Design and In Vitro Evaluation of Polymeric Formulae of Simvastatin for Local Bone Induction

ABSTRACT

Simvastatin (SVS), a cholesterol-lowering drug, has been shown to stimulate bone formation. This study deals with the design and in vitro evaluation of local delivery systems for simvastatin. They are intended to treat bony defects resulting from periodontitis or to induce osteogenesis around the titanium implants. Granules and gels were formulated using bioerodible/biocompatible polymers, namely hydroxypropylmethyl cellulose (H), sodium carboxymethyl cellulose (C), and chitosan (Ch). The in vitro release profiles and kinetics were evaluated and the swelling and/or erosion was monitored. Differential scanning calorimetry (DSC) and infrared (IR) were used to detect any SVS/polymer interactions that may affect drug release. The results revealed variable extents of controlled drug release from the designed formulae depending on the polymer nature. About 50% cumulative SVS was released from both H granules and gel formulae within 24 h and ～66% and ～88% from C granules and gel, respectively. Ch formulae exhibited ～50% release from granules and ～30% from gel.     

Effect of microwave sintering on microstructural and magnetic properties of strontium hexaferrite using sol–gel technique

The sol–gel method is used to prepared hexaferrite using d-Fructose as a fuel. The effect of sintering temperature on the microstructure of SrFe₁₂O₁₉ ceramics is analyzed. The observed XRD results indicate a well-formed crystalline phase of dense hexagonal SrFe₁₂O₁₉ ceramics. From this analysis, no secondary phases are identified. The microstructure of the sintered single phase M-type ferrites ceramics displays a hexagonal-platelet like morphology. Sintering temperature can markedly affect the grains in sintered ferrite. The sintered product is shown to be dense microstructure with relatively small grains. The maximum sintered density 95 % was obtained at lower temperature of 1,150 °C. In addition, saturation magnetization (50.43 emu/g) and the coercivity (H_c) 5,594.53 Gauss were observed.     

Effect of Waste Tire Dust (WTD) Size on the Mechanical and Morphological Properties of Polypropylene/Waste Tire Dust (PP/WTD) Blends

Waste tire dust (WTD) of mechanically reclaimed scrap tires was blended with polypropylene (PP) in five different compositions to prepare PP/WTD blends. Three series of blends with three different sizes of WTD (250–500 µm, 500–710 µm, and 710 µm–1 mm) were prepared in a Haake Rheomix Polydrive R 600/610 at a temperature of 180°C and a rotor speed of 50 rpm for 9 min. The results show that at the same blending composition, the PP/WTD blends with fine WTD size require higher equilibrium torque and exhibit higher values of tensile strength, Young's modulus, and elongation at break (E_b) than that of blends with coarser WTD size. The swelling index of the PP/WTD blends reveals that the blends with fine WTD size have better swelling resistance in both oil and toluene than all blends with coarser WTD. Scanning electron microscope (SEM) observation indicates that the PP/WTD blends with the finest WTD size exhibit better PP/WTD adhesion than blends with coarse WTD sizes.     

White Rice Husk Ash-Filled Natural Rubber Compounds: The Effect of Bonding Agents

White rice husk ash (WRHA)-filled natural rubber compounds were prepared by using a laboratory-size two-roll mixing mill. Curing using a conventional vulcanization system was used and cure studies were carried out on a Monsanto rheometer. The mechanical testing of the vul-canizates involves the determination of tensile properties, tear strength, hardness, and resilience. Scanning electron microscopy (SEM) and swelling measurement were also done. The effects of bonding agents on the curing and mechanical properties have been investigated using re-sorsinol formaldehyde and hexamethylene tetramine as the bonding agents. Results show that the bonding agents prolonged the cure time t ₉₀ and scorch time t ₂ and, at the same time, improved the mechanical properties of the natural rubber vulcanizates. SEM and swelling studies indicate that the rubber-filler interaction is improved with the addition of bonding agents.     

