Development of an in Vitro System to Simulate the Adsorption of Self-Emulsifying Tea (Camellia oleifera) Seed Oil.

In this study, tea (Camellia oleifera) seed oil was formulated into self-emulsifying oil formulations (SEOF) to enhance the aqueous dispersibility and intestinal retention to achieve higher bioavailability. Self-emulsifying tea seed oils were developed by using different concentrations of lecithin in combination with surfactant blends (Span(®)80 and Tween(®)80). The lecithin/surfactant systems were able to provide clear and stable liquid formulations. The SEOF were investigated for physicochemical properties including appearance, emulsion droplets size, PDI and zeta potential. The chemical compositions of tea seed oil and SEOF were compared using GC-MS techniques. In addition, the oil adsorption measurement on artificial membranes was performed using a Franz cell apparatus and colorimetric analysis. The microscopic structure of membranes was observed with scanning electron microscopy (SEM). After aqueous dilution with fed-state simulated gastric fluid (FeSSGF), the droplet size of all SEOF was close to 200 nm with low PDI values and the zeta potential was negative. GC-MS chromatograms revealed that the chemical compositions of SEOF were not significantly different from that of the original tea seed oil. The morphological study showed that only the SEOF could form film layers. The oil droplets were extracted both from membrane treated with tea seed oil and the SEOF in order to evaluate the chemical compositions by GC-MS.

ß-Glucan fragmentation by microfluidization and TNF-α-immunostimulating activity of fragmented ß-glucans.

Fragmentation of ß-glucans secreted by the fungus Ophiocordyceps dipterigena BCC 2073 achieved by microfluidization was investigated. The degree of ß-glucan fragmentation was evaluated based on the average number of chain scissions (α). The effects on the α value of experimental variables like solid concentration of the ß-glucan suspension, interaction chamber pressure, and number of passes through the microfluidizer were examined. Kinetic studies were conducted using the relationships of the α and suspension viscosity values with the number of passes. Evidence indicated that α increases with the interaction chamber pressure and the number of passes, whereas the solid concentration shows the inverted effect. Kinetic data indicated that the fragmentation rate increases with ß-glucan solid concentration and interaction chamber pressure. Furthermore, since ß-glucan molecular weight is a key factor determining its biological activity, the effect of ß-glucans of different molecular weights produced by fragmentation on tumor necrosis factor (TNF)-α-stimulating activity in THP-1 human macrophage cells was investigated. Evidence suggested that ß-glucans have an immunostimulating effect on macrophage function, in the absence of cytotoxic effects. Indeed, ß-glucans characterized by a range of molecular weights produced via microfluidization exhibited promise as immunostimulatory agents.

ORF8a of SARS-CoV forms an ion channel: experiments and molecular dynamics simulations.

ORF8a protein is 39 residues long and contains a single transmembrane domain. The protein is synthesized using solid phase peptide synthesis and reconstituted into artificial lipid bilayers that forms cation-selective ion channels with a main conductance level of 8.9±0.8pS at elevated temperature (38.5°C). Computational modeling studies including multi nanosecond molecular dynamics simulations in a hydrated POPC lipid bilayer are done with a 22 amino acid transmembrane helix to predict a putative homooligomeric helical bundle model. A structural model of a pentameric bundle is proposed with cysteines, serines and threonines facing the pore.

Encapsulation of citral isomers in extracted lemongrass oil with cyclodextrins: molecular modeling and physicochemical characterizations.

The complexation between two isomers of citral in lemongrass oil and varying types of cyclodextrins (CDs), α-CD, ß-CD, and HP-ß-CD, were studied by molecular modeling and physicochemical characterization. The results obtained revealed that the most favorable complex formation governing between citrals in lemongrass oil and CDs were found at a 1:2 mole ratio for all CDs. Complex formation between E-citral and CD was more favorable than between Z-citral and CD. The thermal stability of the inclusion complex was observed compared to the citral in the lemongrass oil. The release time course of citral from the inclusion complex was the diffusion control, and it correlated well with Avrami's equation. The release rate constants of the E- and Z-citral inclusion complexes at 50 °C, 50% RH were observed at 1.32×10(-2) h(-1) and 1.43×10(-2) h(-1) respectively.

Enhanced stability and in vitro bioactivity of surfactant-loaded liposomes containing Asiatic Pennywort extract.

The objective of this work has been the microencapsulation of Asiatic Pennywort (AP) extract with lecithin from soybean. The effect of various quantities of non-ionic surfactant (Montanov82) on liposomes upon physicochemical characteristics as well as their in vitro bio-activities was investigated. An addition of surfactant resulted in a decrease in particle size and an increase in percentage AP entrapment efficiency of liposomes. The surfactant-loaded liposomes demonstrated higher stability than surfactant-free liposomes where higher percentage AP remaining of liposomes can be achieved depending on surfactant concentration. No significant difference was found on AP release profiles among varied surfactant concentrations, although a presence of surfactant resulted in prolonged AP release rate. Liposomal AP with 20% w/w surfactant or higher demonstrated low cytotoxicity, a stronger anti-oxidation effect and collagen production on dermal fibroblast cells when compared with free AP and surfactant-free liposomes, possibly due to better cell internalization and less AP degradation in cells.

