Current Nanoscience - Volume 8, Issue 6, 2012

The current study was designed to find out the cancer cell killing efficacy of as-synthesized dumbbell-shaped Fe3O4 and γ- Fe2O3 magnetic nanoparticles under AC (alternating current) magnetic-fields induction condition. Dumbbell-shaped Fe3O4 and γ-Fe2O3 magnetic nanoparticles were successfully prepared by a modified hydrothermal method. Ferrous chloride tetrahydrate was solely used as a precursor for the nanomaterials. The as-synthesized nanomaterials were characterized by using XRD, FE-SEM and TEM. Dumbbellshaped particle morphology was observed for the first time in all of iron oxides with magnetic properties. The particle size observed was 50–60 nm. The synthesized nanomaterials showed acceptable magnetization values when magnetic hysteresis loops were measured using a superconducting quantum interference device (SQUID) as well as colloidal stability. Moreover, the as-prepared magnetic nanoparticles suspensions showed significant temperature increments and cancer (HeLa) cell destroying potentiality (91% and 95% for Fe3O4 and γ- Fe2O3, respectively) under an AC magnetic-field induction condition at room temperature using the concentration of 150 μg/mL.

Aim of this work was to study the technological parameters influencing the adsorption process of Bovine Serum Albumin (used as model protein) on the surface of PLGA (polylactic co-glycolic acid) based nanoparticles. Several factors as adsorption mediums, concentration ratio between proteins and nanoparticles, temperature, time of incubation were evaluated and main importance was done to the chemical characteristics of polymers and surfactants used for nanoparticles obtainment. Afterward adsorption studies, further tests of permeation through cellular monolayers and synthetic membranes were done in order to study the desorption process of BSA from nanoparticles surface. The mediums influence on the desorption rate of the protein from the nanoparticles and the influence of polymeric excipients on the permeation profile of the protein were evaluated. Data showed demonstrated that the adsorption process as well as the desorption capability and the permeation rate of BSA are strictly influenced by the nanoparticles composition and several kind of interactions between polymers and protein.

The interaction between human serum albumin and cholesterol-modified pullulan (CHP) nanoparticles with different degrees of substitution (DS) of cholesterol moiety was investigated using spectroscopic and thermodynamic methods. Albumin fluorescence intensity was quenched by nanoparticles with maximum emission intensity decreasing at the initial reaction and increasing at the last reacted period. Binding constants (Kb) were 1.12 x 105 M-1, 4.12 x 105 M-1 and 7.44 x 105 M-1 to CHP-3.11, CHP-6.03 and CHP-6.91, respectively, as determined by Stern-Volmer analysis. Adsorption of albumin to nanoparticles was an exothermic reaction process and revealed a higher DS of cholesterol moiety with higher enthalpy and entropy changes. Upon interaction with nanoparticles, albumin conformation changed with a reduction of α-helix, suggesting a partial protein unfolding. Furthermore, albumin could gradually change its helical structure due to the structural change of the complexed nanoparticle. Particle hydrophobicity and shell-core structure play a main role in the alteration of albumin conformation in the nanoparticle-protein interaction process.

Stable silver nanoparticles (AgNPs) with narrow size distribution were non-enzymatically synthesized through hydroxyl ions (OH-) assisted bioreduction of diamine silver complex with dry Aeromonas sp. SH10 cells. The effects of reaction temperature, concentrations of OH-, silver and the dry cells on the reduction of Ag ions as well as on the properties of the AgNPs were investigated. Results show that the introduction of appropriate quantity of OH- ions considerably accelerates the process. In fact, higher yields of AgNPs (> 95%) could be obtained at relatively higher initial silver concentration (1 g·L-1) with more than 1 g(Ag)·g(bio) -1 productivity of AgNPs. Plausible bioreductive mechanism is therefore proposed; wherein [Ag(NH3)2]+ ions initially reacted with OH- to form an unstable AgOH. This is then transformed into Ag2O spontaneously, and finally non-enzymatically reduced into AgNPs by the cells.

