Current Nanoscience - Volume 9, Issue 4, 2013

As the masterpiece of polymer science, biopolymers are among new and exciting areas of research. Apart from their unique physical and chemical properties which make them suitable for different applications, they are widely known as biocompatible, biodegradable and usually nontoxic polymers. Innovating biopolymer products by employing novel production processes such as electrospinning, which is an efficient method to produce nanoassemblies, incites tremendous attention in environmental scopes, industries and novel medicine. Particular properties of nanofibers and nanoweb like the nanometric size of the constructing elements, high specific volume and high porosity, endow these products with great potential for medical applications such as drug delivery systems, tissue engineering and medical equipments and clothing. Growing need for materials suitable for sustainable development and improved healthcare is motivating scientists and engineers worldwide to investigate biopolymers. Success in this direction would hinge on our ability to tailor properties of biopolymers and find cost effective processing methods. Electrospun nanofibers have found extraordinary progress due to their advanced functions. The most important advantage of nanofibers is their fine nanoscale structure which provides a large surface area and ease of functionalization for various purposes, superior mechanical properties and ease of process as suggested by many experts in this field. Authors applied a versatile nanofiber production technique known as electrospinning to process a variety of nanoassemblies from biocompatible, biodegradable and nontoxic natural biopolymers. These nanofibers and nanowebs with tailored physical, chemical, biological and mechanical properties are attractive for design of ecologically friendly products in a range of applications from personal care to healthcare such as hospital apparel, drug delivery systems, and scaffolds for tissue engineering and tissue regeneration.

Nanoparticles of lyotropic liquid crystals loaded with a new photosensitizer (a chlorin derivative) were developed for use in photodynamic therapy (PDT). These systems were characterized by spectrofluorimetric, dynamic light scattering, and small angle X-ray diffraction (SAXRD) analyses. In vitro and in vivo penetration studies in animal models were performed using animal model membranes. The systems had a particle size of 161 ± 4 nm and a polydispersity index of 0.175 ± 0.027. Furthermore, SAXRD studies demonstrated that the preparations remained in the liquid crystalline phase type hexagonal after drug loading. The encapsulation rate was higher than 50%, and cell viability studies revealed that the nanodispersion is not harmful for L929 skin cells. In vitro and in vivo penetration studies confirmed that the nanodispersion of hexagonal phase enabled a higher drug skin uptake compared to the control. Additionally, a fluorescence microscopy study demonstrated a higher biodistribution of the chlorin derivative in the skin layers of hairless mice compared to the control. Taken together, the results show the potential of this nanodispersion for the delivery of the photosensitizer into the skin, which is a crucial condition for successful topical PDT.

In this study, multiwall carbon nanotubes (MWNTs) were modified and functionalized with Amantadine, Pregabalin and Alendronate. We investigated the formation of three anti cancer agents, functionalization on MWNTs, in addition to developing the amidation of MWNTs with amines. Functionalized carbon nanotubes were characterized by Fourier transform infrared (FT-IR), Raman, transmission electron microscopy (TEM), Ultra Violent spectroscopy (UV) and toxicity assay. Biological activity with human gastric cancer cells and MTT test for measurement of viable cell numbers were also performed.

Dry powder inhalers offer many advantages in the management, prevention and treatment of various respiratory diseases and also with tumors associated with lungs. The present study investigated the feasibility of formulating Cisplatin loaded Gelatin nanoparticles as colloidal drug carriers and converting them into dry powders by coating with inhalable lactose by freeze drying. The average particle size of Cisplatin gelatin nanoparticles was found to be 314 nm by two step desolvation technique. The mean geometric size of the carrier particles was found to be 2.8 ± 0.3 μm. Freeze dried nanoparticles were further mixed with various grades of inhalable lactoses and filled into hard gelatin capsules. In-vitro drug deposition pattern and physicochemical characteristics of nanoparticulate and conventional dry powder inhaler capsule formulation were compared. Results indicated that the developed gelatin nanoparticulate dry powder inhaler capsules possessed higher respirable fraction of 31.4% as compared to conventional dry powder capsule formulation. The present investigation demonstrates that there is a possibility of delivering the nanoparticles to the lungs by incorporating them into carrier particles by simple adsorption. This provides an innovative path for delivering cytotoxic drugs to the lungs by inhalation.

