Biocompatible Nanostructures Research Articles

An electrochemical aptasensor based on gold nanoparticles dotted graphene modified glassy carbon electrode for label-free detection of bisphenol A in milk samples

A simple and label-free electrochemical aptasensor for bisphenol A (BPA) determination was developed based on gold nanoparticles dotted graphene (GNPs/GR) nanocomposite film modified glassy carbon electrode (GCE). The electrochemical probe of ferricyanide was used to investigate the interactions between aptamer and BPA. The resulting GNPs/GR layer exhibited good current response for BPA detection. The highly conductive and biocompatible nanostructure of GNPs/GR nanocomposite was characterised by atomic force microscope (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The peak current change (ΔI) of ferricyanide was linear with the concentration of BPA in the range from 0.01μM to 10μM with the detection limit of 5nM. The proposed aptasensor is rapid, convenient and low-cost for effective sensing of BPA. Particularly, the aptasensor was applied successfully to determine BPA in milk products, and the average recovery was 105%.

Combination of theoretical and experimental approaches for the design and study of fibril-forming peptides.

Self-assembling peptides that can form supramolecular structures such as fibrils, ribbons, and nanotubes are of particular interest to modern bionanotechnology and materials science. Their ability to form biocompatible nanostructures under mild conditions through non-covalent interactions offers a big biofabrication advantage. Structural motifs extracted from natural proteins are an important source of inspiration for the rational design of such peptides. Examples include designer self-assembling peptides that correspond to natural coiled-coil motifs, amyloid-forming proteins, and natural fibrous proteins. In this chapter, we focus on the exploitation of structural information from beta-structured natural fibers. We review a case study of short peptides that correspond to sequences from the adenovirus fiber shaft. We describe both theoretical methods for the study of their self-assembly potential and basic experimental protocols for the assessment of fibril-forming assembly.

Spectrally coded optical nanosectioning (SpecON) with biocompatible metal–dielectric-coated substrates

Fluorescence nanosectioning within a submicron region above an interface is desirable for many disciplines in the life sciences. A drawback, however, to most current approaches is the a priori need to physically scan a sculptured point spread function in the axial dimension, which can be undesirable for optically sensitive or highly dynamic samples. Here we demonstrate a fluorescence imaging approach that can overcome the need for scanning by exploiting the position-dependent emission spectrum of fluorophores above a simple biocompatible nanostructure. To achieve this we have designed a thin metal-dielectric-coated substrate, where the spectral modification to the total measured fluorescence can be used to estimate the axial fluorophore distribution within distances of 10-150 nm above the substrate with an accuracy of up to 5-10 nm. The modeling and feasibility of the approach are verified and successfully applied to elucidate nanoscale adhesion protein and filopodia dynamics in migrating cells. It is likely that the general principle can find broader applications in, for example, single-molecule studies, biosensing, and studying fast dynamic processes.

Biocompatible smectic polymer nanostructures with controlled morphologies and reduction-responsive properties

Biocompatible smectic polymer nanostructures with controlled morphologies and reduction-responsive properties

Highly Efficient Bienzyme Functionalized Biocompatible Nanostructured Nickel Ferrite–Chitosan Nanocomposite Platform for Biomedical Application

A new hybrid nanocomposite based on hydrothermally synthesized nanostructured NiFe2O4 (n-NiFe2O4) and chitosan (CH) has been explored for bienzyme (cholesterol esterase (ChEt) and cholesterol oxidase (ChOx)) immobilization for application as total cholesterol biosensor. Results of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Raman spectroscopy (RS) and vibrating sample magnetometer (VSM) studies demonstrate that the ChEt–ChOx/n-NiFe2O4–CH composite film is successfully synthesized. The obtained ChEt–ChOx/n-NiFe2O4–CH nanocomposite film shows large specific area, high conductivity, good biocompatibility, fast redox properties and improved antimicrobial activity. The fabricated ChEt–ChOx/n-NiFe2O4–CH/ITO bioelectrode exhibits largely improved amperometric biosensing performance, i.e., good linearity (5–400 mg/dL), low detection limit (24.46 mg/dL cm–2), high sensitivity of 1.73 μA/(mg/dL cm–2), fast response time of 15s, reproducibility of more than 15 times, shelf life of about 90 days and low Michaelis–Menten constant (Km) value as 7.05 mg/dL (0.1825 mM). Furthermore, this modified bioelectrode has been utilized for estimation of total cholesterol in human serum samples. This efficient strategy provides new insight into the design of novel flexible electrodes for a wide range of applications in biosensing, bioelectronics, and clinical applications.

