Surface-modified superparamagnetic nanoparticles for drug delivery: preparation, characterization, and cytotoxicity studies

Superparamagnetic iron oxide nanoparticles have been used for many years as magnetic resonance imaging (MRI) contrast agents or in drug delivery applications. In this study, a novel approach to prepare magnetic polymeric nanoparticles with magnetic core and polymeric shell using inverse microemulsion polymerization process is reported. Poly(ethyleneglycol) (PEG)-modified superparamagnetic iron oxide nanoparticles with specific shape and size have been prepared inside the aqueous cores of AOT/n-Hexane reverse micelles and characterized by various physicochemical means such as transmission electron microscopy (TEM), infrared spectroscopy, atomic force microscopy (AFM), vibrating sample magnetometry (VSM), and ultraviolet/visible spectroscopy. The inverse microemulsion polymerization of a polymerizable derivative of PEG and a cross-linking agent resulted in a stable hydrophilic polymeric shell of the nanoparticles. The results taken together from TEM and AFM studies showed that the particles are spherical in shape with core-shell structure. The average size of the PEG-modified nanoparticles was found to be around 40-50 nm with narrow size distribution. The magnetic measurement studies revealed the superparamagnetic behavior of the nanoparticles with saturation magnetization values between 45-50 electromagnetic units per gram. The cytotoxicity profile of the nanoparticles on human dermal fibroblasts as measured by standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that the particles are nontoxic and may be useful for various in vivo and in vitro biomedical applications.     

Synthesis of palladium nanoparticles using a continuous flow polymeric micro reactor

A continuous flow polymeric micro reactor, fabricated using a negative photo resist SU-8 on a 10 x 10 cm PEEK (polyetheretherketone) substrate by standard UV lithography, was utilized to synthesize palladium nanoparticles. The nanoparticles were characterized by Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Diffraction. The Pd nanoparticles synthesized in the micro reactor were found to have a narrower size distribution when compared with those obtained by the conventional batch process.     

Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.     

The Number of Neighbors Needed for Connectivity of Wireless Networks

Wireless Networks - Unlike wired networks, wireless networks do not come with links. Rather, links have to be fashioned out of the ether by nodes choosing neighbors to connect to. Moreover the...     

Vapour phase crystal growth under microgravity environment

Vapour phase crystal growth experiments performed in the Skylab and ASTP missions are reviewed. The basic vapour phase crystal growth technique is described and effect of gravity is discussed. The multipurpose furnace specially designed to carry out various experiments in flight conditions is described. Ge Se, Ge Te and GeS as well as ternary GeSe_0·99 Te_0·01 and GeS_0·98 Se_0·02 crystals have been grown in space showing improvement over similarly grown crystals on ground as determined by x-ray diffraction, chomical homogeneity and surface morphology studies. Mass flux rates under microgravity conditions have been found to be up to 10 times larger than expected indicating need for better theoretical and experimental understanding of the effect of gravity on crystal growth.     

Statistical separability of spectral classes of blighted corn

The purpose of this study was to determine the statistical separability of multispectral measurements from corn having varying levels of southern corn leaf blight severity. Multispectral scanner data in twelve spectral channels in the wavelength range 0.4 to 11.7 μm were analyzed for ten selected flightlines of the 1971 Corn Blight Watch Experiment. A total of 168 corn fields having 18,804 sample points were analyzed. The blight rating information for these fields was available from ground observations. Maximum average transformed divergence between spectral classes (found by LARSYS Cluster Algorithm) of all possible pairs of blight levels, maximized over a subset of channels, was computed in each of one, two, three, and four spectral channels for each of ten flightlines. From the statistical analysis of the values of average transformed divergence, it was concluded that the greater the difference between the blight levels, the more statistically separable they are. This result is encouraging considering the fact that there are variables other than the blight severity within and between the flightlines. Although the analysis was done for corn blight only, the conclusions obtained from this analysis may well be applicable to other crop stresses because corn blight is representative of many plant stresses, especially non-systemic stresses.