Advanced Materials Research Vol. 506

Abstract: Chitosan (CS) has a high potential for gene delivery into mammalian cells. However, its uptake mechanism is not well clarified. We investigated the effects of inhibitors of clathrin-mediated endocytosis (chlorpromazine), caveolae-mediated endocytosis (genistein), macropinocytosis (LY 29004 and wortmannin), microtubuli polymerization (nocodazole) and of membrane cholesterol recycle (methyl-β-cyclodextrin) on the transfection efficiency with CS/pEGFP complexes and on the internalization of CS/rhodamine-labeled pEGFP complexes by hepatoma cell line (Huh 7 cells). The transfection was blocked by nocodazole, genistein, and methyl-β-cyclodextrin, respectively. CS/DNA complexes internalization was clearly inhibited by genistein. We conclude that the complexes uptake predominantly by caveolin-mediated pathways. In addition, fluorescence colocalization studies with acidotropic probes, LysoSensor dye, illustrated that CS/DNA complexes are targeted to lysosomes for the degradation after internalization.

Abstract: Pulsatile release dosage forms which time of drug release can be determined have shown advantages for various drugs such as chronopharmacological drugs and drugs with high first pass metabolism. The pulsatile release tablets consisting of drug-containing cores coated with inner swelling layer containing a superdisintegrant (croscarmellose sodium (Ac-Di-Sol^®)) and outer rupturable layer (ethylcellulose (EC)) were previously developed. In this study, two different types of EC coating membrane, EC ethanolic solution (ECS) versus EC aqueous colloidal dispersion (ECD), were compared. Propranolol HCl was used as a model drug. Effect of rupturable coating level on lag time and drug release was investigated. The results demonstrated that using ECS could provide the pulsatile release tablets with obviously longer lag time than ECD. With ECS, increasing of rupturable coating level increased lag time of the pulsatile release tablets because of the lowered water uptake. In addition, rapid drug release after the predetermined lag time was achieved in the pulsatile release tablets using ECS. However, the pulsatile tablets with ECD ruptured within a few minutes even high levels of rupturable coating were used. It was suggested that the different performance of the pulsatile release tablets with different types of EC might be related to the discrepancy in physical properties of the obtained EC membrane.

Abstract: Silicon nitride ceramic is a potential material for clinical indications due to its high fracture toughness, strength, and non-cytotoxicity. For this reason, Si₃N₄ ceramic is interested to apply for dental core. The superiority of Si₃N₄ ceramic is the low coefficient of thermal expansion (CTE) which is lower than that of zirconia and alumina ceramics that are popular in this field. In this study, borosilicate glass powder with 5 wt% of zirconia addition was prepared by melting at 1450 °C for 1 h. The glass melt was quenched and was then ground to be a powder and mixed with polyvinyl alcohol solution to be a paste. The Si₃N₄ specimens coated with the veneer were fired in electrical tubular furnace at 1100 °C for 15 min. The appearance of these specimens shows smooth, glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.05x10^-6 °C^-1 and the Vickers hardness as 4.0 GPa which is close to the human teeth. The specimens were tested by human gingival and periodontal ligament fibroblasts (HGF and HPDLF) and cytotoxicity by MTT assay. The results indicated that Si₃N₄ ceramic and borosilicate glass can be used as dental materials.

Abstract: In development of effervescent-based floating tablets, acrylic polymer is used to prepare a gas-entrapped membrane of the system. The tackiness of this acrylic polymer film causes tablet agglomeration, leading to failure in floatation. Thus, the aim of this study was to investigate the effect of magnesium stearate (MS) used as anti-tacking agent on mechanical and wetting properties of the acrylic polymer (Eudragit^® RL 30D) films. Incorporating MS resulted in the films with a slightly lowered puncture strength, a highly lowered elongation and an increased contact angle. These results indicated that flexibility and wettability of these films were reduced by addition of MS. Furthermore, the film tackiness measurement by peel test showed that 5% (w/w) of MS could significantly decrease the tackiness of the films. It was demonstrated that MS was a promising candidate to be used as an anti-tacking agent for effervescent-based floating tablets.

Abstract: Centella asiatica (4% w/w) oral bases were formulated in order to treat ulcers, both in the oral cavity and topical area. Two types of bases, oleaginous and aqueous, were used. The oral bases were evaluated for their physical appearances, pH, viscosity, physical stability and adhesion. PEG and Carbopol based exhibited suitable properties. The viscosity and adhesion of some bases were enhanced by adding dry powder polymer. The amount of asiaticoside, active ingredient, in the extract and in the formulations was analyzed by HPLC.