Synthesis of adenine mediated superparamagnetic colloidal β-FeOOH nanostructure(s): study of their morphological changes and magnetic behavior

This paper describes the synthesis of adenine-mediated superparamagnetic β-FeOOH nanostructures in aqueous medium. Capping by adenine provides a synthetic control to manipulate their size, morphology, optical and magnetization properties. β-FeOOH binds to adenine mainly through –NH2, N(3); N(9)H and N(7) of the pyridine and imidazole rings, respectively. At low [adenine], it produces nanorods, but at higher [adenine] (>1 × 10−2 mol dm−3), increasing numbers of spherical nanoparticles encapsulating β-FeOOH with an average diameter of 2.5 nm in the core and adenine molecules in the shell are obtained, causing an increase in the specific surface area by about twofold. Dynamic light scattering technique also depicts a regular decrease in their hydrodynamic size with increasing [adenine] and exhibits the highest stability with a zeta potential of ~67 mV for the sample containing 2 × 10−2 mol dm−3 adenine (SP5). An increasing [adenine] from 1 × 10−3 to 2 × 10−2 mol dm−3 in these samples enhanced the value of saturation magnetization (M S), due to β-FeOOH, gradually from 2.0 to 6.9 emu g−1 at 300 K, but at <80 K, a magnetic reversal from superparamagnetic to ferromagnetic is observed. A correlation between morphology and magnetic properties of these nanostructures is discussed. The capping of colloidal β-FeOOH by adenine thus provides a synthetic control to produce novel biocompatible nanostructures exhibiting superparamagnetic behavior with high M S at 300 K having potential for environmental and biological applications.

A novel label-free electrochemical aptasensor based on graphene–polyaniline composite film for dopamine determination

A novel label-free electrochemical aptasensor based on graphene–polyaniline (GR–PANI) nanocomposites film for dopamine (DA) determination was reported. The resulting GR–PANI layer exhibited good current response for DA determination. The good electron transfer activity might be attributed to the effect of GR and PANI. The highly conductive and biocompatible nanostructure of GR–PANI nanocomposites was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To quantify the amount of DA, the peaks of square-wave voltammetry (SWV) were monitored using the redox couple of an [Fe(CN)6]4−/3− probe. The electrochemical aptasensor showed a linear response to DA in the range 0.007–90nmol/L and a limit of detection of 0.00198nmol/L (S/N=3). The electrochemical aptasensor was successfully tested on human serum samples.

Review paper: Progress in the Field of Conducting Polymers for Tissue Engineering Applications

This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomolecules' entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the critical features of the natural extracellular matrix. Due to their capability to electronically control a range of physical and chemical properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivatives and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer-tissue interface through electrical stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topography, chemistry, charge, and other properties as electrical conductivity or mechanical actuation, which depend on the employed synthesis conditions. The biological functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the electrical stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.

A novel electrochemical DNA biosensor based on graphene and polyaniline nanowires

A novel DNA biosensor based on oxidized graphene and polyaniline nanowires (PANIws) modified glassy carbon electrode was developed. The resulting graphene/PANIw layers exhibited good DPV current response for the complementary DNA sequences. The good electron transfer activity might be attributed to the effect of graphene and PANIw. Graphene and PANIw nanolayers film with highly conductive and biocompatible nanostructure were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immobilization of the probe DNA on the surface of electrode was largely improved due to the unique synergetic effect of graphene and PANIw. Under optimum conditions, the biosensor exhibited a fast amperometric response, high sensitivity and good storage stability for monitoring DNA. The current response of the sensor increases linearly with the concentration of target from 2.12 × 10 −6 to 2.12 × 10 −12 mol l −1 with a relative coefficient of 0.9938. The detection limit (3 σ) is 3.25 × 10 −13 mol l −1. The results indicate that this modified electrode has potential application in sensitive and selective DNA detection.

