Varaporn Buraphacheep Junyaprasert

Influence of oil content on physicochemical properties and skin distribution of Nile red-loaded NLC

The aims of this study were to investigate the effect of the oil content on the physicochemical properties of NLC and to elucidate the potential of NLC for skin targeting. The obtained results showed that an increase in the oil content did not affect the mean particle size of NLC but impacted on the zeta potential. The inner structure of NLC was influenced by the increasing proportion of oil towards the less ordered structure as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD), particularly for the higher medium chain triglycerides (MCT) loading. The data from proton nuclear magnetic resonance (1H NMR) revealed that cetyl palmitate nanoparticles did not completely recrystallize after cooling down to room temperature. 1H NMR and DSC results indicate that MCT molecules were restricted in the NLC as compared to the nanoemulsions (NE). Nile red distribution and penetration into skin from NLC were pronounced as compared to NE and dependent on the MCT loading. The deep penetration and high amount of Nile red were related to the occlusion factor. Moreover, the epidermal targeting was achieved by NLC applications, particularly those containing 5% MCT (NLC-5) depending on the amount of MCT loading.

Development of ascorbyl palmitate nanocrystals applying the nanosuspension technology

Ascorbyl palmitate (AP) is an antioxidant used in both cosmetics and food industry. Owing to its poor solubility and instability caused by oxidation having been observed in several colloidal systems, the aim of this study was to investigate the feasibility of applying the nanosuspension technology by high-pressure homogenization (HPH) (DissoCubes) technology) to enhance the chemical stability of AP, followed by lyophilization. Sodium dodecyl sulfate (SDS) and Tween 80 were chosen as emulsifying agents to stabilize the developed AP nanosuspensions. After 3 months of storage at three different temperatures (4 degrees C, 25 degrees C and 40 degrees C), the photon correlation spectroscopy (PCS) analysis of AP nanosuspensions revealed that the mean particle size of those stabilized with SDS significantly increased compared to those stabilized with Tween 80. The results observed from both atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed AP nanocrystals of cubic-like shape. The percentage of AP remaining in nanosuspensions stabilized with Tween 80 was higher than 90% after 3 months storage at 4 degrees C, 25 degrees C and 40 degrees C. To increase the chemical stability of AP nanosuspensions, a drug powder was prepared by lyophilization. The effect of the presence of cryoprotectant trehalose on the physical stability was evaluated at different concentrations. After redispersing the lyophilized product, the mean size of AP nanosuspensions without trehalose was significantly higher compared with the system with trehalose. After 3 months of storage at 25 degrees C the mean size of lyophilized AP nanosuspensions remained constant. X-ray diffraction revealed the crystalline character of AP nanocrystals after HPH and lyophilization.

Physicochemical properties and skin permeation of Span 60/Tween 60 niosomes of ellagic acid.

Ellagic acid (EA) is a potent antioxidant phytochemical substance which has limitation to use due to its poor biopharmaceutical properties, low solubility and low permeability. The aim of the present study was to develop niosomal formulations obtained from the mixture of Span 60 and Tween 60 that could encapsulate EA for dermal delivery. The EA-loaded niosomes were prepared with 1:0, 2:1, 1:1, 0:1 Span 60 and Tween 60, using polyethylene glycol 400 (PEG 400), propylene glycol (PG) or methanol (MeOH) as a solubilizer. The influence of formulations on vesicle size, entrapment efficiency and stability of EA-loaded niosomes was investigated. It was found that all ratios of surfactants could produce EA-loaded niosomes when using 15% (v/v) PG, 15% (v/v) PEG 400 or 20% (v/v) MeOH. The niosomes were spherical multilamellar vesicles showing the localization of EA in the vesicles. The vesicle sizes of the niosomes after extrusion were 124-752 nm with PI less than 0.4. The percentages of entrapment efficiency (% E.E.) of all EA-loaded niosomes varied between 1.35% and 26.75% while PEG 400 niosomes gave the highest % E.E. The most stable and highest entrapped formulation was 2:1 Span 60 and Tween 60 niosomes. Additionally, the in vitro skin permeation revealed that penetration of EA from the niosomes depended on vesicle size, the amount of EA entrapped and the added solubilizers which could act as a permeation enhancer. From skin distribution study, the EA-loaded niosomes showed more efficiency in the delivery of EA through human epidermis and dermis than EA solution. The results indicated that the Span 60 and Tween 60 niosomes may be a potential carrier for dermal delivery of EA.

Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol.

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2∶1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.

Effect of Process Variables on the Microencapsulation of Vitamin A Palmitate by Gelatin-Acacia Coacervation

Microcapsules of vitamin A palmitate were prepared by gelatin-acacia complex coacervation. The effects of colloid mixing ratio, core-to-wall ratio, hardening agent, concentration of core solution, and drying method on the coacervation process and the properties of the microcapsules were investigated. The microcapsules of vitamin A palmitate were prepared using different weight ratios of gelatin and acacia, that is, 2:3, 1:1, and 3:2 under controlled conditions. The other factors studied were 1:1, 1:2, and 1:3 core-to-wall ratios; 30, 60, and 120 min of hardening time; 2, 5, and 10 ml of formaldehyde per 280 g of coacervation system as a hardening agent; and 30%, 40%, and 50% w/w vitamin A palmitate in corn oil as a core material. The drying methods used were air drying, hot air at 40°C, and freeze-drying. The results showed that spherical microcapsules were obtained for all conditions except for 30 min of hardening time, which did not result in microcapsules. The optimum conditions for free-flowing microcapsules with a high percentage of entrapped drug were 1:1 gelatin-to-acacia ratio and 1:2 core-to-wall ratio when hardening with 2 ml formaldehyde for 60 min and using 40% w/w vitamin A palmitate in corn oil as the core concentration. In addition, drying the microcapsules by freeze-drying provided microcapsules with excellent appearance.

Q10-loaded NLC versus nanoemulsions: stability, rheology and in vitro skin permeation.

In this study, nanoemulsions (NE) of medium chain triacylglycerols (MCT) and nanostructured lipid carriers (NLC) of cetyl palmiate/MCT were produced to load coenzyme Q(10) (Q(10)) and characterized for their stability before and after incorporation into xanthan gum hydrogels. After storage at 4, 25 and 40 degrees C, the particles remained in the nanosize range for 12 months, with zeta potential higher than |40 mV|. Similar results were found in xanthan gum-based hydrogels containing NE or NLC. The crystallinity index of Q(10)-loaded NLC increased after being incorporated into hydrogels. The Q(10) entrapped in NLC and NE remained higher than 90% at all temperatures for 12 months but dramatically decreased when exposed to light. From the rheological studies, both NLC and NE dispersions possessed pseudoplastic flow having more liquid characteristics, whereas NLC and NE hydrogels exhibited plastic flow with thixothopy, showing more elastic rather than viscous properties. The occurrence of a spatial arrangement of lipid molecules was observed in the matrix of NLC when entrapped into hydrogels. From in vitro permeation studies, it could be stated that the amount of Q(10) released and occlusiveness were major keys to promote the deep penetration of Q(10) into the skin.

Physicochemical properties and biocompatibility of N-trimethyl chitosan : Effect of quaternization and dimethylation

The aim of this research was to investigate the effect of degrees of quaternization (DQ) and dimethylation (DD) on physicochemical properties and cytotoxicity of N-trimethyl chitosan (TMC). TMC was synthesized by reductive methylation of chitosan in the presence of a strong base at elevated temperature and polymer characteristics were investigated. The number of methylation process and duration of reaction were demonstrated to affect the DQ and DD. An increased number of reaction steps increased DQ and decreased DD, while an extended duration of reaction increased both DQ and DD. The molecular weight of TMC was in the range of 60-550kDa. From the Mark-Houwink equation, it was found that TMC in 2% acetic acid/0.2M sodium acetate behaved as a spherical structure, approximating a random coil. The highest solubility was found with TMC of an intermediate DQ (40%) regardless of DD and molecular weight. The effect of DD on the physicochemical properties and cytotoxicity was obviously observed when proportion of DD to DQ was higher than 1. TMC with relatively high DD showed reduction in both solubility and mucoadhesion and hence decreased cytotoxicity. However, the influence of DD was insignificant when DQ of TMC was higher than 40% at which physicochemical properties and cytotoxicity were mainly dependent upon DQ.

