Current Nanoscience - Volume 3, Issue 2, 2007

The assembly of two or more inorganic nanoparticles results in hybrid materials with enhanced properties. These include improvements in catalytic activity, changes in optical behavior, and potential gains in electronic properties. However, these are only attained through precise synthetic control of the resulting material with respect to structure, organization, size, and composition. Fortunately, biological systems are exceptional at the synthesis and assembly of diverse inorganic materials at many different length scales; and as result, has inspired many different approaches towards the biomimetic synthesis of hybrid inorganic materials.

Pd/ZrO2 nanocomposite materials were synthesised following a two-step procedure. Firstly, tetragonal zirconia was prepared via a chemical route; then it was subjected to an in-situ electrochemical impregnation with palladium nanoparticles. Different process times lead to a different Pd loading in the resulting material. Pd/ZrO2 powders were subjected to morphological and spectroscopic characterisation. Transmission electron microscopy (TEM) analysis showed that ZrO2 nanograins have an average size of 150±70nm, and are composed of smaller sub-grains (average diameter = 40±10 nm). Spherical Pd nanoparticles are evenly dispersed on the oxide support, their average core diameter being 6.9±1.8 nm. X-ray Photoelectron Spectroscopy (XPS) was used to asses the materials surface chemical composition. Testing the catalysts for the CO oxidation revealed an appreciable activity of the Pd-modified ZrO2 samples. TEM and XPS analyses were also performed on materials exposed to prolonged catalytic runs and contributed to shed light on the catalysis mechanism. A rationale for the results obtained on the CO conversion process was proposed, invoking a key- catalytic role of finely dispersed PdO sites. The nanomaterial morphological stability and reactivity encouraged to employ it in the Heck synthesis of butyl cinnamate. This process was demonstrated to take place with high conversion values and interesting stability towards catalyst recycling.

Although many sophisticated methods for specific detection of a biological material (from cells, through viruses to nucleic acids and proteins) are available, there is still a need for their improvement. Particularly, an optimal method should be sensitive, rapid and quantitative. However, it appears that traditional molecular biology procedures are often either too long or semi-quantitative at best. This makes particular problems in medical and biotechnological approaches, where rapid and quantitative assays are required for either detection of specific pathogens or continuous monitoring of biotechnological processes (e.g. production of certain components by microbes in bio-reactors or detection of bacteriophage contamination in bacterial cultures). In this review, we present a recently developed nanotechnique of electric bio-chips, which appears to be suitable for rapid and quantitative detection of various biological materials. One of variants of this technique is based on miniaturized amperometric biosensor devices that enable evaluation of biomolecular interactions by measuring the redox recycling of enzymatic reaction products. Electric bio-chips were reported to be useful for detection and quantification of both biological macromolecules (nucleic acids and proteins) and microorganisms (bacteria and viruses). Thus, it appears that this technique may be successfully employed in various bio-medical and biotechnological applications.

The instrumentation literature associated with nanoscience and nanotechnology research was examined. About 65000 nanotechnology records for 2005 were retrieved from the Science Citation Index/ Social Science Citation Index (SCI/SSCI) [1], and ∼27000 of those were identified as instrumentation-related. All the diverse instruments were identified, and the relationships among the instruments, and among the instruments and the quantities they measure, were obtained. Metrics associated with research literatures for specific instruments/ instrument groups were generated.

A molecularly alternating self-assembled film and heterostructured capsule of titania nanosheets/gold nanoparticles has been successfully fabricated by layer-by-layer self-assembly of titania nanosheets and positively charged gold nanoparticles as electrostatic building blocks. The films were characterized with atomic force microscopy and UV-vis absorption spectroscopy. The nearly linear increase in both UV-vis absorbances as a function of the sequential assembly number demonstrates the regular growth of the composite film. The electrochemcial property of the fabricated (titania nanosheet/Au nanoparticle)n multilayer film was examined by measuring cyclic voltammograms. The heterostructured capsule from a UV-sensitive poly(methyl methacrylate) as a sacrificial template was characterized by field-emission scanning electron microscopy and transmission electron microscopy. The energy-dispersive X-ray spectrometer verifies the composition of Ti and Au elements of the heterostructured capsule.

DNA, the blueprint of life, has taken centre stage in biological research during the past few decades. DNA plays an important role in molecular biology as the carrier of genetic information in all living species. Bio-physicists and chemists have become increasingly interested in the electronic properties of the “molecule of life”; DNA. Experiments are now starting to provide the first clues about the mechanisms that underlie charge transport in DNA. They sparked the creation of whole new industries based on this knowledge and on the various biotools and technologies that have subsequently developed. Biologically, the well-known function of DNA is to code for functional proteins that are the expressed form of hereditary, genetic information. But in the past few years, the discovery that DNA can conduct an electrical current has made it an interesting molecule for other roles that nature did not intend for this molecule. DNA could be useful in nanotechnology for the design of electronic circuits, which could help to overcome the limitations that classical silicon-based electronics is facing in the coming years.