Alpha-fetoprotein (α-FP, AFP) was the only serological marker currently available for the detection of hepatocellular carcinoma (HCC). As a novel biological luminescent label, the favorable properties of water-soluble CdTe quantum dots (QDs) have advantages over conventional fluorescent materials. Meantime, the magnetic separation technique has widely been applied to various aspects in biotechnology in recent years. In this paper, CdTe QDs and dextran–Fe3O4 magnetic nanoparticles were both applied on immunoassay for the determination of AFP concentration. Firstly, a mouse anti-human AFP antibody (primary antibody) was immobilized on magnetic nanoparticles, which were used as solid support. Secondly, another mouse anti-human AFP antibody (secondary antibody) was attached to the surface of the CdTe QDs via electrostatic interaction. It was found that when the pH value was 6.0, the volume ratio of CdTe (3×10-4 mol/L) to antibody (2 mg/mL) was 50:3, and the reaction time was more than 10 min, the complex of the secondary antibody and CdTe was formed and the strongest PL intensity was obtained. Thirdly, the above two complexes were conjugated with a serial of AFP concentrations. Then the relationship between the PL intensity and the AFP concentration was determined and the calibration equation— Y=k(X-9.31)/V—was obtained. Finally, ten samples of human serum were tested based on this equation. The results, to a large extent, were consistent with those obtained by Time-resolved Fluorescence. More importantly, the current method could be applied in many other antibody-antigen systems.

The present study deals with the green synthesis of silver nanoparticles (AgNPs) using Citrus reticulata juice as the reducing agent. The reaction carried out at room temperature (25°C) and at 55°C. The AgNPs were characterized by UV-Vis, TEM, XRD, AFM and FTIR measurements. The produced AgNPs were also evaluated for their increased antibacterial activities with tetracycline and penicillin against Gram-positive and Gram-negative bacteria. In this study, combination of AgNPs (at 55°C) and penicillin showed high inhibition zone in E. coli (18 mm) compared to that of AgNPs (at 25°C) and tetracycline. The cytotoxic effects of AgNPs from the Citrus reticulate juice on B16/ F10 melanoma cell line were evaluated by MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium Bromide) assay. MTT assay showed a minimum cell inhibition (14.83%) at 0.125 mM (AgNPs at 25°C) and a maximum cell inhibition (31.29%) was observed at 1 mM (AgNPs at 55°C).

Selenium is known to have cytoprotective role, which is important especially in reducing mortality due to cancer, a leading cause of death worldwide. The present work addresses synthesis and evaluation of selenium nanoparticles (SeNPs) as therapeutic alternative to conventional chemotherapeutic agents. Selenium nanoparticles were synthesized by an eco friendly method using whole cells of Saccharomyces boulardii. Parameters like culture age (stationary phase growth), cell mass concentration (100 mg/ml), temperature (35°C) and reaction time (72 h) were optimized to produce nanoparticle with controlled properties. Nanoparticles were recovered by alkali hydrolysis and subjected to UV-Vis spectroscopy, EDX (energy dispersive X-rays) analysis, electron microscopy, elemental analysis and size determination. Dynamic light scattering analysis reveals negative zeta potential value of 14.8 mV and PDI of 0.25. Experiments to prove possible involvement of sulfite reductase in nanoparticle formation has been carried out. Moreover, cytoprotective role of selenium nanoparticle has been shown by cell viability in MTT assay.

Zinc oxide nanomaterials have sought considerable biomedical applications. The varying grain sizes of zinc oxide nanoparticles (ZnO NPs) were prepared by wet chemical precipitation method. Particle size and morphology of the as-prepared ZnO powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectroscopy, dynamic light scattering and transmission electron microscope (TEM). The antimicrobial and cytotoxic activity of varying sizes of ZnO NPs was investigated in gram negative microorganisms and in colo 320 human adenocarcinoma cancer cells. The relationship between physico-chemical properties and oxidative stress response in cell viability and toxicology was determined. The zone of inhibition by nanoparticles ranged from 18 mm to 22 mm. The estimated inhibitory concentration (IC50) values for different sizes of zinc oxide nanoparticles were calculated as 156.25 µg.ml-1 for 15 nm ZnO NPs, 191.5 µg.ml-1 for 25 nm ZnO NPs and 225.3 µg.ml-1 for 38 nm ZnO NPs. Varying sizes of ZnO NPs were partially dissolved to Zn species (Zn(dis)) in Roswell Park Memorial Medium (RPMI) and in milli-Q water. Maximum dissolution of Zn species was observed in milli-Q water. According to the results of the present study, mechanisms of action and cellular consequences resulting from varying sizes of ZnO NPs interactions with infectious microbes and cancer cells suggest that particle size not exceeding 25 nm can be further improved with surface functionalization and loading anti-cancer and anti-bacterial agents.

