Current Nanoscience - Volume 10, Issue 4, 2014

The multifunctional nanostructured materials hold the promise for the applications in future clinical treatment to enhance therapeutic efficacy. In the past several decades, various types of nanostructured materials with multifunctional properties have been developed and investigated for the biomedical applications. Although many achievements have been made, the design and preparation of novel multifunctional nanostructured biomaterials with well-defined structures, sizes and morphologies are still a long-term research direction. Calcium phosphate (CaP) nanostructured biomaterials with high biocompatibility are the ideal candidates for multifunctional nanosystems, and have been studied and applied in many biomedical fields such as bone repair/tissue engineering, drug/gene delivery. Compared with pure CaP materials, CaP based composite nanostructured materials, prepared by adding functional elements, molecules or other materials, have excellent properties and promising applications in hard tissue engineering, drug delivery, magnetic targeting and hyperthermia treatment for cancer, antibacterial, bioimaging, and so on. This review article is not intended to offer a comprehensive review on the research on CaP based multifunctional nanostructured materials and their applications in the biomedical fields, but shall present a brief summary of the recent progress in this exciting and rapidly evolving research field.

Surface-enhanced Raman spectroscopy (SERS) is rapidly emerging as a powerful analytical tool for trace analysis of metallic substrates. While innovative numerical applications of SERS have been developed, it is still a challenge to fabricate cost-effective and reproducible metallic substrates for SERS probes. Laser processing, especially using ultrafast pulsed laser, can address this issue owing to their high quality processing. Herein, we investigate critical technical requirements and the latest advancements in laser-processing substrates for SERS, while highlighting several diverse applications. In light of its powerful enhancement of Raman scattering, SERS will remain an exciting research area for highly sensitive, resolved analysis into the foreseeable future.

This paper examines the field emission synthesis of multi-walled carbon nanotubes (MWCNTs) grown on various interlayers on carbon cloth (CC) substrates, such as Ni/CC, Ni/Ti/CC, and Ni/Al/CC, by thermal chemical vapor deposition using ethylene (C2H4) as the carbon source and nickel (Ni) as the catalyst. The Al interlayer activates the substrate for MWCNTs growth on carbon cloth with Ni as the active catalyst. Field emission SEM was utilized to study the morphology of the catalyst and MWCNTs, and a Raman spectrometer was used to characterize the quality of CNTs. As a result, catalyst particles initiate the nanotube growth and the tube diameters were found to be governed by the size of the associated particles. In our experiment, the smallest size and highest density of catalyst nanoparticles was formed on Al/CC substrate, so that the MWCNTs have a smaller diameter and higher density on this than on Ni/CC and Ni/Ti/CC substrate. Therefore, MWCNTs grown on flexible carbon cloth with an Al interlayer have the best quality and field emission characteristics of the materials examined in this paper.

In this paper, a CVD method is used for the synthesis of multi-wall carbon nanotubes (MWCNT) which have been purified and functionalized. The approach consists of thermal oxidation and subsequent chemical oxidation. According to TEM images, the CNTs have a diameter about 20-30 nm. We synthesized the FePt nanoparticles on the surface of the functionalized carbon nanotubes through a polyol process. The synthesized FePt nanoparticles have the chemicallydisordered face-centered cubic (fcc) structure with superparamagnetic behavior and with a size of about 2.5 nm. To achieve phase transition from fcc to ordered structure (fct-L10 phase), high-temperature annealing under a reducing atmosphere (90% Ar + 10% H2) is required. The CNTs as a substrate prevent the aggregation of particles during thermal treatment. The FePt nanoparticles after phase transition have ferromagnetic behavior. Furthermore, they have finite size with an average about 5.6 nm and their coercivity reaches to 5.1 KOe at 700°C. We characterized the structure, composition and magnetic properties of FePt/CNT by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM).

The main purpose of this study is to develop a sensitive and selective modified carbon-paste electrode (CPE) with multiwall carbon nanotubes (MWCNTs) for the determination of 6-mercaptopurine (6-MP) in the presence of methyldopa (MD) as a mediator. Electrochemical methods, such as cyclic voltammetry, double step chronoamperometry and square wave voltammetry (SWV), used to study the characterization of the proposed modified electrode. The results show that MD can catalyze the oxidation of 6-MP in aqueous solution. Also, the catalytic rate constant (k), and diffusion coefficient (D) for 6-MP were estimated. The pick currents of 6-MP increased linearly with concentration in the ranges of 0.31–550 μmol L-1, with detection limit of 0.1 μmol L-1. The relative standard deviation (RSD %) for seven replicate measurements of 0.7 μmol L-1 6-MP was 1.6%. The prepared electrode is successfully applied for the voltammetric determination of 6-MP in pharmaceutical and biological samples.

