Current Nanoscience - Volume 7, Issue 3, 2011

Single-walled carbon nanotubes (SWNTs) were grown using methane CVD with lava as a catalyst and substrate. Metal-oxide phases embedded in the lava are reduced in the presence of hydrogen, thereby promoting catalytic growth. Scanning electron microscopy and energy-dispersive X-ray spectroscopy show a correlation between the growth of carbonaceous nanomaterials and the presence of iron in the alumina matrix. Raman spectroscopy of the carbon deposits proves the occurrence of SWNTs. Although this growth route lacks efficiency, it provides evidence for the claim that SWNTs are a natural allotrope of carbon and that volcanoes may provide an environment for their synthesis.

New nanomaterials have been extensively explored in recent years for drug delivery applications to address problems associated with the conventional drug therapies such as limited drug solubility, poor biodistribution, lack of selectivity and unfavourable pharmacokinetics. Among them, carbon nanotubes (CNTs) have attracted great attention due to their unique physicochemical architecture and properties. This comprehensive review summarizes the recent advances regarding the use of CNTs for drug delivery. This review includes general information about CNT structures and properties, methods for their dispersion in aqueous solution and basic concepts for CNTs functionalization relevant for their applications in biological systems and delivery of therapeutics. Some toxicological and biocompatibility issues related to the use of CNTs as pharmaceutical excipients are discussed. Last, recent progress on development of CNT drug delivery systems with a specific emphasis on gene delivery was reviewed.

The catalytic growth of multi-wall carbon nanotubes on carbon paper is reported. The study employed three cobalt carbonyl clusters as catalyst precursors. These were deposited on graphitic paper prior to chemical vapour deposition (CVD) of methane or ethylene. The clusters show differentiated growth behaviour in accordance with precursor size, and with Co2(CO)8 displaying additional activity in the growth of helical nanotube structures. We therefore report an approach for the decoration of graphitic papers with carbon nanotubes with a view to the production of high area supports.

This paper reports on the synthesis and characterization of novel poly(L-lactide)/multi-walled carbon nanotube (PLLA/MWCNT) porous scaffolds prepared by the freeze-extraction method. The obtained scaffolds showed well-distributed and interconnected porous structures with more than 80% porosity and median pore size around 40 μm distributed within a region between 50 and 150 μm in size. As a result of high interfacial interaction between PLLA and the MWCNTs, the scaffolds exhibited remarkable improvements in mechanical properties such as strength, modulus and elongation. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed enhanced thermal stability and compatibility for PLLA/MWCNT scaffolds. The structural properties of the scaffolds were investigated by Fourier-transform infrared spectroscopy (FTIR). In vitro degradation studies of the scaffolds were assessed by immersing the scaffolds in phosphate buffered saline (PBS) for up to 24 weeks. It was found that the incorporation of MWCNTs in PLLA scaffolds decreased the rate of in vitro degradation.

Carbon nanotubes are synthesized by Low Pressure Chemical Vapor Deposition (LPCVD) system using NH3: C2H2:H2 gas mixtures on iron coated silicon substrate. The iron catalyst was coated on silicon using RF-sputtering method. The growth temperature was kept at 600 °C and growth time was 10 mins. The carbon nanotubes are found to have diameters ranging from 50 to 80 nm and length of up to a few tens of microns. Raman spectra indicate that the CNTs are highly graphitized and several peaks are also found at low frequency range from 100 cm-1 to 500 cm-1 , which are assigned to the radial breathing mode (RBM) which is the characteristic of single wall carbon nanotubes. Therefore, this sample also contains single walled carbon nanotubes also. The carbon nanotubes showed a turn-on field of 2.63 V/μm and the maximum current density of 2 mA/cm2. The field enhancement factor was calculated to be 3.941 X 103 for as grown carbon nanotubes. The carbon nanotubes grown at this lower temperature show good field emission and are suitable for device applications.

