Current Nanoscience - Volume 5, Issue 1, 2009

Controlled drug delivery systems and polymeric carriers have undergone significant development in recent years. Polymers like polylactides (PLA), polyglycolides (PGA), poly(lactide-co-glycolides) (PLGA), are approved by the World Health Organization (WHO) and Food and Drug Administration (FDA) as materials that can be used in medicine and pharmacy. Owing to their biodegradable nature, polymer materials, such as copolymer poly(DL-lactide-co-glycolide), are widely used in various medical applications; controlled release of delivering drugs, carriers in the tissue engineering, fixation of bone fractures, chirurgical strings, etc. Polymeric particles are used for the controlled delivery of several types of medicaments, including anticancer agents, antihypertensive agents, immunomodulatory drugs, hormones, vitamins and macromolecules, such as nucleic acid, proteins, peptides, antibodies, etc. Preparation of poly(lactideco- glycolide) submicron spheres poses serious challenges. The present review attempts to address some important issues related to micro/ nanoparticle-based delivery systems comprising poly(lactide-co-glycolide), with a special reference to PLGA for the controlled delivery of vitamins. A range of topics is discussed, including formulation aspects of micro- and nanoparticles, the effects of particle size and size distribution, most commonly used incorporation techniques, surface modification with stabilizers, surface functionalization, and factors affecting degradation and drug release rate.

Brain is a delicate organ, isolated from general circulation and characterized by the presence of relatively impermeable endothelial cells with tight junctions, enzymatic activity and the presence of active efflux transporter mechanisms. These formidable obstacles often block drug delivery to the brain across the blood-brain barrier (BBB). Although several promising molecules have the potential in the in vitro settings but lack of in vivo response is probably because the molecule cannot reach the brain in a sufficient concentration. Drug delivery across the BBB is a major limitation in the treatment of central nervous system (CNS) disorders and CNS infections. This review deals with the role of nanobiotechnology in CNS drug delivery, in which three categories of carbon nanotubes, nanowires and nanoparticles (NPs) are explained. The small size of the NPs makes them an ideal choice to penetrate the BBB. Several mechanisms are involved in this process and various strategies are used. There are some concerns about the safety of NP entry in the brain that need to be resolved before human use. Although there is no approved nanotechnology-based CNS drug available the future for such neuronanobiotechnology based delivery system developments is promising.

Ferulic acid (FA), a phenolic compound with a significant antioxidant activity in Alzheimer's disease, was entrapped into several solid lipid nanoparticles (SLN and NLC) by using the microemulsion technique. Stable SLN and NLC formulations having mean size ranging between 94-140 nm and high zeta potential were obtained. The SLN sample obtained by using as lipid matrix Compritol 888 ATO was chosen for further characterization because, among these particles, showed high Loading Capacity (LC%) and the best characteristics in terms of size, PDI, and drug release profile. Empty SLN showed no cytotoxicity on human neuroblastoma cells (LAN 5) at tested concentrations and the ability to penetrate into these cells. Moreover, cells treated with FA-loaded SLN showed a higher reduced ROS production than cells treated with free FA. These findings demonstrate that FA-loaded SLN possess a higher protective activity than free FA against oxidative stress induced in neurons and suggest that SLN are excellent carriers to transport FA into the cells.

Whereas several biomedical applications of carbon nanotubes have been proposed, the use of boron nitride nanotubes (BNNTs) in this field has been largely unexplored despite their unique and potentially useful properties. Our group has recently initiated an experimental program aimed at the exploration of the interactions between BNNTs and living cells. In the present paper, we report on the magnetic properties of BNNTs containing Fe catalysts which confirm the feasibility for their use as nanovectors for targeted drug delivery. The magnetisation curves of BNNTs characterised by the present study are typical of superparamagnetic materials with important parameters, including magnetic permeability and magnetic momentum, derived by employing Langevin theory. In-vitro tests have demonstrated the feasibility for influencing the uptake of BNNTs by living cells by exposure to an external magnetic source. A finite element method analysis devised to predict this effect produced predictive data with close agreement with the experimental observations.