Cotton is a widely used raw material for textiles but drawbacks regarding their poor mechanical properties often limit their applications as functional materials. The present investigation involved process development for one step coating of cotton with silver nanoparticles (SNP) synthesized using Azadirachta indica and Citrus limon extract to develop functional textiles. Addition of starch to functional textiles led to efficient binding of nanoparticles to fabric and led to drastic decrease in release of silver from fabricated textiles after ten washing cycles enhancing their environment friendliness. Differential scanning calorimetry, scanning electron microscopy, FTIR analysis and mechanical studies demonstrated efficient binding of nanoparticles to fabric through bio-based processes. The functionalized textiles developed by the bio-based methods showed significant antibacterial activity against E. coli and S. aureus (with 99% microbial reduction). Present work offers a simple procedure for coating SNP using bio-based approaches with promising applications in specialized functions.

PVA/PAA/PEG/PVP nanofibers with HPMC and aloe vera were fabricated by electrospinning method. HPMC was added to the hybrid polymer solution as the water retention agent and aloe vera which are known over centuries were also added to the system to promote the healing of wounded or infected skin. The fabricated nanofiber mats were characterized using SEM, DSC, and FT-IR. SEM Images exhibited that the electrospun nanofibers were homogenous and linear. The nanofiber diameters ranged between 80-480 nm.

We have prepared different sizes of CdSe nanoparticles with different amounts of capping molecules on their surface. Through Colloidal method, the nanoparticles were prepared using different starting precursors and different ratios of the starting reagents. We have characterized the prepared nanoparticles by Energy dispersive X-ray (EDX), X-ray diffraction (XRD), UV-Vis optical absorption, infrared spectroscopy and thermogravimetric analysis. The EDX analysis showed that the extracted nanoparticles have different ratios of the constituent of the capping molecule relative to CdSe core. X-ray and UV-Vis analysis revealed that there is a graded diffusion of sulfur on the surface of the nanoparticles. The graded diffusion of sulfur decreased for the rich selenium prepared samples. Infrared analysis proved the coordination of thiol and carboxylate groups to the surface of the nanoparticles. On the other hand, thermogravimetric analysis showed that the size of the nanoparticles and amount of capping molecules have a high influence the thermal degradation of the nanoparticles.

A comparison of the performance of some specific topological indices was conducted. The study was concentrated on determining which topological indices are included in the best linear correlation models constructed for modeling the total energy of zig-zag nanotubes. The normalization of some particular widely used topological indices such as the Wiener index, Shultz index, hyper Wiener index, Harary index, Szeged index, multiplicative Wiener index and reciprocal complementary–Wiener index plus total energy of 56 zigzag polyhex nanotubes was considered in this study.

In the backdrop of probabilistic computing defining the landscape of nanoscale digital logic circuits, a combinational circuit is usually specified in terms of a set of fully connected variable nodes called the ‘clique’. The clique energy or clique potential is an indicator of correct circuit operation under the premise of non-deterministic nature of device parameters at nanoscale dimensions. Also, the clique potential forms an important parameter in the probabilistic analysis of digital circuits with respect to the Markov random field model as well as in computing the probability density function. The major problem inherent in determining the clique energy expression of an arbitrary logic function that features multiple inputs and outputs is the computational complexity. The number of primary inputs and outputs governs the order of the clique potential, and hence an explosion of input and output state spaces is imminent. In this context, this paper presents a novel scheme of deriving the clique expression by segregating the primary outputs and operating upon them in parallel, thus restraining the state space expansion significantly by O(2n-1) where n signifies the number of primary outputs of the combinational logic. The important result shown in this work is that the clique potential of an arbitrary combinational circuit is equal to the Boolean product of clique potentials of its primary outputs.

The electrical, electronic and optical properties of multilayer graphene (MLG) films have been investigated systematically using a 4-point probe method, ultraviolet photoelectron spectroscopy, and ultraviolet/visible spectrometer. Monolayer graphene and MLG (2, 3, 4 and 5 layers) films were prepared on glass and SiO2 substrates using a chemical vapor deposition and multi-transfer process. Raman spectroscopy was used to evaluate the quality of MLG films. Sheet resistance, work function and transmittance were measured systematically for each monolayer graphene and MLG films. In addition, surface treatment with HNO3 was performed to reduce the sheet resistance of the MLG films. The sheet resistance was reduced to 198 Ω/square after the treatment without any significant change in the MLG film quality. These results will provide useful information for the optoelectronic devices based on MLG films.

