Apinan Soottitantawat

Characterization and mosquito repellent activity of citronella oil nanoemulsion

Encapsulated citronella oil nanoemulsion prepared by high pressure homogenization at varying amounts of surfactant and glycerol, was studied in terms of the droplet size, stability, release characteristics and in vivo mosquito protection. Transparent nanoemulsion can be obtained at optimal concentration of 2.5% surfactant and 100% glycerol. Physical appearance and the stability of the emulsion were greatly improved through an addition of glycerol, owing to its co-solvent and highly viscous property. The increasing emulsion droplet increased the oil retention. The release behavior could be attributed to the effect of droplet size and concentrations of surfactant and glycerol. By fitting to Higuchis equation, an increase in glycerol and surfactant concentrations resulted in slow release of the oil. The release rate related well to the protection time where a decrease in release rate can prolong mosquito protection time.

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

Inclusion complex between water-soluble βCD-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 βCD 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 βCD 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.

Increased dispersion and solubility of carbon nanotubes noncovalently modified by the polysaccharide biopolymer, chitosan: MD simulations

Abstract In order to explain the solubility of carbon nanotubes (CNT), including single walled CNTs, wrapped with chitosan of a 60% degree of deacetylation, MD simulations were applied to represent three chitosan concentrations, using two pristine CNTs (pCNT–pCNT), and one and two CNTs wrapped (pCNT–cwCNT and cwCNT–cwCNT). The CNT aggregation was observed in pCNT–pCNT and pCNT–cwCNT due to van der Waals interactions between tube–tube aromatic rings, and inter-CNT bridging by chitosan, respectively. At higher chitosan concentrations, such that most to all of CNTs were wrapped with chitosan, charge–charge repulsion was found to separate robustly the cwCNTs and lead to a well dispersed solution.

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 βCD grafted chitosan were synthesized and compared based on similar degree of N-substitution of βCD 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.

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, β-CD, and HP-β-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.

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

Two guest molecules (eugenol and (-)-menthol) were investigated on inclusion complex formation with water-soluble quaternized β-CD grafted with chitosan (QCD-g-CS). The inclusion complexes were prepared at varying mole ratios between eugenol or (-)-menthol and β-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.

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.

Encapsulation of lemongrass oil with cyclodextrins by spray drying and its controlled release characteristics

Inclusion of the two isomers of citral (E-citral and Z-citral), components of lemongrass oil, was investigated within the confines of various cyclodextrin (α-CD, β-CD and γ-CD) host molecules. Aqueous complex formation constants for E-citral with α-CD, β-CD and γ-CD were determined to be 123, 185, and 204 L/mol, respectively, whereas Z-citral exhibited stronger affinities (157, 206, and 253 L/mol, respectively). The binding trend γ-CD > β-CD > α-CD is a reflection of the more favorable geometrical accommodation of the citral isomers with increasing cavity size. Encapsulation of lemongrass oil within CDs was undertaken through shaking citral:CD (1:1, 1.5:1, and 2:1 molar ratio) mixtures followed by spray drying. Maximum citral retention occurred at a 1:1 molar ratio with β-CD and α-CD demonstrating the highest levels of total E-citral and Z-citral retention, respectively. Furthermore, the β-CD complex demonstrated the slowest release rate of all inclusion complex powders. Graphical Abstract The inclusion between two isomers of citral (E-citral and Z-citral) in lemongrass oil and cyclodextrins by spray drying were studied.

Controllable encapsulation of α-mangostin with quaternized β-cyclodextrin grafted chitosan using high shear mixing

In this study, the inclusion complex formation between α-mangostin and water-soluble quaternized β-CD grafted-chitosan (QCD-g-CS) was investigated. Inclusion complex formation with encapsulation efficiency (%EE) of 5, 15 and 75% can be varied using high speed homogenizer. Tuning %EE plays a role on physicochemical and biological properties of α-mangostin/QCD-g-CS complex. Molecular dynamics simulations indicate that α-mangostin is included within the hydrophobic β-CD cavity and being absorbed on the QCD-g-CS surface, with these results being confirmed by Fourier transform infrared (FTIR) spectroscopy. Probing the release characteristics of the inclusion complex at various %EE (5%, 15% and 75%) in simulated saliva (pH 6.8) demonstrated that α-mangostin release rates were dependent on % EE (order 5% > 15% > 75%). Additionally, higher antimicrobial and anti-inflammation activities were observed for the inclusion complex than those of free α-mangostin due to enhance the solubility of α-mangostin through the inclusion complex with QCD-g-CS.

Use of reactive distillation for triacetin production from crude glycerol: Simulation and performance analysis

Abstract This study is focused on the use of crude glycerol from biodiesel production to produce triacetin via esterification reaction with acetic acid by using a reactive distillation. In general, a composition of crude glycerol consisting mostly glycerol and methanol varies with biodiesel feedstock and processes. Simulation studies are performed to investigate the effect of using crude glycerol with different fractions of methanol on triacetin production. Three process configurations are considered: (i) direct feed of crude glycerol to reactive distillation, (ii) separation of crude glycerol coupled with reactive distillation and (iii) reactive separation of crude glycerol coupled with reactive distillation.