In this paper we used Multi Wall Carbon Nanotubes (MWCNTs) containing 3% of residuals and impurities of Fe, Al, and Zn. MWCNTs, by virtue of Fe at their tips, are able to respond to the effects of external magnetic fields. We demonstrated that MWCNTs interact with PC12 cells without compromising their viability and differentiation with outgrowth of neurites. We also document that when exposed to a magnetic field, both undifferentiated and differentiated PC12 cells cultured in CNT-containing medium solution are able to move towards the magnetic source.

Tricyclic antidepressants (TCAs) have potent local pain blockade properties that could be of interest in relieving chronic pain states as neuropathic pain. The aim of this work was to reach a persistent control of nociceptive and neuropathic pain by means of an injectable controlled release system using lower than usual doses of TCAs. To address this issue, amitriptyline, doxepin and imipramine were encapsulated with poly (lactic-co-glycolic) acid (PLGA) as polymer. Nanoparticles were characterized. The in vitro drug release profile and mechanism was evaluated, and the in vivo analgesic and anti-allodynic activity in front of heat-induced nociceptive pain and sciatic nerve chronic constriction injury, respectively, was tested. The mean±SD particle size and drug loadings (%) of the nanoparticles obtained were 420±13, 480±73 and 373±25nm, and 40.46±4.11, 31.09±3.02 and 32.20±3.20 % for amitriptyline, doxepin and imipramine, respectively. According to the Korsmeyer-Peppas model, the release mechanism of doxepin was diffusion controlled, while a combination of Fickian diffusion and polymer relaxation/erosion of the PLGA matrix was involved for amitriptyline and imipramine. After local infiltration of nanoparticles in rats, the antinociceptive and anti-allodynic activity of the encapsulated drugs were long-lasting and higher than that observed from the solutions. Amitriptyline elicited the lower analgesic effect. Doxepin showed the most outstanding results and its encapsulation led to a 62% and 229% increase in antinociceptive and anti-allodynic activity, respectively. So, this drug could be considered as a therapeutical alternative in pain relieving treatments.

This paper reports the fabrication of multi-functionalized gold nanoparticles (MFAuNPs) and the application to electrochemical detection of nitrite. While gold nanoparticles are modified with thiolated oligonucleotides as usual, they are also immobilized with 5- [1, 2]dithiolan-3-yl-pentanoic acid [2-(naphthalene-1-ylamino)-ethyl]amide (DPAN). Therefore, the oligonucleotides molecules can enhance the solubility of the MFAuNPs and absorb hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) as electrochemical species on the one hand, with the help of nitrite ions, DPAN immobilized on MFAuNPs will react with 4-(2-aminoethyl)benzenamine which has been previously modified on the surface of a gold electrode on the other hand, thus an electrochemical method for nitrite detection is also proposed. Although the maximum contaminant level (MCL) defined by the Environmental Protection Agency (EPA) for nitrite in drinking water is as low as 1 ppm (21.7 μM), which is difficult to make detections by the current techniques, the proposed method in this work can give very satisfactory results.

Gold nanoparticles have been widely adopted to fabricate DNA sensors and aptasensors. Nevertheless, detailed information deep into the mechanism of the interaction between gold nanoparticles and DNA is still under investigation. In this work, we have employed colorimetric and electrochemical methods to study the interaction between unmodified DNA and colloidal as well as surfaceconfined gold nanoparticles. It is observed that in both cases, only single-stranded DNA may interact with the nanoparticles; however, the interaction processes are quite different. Single-stranded DNA binds to colloidal gold nanoparticles rapidly and weakly, while the binding is much longer and stronger in the case of surface-confined gold nanoparticles. We have discussed the differences and further proposed possible mechanisms. The results we present in this paper might be helpful for the deep understanding of the interaction between nanomaterials and DNA, and benefit the design of AuNPs-based DNA sensors and aptasensors.