In the present work, the effect of chirality on the resonant behavior of the single walled boron nitride nanotube (SWBNNT) based on nanomechanical resonator has been reported. The structural molecular mechanics based on finite element model has been developed to simulate the different chiralities of the SWBNNTs. The cantilevered configuration of SWBNNT is considered to analyze the resonant behavior of the SWBNNT based resonators. The resonant behavior due to different values of added mass at the free-end of the nanotube is analyzed for the nanotubes of three different diameters, 0.6924 nm, 0.7993 nm and 0.8990 nm. The variation in chiral angle, between zigzag form (chiral angle,  = 0°) to armchair form ( = 30°) is considered. The resonant frequency variation due to attached mass is analyzed for different chiral angles for particular diameter and for different lengths of the nanotube in terms of the aspect ratio (length/diameter). The analysis of sensitivity check of zigzag form and armchair form is performed using present methodology. The resonant frequency variation due to change in length of nanotube is more significant as compared to that due to change in diameter of nanotube. The mass sensitivity limit of 10-25 kg can be achieved using SWBNNT based nanomechanical resonators. The change in chirality alters the resonant behavior of the nanotube. The obtained results show that with the decrease of chiral angle, the resonant frequency of the nanotube also decreases, which indicates that as the chiral angle decreases then the atomic structure of the nanotube turns to more closely packed structure and become more sensitive. The zigzag form of nanotube is more sensitive as compared to the armchair form of SWBNNTs.

Tin doped antimony sulfide thin films have been grown on glass substrates at room temperature by vacuum thermal evaporation method. The doping was carried out during the growth by two source method with the aim to investigate its effects on electrical, structural and optical properties of 1, 2 and 3 wt.% Sn-doped Sb2S3 thin films. Using transmission spectra in the range of 200-1800 nm, the absorption coefficient of the deposited films in the fundamental absorption edge has been analyzed to identify the possible optical transition in these films, where the energy band gap corresponding to the optical transition is calculated. Hot point probe method has been used to study the conductivity type and photoconductivity values of the thin films in the wavelength range 380-1100 nm of the incident photons. Effects of doping on external quantum efficiency (EQE) are also investigated.

In this paper new glutamic acid diethyl ester imide derivatives with different alkyl substituent chains were designed and synthesized. Their gelation behaviors in 21 solvents were tested as novel low-molecular-mass organic gelators. It was shown that the length of alkyl substituent chains linked to benzene ring in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. Longer alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. SEM and AFM observations revealed that the gelator molecules self-assemble into different aggregates from wrinkle, lamella, belt, to fiber with change of solvents. Spectral studies indicated that there existed different H-bond formations and hydrophobic forces, depending on the alkyl substituent chains in molecular skeletons. The present work may give some insight to design and characterize new versatile organogelators and soft materials with special molecular structures.

20nm SiNWs transducers have been fabricated by means of simple in-house fabrication method. A low cost, simple top-down approach has been successfully used for the fabrication of very sensitive SiNWs. The fabrication was done without using costly deep reactive ion etching (DRIE) or reactive ion etching (RIE). The process started by patterning wire marked through photoresist and the marked resist was deepened into buffered oxide etch (BOE) for 30mins to etch away the oxide present on the polysilicon surface leaving the photoresist masked portion un etched. Wires of <3µm were obtained with 6 buffered thermal re-etch processes. The wire pattern was trimmed to 20nm using dry etching with constant 5% reduction at 1100°C for 40/5 minutes for Oxidation/BOE respectively. Electrical characterization conducted has shown an increase in sensitivity with the reduction in size while resistance increases at constants 70V supply, the characterized device was surface modified and tested on real sample. The device shows a very good response to the concentration of molecular species in the sample and surface morphology of the device was verified using high powered microscope (HPM) and scanning electron microscope (SEM) for the size reduction. Moreover, the technique can be easily employed for different semiconductor materials without any additional complexity. Hence, a novel and simple approach for fabricating SiNWs as sensors in nanosized with high uniformity is demonstrated.

M-type lead hexaferrites with compositions of PbFe12O19 and PbSnZnFe10O19 were synthesized by the citrate sol–gel method. The structural and magnetic properties of resultant particles were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer. The magnetic properties such as saturation magnetization (Ms) and coercivity (Hc) were calculated from the hysteresis loops. Microwave absorption properties of ferrite–polymer composites prepared with different ferrite ratios of 50%, 60%, 70% and 80% have been investigated in the frequency range of 12–20 GHz. The composite powder with 80 wt% lead ferrite possesses good microwave absorption properties. The minimum reflection loss of the composite powder reaches –30 dB at the thickness of 2 mm for composite powder with 80 wt% ferrite. The composite with 80% ferrite content has shown a minimum reflection loss of -24.5 dB at 18.6GHz with the -15 dB bandwidth over the extended frequency range of 16.3– 19.4GHz for an absorber thickness of 1.8 mm. The prepared composites can fruitfully be utilized for suppression of electromagnetic interference (EMI) and reduction of radar signatures (stealth technology).

One-pentagonal carbon nanocone consists of one pentagon as its core surrounded by layers of hexagons. If there are n layers, then the graph of the molecules is denoted by Gn. In this paper our aim is to explicitly calculate the hyper-Wiener index of Gn.