Enhanced antibacterial activity of bifunctional Fe3O4-Ag core-shell nanostructures

We describe a simple one-pot thermal decomposition method for the production of a stable colloidal suspension of narrowly dispersed superparamagnetic Fe3O4-Ag core-shell nanostructures. These biocompatible nanostructures are highly toxic to microorganisms. Antimicrobial activity studies were carried out on both Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus megaterium and Staphylococcus aureus) bacterial strains. Efforts have been made to understand the underlying molecular mechanism of such antibacterial actions. The effect of the core-shell nanostructures on Gram negative strains was found to be better than that observed for silver nanoparticles. The minimum inhibitory concentration (MIC) values of these nanostructures were found to be considerably lower than those of commercially available antibiotics. We attribute this enhanced antibacterial effect of the nanostructures to their stability as a colloid in the medium, which modulates the phosphotyrosine profile of the bacterial proteins and arrests bacterial growth. We also demonstrate that these core-shell nanostructures can be removed from the medium by means of an external magnetic field which provides a mechanism to prevent uncontrolled waste disposal of these potentially hazardous nanostructures.

Synergistically improved sensitivity for the detection of specific DNA sequences using polyaniline nanofibers and multi-walled carbon nanotubes composites

A sensitive electrochemical DNA biosensor was successfully realized on polyaniline nanofibers (PANI), multi-walled carbon nanotubes (MWNT) and chitosan (CHIT) modified carbon paste electrode (CPE) based on the synergistic effect between PANI and MWNT nanoparticles in chitosan film. PANI and MWNT nanocomposites resulted in highly enhanced electron conductive and biocompatible nanostructured film, which was examined by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immobilization of the probe DNA on the surface of electrode was largely improved due to the unique synergistic effect of PANI and MWNT. The DNA hybridization events were monitored with an EIS label-free detection strategy. Under the optimal conditions, the dynamic detection range of this DNA electrochemical biosensor was from 1.0×10−13 to 1.0×10−7mol/L and a detection limit of 2.7×10−14mol/L for the detection of DNA specific sequence of the phosphinothricin acetyltransferase gene (PAT, one of the important screening detection genes for the transgenic plants). Simultaneously, the polymerase chain reaction (PCR) amplification of the terminator of nopaline synthase gene (NOS) from the sample of one kind of genetically modified soybean was also detected satisfactorily.

Detection of Cytochrome c at Biocompatible Nanostructured Au-lipid Bilayer-modified Electrode

The present work describes the dectection of cytochrome c (cyt c) at biocompatible aurum (Au) nanoparticle-structured supported bilayer lipid membrane (sBLM) modified with anionic sites. Au nanoparticles were directly deposited through sBLM modified with lauric acid (LA) to build a hybrid device of nanoscale electrode array via potential cycling in 10 mM HAuCl4 solution containing 0.1 M KCl. The properties of Au nanoparticle-doped sBLM composite were then characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Results indicated that Au nanoparticles grew in voids of the sBLM with size around 20 - 30 nm. With SWV, after optimization, the results of the experiments indicate that the currents of cyt c were linear functions of its concentrations over the range from 1.0 x 10(-7) to 3.2 x 10(-6) M and the limit of detection (LOD, S/N = 3) was 5 x 10(-8) M. The influences of several common base pairs, amino acids and metal ions on determination of cyt c via this Au nanoparticle-doped sBLM composite were relatively low in experiments, suggesting the excellent biocompatibility of this detection method.