The least efficacy of most of the active pharmaceutical ingredients in the brain is attributed to the blood–brain barrier (BBB), which represents insurmountable obstacle for the effective management of majority of CNS disorders. The present research was planned with the objective to design novel poly (d, l) lactide (PLA) nanoparticles coupled with natural tripeptide i.e. glutathione to enhance drug delivery to brain. To evaluate the brain targeting efficiency of the glutathione conjugated nanoparticles, fluorescein sodium was explored as a model compound due to its polar nature and least possibility to cross BBB. The entrapment efficiency of fluorescein sodium was improved by screening several formulation variables like drug: polymer ratio, solvent selection, electrolyte addition and pH alteration. Scanning Electron Micrograph (SEM) and dynamic light scattering results of optimized formulation showed that prepared nanoparticles have a round and regular shape with a mean diameter of 257.8 ± 3.78 nm with narrow size distribution. Biodistribution pattern and brain targeting potential of optimized glutathione conjugated PLA nanocarriers was determined using wistar rat as an animal model in comparison to non-conjugated PLA nanoparticles and fluorescein sodium solution. The results showed significant increase in fluorescein sodium uptake in brain with glutathione conjugated PLA nanoparticles as compared to fluorescein sodium solution. The present investigations demonstrated that glutathione can serve as a potential ligand for brain drug delivery, which was observed with glutathione coupled PLA nanoparticles resulting into enhanced delivery of drug to nearly 5 folds in the brain.

Nanosized Nd-doped strontium ferrites, SrNdxFe12-xO19, with x=0.3, were successfully prepared through a chemical coprecipitation process. The samples were characterized by TG-DSC, XRD, FT-IR. The results of TG-DSC and XRD showed that the single phase of Nd-doped strontium ferrite formed directly through the reaction of SrCO3, amorphous Fe2O3 and Nd2O3, without other intermediate phases. The crystallite size was around 35 nm.

The core-shell structure SiO2@Ag nanoparticles were synthesized by a facile chemical reduction method. Firstly, the mercapto- silica spheres had been prepared by the stober method, in which 3-mercaptopropyltrimethoxysilane (MPS) was used as a sole silica source. The reaction involves mixing the MPS precursor, ammonia in aqueous solvent at room temperature. Secondly, the core-shell structure SiO2@Ag nanoparticles were synthesized by reducing AgNO3 on the surface of mercapto-silica spheres in the presence of the reducing agent. The core-shell structure SiO2@Ag nanoparticles were investigated by means of ultraviolet–visible absorption spectroscopy (UV-vis), high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Antibacterial properties of the as-synthesized SiO2@Ag nanoparticles were investigated using both Gram negative of Escherichia coli (E. coli) and Gram positive of Staphylococcus aureus (S. aureus) as bacterial strains. The results show that the coreshell structure SiO2@Ag nanoparticles exhibit excellent antibacterial properties against E. coli and S. aureus bacteria.

Nanoparticles as antimicrobial agents are a novel field in nanomedicine and nanobiotechnology. Unlike many investigations about antimicrobial effects of silver nanoparticles, few experiments have been conducted about the impact of iron-oxide nanoparticles on microorganisms. In the current paper, we have synthesized and characterized amino acid (L-arginine and L-lysine)-coated magnetite nanoparticles and evaluated the effects of these particles on a pathogen strain of Listeria monocytogenes. Primary antibacterial tests were done by the microdilution method and for more investigation the effects of nanoparticles on the growth curve of L. monocytogenes were analyzed by a microbiological analyzer. We found that, in low concentrations (below 20 μg/ mL), L. monocytogenes can benefit from magnetite nanoparticles for more growth, probably as an iron source, but as concentration increases gradual bacteriostatic effects would appear and at 40 μg/mL magnetite nanoparticles have a significant bacteriostatic effect.

Mesoporous, magnetite based nanoparticles (MNPs) were successfully synthesized by a modified precipitation method. For this purpose, the precursors' solution was sprayed into a sodium hydroxide or sodium hydroxide/citrate precipitation bath. In order to determinate the structure and morphology of the as-synthesized mesoporous MNPs the following methods were used: X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), infrared spectra (IR), high-resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED) and energy dispersive spectrometry (EDS). The Brunauer–Emmett–Teller (BET) analysis revealed a mesoporous structure of the samples which has a specific surface area of about 160m2/g (unstabilized Fe3O4 nanoparticles) and 247 - 257 m2/g (for the stabilized Fe3O4 nanoparticles). The average pore size of the MNPs is 2 – 5nm which means that mesoporous materials were obtained.

