Wirach Taweepreda

Characterization of muco- and bioadhesive properties of chitosan, PVP, and chitosan/PVP blends and release of amoxicillin from alginate beads coated with chitosan/PVP

Purpose: To investigate the muco/bioadhesive properties of chitosan, polyvinylpyrrolidone (PVP), and chitosan/PVP blends and the release of amoxicillin (AMX) contained in AMX-alginate beads coated with these materials. Method: Chitosan, PVP, and chitosan/PVP blends at various volume ratios were coated onto calcium alginate beads containing AMX. The muco/bioadhesive properties of all materials and the AMX-alginate beads coated with these materials were characterized. Results: Measurements of their viscosity, texture, and adhesion to HT29 cells demonstrated that chitosan/PVP at a volume ratio of 5/5 had the best muco/bioadhesive properties when compared with chitosan, PVP, and blends of other ratios. Wash-off tests indicated that the mucoadhesive property of the coated AMX-alginate beads was significantly higher than that of the uncoated beads. Diffuse reflectance infrared Fourier transform spectroscopy showed that there were interactions between chitosan–PVP, chitosan–mucin, PVP–mucin, and chitosan/PVP blend–mucin. Scanning electron microscopy revealed that the surfaces of the coated beads were smoother than those of the uncoated beads. All coated AMX-alginate beads were able to provide a controlled release of AMX with Super Case II transport properties, at a pH of 4. This was probably a result of the rapid and extensive swelling of the alginate beads. The more rapid release of AMX at pH 1 was probably because of the rapid dissolution of the drug at this pH. Conclusions: From the controlled drug release and muco/bioahesive properties of these coated AMX-alginate beads, we suggest that the alginate-coated beads might be a promising drug delivery system to assist with the eradication of Helicobacter pylori infections.

Deproteinized natural rubber film forming polymeric solutions for nicotine transdermal delivery

Film forming polymeric solutions were prepared from DNRL blended with MC, PVA, or SAG, together with dibutylphthalate or glycerine used as plasticizers. These formulations were easily prepared by simple mixing. In a preliminary step, in situ films were prepared by solvent evaporation in a Petri-dish. Their mechanical and physicochemical properties were determined. The in vitro release and skin permeation of nicotine dissolved in these blended polymers were investigated by a modified Franz diffusion cell. The formulations had a white milky appearance, and were homogeneous and smooth in texture. Their pH was suitable for usage in skin contact. The mechanical property of in situ films depended on the ingredients but all compatible films were in an amorphous phase. The DNRL/PVA was shown to be the most suitable mixture to form completed films. The in vitro release and skin permeation studies demonstrated a biphasic release that provided an initial rapid release followed by a constant release rate that fitted the Higuchi’s model. Nicotine loaded DNRL/PVA series were selected for the stability test for 3 months. These formulations needed to be kept at 4°C in tight fitting containers. In conclusion, film forming polymeric solutions could be developed for transdermal nicotine delivery systems.

Transdermal nicotine mixed natural rubber-hydroxypropylmethylcellulose film forming systems for smoking cessation: in vitro evaluations

Abstract Novel film forming polymeric dispersions for transdermal nicotine delivery were prepared from deproteinized natural rubber latex (DNRL) blended with hydroxypropylmethylcellulose (HPMC) and dibutyl phthalate (DBP) or glycerin (GLY) as plasticizer. The preliminary molecular compatibility of ingredients was observed by Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffractometry characterizations. All film forming polymeric dispersions were elegant in appearance and smooth in texture without agglomeration. Their pH was 7–8. In addition, their viscosity and spreadability showed good characteristics depended on HPMC and plasticizers blended. The transparent in situ dry films with good strength and elasticity were also confirmed by peeling-off. The nicotine release from them revealed an initial fast release that was similar to the release from a concentrated nicotine solution, and followed by slow release pattern from the in situ films. GLY blended formulation produced a higher amount of nicotine permeation through the in vitro pig skin than DBP blends. Ethanol mixing also enhanced nicotine permeation, but it affected the integrity of in situ films. The nicotine release and skin permeation kinetics were by a diffusion mechanism that was confirmed by the Higuchis model. These formulations were safe without producing any severe skin irritation. However, for the stability they needed to be stored at 4 °C in tightly sealed containers.

Preparation and Properties of Electrospun PVC Nanofiber

Nanofibrous membranes based on poly (vinyl chloride) (PVC) were prepared by electrospinning. The morphology of nanofibrous was observed under field emission scanning electron microscope (FE-SEM) and effects of instrument parameters including electric voltage, tip to collector distance, and solution parameters such as PVC concentration and mixed solvent of THF and DMF (50:50) were evaluated. The beads on the fiber were formed with low concentration of PVC. The dielectric constant, thermal properties and crystallinity of the electrospun membranes were characterized by precision LCR meter, and differential thermal analysis (DTA), respectively. It was found that smooth surface of electrospun PVC nanofiber had a high ionic conductivity and their thermal properties were improved comparing with PVC sheet.