In the paper, the dispersion stability of Fe3O4 nanoparticles in water by ball milling with surfactant sodium 2- dodecylbenzenesulfonate (SDBS) was studied. The ball milling time as influence factor on the stability of magnetic fluid was investigated. Then, the nano-Fe3O4 magnetic fluid was prepared and characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), particle size analyzer, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results show that the best time of ball milling is about 5h. The stably dispersed Fe3O4 mean size is about 34.1 nm. SDBS is adsorbed on the surface of nanoparticles by chemical bonds. SDBS covers Fe3O4 nanoparticles through sulfonate group links. Then another SDBS continues to adsorb by physical forces to disperse stably in the water solution by the steric hindrance and electrostatic effect.

CoFe2O4 nanoparticles of different sizes were synthesised by controlling the digestion time using precipitation method and were characterised by X-ray diffraction, transmission electron microscopy, dynamic light scattering, and vibrating sample magnetometer. The average crystalline size increases from 13.9 to 19 nm as the digestion time is increased from 1.3 to 120 minutes. The CoFe2O4 nanoparticles were coated with two biological polymers, namely polyvinyl alcohol (PVA) and polyethylene glycol (PEG) at various ratios to enhance their biocompatibility. Coated nanoparticles were analysed for their cytotoxicity by MTT assay against 3T3-L1 adipocytes. Coated nanoparticles were found to be less cytotoxic when compared to uncoated one. The cell viability decreased as the concentration of the polymer (either PVA or PEG) coating increased. Cell viability decreases as the concentration of nanoparticle increases. At 5 μg/ml the cell viability with PEG coated nanoparticles (1:4) was 92.5%, with PVA coated nanoparticles (1:4) was 82.7% and with uncoated nanoparticles it was 46.4%. As the ratio of biopolymers (PVA and PEG) to nanoparticle increases, the viability of the cell increases. The difference between the effect of these two polymers increases as the concentration of the nanoparticle decreases. The antiinflammatory properties of these nanoparticles were determined by RTPCR by measuring the two pro-inflammatory cytokines (namely tumor necrosis factor α and IL6). TNF-α and IL6 were upregulated by 3.57- & 2.86 folds their base level with uncoated nanoparticles. Whereas it was upregulated by 1.54- & 1.68-folds with PEG coated and 1.9- & 2.18-folds with PVA coated nanoparticles. Thus the coated nanoparticles can be used for further biological experiments including magnetic resonance imaging, and in targeted drug delivery systems for various diseases.

In this paper, we investigate the effects of a coated dielectric wall on the resonance light scattering (RLS) properties of a long gold nanowire. The RLS is shown to be strongly influenced by the presence of the dielectric surrounding which induces the changes of the surface plasmon resonance (SPR) and local polarized field characters. For gold nanowire coated by a dielectric wall, the RLS peak red shifts nonlinearly when the wall thickness is increased, which is different from the linear shift fashion of a bare gold nanowire embedding in immense dielectric surrounding. Furthermore, the scattering distribution patterns in the transversal section are also dependent on the coated dielectric wall. When dielectric constant of outer surrounding is greater than that of the dielectric wall, the intense scattering takes place at the poles of the wall along the incident polarization. On the contrary, greater wall dielectric constant may bring opposite scattering distribution. This tunable light scattering in dielectric wall coated gold nanowire makes it potentially useful in optical biosensing based on metallic nanoparticle enhanced RLS.

