Sirapat Pratontep

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.

Poly(methyl methacrylate) and thiophene-coated single-walled carbon nanotubes for volatile organic compound discrimination

Poly(methyl methacrylate) (PMMA) and thiophene-coated single-walled carbon nanotubes (SWNTs) were fabricated for use in volatile organic compound (VOC) detection. Pristine SWNTs were separately coated with PMMA (PMMA/SWNTs) and thiophene (thiophene/SWNTs) by spin-coating. Pristine SWNTs showed the highest response to methanol, while PMMA/SWNTs enabled 5.4-fold improved dichloromethane detection and thiophene/SWNTs enabled 1.4-fold improved acetone detection compared with pristine SWNTs. The sensor response of PMMA/SWNTs to dichloromethane and that of thiophene/SWNTs to acetone can be attributed to the Hildebrand solubility parameter (HSP). The more similar the HSP, the higher the sensor response. The sensor response of pristine SWNTs to methanol is related to the diffusion coefficient and molecular size. The relationships between the vapor concentration and sensor response of PMMA/SWNTs to dichloromethane and thiophene/SWNTs to acetone are based on Henrys adsorption isotherm, while that of pristine SWNTs to methanol is based on the Henry–clustering model. Principal component analysis (PCA) results show that dichloromethane, acetone, and methanol were successfully discriminated.

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

Abstract 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.

Fabrication of Low Cost Anodic Aluminum Oxide (AAO) Tubular Membrane and their Application for Hemodialysis

This paper reports the fabrication of AAO tubular membrane using 99.35% and 99.56% pure Al and their potential application for hemodialysis. Here we discussed the effect of impurity on membrane structure. We found that the self organized structure of AAO nanochannels minimizes impurity defects in membrane. If micro size impurity blocks the generation of nanochannels then the neighboring nanochannels bend and make branches to fulfill that gap. We observed that if impurity size is less than the AAO membrane thickness then it does not produce any micro size hole. In low grade Al the periodic hexagonal order was disturbed however there was no big difference in pore diameter. It was observed that such type of membrane do not have any leakage and it can be used for fluid filtration. The fabricated tubular membrane was used for hemodialysis successfully. The hemodialysis results show that AAO tubular membrane can be used for both diffusive and convective filtration

Alcohol gas sensors based on magnesium tetraphenyl porphyrins

Metallo-porphyrins thin films have been demonstrated as optical gas sensors for detecting various kinds of gases. In this work, magnesium 5,10,15,20-tetraphenyl porphyrin (MgTPP) thin films were prepared by spinning the solution using chloroform as solvent onto clean glass substrates, then subjected to a thermal annealing at 280degC in the argon atmosphere. These MgTPP optical gas sensors have higher responses with methyl alcohol than ethyl alcohol based on dynamic flow of alcohol vapors at 25degC. Quantum mechanical calculation based on density functional theory has found that the interaction energy between MgTPP with methyl alcohol is higher than ethyl alcohol. Principal component analysis (PCA) was used to classify the data from the optical absorbance spectra into three groups of alcohols, which are McOH (100%), EtOH (100%) and a mixture of McOH (50%) and EtOH (50%). From these results, MgTPP thin film can be an efficient sensing material to discriminate alcohols.

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 presents 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 noses was tested to discriminate various volatile organic compounds (VOCs) and Thai beverages. Atomic force microscopy (AFM) and X-rays diffraction 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 water and methanol. The classification results of VOCs and Thai beverage vapors using the principle component analysis indicate that both MgTPP and ZnTPP-based artificial noses can be an efficient tool for quality assurance of alcoholic beverages.

Composite Polymer Electrolyte for Dye-Sensitized Solar Cells: Role of Multi-Walled Carbon Nanotubes

We focus on the energy conversion improvement of dye-sensitized solar cells by using poly(ethylene oxide)-multi-walled carbon nanotube (PEO-MWCNT) electrolyte. Compared with the MWCNT-free solar cells, the addition of 0.05 wt.% MWCNTs in the polymer electrolyte results in a dramatic increase of the short-circuit current (Jsc), consequently raising the device performance by approximately 9% under a direct light of the Air Mass 1.5 irradiation at 100 mW cm-2. The role of the conductive carbon materials in the polymer electrolyte have been investigated by means of ionic conductometry, electrochemical impedance spectroscopy and UV-visible spectroscopy. This work demonstrates that MWCNT additives in polymer electrolytes is a convenient yet effective strategy for improving the performance of photovoltaic devices.

Investigation of thermal and methanol-vapor treatments for MgTPP as an optical gas sensor

In this paper, we have investigated the sensing properties of magnesium - 5,10,15,20 - tetraphenyl - porphyrin (MgTPP) to various volatile organic compounds (VOCs). The spin-coated MgTPP thin films were subjected to thermal annealing and methanol-vapor exposure to study the effects of pre-treatment on the sensing properties. Atomic force microscopy (AFM) has shown that both pre-treatment techniques have induced re-crystallization of the film, thereby improving the sensitivity over the as-deposited film. The thermally annealed films were found more effective than the methanol-vapor treated ones. The in-house optical sensor setup was applied to discriminate various VOCs and alcoholic beverages. Principal component analysis (PCA) confirms that the thermally annealed MgTPP thin film can distinguish several kinds of VOCs. Computational density functional theory (DFT) indicates that the interaction energy between analyte and sensing molecules can be used to explain comparative sensitivity.

Theoretical Investigation of Rhodamine6G Derivative as Fluorescence Metal Ion Sensor

The structural, energetic and optical properties of a Rhodamine6G derivative as the fluoroionphore for metal ion detection, particularly mercury, have been investigated using the time-dependent density functional theory (TD-DFT), compared to experiments. The TD-DFT calculations with the B3LYP method were conducted in the absence and the presence of metal ions. The results indicate that the absorption peaks of the pristine molecules are located at 236 and 282 nm, whereas the selective Hg2+ binding peaks emerge at 263, 371 and 551 nm. A distinctive new band emerges around 550 nm, in accordance with the experiments, attributed to the metal-to-ionophore electron transfer.

A Density Functional Theory Study on the Metal Binding Properties and Electronic Transitions of Dithienopyrole Derivatives

The metal binding energies and electronic properties of the complexes M-Py1A (M: Cd, Fe, Co, Cu, Hg, Ni, Pb, Zn; Py1A = deprotonated cyanoacetic) were studied using density functional theory (DFT) with B3LYP method. Comparative metal binding energies of metal complexes are as follows: Pb2+>Cu2+>Ni2+>Co2+>Fe2+> Hg2+>Cd2+>Zn2+. The electronic transitions of Fe, Ni, Co, Zn, Cd, Hg, Cu, and Pb are assigned as LLCT, LLCT, LMCT, LMCT, LMCT/LLCT, MLCT and LMCT, respectively. Solvation effect of Cu-Py1A complex was calculated in gas phase and tetrahydrofuran(THF). The results provide slightly red-shifted spectra from 540 to 541 nm.