Improved Deproteinization Process for Protein-Free Natural Rubber Latex

Hev b1-14 type proteins in natural rubber latex (NRL) have been identified as allergens in immunogenic responses. Several methods have been developed to reduce these proteins from NRL such as enzyme treatment, centrifugation, creaming, simple or ultrasonic leaching, and chlorination. In this work, the improvement of deproteinization of NRL was developed using the combination of enzyme treatment and leaching processes. The fresh NRL was incubated with 0.2 phr proteolytic alcalase enzyme, and preserved with 2%v/v paraben concentrate in the presence of a 2%v/v sodium lauryl ether sulfate (SLES) as a surfactant at 37°C for 24 hours, and then centrifuged. The upper rubber mass was then leached for three times with either distilled water, a 1%v/v SLES solution, or a mixture of 1%v/v SLES and 2.5%v/v ethanol, and then finally re-dispersed in distilled water. It was found that the increasing process of leaching with either 1%v/v SLES or a mixture of 1%v/v SLES and 2.5%v/v ethanol had the higher efficacy to reduce the remained protein in deproteinized NRL (DNRL). The best deproteinized process was the enzyme treatment and followed by the three times leaching process with a mixture of 1%v/v SLES and 2.5%v/v ethanol, that could completely reduce the proteins in DNRL to 0%. This DNRL had the pH value, viscosity, dry rubber content, and total solid content of 7.41, 13.82 cps, 42.57%, and 44.63%, respectively. Its particle size was 626.23 nm with low polydispersity index of 0.16. The negative charge of SLES could increase the higher negative charge of DNRL to-63.20 mV that exhibited very good physical stability during storage. In conclusions, the combination of enzyme treatment and leaching process with both SLES and ethanol was successful to produce the protein-free DNRL. This DNRL could be further used for several applications including medical skin products.

Removal of organic impurities in waste glycerol from biodiesel production process through the acidification and coagulation processes.

Treatment of waste glycerol, a by-product of the biodiesel production process, can reduce water pollution and bring significant economic benefits for biodiesel facilities. In the present study, hydrochloric acid (HCl) was used as acidification to convert soaps into salts and free fatty acids which were recovered after treatment. The pH value, dosages of polyaluminum chloride (PACl) and dosage of polyacrylamide (PAM) were considered to be the factors that can influence coagulation efficiency. The pH value of waste glycerol was adjusted to a pH range of 3-9. The PACl and PAM added were in the range of 1-6 g/L and 0.005-0.07 g/L. The results showed best coagulation efficiency occurs at pH 4 when dosage of PACl and PAM were 2 and 0.01 g/L. The removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD(5)), total suspended solids (TSS) and soaps were 80, 68, 97 and 100%, respectively. The compositions of organic matters in the treated waste glycerol were glycerol (288 g/L), methanol (3.8 g/L), and other impurities (0.3 g/L).

Properties of Deproteinized Natural Rubber Latex/Gelatinized Starch Blended Films

This research aimed to study the compatibility and properties of deproteinized natural rubber latex (DNRL)/gelatinized starch blended films for use as transdermal patches. Various starches were previously gelatinized by heat treatment. Then, the DNRL/gelatinized starch blended films were prepared by simple mixing of DNRL with gelatinized starch and then drying at 50°C. The various parameters such as types (potato, sago, bean, corn, tapioca, rice and glutinous starches), amounts (5, 10, 15 and 20 part per hundred of rubber (phr)) and concentrations of gelatinized starch pastes (5, 10, 20 and 50%) were evaluated. It was found that all starch types could be blended as a homogeneous mixture with DNRL only in 5 phr. Bean starch also provided the good mixture in 10 and 15 phr. Rice and corn starches in the concentrations up to 20 phr could also be blended. Higher concentration of gelatinized starch pastes obtained the higher viscous liquids that were difficult to blend as a homogeneous mixture with DNRL, and provided inhomogeneous blended films. The dried films of all homogeneous DNRL/gelatinized starch mixtures were slightly yellowish transparent with good physical appearances. The tensile strength, swelling and erosion of these blended films increased when increasing amounts of gelatinized starch, but their elasticities were not different comparing to that of DNRL film itself. However, their strengths should be further improved by adding some plasticizers. Some drugs would be further loaded in these homogeneous film formulations for transdermal delivery.

Electrospun Epoxidized Natural Rubber with Poly(vinyl chloride) (ENR-PVC) Nanofibrous for PEMFC Applications

Various electrospun epoxized natural rubber / poly (vinyl chloride) (ENR/PVC) blend nonwoven membranes were prepared by electrospinning technique. Various concentration of epoxidized natural rubber (ENR) solution in N,N-dimethylformamide (DMF) were directly added to PVC solution for plasticization of the electrospun nanofibrous. Differencial thermal analysis (DTA), thermogravimetry analysis (TGA), fourier transfrom infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) were used to characterize the pristine and plasticized nanofibrous. DTA results indicated that the addition of ENR resulted in the shifting of glass transition temperature (Tg) towards lower temperatures. The blending of PVC with ENR is thermodynamically incompatible.

Characterization of Lidocaine Transdermal Patches from Natural Rubber Latex

The mucous liquid of Hevea brasiliensis or Para rubber tree, called natural rubber latex (NRL), composes of cis-1,4-polyisoprene which can form a patch under suitable formulation. In this study, blank and 5% lidocaine-loaded NRL patches were formulated and then characterized for physicochemical properties as well as evaluated in vitro drug release and stability. The patches were observed for their appearances. Surface morphology of the patches was investigated using a SEM. XRD was employed to study the crystallinity of the drug, the patch, and the drug-loaded patch. The extractions of lidocaine-loaded patches were analyzed for drug contents by HPLC. In vitro drug release study was performed using modified Franz diffusion cells. The patches at initial preparation and after kept at 4, 25, and 45 °C for 3 months were investigated for the stability determination. The results suggested that NRL could be used as a main component in pharmaceutical transdermal patches with acceptable physicochemical properties. Lidocaine-loaded NRL patches provided desirable drug release but high storage temperatures could age the patches resulting in darken color and lower release amount.

Model Compound Vulcanization Studied by XANES

Squalene has been used as a model compound for the investigation of sulphur crosslink in the vulcanization process. The effects of the accelerator on the crosslink were deduced from the sulfur K-edge absorption spectra. The majority of the crosslinks for the squalene vulcanized with ZDEC or TMTD is likely disulfidic, while that vulcanized with CBS or MBTS is monosulfidic.