The aim of this research was the preparation, optimization, and in-vitro characterization of acyclovir loaded chitosan nanoparticles. Experimental design D-optimal response surface methodology was used for the optimization of the nanoparticles. Therefore, the polymeric nano-drug controlled release system has been designed for varied variables such as the concentration of Acyclovir, concentration ratio of chitosan/ TPP and pH using the ionic gelation method. The optimized nanoparticles were characterized morphologically by Scanning Electron Microscopy (SEM), particle size analyzer (DLS) for determining size, zeta and PdI, Fourier Transform Infra-Red (FTIR) Spectroscopy for determination of chemical structure of nanoparticles molecules and Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for studying thermal behavior. The size of the optimized particles was detected to be 132 ± 24.3 nm; zeta potential was 32 ± 2.87 mV; PdI of particles was 0.159 ± 0.05; and calculated EE% was 85 ± 4.38%. SEM image shows segregated and non-aggregated nanoparticles with sub-spherical smooth morphology. An in-vitro release study of the prepared nanoparticles illustrated that the percentage of acyclovir released from the nanoparticles was 80.17 ± 2.45% within 48 hrs. Kinetic release profiles of acyclovir from nanoparticles appeared to fit best with Korsmeyer-Peppas and First-order models, the Fickian diffusion being premier phenomenon.

Lipid nanoparticles have been paid growing interest for topical application of non-steroidal anti-inflammatory drugs to increase skin penetration and to reduce side effects. Solid lipid nanoparticles and nanostructured lipid carriers of celecoxib were prepared by high-pressure homogenization technique. Transmission electron microscopy, fourier transform infrared spectroscopy, differential scanning calorimetry, photon correlation spectroscopy and laser diffraction were used for characterization of nanoparticles. Their physical stability was investigated for 6 months of storage at the room temperature, 40C and 400C. Nanoemulsions were also prepared at the same conditions for comparison with the aim of pyhsico-chemical characterization of nanoparticles. Spherical nanoparticles with high drug payload were obtained below 250 nm when similar particle sizes were observed for 3 months of storage at all temperatures. Low microparticle content was detected in formulations after 6 months when d(0.5) values were below 270 nm at room temperature and 40C. 400C was not detected as a suitable storage condition for formulations. Nanoparticles were observed to provide controlled drug release. Their release profiles fitted Korsmeyer-Peppas model indicating Fickian diffusion release (case I diffusional) as the dominant mechanism. In ex-vivo skin penetration experiments through abdominal rat skins, solid lipid nanoparticles, nanostructured lipid carriers and nanoemulsion significantly increased drug penetration rate 1.4-2.2 times higher compared to a traditional gel formulation containing celecoxib (p<0.05). Penetration profiles were significantly similar for lipid nanoparticles (p>0.05). Nanoemulsion displayed the highest drug penetration rate among nano-formulations. Lipid nanoparticles and nanoemulsion were found as good canditates in order to transport celecoxib through deeper skin layers increasing drug penetration.

We report here the fabrication, characterization and use of PLGA hollow microbubbles (HMs) loaded with iron oxide (Fe3O4) nanoparticles (NPs) and anticancer drug doxorubicin (DOX) for dual-mode ultrasound (US)/magnetic resonance (MR) imaging and drug delivery applications. In this study, a double emulsion technique was employed to prepare PLGA HMs, where hydrophobic superparamagnetic Fe3O4 NPs were encapsulated in the shell of the HMs, while DOX molecules were incorporated within the interior of the PLGA HMs. The formed multifunctional PLGA HMs were characterized via different techniques. We show that the HMs having a size of 1.0 μm are stable and can be potentially used as dual-mode contrast agents for US imaging and MR imaging applications. Furthermore, the HMs encapsulated with DOX are able to release DOX in a sustained manner with a higher release rate under an acidic pH condition than under the physiological pH condition. Importantly, cell viability assay data reveal that the DOX-loaded HMs are able to effectively inhibit the growth of cancer cells with a therapeutic efficacy comparable to free DOX. The fabricated PLGA-Fe3O4-DOX HMs could potentially be used as a theranostic agent for dual-mode US/MR imaging and anticancer drug delivery.