Metal nanoshells have found promising applications in biomedical imaging and cancer therapy. To facilitate the application of nanoshells in scattering based imaging techniques, it is essential to characterize their light scattering properties. We have studied the light scattering from nanoshells at the quadrupolar and octupolar frequencies of the surface plasmon resonance, and our measurements are in good agreement with Mie theory calculations for both wavelengths. For in vivo use of nanoparticles in biomedical imaging and therapy, surface modification is of great importance in enhancing the stability and biocompatibility of these particles, and polyethylene glycol is commonly used for the surface modification of metal and semiconductor nanoparticles. However, the influence of surface modification on the optical properties of nanoparticles has not been systematically studied yet. Here, we also report the study on the polarized and angularly- resolved light scattering properties of gold nanoshells before and after polyethylene glycol modification. We find that polyethylene glycol does not influence the extinction profile of gold nanoshells. Furthermore, there is no significant change in the scattering phase function of nanoshells after polyethylene glycol modification.

Magnetite (Fe3O4) nanosheets have been prepared by a simple microwave heating method using ferrous sulfate and sodium hydroxide in mixed solvents of ethylene glycol and water. Fe3O4 nanosheets were obtained by the oxidation of the deep green precursor with the sheet morphology in an alkaline solution. Our experiments show that iron salt, the ratio of OH- to iron ions and the heating method have effects on the morphology or crystalline phase of Fe3O4. Both Fe3O4 nanosheets and nanoparticles exhibit a small hysteresis loop at room temperature. The saturation magnetization of Fe3O4 nanosheets is smaller than that of Fe3O4 nanoparticles.

Fabrication of nanomaterials with hollow interiors is an important research area in nanoresearch, owing to their potential applications in photonic devices, drug delivery, material encapsulation, ionic intercalation, surface functionalization, nanocatalysts, membrane nanoreactors, and many other technologies. The common preparative methods for this new class of materials can be broadly divided into hard and soft template-assisted syntheses. In recent years, furthermore, the interest in template-free techniques for these materials has also increased, as the new processes involved in these techniques are relatively simple and less demanding, compared to the template-assisted processes. In this short review, we will introduce the application of a well-known physical phenomenon of crystal growth - Ostwald ripening - in the fabrication of hollow nanomaterials. It has been demonstrated that formation of the interior spaces of nanostructures depends on the aggregative states of the primary crystallites during the synthesis. With this new development, many inorganic nanomaterials with interior spaces can now be fabricated in solution media together with the materials synthesis. Different types of Ostwald ripening observed in this synthetic approach have been reviewed. In particular, various geometric structures and configurations prepared with these methods have been discussed. The prepared hollow materials also allow further compositional and structural modifications under the similar process conditions. Future directions in this research area are also discussed.

An increasing percentage of drug development candidates suffer from poor aqueous solubility which in turn often times leads to poor oral absorption. This poses significant challenges in formulation development to ensure bioavailability following oral administration. Traditional approaches to increase dissolution of immediate release formulations include incorporation of surfactants, reduction of particle size and liquid vehicle formulations. More recently, size reduction of either the active pharmaceutical ingredient (API) particle or the drug delivery system down to the sub-micron range appears as a new promising approach to further increase dissolution rates of hydrophobic molecules. Nanonization of either the API, in the form of nanosuspensions typically stabilized with surfactants, or of the formulation vehicle such as with the use of self-nanoemulsified drug delivery systems and solid lipid nanoparticles has been successfully utilized to increase in vivo dissolution. Such nanotechnology has demonstrated significant impact on enhancing the bioavailability of drug candidates and addressing issues such as inadequate exposure or food effect. The goal of this review is to summarize recent advances in the utilization of nanosuspensions, solid lipid nanoparticles or nanoemulsions in drug delivery of immediate release dosage forms.

Albendazole, a lipophilic anthelmintic drug, has low solubility and bioavailability. Albendazole nanosuspensions (ABZNS) were developed using different surfactants (Polysorbate 80 & Poloxamer 188) and hydrophilic mucoadhesive polymers (Hydroxypropyl Methylcellulose) by pre-homogenization followed by high pressure homogenization. Particle size and charge measurements were made with a Malvern Zetasizer. Pharmacokinetics of optimized albendazole nanosuspensions after oral administration to conscious Wistar rats was studied. Average size and zeta potential of optimized formulations of albendazole nanosuspensions ranged from 385.7± 4.3 to 576.2 ± 4.8 nm and - 23.5 ± 1.8 to - 40.5 ± 0.8 mV, respectively. Bioavailability of albendazole nanosuspensions was 2.14 to 2.96 fold after oral administration compared with that of control suspension. These results indicate the potential of nanosuspension in improvement of oral bioavailability of lipophilic drugs such as albendazole.