuNPs hybrid nanocomposite platform was prepared from nanodisperse AuNPs in N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) sol–gel matrices with purified MWCNT.

Optothermally responsive nanocomposite generating mechanical forces for cells enabled by few-walled carbon nanotubes.

We have designed and fabricated a nanocomposite substrate that can deliver spatially and temporally defined mechanical forces onto cells. This nanocomposite substrate comprises a 1.5-mm-thick near-infrared (NIR) mechanoresponsive bottom layer of few-walled carbon nanotubes (FWCNTs) that are uniformly distributed and covalently connected to thermally responsive poly(N-isopropylacrylamide) and an approximately 0.15-mm-thick cell-seeding top layer of collagen-functionalized poly(acrylic acid)-co-poly(N-isopropylacrylamide) that interpenetrates into the bottom layer. Covalent coupling of all the components and uniform distribution of FWCNTs lead to a large local mechanoresponse. As an example, 50% change in strain at the point of irradiation on the order of 0.05 Hz can be produced reversibly under NIR stimulation with 0.02 wt % FWCNTs. We have further demonstrated that the mechanical strain imposed by NIR stimulation can be transmitted onto cells. Human fetal hepatocytes change shape with no sign of detrimental effect on cell viability. To the best of our knowledge, this is the first demonstration of a nanocomposite platform that can generate fast and controlled mechanical force to actuate cells. Since the amplitude, location, and timing of force can be controlled remotely with NIR, the nanocomposite substrate offers the potential to provide accurately designed force sequences for tissue engineering.