A comparison of eugenol and menthol on encapsulation characteristics with water-soluble quaternized ß-cyclodextrin grafted chitosan.

Two guest molecules (eugenol and (-)-menthol) were investigated on inclusion complex formation with water-soluble quaternized ß-CD grafted with chitosan (QCD-g-CS). The inclusion complexes were prepared at varying mole ratios between eugenol or (-)-menthol and ß-CD (substituted on QCD-g-CS) by a conventional shaking method and obtained as solid powder by freeze-drying process. The results showed that encapsulation efficiency %EE decreased with increasing of initial eugenol or (-)-menthol loading whereas %loading increased with increasing of initial eugenol or (-)-menthol loading. The results indicated that inclusion complex formation between eugenol and QCD-g-CS was more favorable than that of (-)-menthol. To clarify this mechanism, molecular dynamics simulations were performed to explore their binding energy, solvation energy and total free energy of those complexes. It was found that the total free energy (ΔG) of eugenol and (-)-menthol against QCD-g-CS (mole ratio of 1) in water-explicit system were -2108.91 kJ/mol and -344.45 kJ/mol, respectively. Moreover, molecular dynamic simulation of eugenol absorbed on surface QCD-g-CS (-205.73 kJ/mol) was shown to have a higher negative value than that of (-)-menthol on QCD-gCS (3182.31 kJ/mol). Furthermore, the release characteristics of the encapsulated powder were also investigated in simulated saliva pH 6.8 at 32 °C. The results suggested that (-)-menthol had higher release rate from the complexes than eugenol. In all cases, the release characteristics for those guest molecules could be characterized by the limited-diffusion kinetics.

Intra-subunit residue interactions from the protein surface to the active site of glutathione S-transferase AdGSTD3-3 impact on structure and enzyme properties.

Structural residues are one of the major factors that modulate the catalytic specificity as well as having a role in stability of the glutathione S-transferases (GST). To understand how residues remote from the active site can affect enzymatic properties, four mutants, His144Ala, Val147Leu, Val147Ala and Arg96Ala, were generated. The selected residues appear to be in a putative intra-subunit interaction pathway from the exterior Asp150 to the active site Arg66 of AdGSTD3-3. The analysis of the four mutants suggested that the interaction formed between Asp150 and His144 is required for the packing of the hydrophobic core in domain 2. Mutations of both Asp150 and His144 impacted upon enzymatic properties. Two Val147 mutants also showed contribution to packing and support of the N-capping box motif by demonstrating shorter half-lives. The planar guanidinium of Arg96 is in a stacked geometry with the face of the aromatic ring of Phe140 in a cation-pi interaction. The Arg96 also interacts with several other residues one of which, Asp100, is in the active site. These interactions restrict movement of the residues in this region and as the data demonstrates when Arg96 is changed have dramatic impact on stability and enzyme properties. These findings indicate the significance of the roles played by residue interactions which can cause conformational changes and thereby influence the catalytic activity and stability of an enzyme.

Specific mutations within the alpha4-alpha5 loop of the Bacillus thuringiensis Cry4B toxin reveal a crucial role for Asn-166 and Tyr-170.

The widely accepted model for toxicity mechanisms of the Bacillus thuringiensis Cry delta-endotoxins suggests that helices alpha4 and alpha5 form a helix-loop-helix hairpin structure to initiate membrane insertion and pore formation. In this report, alanine substitutions of two polar amino acids (Asn-166 and Tyr-170) and one charged residue (Glu-171) within the alpha4-alpha5 loop of the 130-kDa Cry4B mosquito-larvicidal protein were initially made via polymerase chain reaction-based directed mutagenesis. As with the wild-type toxin, all of the mutant proteins were highly expressed in Escherichia coli as inclusion bodies upon isopropyl-beta-Dthiogalactopyranoside induction. When E. coli cells expressing each mutant toxin were assayed against Aedes aegypti mosquito larvae, the activity was almost completely abolished for N166A and Y170A mutations, whereas E171A showed only a small reduction in toxicity. Further analysis of these two critical residues by induction of specific mutations revealed that polarity at position 166 and highly conserved aromaticity at position 170 within the alpha4-alpha5 loop play a crucial role in the larvicidal activity of the Cry4B toxin.

Ex vivo cytotoxicity of the Bacillus thuringiensis Cry4B delta-endotoxin to isolated midguts of Aedes aegypti larvae.