Gold nanoparticles have suitable chemical surfaces, are neutral and have resistant to surface reduction. Due to these properties gold nanoparticles are frequently used in biological fields as biosensors as well as targeted drug and antibody delivery systems. The aim of this study was the biosynthesis of gold nanoparticles using Escherichia coli and the conjugation of these nanoparticles with streptomycin in order to evaluate its effect on obligate anaerobic bacteria. For this purpose, gold nanoparticles were biosynthesized using E. coli DH5α and confirmed using UV/Vis spectroscopy, SEM, TEM and DLS analysis. These nanoparticles were conjugated with streptomycin and its effect was evaluated against E. coli, Clostridium perferingens and Clostridium botulinum. As a result of this study 5-20 nm nanoparticles were synthesized from 5 mM HAuCl4. Distilled water was shown to be a suitable solvent and agitation facilitate the reaction. A range of ratios of antibiotics to nanoparticle and also different concentrations of antibiotics had little effect on the efficiency of conjugation. Conjugation of antibiotics with the nanoparticles resulted in a significant reduction in MIC and MBC of streptomycin against E. coli. Interestingly, this conjugate was able to overcome natural resistance of C. perferingens and C. botulinum to streptomycin. The process of biological synthesis is more ecologically friendly than traditional methods. The improvements in the efficacy of the antibiotics warrant further in vivo studies.

Chemical precipitation method was used in order to synthesize of CdSe quantum dots (2 - 3nm). Their physical properties and characteristics were assessed by X-ray diffraction, ultraviolet-visible spectrophotometery and scanning tunneling microscopy and it was shown that the obtained CdSe quantum dots have a cubic crystal structure. It was also shown that size and optical properties of CdSe quantum dots are related to the temperature (The temperature used by UV-Vis photometer). Antibacterial effects of CdSe nanoparticles against some pathogenic bacteria were investigated. Pseudomonas aeruginosa, Actinomycet and Salmonella typhi were used as test microorganisms. Disc bacteriological tests were used in order to assess the antibacterial effects of CdSe. The concentrations from 0.3 to 20 mg/mL of CdSe were investigated and it was concluded that the zone of inhibition diameter was strongly and directly related to the CdSe concentration. Actinomycet being the most affected bacteria.

Aligned MoO3 nanobelts and tree-like arrays have been synthesized onto silicon substrates by an ordinary gas cooker. The synthesis method is simple, rapid, low-cost, safe, and also suitable for large-scale fabrication. A possible growth mechanism of the nanobelts is presented based on the experimental observations. Via integrating nano-Al with the MoO3 nanobelt arrays, metastable intermolecular composites (MICs) based on Al/MoO3 nanobelt arrays are achieved. The Al/MoO3 MIC arrays have high energy density and can combust continuously by themselves at small dimensions and low density, which makes the MIC arrays synthesized on the silicon substrate, have promising applications in nanoenergetics- on-a-chip based functional devices at the micro and nanoscale.

The elastic properties of armchair and zigzag graphene nanoribbons grafted with different functional groups are investigated using molecular dynamics. The simulation results show that the Young’s moduli of graphenes with autoupdate- grafted hydrogen (-H) are 982 GPa for zigzag and 1046 GPa for armchair. When the graphenes are grafted with hydroxyl (-OH), amine (–NH2), carboxylic (–COOH), and thiol (–SH) groups, Graphene–OH shows the highest Young’s modulus, followed by graphene–COOH. Among the moduli obtained, those for graphene–NH2 and graphene–SH, which are nearly identical to that of graphene–H, are the lowest. The modulus variations of the zigzag and armchair graphenes with different grafts have similar trends, but the moduli for armchair graphenes are always higher than those for zigzag graphenes. This phenomenon is analyzed on the basis of the radial distribution function, deformation electron density, and chemical bond theory. The results indicate that smaller oxygen-containing functional groups, as well as the C–O or C–C–O bond formations caused by grafted atoms with dangling bonds, could effectively enhance the flexibility of the graphenes while maintaining their stability. The elastic performance of the grafted armchair graphenes is superior to that of the grafted zigzag graphenes.

A modified sol-gel method was applied to prepare La and In co-doped TiO2 photocatalyst. The materials were investigated by XRD, XPS, SEM, and N2 adsorption-desorption methods. Photocatalytic activity of the material was evaluated using methyl orange as the pollutant. The results indicate that the materials containing different content of La are in anatase TiO2 structure. The doping of La inhibits TiO2 crystal formation, while La exists in TiO2 crystal lattice by substituting Ti. La doping in suitable amount results in shrinking pore size and increasing surface area of the material. The 0.3%La-3%In-TiO2 sample has the maximum photocatalytic activity, high adsorption capacity, and satisfactory reusability. Total methyl orange decoloration efficiency only decreases from 100% to 84.8% on 0.3%La-3%In-TiO2 after 6 reaction cycles.