Release Properties and Acute Biosecurity Determination of Collagen-Polyvinylpyrrolidone Loaded in Ordered Mesoporous Silica

Mesoporous silica type SBA-15 has high specific surface area, well ordered pores and renders larges volumes, reasons for its potential use in controlled drug delivery system; in addition its non toxic nature and good biocompatibility. The aim of this work is to determine the feasibility of loading collagen-polyvinylpyrrolidone (collagen-PVP) molecules into Biocompatible Nanostructured Ordered Mesoporous Silica (BINOM-Silica). Collagen-PVP has several medical uses, such as fibrolytic activity and tissue regeneration. Therefore, this BINOM-Silica/collagen- PVP material could be used as drug delivery system for hypertrophic scarring. Different BINOMSilica materials were prepared using a triblock copolymer in an acid medium and stabilized at 557°C and later, collagen-PVP was loaded into the material. The small angle powder X-ray diffraction patterns of BINOM-Silica materials, in some cases, indicate the existence of a high degree of hexagonal mesoscopic organization. The nitrogen sorption isotherms are type IV typical of mesoporous materials with large surface area. In vitro release of collagen-PVP was carried out by mean of UV/VIS spectroscopy. The cumulative release profiles of Silica-collagen PVP in distilled water indicate a two step release, an initial fast release and a relatively slow subsequent release, indicating an appropriate delivery of collagen-PVP for therapeutic administration. BINOMSilica/ collagen-PVP intradermical administration stimulated inflammatory infiltrates only in an acute phase (day 3), demonstrating that silica materials and their combination with chemical and biological drugs could be safe for therapeutics. The absence of inflammatory infiltrates at day 7 suggested an appropriate integration of BINOM-Silica/collagen-PVP into the tissue. These results indicate that we obtained biocompatible nanostructured ordered mesoporous silica materials useful for delivery systems.

Multifunctional biocompatible nanostructured coatings for load-bearing implants

To take advantage of the self-propagating high-temperature synthesis (SHS) technique, magnetron sputtering (MS), and ion implantation assisted magnetron sputtering (IIAMS), a new type of biocompatible nanostructured film was developed and studied. Films of Ti–Ca–C–O–(N), Ti–Ca–P–C–O–(N), Ti–Si–Zr–O–(N), and Ti–Zr–C–O–(N) were deposited by DC MS or IIAMS of SHS composite targets TiC 0.5 + CaO, TiC 0.5 + CaO + TiO 2, TiC 0.5 + Ca 10(PO 4) 6(OH) 2, Ti 5Si 3 + ZrO 2, and TiC 0.5 + ZrO 2 in an Ar atmosphere or reactively in a gaseous mixture of Ar + 14% N 2. The films were characterized in terms of their structure, chemical, mechanical, and tribological properties. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading and proliferation of Rat-1 fibroblasts, MC3T3-E1 osteoblasts, and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton and focal contacts staining of the cells cultivated on the films. Alkaline phosphatase activity and von Kossa staining of osteoblastic culture were investigated. Three groups of the in vivo investigations were fulfilled. Teflon plates coated with the tested films were inserted subcutaneous in mice and analysis of the population of cells on the surfaces was performed. Implantation studies of Ti rings and Ti rods coated with tested films using rat calvarian and hip defect models were also fulfilled. The results obtained show that Ti-based multicomponent films possess a combination of high hardness and adhesion strength, reduced Young's modulus, low wear and friction, high corrosion resistance with bioactivity, biocompatibility and non-toxicity that makes the films promising candidates as tribological coatings to be used for various medical applications like orthopedic prostheses, materials for connective surgery and dental implants.

Biocompatible Nanostructured High-Velocity Oxyfuel Sprayed Titania Coating: Deposition, Characterization, and Mechanical Properties

Nanostructured titania (TiO2) coatings were produced by high-velocity oxyfuel (HVOF) spraying. They were engineered as a possible candidate to replace hydroxyapatite (HA) coatings produced by thermal spray on implants. The HVOF sprayed nanostructured titania coatings exhibited mechanical properties, such as hardness and bond strength, much superior to those of HA thermal spray coatings. In addition to these characteristics, the surface of the nanostructured coatings exhibited regions with nanotextured features originating from the semimolten nanostructured feedstock particles. It is hypothesized that these regions may enhance osteoblast adhesion on the coating by creating a better interaction with adhesion proteins, such as fibronectin, which exhibit dimensions in the order of nanometers. Preliminary osteoblast cell culture demonstrated that this type of HVOF sprayed nanostructured titania coating supported osteoblast cell growth and did not negatively affect cell viability.