Abstract: Dentin matrix extract (DME) was reported to induce differentiation of bone cell line MC3T3-E1, since it contained a number of growth factors. Human DME was prepared from human teeth milled under liquid nitrogen. The resulted powder was demineralized in 0.5M EDTA and the crude proteins were separated using dialysis. DME contained proteins with molecular weight in the range of 55-72 kDa and had Zeta-potential value at-10.53 ± 0.12 mV, and-13.53 ± 0.12 mV, in PBS (pH 7.5), and in deionized water (pH 5.5), respectively. Three types of hydrogel carriers were fabricated from gelatin and Thai silk fibroin (G:SF) at the weight ratio of 100:0, 70:30, and 50:50. Glutaraldehyde was used as crosslinker. The carriers had water absorption 90.43 ± 0.29 %, 87.73 ± 0.29 %, 86.60 ± 0.76 % by weight respectively. In vitro release experiment of DME from these carriers showed controlled-release mechanism. The G:SF 100:0 released the highest DME content within 48 h, while the G:SF 50:50 hardly released DME within 2 days. These results shows the G:SF system can be used for controlled-release for DME.

Abstract: The purpose of this work was to study the effect of ZnO on properties of P₂O₅-CaO-Na₂O glass system for bone substituting applications. The glass formula used in this study is 45P₂O₅ - (30-x)CaO - 25Na₂O - xZnO where x = 0, 1 , 3, and 5 mol%. The corresponding glasses were prepared by conventional glass melting technique at 1000 °C for 1 h. Thermal parameters of each glass were studied by differential thermal analysis (DTA). These glasses were investigated in terms of infrared spectra and in vitro bioactivity. DTA results gave the glass transition temperatures in a range 227-280°C and crystallization temperatures in the range 521-529°C. Form FTIR results, the infrared spectra of all glass samples showed vibrations of phosphate network and the transmittance intensity of glass systems decreased with increasing ZnO content. All glass samples were exhibited the growth of apatite cells at the surface after immersed in SBF for 7 days. The optimum composition was found for the glass samples containing 5 mol% ZnO which contained the most apatite layer formation.

Abstract: Localized antibiotic beads are often used for treating patients with osteomyelitis or infections of the bone by providing local, sustained and high concentrations of antimicrobial agents to the area of infection, without systemically exposing an individual to antibiotic levels that could result in numerous toxic side effects. In this study, antibiotic impregnated hydroxyapatite spheres were prepared aiming for a functional device of drug carrier and bone graft. Three types of antibiotics were employed including gentamicin, vancomycin and fosfomycin. Antimicrobial susceptibility of antibiotic impregnated beads were tested against two bacterial strains (Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 25923) by using modified agar diffusion assay. Differences in antimicrobial efficiency were observed and related with respect to differences in molecular weight, mechanism of action and spectrum of activity for each antibiotic. Cytotoxicity by serial extraction technique of all antibiotic impregnated beads were determined by MTT assay. No cytotoxic potential at all extraction periods was observed for vancomycin impregnated on beads. Gentamicin and fosfomycin impregnated beads showed cytotoxic potential only on day 1 extraction, but no cytotoxic potential on longer periods.

Abstract: Tetrahydrocurcumin (THC), one of the curcumin metabolites, exhibits pharmacological activities such as antioxidant, anti-inflammatory and anti-carcinogenic properties. However, the pharmacological effect of THC is limited due to its low aqueous solubility. Floating alginate beads containing self-emulsifying drug delivery system (SEDDS) of THC were developed to increase drug solubility and prolong gastric residence time. Use of different weight proportions of sodium alginate (Na-alg.), calcium chloride (CaCl₂) and water soluble pore former (Polyvinylalcohol-polyethylene glycol copolymer; Kollicoat^® IR) in bead formulations had different effects on the floating abilities and in vitro rate of THC release. The release profile of the optimized THC-SEDDS floating alginate beads (D3) indicated a significant increase in the dissolution rate of THC and provided a controlled release of THC over an 8 h period in a simulated gastric fluid. The release of about 80% of THC from the optimized beads as an o/w microemulsion with a particle size of less than 50 nm, compared to only 30 % by an aqueous suspension from the unformulated THC could be considerable greater absorbed. The self-emulsifying floating alginate beads may provide a useful solid dosage form for oral delivery of THC and other hydrophobic compounds.

Abstract: The aim of this research is to study the mechanical properties such as hardness ,wear resistance etc , of the magnesium oxide (MgO) doped alumina (Al₂O₃) and yttria stabilized zirconia (YSZ) composite, We first prepared MgO-doped Al₂O₃ (denoted as Al₄) by mixing Al₂O₃ powder and 0.4 wt% of MgO powder. After that Al₄ powder was mixed YSZ powder, with the formula [(x)Al₄ - (100-x)YS when x was varied from 0 - 100 by wt%. The samples were sintered at 1450, 1500, 1550, 1600 and 1650 °C. In addition, microstructure of the surface was studied employing both optical and scanning electron microscopes. The hardness of the surface was investigated by Vickers indentation technique and pin on disk apparatus was employed for wear rate measurement. The results showed that the density and volume shrinkage decreased with the increase of Al₄ content. The grain size and porosity of the specimens tend to decrease when the sintering temperature increases. The hardness and wear resistance of the samples increased with the increase of Al₄ up to 90 %. It was also found that the material is not toxic to the body.