The development of reliable, eco-friendly processes for the synthesis of nanomaterials is an important aspect of nanotechnology. One approach that shows immense potential is based on the biosynthesis of nanoparticles using microorganisms such as bacteria. In this report, we demonstrate the extracellular biosynthesis and complete characterization of metal sulfide (PbS, ZnS, MnS and NiS) nanoparticles using fungus, Fusarium oxysporum. We observed that the exposure of aqueous solution of 1 mM metal sulfate to fungus Fusarium oxysporum resulted in the formation of highly stable technologically important metal sulfide semiconductor nanoparticles. Fusarium oxysporum synthesizes lead sulfide and zinc sulfide nanoparticles of fractal type structure whereas manganese sulfide and nickel sulfide nanoparticles are of variable polydispersed morphology. The variable morphology may be due to the dissimilar interaction of metal sulfide nanoparticles with capping proteins secreted by the fungus in solution. The nanoparticles solution is found to be extremely stable with little evidence of aggregation even after a month of storage. The long term stability of the nanoparticles is due to the proteins secreted by fungus in the nanoparticle solution which bind to the surface of the nanoparticles and thus prevent aggregation.

Preyssler acid, H14[NaP5W30O110], was used in the presence of marine algae Chaetomorpha linum as a green co-reducing agent in the bio-synthesis of gold nanoparticles at ambient temperature. The prepared nanoparticles were characterized by UV-Vis spectroscopy, particle size distribution, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The effect of various factors such as the concentration of extract as well as gold complex concentration, and time of the reaction, on the size of gold nanoparticles was investigated. All solutions including nanoparticles were enough stable, being efficiently used at least for couple of months.

Nanometal oxides are used extensively in various industries such as cosmetics, medicine, and food. Because of the increased use of nanoparticles, it is necessary to understand their influence on the environment. In this investigation, we have focused on the ecotoxicological behavior of nano and bulk silica (SiO2) and alumina (Al2O3) particles on plant growth–promoting rhizobacteria (PGPR). Nano Al2O3 had shown 15 ± 0.91 mm (Pseudomonas fluorescens), 14 ± 0.53 mm (Bacillus megaterium), 13 ± 0.26 mm (Bacillus brevis), and 16 ± 0.65 mm (Azotobacter vinelandii) zones of inhibition. The influence of nano and bulk particles on soil and its nutrients (total organic carbon, total nitrogen, phosphorus, and available potassium) was also analyzed using standard soil analytical techniques. Our findings showed that nano and bulk SiO2 particles were nontoxic toward PGPR up to 1000 mg L-1 concentration. In addition, bulk Al2O3 particles were less toxic toward PGPR, whereas nano Al2O3 particles were highly toxic at 1000 mg L-1 concentration. Moreover, nano Al2O3 particles led to a decrease in microbial population of the soil, leading to decrease in available forms of nutrients. In addition, this investigation concluded that zeta potential and contact angle have major role in toxicity. Thus, precautions should be taken during disposal and use of such toxic nanomaterials in the soil to prevent their hazardous effects.

Tea-gold nanosponges (T-Au NSs), tea-silver nanoparticles (T-Ag NPs), and tea-gold/silver nanosponges (TAu/ Ag NSs) synthesized by mixing a tea infusion with gold (silver) ions were demonstrated. UV-Vis spectroscopy, transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and powder X-ray diffraction (XRD) analysis were used to characterize as synthesized nanomaterials. Thereafter, the potential for use of the T-Au NSs, T-Ag NPs, and T-Au/Ag NSs in surface-enhanced Raman scattering (SERS) applications was investigated. The T-Au NSs provided a more intense SERS signal than the T-Ag NPs because of extremely intense local electromagnetic fields. In addition, the SERS enhancement factor for the T-Au NSs was further enhanced when Ag NPs were adsorbed on their surface.

We study the structural instability of gold (Au) and silver (Ag) islands with the size of the order of 103nm on silicone oil surfaces at room temperature. The samples are prepared by the thermal evaporation method. For the Ag system, after the sample is removed from the vacuum chamber, the apparent island coverage of the total area decreases obviously (≥8.0%). As the topological structure of the islands evolves, the decay of the total area of each island may be more than 12%. The microstructure of the Au islands, however, is relatively stable. The interpretation for the experimental results is presented.