Magnetite (Fe3O4) nanoparticles in the interval of 9∼12nm have been synthesized by an non-alkoxide sol-gel method. Through this simple technique, sol-gel materials were prepared from ethanolic solutions of metal chlorides without the need for alkoxides, polymeric gel agents, or elaborate reaction schemes. The gel formation has been studied, and the research shows that gel formation appears to be driven primarily by the formation of an Fe(III)-based network which incorporates Fe(II) into its nanoscale solid domains. The research of the annealing process indicates that magnetite (Fe3O4) nanoparticles can be obtained by annealing only under vacuum, but not in air. Future, Fe3O4 can be oxidized to Fe2O3, as evidenced by XRD, and VSM. The phase structures, morphologies, and particle sizes of Fe3O4 nanoparticles were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The results indicate that magnetite (Fe3O4) nanoparticles are homogeneous and have near-spherical shape with a narrow distribution in particle size. Finally, an investigation of the possible mechanism of Fe3O4 nanoparticles formation was performed. Both TG-DTA and X-ray Diffraction (XRD) studies suggest that the reaction of the decomposition of the precursor under vacuum conditions leads to Fe3O4 nanoparticles, while the precursors in air atmosphere is directly oxidized to gamma iron oxide. In addition, this approach may suggest a general route to produce complex multicomponent metal oxide in which the nanoscale oxide is stabilized and spatially distributed.

Nanoparticles (NPs) are currently widely used for different applications like cosmetics, personal care products and drug delivery agents. The enormous use and production of NPs resulted in release of NPs into the environment. These NPs find their way into aquatic, terrestrial and atmospheric environments. These NPs interact with their immediate environments and cause adverse affects on them. The rapidly growing field of nanotechnology will result in new routes of exposure through inhalation, ingestion, and injection. They can have damaging effects on cellular organells like mitochondria and macromoleculs like DNA. In view of this, there is a need to better understand the interactions between the NPs, environment and the organisms. In this article, we have reviewed the well known cytotoxicity assays and toxicity associated with therapeutic NPs.

Electrospinning of chitosan, a naturally occurring polysaccharide biopolymer, has been investigated. In this paper, we report the optimization of electrospinning process and solution parameters using factorial design approach to obtain uniform chitosan nanofibres. The parameters studied were electric field strength, ratio of solvents - trifluoroacetic acid (TFA)/ dichloromethane (DCM), concentration of chitosan in the spinning solution, their individual and interaction effects on the diameter of nanofibres. The selected parameters were varied at three levels (-1, 0 and +1) using Box and Behnken factorial design. The interaction effect between electric field strength (FS) and concentration of chitosan (CC) as well as that between the ratio of solvents - TFA/DCM (SC) and electric field strength played the most significant role, followed by the concentration of chitosan and lastly by the electric field strength in obtaining uniform nanofibres.

A simple and environmentally benign process for the synthesis of Bi2S3 nanorods and their electrochemical sensing properties are desirable to be developed in electrochemical sensor application. Orthorhombic Bi2S3 nanorods have been synthesized via a singlesource approach using bismuth diethyldithiocarbamate as the precursor under hydrothermal conditions. The products were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, IR, UV-vis spectra and electrochemical sensing analysis. The decomposition of the complex bismuth diethyldithiocarbamate produces Bi2S3 nanorods with the average diameter of about 80 nm and length of less than 5 μm. The electrochemical responses of Bi2S3 nanorod modified glassy carbon electrode to cysteine and ascorbic acid are greatly enhanced suggesting that hydrogen ions participate in the electrochemical oxidation process. The electrochemical results demonstrated that the Bi2S3 nanorods are expected to have great potential as the electrochemical sensing cell for detecting cysteine and ascorbic acid.

In this work, a facile route using a simple solvothermal reaction and sequential heat treatment process to prepare 3D La2O3 flower-like nanostructures without employing templates or matrices for self-assembly is presented. The as-synthesized products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), highresolution TEM (HRTEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG), differential thermal analysis (DTA), and Fourier transformation IR (FTIR). SEM results demonstrate that the as-prepared flower-like precursor with average size of 5- 7 μm in diameter is composed of numerous nanoplates with a thickness of about 100 nm. Influencing factors such as solvothermal reaction temperature, surfactants, reaction time, and solvents were systematically investigated. 3D flower-like La2O3 nanostructures with many holes on the petals were obtained after calcinations of the flower-like precursor at 800 °C for 4 h. The BET surface area of the flower-like La2O3 nanostructures is 9.98 m2/g. Eu3+ doped flower-like La2O3 nanostructures were also prepared employing the same preparation process. The flower-like La2O3:Eu3+ nanostructures show a strong red emission corresponding to 5D0 -7F2 transition (625 nm) of Eu3+ under ultraviolet excitation (267 nm). The possible formation mechanism for the 3D flower-like precursor was briefly discussed.