In the present paper, we have described the interesting behavior of molybdophosphoric acid (H3[PMo12O40], HPMo) in the size-controlled synthesis of silver nanoparticles under UV-irradiation. In this process which is based on the reduction of Ag+ (AgNO3), HPMo plays the role of photocatalyst, reducing agent as well as stabilizer, and propan-2-ol acts as a sacrificial agent. The method allows the rapid synthesis of uniform spherical nanoparticles with an average size that varies between 2.2 and 35.2 nm by altering the silver ion concentration, molar ratio of silver ion to HPMo (or dose of HPMo) and Propan-2-ol amount. It is found that there is a critical ratio for [Ag+]/[HPMo] (i.e. 3.8 in the present case), in which two opposing trends in the size of silver nanoparticles take place.

Vinorelbine tartrate is a semi-synthetic drug with a broad-spectrum anti-tumor activity. An injectable formulation of vinorelbine (Navelbine® IV) has been widely used in the world, despite existing some disadvantages. In this study, in order to improve the efficacy of vinorelbine injection metabolism with minimal side effects, rHSA nanoparticles entrapping VLBT were prepared by a desolvation procedure, and subsequently decorated by folic acid. A central composite design was applied for modeling the process. To some extent, the drug release rate could be adjusted by cross-linking with different amount of glutaraldehyde. In this paper, FarHSANPs- VLBT with three degrees (25%, 50% and 75%) of cross-linking were obtained under the optimum conditions for preparing the nanoparticles. Then we carried out a further study to compare the characteristics of the nanoparticles, such as drug entrapment efficiency (DEE), drug-loading efficiency (DLE), surface morphology, surface chemistry, physical status of VLBT in Fa-rHSANPs-VLBT, amount of folate conjugation, and release kinetics in vitro. The experiment results displayed that as the degree of cross-linking increased, both the zeta potential (ZP) and folate content associated with the VLBT-rHSANPs showing a reduced tend. Moreover, the increasing glutaraldehyde concentration made the rate of release of the VLBT from these nanoparticles decrease.

Self-decoration of silver (Ag) nanoparticles on the surface of titanium dioxide (TiO2, Degussa P25) photocatalyst are prepared via simple solution chemistry in absence of specific organic ligands for metal reduction, with an available natural light source. An in-situ method is carried out for the self-induced decoration of Ag nanoparticles onto the TiO2 surfaces and the properties of the metal nanoparticle have been revealed based on the photocatalytic activity. The average particle size of the self-decorated Ag nanoparticle on the TiO2 surface was ~2 nm. The photocatalytic degradations of fluorescein dye in aqueous suspensions of pure TiO2 and Ag/TiO2 photocatalysts were studied under Xenon light irradiation. We found that the photocatalytic degradation rate was largely influenced by the particle size of the self-decorated Ag nanoparticles on the TiO2 surface. The proposed photodegradation mechanism proved the possibility visible light excitation due to localized surface plasmon resonance and the electron transfer from the plasmonically excited Ag nanoparticles to the conduction band of TiO2 in addition to the usual ultra-violet excitation. The combined UV and visible light excitation improve the photodegradation behavior on fluorescein dye molecules effectively over the 83% of dye degradation.

A study on the uptake of silica source by maize seeds was conducted under hydroponic conditions and pot experiments supplemented with nano-SiO2 (20–40 nm) extracted from natural source (rice husk) and their bulk silica counterparts such as micro-SiO2, sodium silicate, and silicic acid. Employing hydroponic incubation experiment to explore the nanosilica absorption is a novel approach in maize. Seeds after different silica source treatments were analyzed with regard to germination percentage (GP %), elemental analysis, and root growth parameters to investigate the efficiency of nano-SiO2. Hydroponic culture studies revealed an increase in GP (95.5%), dry weight (6.52±0.2), silica accumulation (18.2%), and better nutrient alleviation in seeds exposed to nano-SiO2 than in those exposed to bulk sources. Variations in the pH, conductivity and SiO2 content in the hydroponic solution reflect the utilization of silica by seeds. Maize seeds and roots during pot experiments absorbed nano-SiO2 better when compared with absorption of other micron sources, which led to the conclusion that nano-SiO2 can be used as an immediately utilizable source for plants.