The pathological effect of the Bacillus thuringiensis Cry delta- endotoxins on susceptible insect larvae had extensive damage on the midgut epithelial cells. In this study, an ex vivo assay was devised for assessing the insecticidal potency of the cloned Cry4B mosquito-larvicidal protein that is expressed in Escherichia coli. Determination of toxicity was carried out by using a cell viability assay on the midguts that were dissected from 5-day old Aedes aegypti mosquito larvae. After incubation with the toxin proteins, the number of viable epithelial cells was determined photometrically by monitoring the quantity of the bioreduced formazan product at 490 nm. The results showed that the 65-kDa trypsin-activated Cry4B toxin exhibited toxic potency ca. 3.5 times higher than the 130-kDa Cry4B protoxin. However, the trypsin-treated products of the non-bioactive Cry4B mutant (R158A) and the lepidopteran-specific Cry1Aa toxin displayed relatively no ex vivo activity on the mosquito-larval midguts. The ex vivo cytotoxicity studies presented here confirms data that was obtained in bioassays.

A non-active site residue, cysteine 69, of glutathione S-transferase ADGSTD3-3 has a role in stability and catalytic function.

The Cys69 residue of an Anopheles dirus glutathione S-transferase isoform (adGSTD3-3), was characterized to elucidate its contribution in both catalysis and structural support. Nine mutants were generated at this position by replacing the residue with polar, non-polar and charged residues. The polar residues changed the Vm of the enzymes. With non-polar residues, the enzymes were unable to fold and were expressed in the insoluble inclusion form. With charged residues, the soluble enzyme yields were only 3% of the wild type protein. Molecular dynamics simulation also was performed to understand the changes in the enzyme structure. These findings are additional evidence of the importance of structural residues that affect the enzymatic properties such as Vm, Km and enzyme specificity.

A comparison of spacer on water-soluble cyclodextrin grafted chitosan inclusion complex as carrier of eugenol to mucosae.

In this study two types of water-soluble ßCD grafted chitosan were synthesized and compared based on similar degree of N-substitution of ßCD moiety; QCD23-g-CS contained methylene spacer and QCDCA22-g-CS contained citric acid spacer. The QCD23-g-CS demonstrated greater eugenol (EG) encapsulation efficiency than that of QCDCA22-g-CS. The micelle-like assemblies of QCD23-g-CS led to slower release of EG while it did not observe in case of QCDCA22-g-CS. It was found that EG could absorb on chitosan backbone according to in silico modeling. Cytotoxicity of both derivatives against buccal mucosa cell is concentration-dependent. The QCDCA22-g-CS demonstrated stronger mucoadhesive response than that of QCD23-g-CS, due to hydrogen bonding according to mucin particle and SPR methods. Our results revealed that the spacer on both derivatives played an important role on binding affinity with EG, releasing profile and mucoadhesive property. These derivatives could be considered as promising carriers for mucosal delivery system.

Water-soluble ß-cyclodextrin grafted with chitosan and its inclusion complex as a mucoadhesive eugenol carrier.

Inclusion complex between water-soluble ßCD-grafted chitosan derivatives (QCD-g-CS) and eugenol (EG) was investigated as a new type of mucoadhesive drug carrier. The QCD-g-CSs were synthesized with various ßCD moieties ranging from 5 to 23%. Spontaneous inclusion complex of these derivatives and EG were found and confirmed by FTIR and simulation study. Self-aggregated formations of QCD-g-CS were found, according to fluorescence and TEM studies, where the formations were preferable for QCD11g-CS and QCD5-g-CS. EG can be included in both ßCD hydrophobic cavity and hydrophobic core of QCD-g-CS self-aggregates, resulting in varying entrapment efficiencies. Degree of QCD substitution on QCD-g-CS plays an important role on their physical properties, due to steric hindrance. The QCD11-g-CS showed excellent mucoadhesion, compared to the QCD5-g-CS and QCD23-g-CS. Moreover, the inclusion complex between QCD-g-CS and EG tend to express higher antimicrobial activities against Candida albicans, Streptococcus oralis and Streptococcus mutans, than the native QCD-g-CS.

Self-aggregates formation and mucoadhesive property of water-soluble ß-cyclodextrin grafted with chitosan.

Water-soluble ß-cyclodextrin grafted with chitosan (CD-g-CS) was carried out by quaternizing the CD-g-CS with glycidyltrimethyl ammonium chloride (GTMAC) under mild acidic condition, corresponding to the quaternized CD-g-CS (QCD-g-CS). The degrees of substitution (DS) and quaternization (DQ), ranging from 5% to 23% and 66% to 80%, respectively, were determined by (1)H NMR spectroscopy. Self-aggregates formation of all QCD-g-CSs were investigated in water using dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM) techniques. The result revealed that all QCD-g-CSs are able to form self-aggregates in water. Large particle sizes ranged from 800 to 3000nm were obtained by DLS while zeta-potentials were ranging from 25 to 40mV. AFM and TEM depicted a spherical shape with particle sizes ranging from 100 to 900nm. Mucoadhesive and cytotoxic properties of all QCD-g-CSs were evaluated using a mucin particle method and MTT assay compared to quaternized chitosan (QCS). It was found that the mucoadhesive property increased with decreasing DS due to less quaternary ammonium moiety into the chitosan backbone. On the other hand, the cytotoxicity increased with increasing DS even though the DQ is decreased.