Nanofiber yarns are introduced in this work, formed by PAN nanofibers electrospun from the dimethylformamide (DMF) solution via a novel process we recently developed. The fiber properties comparison at selected electrospinning parameters and different polymer concentrations are made in order to determine the influences of such parameters on the morphology and the cross-sectional shape of the nanofibers. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM), along with image processing technique are then conducted to investigate the profiles of these PAN nanofibers, in challenging the common conception of a circular cross-section for such fibers. Our results suggest that is nanofibers are in general with irregularity along the fiber longitudinal axis, it is overly simplistic to use diameter alone in describing the nanofiber thickness. So the cross-sectional shape and area are more desirable.

To date, the activation induced reorganization in membrane nanostructures and alteration in membrane adhesion property of CD4 + T lymphocytes largely remain unclear yet even though their immunological functions have been well elucidated. The present work focused on detecting the differences in topography, membrane nanostructures and adhesion/friction behaviors of CD4 + T cells in the absence and presence of stimulus (Phorbol dibutyrate, PDB, plus Ionomycin, ION). The results showed that, due to cell activation in vitro, (a) the formation of pseudopodia, lamellipodia; (b) the appearance of membrane pores with 200∼450 nm in diameter and 70∼110 nm in depth; (c) the formation of nanostructural domains with different adhesion behavior; (d) the loading rate and loading force could affect the measured adhesion force nonlinearly; (e) the dynamic changes in membrane adhesion force, from 348±9.08 pN for resting cells, 827.07±24.61 pN for 24 hours of activation, 372.87±9.26 pN for 48 hours of activation, to 302.45±11.42 pN for 72 hours of activation. This work achieved the biophysical changes of CD4 + T cells with and without stimulation, which would enable us to seek new implications and potential links between cytoarchitectures, membrane adhesion and immunological functions at the single-cell and nanoscale level.

The aim of the present study is to investigate the vitamin B12 conjugated doxorubicin loaded sterically stabilized liposomes for tumor targeting. Plain and sterically stabilized liposomes were prepared by modified ethanol injection method followed by remote loading of doxorubicin by ammonium sulphate gradient method. The sterically stabilized liposomes were coupled with vitamin B12 using post insertion technique. The average size of liposomes was found to be in range 105-128 nm and maximum entrapment efficiency was found to be 89.3-94.5 %. In vitro cell binding of SL-VB12 exhibits 6.28 folds higher binding to B16F10 melanoma cells in comparison to sterically stabilized liposomes. In vitro cytotoxicity study was conducted on B16F10 melanoma cells. SL-VB12 demonstrated strongest cytotoxicity to the tumor cells as compared to non targeted formulations i.e. PL and SL confirming that SL-VB12 was effectively taken up by tumor cells. The pharmacokinetic, tissue distribution and tumor growth inhibition studies were carried out followed by intravenous administration of liposomal formulations in C57BL/6 mice carrying B16F10 melanoma tumor. The half-life of SL-VB12 and SL was about 7.2 and 8.5 fold higher than that of free DOX, respectively. Accumulation of SL-VB12 in the tumor tissue was 18.9 and 2 times higher as compared to free DOX and SL respectively after 8 hours. SL-VB12 at the dose of 5 mg DOX/kg resulted in effective retardation of tumor growth. The liposomal formulation also prolong the survival time of mice as compared to free drug. Results indicate that vitamin B12 coupled liposomes bearing doxorubicin are significantly active against primary tumor than non targeted liposomes. In summary, our study indicated that the vitamin B12 coupled sterically stabilized liposomes (SL-VB12) could be used as a targeted carriers to facilitate the delivery of the encapsulated anticancer drugs into tumor cells by receptor mediated way.