The prospect of improved cancer therapy using Solid Lipid Nanoparticles (SLNs) as drug delivery system is promising. Several obstacles frequently encountered with anticancer compounds, such as poor drug solubility, are overcome by delivering them using SLN. Moreover, the intravenous administration of drugs into SLNs can potentially enhance drug blood circulation time and improve drug performance by inducing accumulation into tumours by enhanced permeability and retention (EPR) effect. This paper deals with the development of SLN containing nimesulide, a non-steroidal anti-inflammatory drug with antitumour effect and low solubility in water. Here, SLNs carrying nimesulide were prepared and characterized, and the antiproliferative effect of drug-loaded SLN versus free drug on HT-29 and SW-480 cell lines was here evaluated. All the obtained systems possess colloidal size, ranging from 85 to 132 nm and negative zeta potential values. Moreover these systems show good loading capacity and drug release profile, and an in vitro antitumour activity comparable to free drug.

This is a summary of the Third Annual Cancer Nanobiology Think Tank hosted by the Nanobiology Program at the Center for Cancer Research at the National Cancer Institute-Frederick, National Institutes of Health. The Third Annual Nanobiology Think Tank was held in May of 2008 and was entitled “Understanding the Design Principles of Living Systems at the Nanoscale.”

The Padmakar-Ivan (PI) index of a graph G is defined as PI(G) = Σ[mu(e)+ mv(e)], where mu(e) is the number of edges of G lying closer to u than to v, mv(e) is the number of edges of G lying closer to v than to u and summation goes over all edges of G. The edge Szeged index is a new molecular structure descriptor equal to the sum of products mu(e)mv(e) over all edges e = uv of the molecular graph G. In this paper, the PI and edge Szeged indices of one-heptagonal carbon nanocone CNC7[n] computed for the first time.

In this paper, we report a significant improvement of electron field emission property in patterned carbon nanotubes films by using a high temperature (650 °C) hydrogen plasma treatment. This treatment was found to greatly increase the emission current, emission uniformity and stability. The mechanism study showed that these enhanced properties are attributed to the lowering of the potential barrier and the creation of geometrical features through the removal of amorphous carbon, catalyst particles and the saturation of dangling bonds after such a hydrogen plasma treatment.

It is widely accepted that the self-assembling nanostructure of metals, semiconductors and organic molecules with a welldefined spatial order is one of the promising ways of engineering new materials. Recent years have revealed substantial progress in fabricating metal nanoparticles on ultrathin oxide films due to their ordered surface and novel electronic structures. In this article, we first briefly introduce the preparation, surface structures and physical properties of ultrathin alumina films on different metal- and alloysubstrates, which result in different structures of alumina films. Secondly, the deposition of metal nanoparticles on these ultrathin alumina films that are mainly prepared on the NixAl alloy surfaces is reviewed from the aspects of electronic properties, surface morphology & thermal stability, and physical & chemical properties, because the ordered alumina films can be more easily prepared by oxidation of these Al-alloy surfaces in ultrahigh vacuum conditions.

Geometrical compatibility is a very important factor for molecular self-assembly. In the self-assembling systems of peptide detergents and bolaamphiphilic peptides, the effect of the geometrical shape of hydrophobic section on the self-assembling behavior has been investigated by nanostructure characterization. It is shown that in aqueous solutions of both peptide detergent and bolaamphiphilic peptide systems, peptides bearing hydrophobic sections with constant size tend to form discrete structures including nanofibers, nanorods and nanospheres, while peptides bearing wedge-shaped hydrophobic sections tend to form haploid long nanofibers. And a peptide detergent with inverted-wedged hydrophobic tail tends to form reversed micelle in nonpolar solvent environment. These results indicate that the self-assembling behavior of peptide amphiphiles could be rationally controlled by the geometrical shape of the hydrophobic section, suggesting a novel strategy for fabricating controllable nanostructures.