The temperature-dependent property of band gap in colloidal PbSe quantum dots has been investigated from both experiment and theory above room temperature. When the particle size increases, the temperature coefficient evolves from negative values to zero and then to positive value following the trend to its bulk material value. The calculated critical size of 4.88 nm for the temperature coefficient dE / dT = 0 is consistent with the experimental result. When the particle size is smaller than the critical size, the temperature coefficient dE / dT is also dependent on the temperature, which has not been observed before. However, this phenomenon is not obvious at large particle sizes. The functions of size- and temperature-depended band gap E and temperature coefficient dE / dT are achieved through theoretical calculation and experimental calibration. Temperature-induced variations of quantum confinement energy and exciton- phonon coupling are the key factors for the temperature coefficient. The balance between the variations of confined effect and exciton- phonon coupling causes the critical size of temperature coefficient in colloidal PbSe quantum dots.

We report efficient conversion of any of the primary colors to white light under ambient conditions, by ZnO nanostructures. Not only UV, blue, and NIR LEDs, but also the green and red LEDs can be used for the production of white light. The conversion efficiency is supposed to be high and it is possible to tune the nature of white light (warm, natural and cool). Correlated color temperature can be tailored by changing the excitation source. The white light emission does not depend on vacuum, or doping or any magic size or any specific design of nanocrystal.

High quality 3%Cu-SnO2 nanoparticles have been prepared onto the glass substrate by using novel and economical ultrasonic spray pyrolysis technique. The X-ray diffraction patterns showed that 3% Cu-SnO2 nanoparticles formed in tetragonal rutile structure. The intensities of peaks shown by X-ray pattern were indexed as (110), (101), (200) and (211). The microstructure, surface morphology, particle size and elemental properties of 3%Cu-SnO2 nanoparticles were characterized using, scanning electron microscope (SEM), and Transmission electron microscopy (TEM). These nanoparticles were tested for H2S sensors applications. It was observed that 3% Cu-SnO2 nanoparticles exhibited remarkable sensitivity to H2S (200 ppm) gas at 150ºC, more precisely showing good response and recovery.

Silicon and polysilicon based nanogap electrode devices have been developed. The devices are able to detect lower concentrations of yeast at various pH values. Nanogap electrodes sense subtle changes due to molecular species perturbing the electrochemical signals across the gap. Two different materials and size of the nanogap electrodes were used to detect the biochemical solutions. Silicon and polysilicon nanogaps electrodes were characterized electrically by measuring the current-voltage and by optical imaging using SEM and FESEM. The capacitance, permittivity and conductivity were measured using a dielectric analyzer to sense and to profile pH under a simple and complex background. Polysilicon based electrode showed slightly higher sensitivity to the permittivity and conductance as compared to silicon based electrode over the same range of concentration. The data suggest that these electrodes can be used as low cost electrical devices for biomolecular sensing while consuming very low power (voltage).

In this communication, we report on a novel green photocatalytic route to synthesize Au nanoparticles/multi-walled carbon nanotubes (AuNPs/MWCNTs) nanocomposites with the use of Sn-porphyrin (SnP) as a high-efficiency photocatalyst to reduce Au3+ to form AuNPs onto MWCNTs. Such AuNPs/MWCNTs nanocomposites exhibit good catalytic performance toward both oxidation and reduction of H2O2. An electrochemical glucose biosensor was further constructed by dropping glucose oxidase on the surface of AuNPs/MWCNTs nanocomposites modified glassy carbon electrode. The biosensor shows linear response toward different concentrations of glucose from 1 to 33 mM (r = 0.998) and the detection limit at 0.5 V is estimated to be 240 μM at a signal-to-noise ratio of 3.