Effects of Dynamic Vulcanization and Acrylic Acid on Properties of Recycled Poly(vinyl chloride)/Acrylonitrile Butadiene Rubber (PVCr/NBR) Blends

Effects of dynamic vulcanization and acrylic acid (AAc) on processability, mechanical properties, swelling behavior, morphology, and thermal stability of recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were investigated. Blends were prepared in a Haake Rheomix at a temperature of 150°C and a rotor speed of 50 rpm. Recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were also prepared as comparison. It was found that the dynamic vulcanization and the addition of acrylic acid improved the stabilization torque, mechanical energy, stress at peak, stress at 100% elongation (M₁₀₀), swelling resistance, and thermal stability but decreased the elongation at break of the blends. The introduction of a cross-link into the elastomer phase and better compatibility between PVCr and NBR are responsible for the enhancement of thermal stability and mechanical properties of dynamically vulcanized PVCr/NBR + AAc as evidence from the scanning electron microscopy (SEM) of the tensile fracture surfaces and infrared spectroscopy study of the dynamically vulcanized of PVCr/NBR + AAc shows.     

Effects of Bonding Agents on the Mechanical Properties of the Composites Made of Natural Rubber and Oil Palm Empty Fruit Bunch

The effects of various bonding agents on natural rubber-oil palm wood flour (OPWF) composites were studied. Results indicate that the maximum torque increases with increasing OPWF loading and the incorporation of various bonding agents. Compared to the composite without a bonding agent, the incorporation of bonding agents improves the tensile modulus, tear strength, tensile strength, and hardness of the composites. Scanning electron microscopy studies and rubber-fiber interaction measurements indicate that the OPWF-rubber adhesion can be enhanced by the use of bonding agents.     

The Properties of Acrylonitrile-Butadiene Rubber (NBR) Composite with Halloysite Nanotubes (HNTs) and Silica or Carbon Black

The properties of acrylonitrile-butadiene rubber (NBR) composites were studied at five different compositions of NBR/HNTs/Silica or NBR/HNTs/CB (i.e., 100/5/0, 100/4/1, 100/3/2, 100/2/3, 100/0/5 parts per hundred rubber (phr)). The tensile strength and modulus (M100) of both composites decreased, whereas elongation at break increased and maximum torque with increasing the silica or carbon black content. However, both composites show opposite trends for cure time and scorch time, where NBR/HNTs/Silica composite exhibited an increasing trend, while NBR/HNTs/CB composite shows the decreasing trend. The rubber-filler interaction studies showed that carbon black is a more reinforcing filler than silica.     

The Effect of Presence of Glycopolymer Grafts in Poly N-Isopropylacrylamide/Clay Nanocomposite Hydrogels

Two types of poly-N-isopropylacrylamide (p-NIPAM)/Cloisite 30B clay nanocomposite (NC) hydrogels were synthesized where the first one contained Cloisite 30B without modification. However, the second one contained Cloisite 30B with glycopolymer units attached onto its surface by surface-initiated atom transfer radical polymerization. The main purpose of this article was to study the effect of surface grafting of glycopolymer onto Cloisite 30B clay surface on the physical properties of the resulting NC hydrogels such as swelling ratio, deswelling behavior and thermal behavior. It was found that NC hydrogels containing glyco-units had better properties than the first one.     

Circular polarisation diversity with small size microstrip antenna

The circular polarisation diversity with the square patch microstrip antenna was obtained by the implantation of the quadrature hybrid as a microstrip feed line. The small size antenna is achieved by using the aperture coupled structure. The cavity model has been used to design an aperture coupled microstrip antenna (ACMSA) and determine the length of the open microstrip stub line in order to match microstrip antenna. The MATLAB and Advanced Design Software (ADS) have been used for designing and simulating the ACMSA. There is a good agreement between the simulated and the experimental results.     

A fuzzy logic sliding mode controlled electronic differential for a direct wheel drive EV

In this study, a direct wheel drive electric vehicle based on an electronic differential system with a fuzzy logic sliding mode controller (FLSMC) is studied. The conventional sliding surface is modified using a fuzzy rule base to obtain fuzzy dynamic sliding surfaces by changing its slopes using the global error and its derivative in a fuzzy logic inference system. The controller is compared with proportional–integral–derivative (PID) and sliding mode controllers (SMCs), which are usually preferred to be used in industry. The proposed controller provides robustness and flexibility to direct wheel drive electric vehicles. The fuzzy logic sliding mode controller, electronic differential system and the overall electrical vehicle mechanism are modelled and digitally simulated by using the Matlab software. Simulation results show that the system with FLSMC has better efficiency and performance compared to those of PID and SMCs.