Because of the dense chemical varieties and the vast chemical scales, it is feasible to produce complex nanoscale architectures with well-defined structural motifs organized over large areas in two dimensions or volumes in three dimensions. Various methods based on electrostatic interaction and hydrophobic interaction, in situ mineralization, covalent bond and inorganic scaffold, and protein- protein interaction and DNA hybridization, have all been demonstrated to successfully construct multidimensional nanoscale architectures from bottom up. In this review, the existing physical, chemical and biological methods for constructing nanoscale architectures by either directed synthesis or self-assembly are surveyed, with a focus on biological methods, and the mechanisms involved are systematically discussed with selected examples.

In cardiology and oncology, early disease detection produces better patient outcomes. Imaging approaches, particularly Magnetic Resonance Imaging (MRI), are attractive for screening large, mostly disease-free populations because they are noninvasive and produce high-resolution anatomical/morphological images from disease sites. Biochemically targeted nanoparticulate contrast agents (ultrasmall superparamagnetic iron oxide particles called USPIOs, superparamagnetic iron oxide nanoparticles called SPIONs, cross-linked iron oxides called CLIOs, Gadolinium chelates, and other superparamagnetic or paramagnetic particles) can be administered parenterally to define lesional biochemical/cellular composition, in addition to giving excellent definition of morphological features. Such targeted contrast agents can be considered modular nanobiological devices containing, at minimum, a contrast module and a targeting moiety. Here we review synthesis, surface chemistry and physics of superparamagnetic iron oxide MRI contrast agents (USPIOs and SPIONs) and results to date from the use of biochemically targeted and untargeted iron oxide MRI contrast agents in vivo, in vitro and ex vivo in vascular disease, and to a lesser extent, in oncology applications. We discuss design parameters critical to in vivo use of targeted contrast particles, including parameters influencing particle biodistribution/pharmacokinetics and immunogenicity. We discuss the increasing sophistication of theranostic contrast agents that provide other physiological services concurrent with their MRI function.

Nanofluids are fluids containing suspended solid nanoparticles. It is expected that the nanofluids will be the next generation of heat transfer fluids due to their unique thermal properties. At present, the study on nanofluids is still in its infancy. Some issues became the barriers to the development and application of the emerging nanofluid technology. In this paper, the critical issues in nanofluids preparation, characterization and thermal conductivity are present based on a review of available work in the literature.

In this study, nanostructured mesoporous TiO2 was prepared by sol-gel process, and the synthesis was accomplished by using block copolymer as the structure-directing agent and TiCl4 as the inorganic precursor. TGA, XRD, SAXS, TEM and N2 adsorptiondesorption isotherms were used to characterize the microstructure, pore size, and pore structure after calcination. The powders were found to have a wormhole-like pore structure after calcination. When the addition of block copolymer increased from 0.1 to 1.5 g, the specific surface areas increased from 113.23 to 284.75 m2/g, but the average pore sizes decreased from 7.4 to 4.8 nm, and the average crystallite sizes decreased from 9.0 to 5.5 nm after being calcinated at 300 °C for 5 h. These results show that the mesostructure and crystallinity of TiO2 can be controlled by the additive concentrations of block copolymer.

Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. The present study deals with the synthesis of silver nanoparticles using Gliricidia sepium. On challenging, leaf broth of Gliricidia sepium and aqueous AgNO3 (1mM) solution changed from yellowish green to brown, the final color appeared gradually with time. The entire reaction mixture turned to brown color after 12 hrs of reaction, and exhibits an absorbance peak around 440 nm characteristic of Ag nanoparticle, its surface plasmon absorbance and due to different shapes of lone spherical or roughly spherical Ag nanoparticles. Transmission electron microscopy (TEM) analysis showed silver nanoparticles which are polydispersed and ranged in size from 10-50 nm with an average size of 27 nm, the particles were predominantly spherical. X-ray diffraction (XRD) studies reveals a number of Braggs reflections that may be indexed on the basis of the face centered cubic structure of silver nanoparticle and Fourier Transform Infrared Spectroscopy (FTIR) analysis, which showed that silver nanoparticles are capped. Phytosynthesized silver nanoparticles show the antibacterial activity against the Staphylococcus aureus ATCC 6538P, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027 and Klebsiella pneumoniae (clinical isolate). The approach of phytosynthesis appears to be cost efficient eco-friendly and easy alternative to conventional methods of silver nanoparticles synthesis.