The role of mucoadhesion of trimethyl chitosan and PEGylated trimethyl chitosan nanocomplexes in insulin uptake

The aim of this work was to investigate the role of mucoadhesion in the insulin uptake of nanocomplexes (NC) based of trimethyl chitosan (TMC) and poly(ethylene glycol) (PEG)-graft-TMC copolymers. Self-assembled insulin NC were prepared by polyelectrolyte complexation. The effects of PEGylation and positive charge density on mucoadhesion were assessed using a mucin assay and mucus-secreting HT29-MTX-E12 (E12) monolayers. The behaviors of corresponding insulin NC after adhesion to E12 were also established. All PEGylated TMC copolymers showed significantly higher levels of adhesion to mucus than unmodified TMC. The copolymer composed of 298 PEG chains per TMC macromolecules exhibited the highest level of mucoadhesion, being 3.4 times higher than TMC. The higher mucoadhesive properties of PEGylated TMC copolymers resulted from the synergistic effects of interpenetration of PEG chains into the mucus and electrostatic interaction between positive charged TMC and anionic glycoproteins present in the mucus layer. Compared to TMC, insulin NC based on PEGylated TMC copolymers demonstrated no evidence of insulin uptake improvement due to complete release of insulin from NC after adhering to mucus. CLSM revealed the localization of TMC and its corresponding insulin NC at cell surface membranes of E12.

Bioadhesion and oral absorption of enoxaparin nanocomplexes

Polyelectrolyte complexes (PEC) formed between chitosan derivatives and enoxaparin were prepared by a self-assembly process and were characterized in terms of particle size and surface charge. The morphology was observed by atomic force microscopy (AFM). The colloidal stability and bioadhesion of the PEC were characterized by dynamic light scattering (DLS). The absorption of enoxaparin in rats was evaluated by activated partial thromboplastin time (APTT) assay. It was shown that the prepared PEC had a spherical shape with positive charge and a mean diameter in the range of 200-600 nm. An increase in temperature led to a decrease in particle size (ca. 10%) with an increased kcps value (ca. 10-20%) for the PEC studied, depending on the polymer structure. Thiolation and methylation of chitosan could significantly improve the corresponding PECs bioadhesion and hence the oral absorption of enoxaparin. A good relationship between bioadhesion and in vivo absorption was established. However, PEC of PEGylated chitosan did not display a significantly enhanced permeation of enoxaparin compared with unmodified chitosan. In conclusion, the oral bioavailability of enoxaparin can be enhanced by improving the bioadhesive properties of PEC via the chemical modification of chitosan employed.

Physicochemical characterization and in vitro release studies of ascorbyl palmitate-loaded semi-solid nanostructured lipid carriers (NLC gels)

The aim of this study was to characterize the physicochemical properties and to study in vitro release of ascorbyl palmitate from semi-solid lipid nanoparticles based on nanostructured lipid carriers (NLC gels) systems with the desired viscosity for dermal delivery. NLC gels were obtained by a one-step production procedure employing a high pressure homogenization technique using different solid lipid matrices. Ascorbyl palmitate (AP) was selected as a lipophilic active ingredient due to its range of cosmetic applications. After the production, particles within the size range 170–250 nm having polydispersity index lower than 0.3 were obtained from all formulations. After the AP incorporation into the NLC gels, the zeta potential increased to values higher than |30 mV|. Almost 100% encapsulation efficiency was observed. The obtained SEM and AFM data revealed non-spherical shaped nanoparticles. From DSC and X-ray diffraction studies, it was shown that the lipid recrystallized in the solid state possessing a less ordered structure as compared to the bulk material. The release study of active-loaded NLC gel formulations using Franz diffusion cells revealed that the type of lipid matrix affects both the rate and the release pattern. The viscoelastic measurements revealed a more elastic than viscous behaviour of NLC formulations indicating a typical gel-like structure.