The effect of surfactant composition on the chemical and structural properties of nanostructured lipid carriers.

Fine-tuning the nanoscale structure and morphology of nanostructured lipid carriers (NLCs) is central to improving drug loading and stability of the particles. The role of surfactant charge on controlling the structure, the physicochemical properties and the stability of NLCs has been investigated using three surfactant types (cationic, anionic, non-ionic), and mixed surfactants. Either one, a mixture of two, or a mixture of three surfactants were used to coat the NLCs, with these classified as one, two and three surfactant systems, respectively. The mixed (two and three) surfactant systems produced smaller NLC particles and yielded NLCs with lower crystallinity than the one surfactant system. The combined effects of the ionic and the non-ionic surfactants may play a key role in assisting the lipid-oil mixing, as well as maintaining colloidal repulsion between NLC particles. In contrast, for the three surfactant system, the lipid-oil mixture in the NLCs appeared less homogenous. This was also reflected in the results of the stability study, which indicated that NLC particle sizes in two surfactant systems appeared to be retained over longer periods than for other surfactant systems.

An artificial nose based on M-porphyrin (M = Mg, Zn) thin film and optical spectroscopy.

Artificial nose has recently become an emerging instrument for quality assurance in the food industry. These paper present the optical gas sensors based on Magnesium-5, 10, 15, 20-tetra phenyl-porphyrin (MgTPP) and Zinc-5, 10, 15, 20-tetra phenyl-porphyrin (ZnTPP) thin films and their application as an artificial nose. Based on the measurement of optical absorbance response using a general UV-Vis spectroscopy, this artificial nose was tested to discriminate various volatile organic compounds (VOCs) and Thai beverages. Atomic force microscopy (AFM) and X-rays diffraction (XRD) were used to confirm the polycrystalline structure of the sensing materials. Density functional theory (DFT) calculations reveal that MgTPP interacts more strongly with the VOCs than ZnTPP, especially with methanol. The classification results of VOCs and Thai beverage vapors using the principal component analysis indicate that both MgTPP and ZnTPP-based artificial noses can be an efficient tool for quality assurance of alcoholic beverages.

Performance improvement of zinc oxide photoanode-based dye-sensitized solar cells by multi-walled carbon nanotube.

Unique electrical and surface-to-volume properties of carbon nanotubes have made these conductive molecules highly attractive in many applications. In this work, the influence of multi-walled carbon nanotubes into a zinc oxide active layer of dye-sensitized zinc oxide solar cell has been investigated. With this method, a significant improvement in the performance of the solar cell has been achieved. Compared to the typical zinc oxide photoelectrochemical cells, the photocurrent-voltage characteristics of the fabricated cell containing 0.05 percent by weight of carbon nanotubes in the metal oxide film displayed a higher short-circuit photocurrent, consequently caused an increase of the solar-to-electricity conversion efficiency by a factor of approximately 1.4. Further increase of the conductive carbon material resulted in a decrease of the energy conversion of the photovoltaic cell. The enhancement of the energy conversion at this optimum carbon nanotube loading may be attributed to the dye-adsorption ability and the electrochemical activity of the composite photoanodes. The fabricated photovoltaic cells with the highest efficiency exhibited the maximum dye adsorption intensity and the minimum charge transfer resistance, as measured by ultraviolet-visible spectroscopy and electrochemical impedance spectroscopy, respectively.

Chemical and structural investigation of lipid nanoparticles: drug-lipid interaction and molecular distribution.

Lipid nanoparticles are a promising alternative to existing carriers in chemical or drug delivery systems. A key challenge is to determine how chemicals are incorporated and distributed inside nanoparticles, which assists in controlling chemical retention and release characteristics. This study reports the chemical and structural investigation of gamma-oryzanol loading inside a model lipid nanoparticle drug delivery system composed of cetyl palmitate as solid lipid and Miglyol 812 as liquid lipid. The lipid nanoparticles were prepared by high pressure homogenization at varying liquid lipid content, in comparison with the gamma-oryzanol free systems. The size of the lipid nanoparticles, as measured by the photon correlation spectroscopy, was found to decrease with increased liquid lipid content from 200 to 160 nm. High-resolution proton nuclear magnetic resonance ((1)H-NMR) measurements of the medium chain triglyceride of the liquid lipid has confirmed successful incorporation of the liquid lipid in the lipid nanoparticles. Differential scanning calorimetric and powder x-ray diffraction measurements provide complementary results to the (1)H-NMR, whereby the crystallinity of the lipid nanoparticles diminishes with an increase in the liquid lipid content. For the distribution of gamma-oryzanol inside the lipid nanoparticles, the (1)H-NMR revealed that the chemical shifts of the liquid lipid in gamma-oryzanol loaded systems were found at rather higher field than those in gamma-oryzanol free systems, suggesting incorporation of gamma-oryzanol in the liquid lipid. In addition, the phase-separated structure was observed by atomic force microscopy for lipid nanoparticles with 0% liquid lipid, but not for lipid nanoparticles with 5 and 10% liquid lipid. Raman spectroscopic and mapping measurements further revealed preferential incorporation of gamma-oryzanol in the liquid part rather than the solid part of in the lipid nanoparticles. Simple models representing the distribution of gamma-oryzanol and lipids (solid and liquid) inside the lipid nanoparticle systems are proposed.

The kinetics of radiation damage to the protein luciferase and recovery of enzyme activity after irradiation.

Experimental observations are reported which follow the bioluminescence intensity of luciferase during irradiation by a 5 MeV proton beam. Bioluminescence is a measure of the protein enzyme activity and provides an assay of the enzyme rate of reaction in real time. Transient responses after a pulse of protons show recovery of the reaction rate with two time constants of 0.3 s(-1) and 0.01 s(-1). Changes in the reaction rate are due to radiation damage to the active form of the protein luciferase. Quantitative analysis of the radiation damage and recovery of the protein shows that products of the radiolysis of water play major part in the process of enzyme damage at room temperature. A few minutes after the pulse of protons, most of the enzyme activity has recovered. We attribute the fast recovery to the removal of charged ions, while the slow recovery involves refolding of denatured protein.