Bambang Sunendar Purwasasmita

Novel pH-sensitive drug carriers of carboxymethyl-hexanoyl chitosan (Chitosonic® Acid) modified liposomes

In this study, novel hybrid nanocarriers composed of carboxymethyl-hexanoyl chitosan (Chitosonic® Acid, CA) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-liposomes were developed. CA was immobilized onto the DSPE-liposomes by EDC/NHS reaction using the carboxyl group of CA and the amino group of DSPE. The characteristics of the resultant CA-modified liposomes were evaluated by transmission electron microscopy, dynamic light scattering, zeta potential, FTIR spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurement. The results show that the particle size and surface charge of the CA-modified liposomes varied with the concentration of CA, and exhibited pH-sensitive behavior. In vitro drug release studies demonstrated the sustained release behavior of the doxorubicin in the CA-modified liposomes, related to the rapid release in the free doxorubicin. Interestingly, the doxorubicin release rate from CA-modified liposomes was lower at higher pH values (pH 7.4) than at lower pH values (pH 4), indicating that the drug carrier displayed pH-sensitive released behavior. Furthermore, CA-modified liposomes exhibited no cytotoxicity toward the fibroblast cells (L-929 cells), suggesting an excellent biocompatibility. Fluorescence and confocal microscopy images showed good cellular internalization of the CA-modified liposomes into the cellular compartment. These results confirm that the novel CA-modified liposomes could respond to pH environment, which is promising for drug controlled release applications, especially in the field of cancer cell therapy (lower pH environments).

Microstructural and Thermal Properties of Nanocrystalline Silica Xerogel Powders Converted from Sago Waste Ash Material

In the present investigation, nanocrystalline silica xerogel (NSX) powders were produced from an amorphous silica xerogel (ASX) extracted from sago waste ash. The NSX powders have been calcined at 1200oC, milled and then annealed at temperatures ranging from a room temperature to 1200oC. Their properties (and most notably the size of the particles) have been characterized on the basis of the experimental data obtained using thermal analysis (DSC/TGA), X-ray diffraction (XRD), Infrared and Raman spectroscopy. For the crystalline silica xerogel powders the results show a narrow distribution of the particle sizes centered around an average value of 636  67 nm. The DSC analysis of NSX indicates that in the temperature range from a room temperature to 300oC five distinct stages of the crystallization process take place, which are delimited by the transition temperature of 38oC, 92oC, 129oC, 168oC, and 246oC, respectively. Above 300oC, the crystalline phase is similar to an amorphous silica xerogel (ASX), i.e. cristoballite-like and tridymite-like crystalline silica phases confirmed by the XRD analysis. It has been observed that the characteristic band of cristoballite is strongly dependent on the thermal history and the NSX transforms into a stable form at a temperature of 1200oC. Both the Raman and the FTIR spectra elucidate the bonding system of the constituent atoms and groups (such as Si, O and OH) and throw light on their underlying structure. The obtained results are important for optimization of the parameters of the technological processes for production of nanocrystalline silica glass ceramics used as a host matrix for luminescence materials, each of which requires a specific porosity and structure.

Basic Properties of PMMA Reinforced Using Ceramics Particles of ZrO2-Al2O3-SiO2 Coated with Two Types of Coupling Agents

In this study, novel composites materials composed of polymethyl methacrylate (PMMA) reinforced ZrO2-Al2O3-SiO2 filler system were developed. Zirconia-alumina-silica filler system were synthesized through sol-gel technique. Chitosan and trimethoxypropilsilane (TMPS) were used to modify the composites system. The resulting composites material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness test. SEM images displayed the composites particles in nanometer size with minor agglomeration. The XRD results revealed the presence of cubic and tetragonal phase of zirconia and also monoclinic silica phases in the composites system. These crystallographic characteristic could affect the mechanical properties of the composites. The hardness value for un-modified composites was 15.27 ± 0.25 VHN and for TMPS 19.43 ± 1.89 VHN and chitosan modification 18.75 ± 2.05 VHN, respectively. Therefore, these novel composites materials composed of PMMA reinforced filler system of zirconia-alumina-silica would provide the potential to apply in dental technology.

Preparation of Porous Ceramic with Controllable Additive and Firing Temperature

P orous ceramics were produced by mixing clay and ash of sago waste from the sago processing industry in Indonesia. The composition was prepared by adding an amount from 0 to 40 wt% of ash into the clay, and then the samples were milled for 6 h. The samples were dry pressed and sintered in the temperature range between 900°C and 1300°C. The influence of the ash content and the sintering temperature on the bulk density, firing shrinkage, and porosity was studied in detail. The results show that an amount of 10 wt% ash can be incorporated into the clay material without any appreciable effect on the bulk density and porosity of the samples sintered at 1000°C. It was found that if the amount of ashes is greater than 20 wt% and the sintering temperatures are lower than 1100°C, then the percentage of the porosity is greater than 30%. These results are important for optimization of the parameters of the technological processes for production of porous ceramics for various applications, each of which requires a specific porosity.

Preparation and Characterization of Biomass-Derived Advanced Carbon Materials for Lithium-Ion Battery Applications

In this study, carbon-based advanced materials for lithium-ion battery applications were prepared by using soybean waste-based biomass material, through a straightforward process of heat treatment followed by chemical modification processes. Various types of carbon-based advanced materials were developed. Physicochemical characteristics and electrochemical performance of the resultant materials were characterized systematically. Scanning electron microscopy observation revealed that the activated carbon and graphene exhibits wrinkles structures and porous morphology. Electrochemical impedance spectroscopy (EIS) revealed that both activated carbon and graphene-based material exhibited a good conductivity. For instance, the graphene-based material exhibited equivalent series resistance value of 25.9 Ω as measured by EIS. The graphene-based material also exhibited good reversibility and cyclic performance. Eventually, it would be anticipated that the utilization of soybean waste-based biomass material, which is conforming to the principles of green materials, could revolutionize the development of advanced material for high-performance energy storage applications, especially for lithium-ion batteries application.

Characterization of Silica Extracted from Rice Husk Ash Wastes Doped by Tin Dioxide for Wave Guide Material

A series of experiments is made to produce silica, mixing with tin dioxide (SnO2), and characterizing for application of waveguide device. Silica xerogels (SX) are prepared from raw materials derived from rice husks ash (RHA), which abundant in South East Sulawesi. The synthesis conditions have been optimized to obtain the ash of rice husks with the maximum silica content. SnO2 are prepared from a commercial powder. The ceramic waveguide materials are produced by mixing SX and SnO2 with various composition. The mixtures are molded to form the rectangular shape of 20 mm, 40 mm, and 5 mm in size. The samples will be sintered at different level of temperatures (from 300°C to 1200°C) by using microwave heating system as well as electric furnace. The microstructural of sintered samples were characterized on the basis of the experimental data obtained using densification measurement method (Archimedes method), crystallization (X-ray diffraction, XRD), microstructure (Scanning electron microscope, SEM). Optical and related properties such as the functional groups, structure, and absoption were characterized by using FTIR, Infrared and Raman Spectroscopy and absorption (UVVis). The permittivity and permeability will be calculated from S-parameters determined by using Vector Network Analyzer (VNA). Characterization results are presented in this paper and the others are will be published in another separated papers. Furthermore, the relationship between properties with SnO2 content and sintering temperature is also studied.

Synthesis of Hydrophobic Viscose Rayon Fiber Using Nanorod Silica and Chitosan as Surface Modifier

Hydrophobic textile is a type of smart fabrics. Some of it are commonly coated with small particles and finally treated by water repellent agent in terms of acquiring its hydrophobic property. This research describes how hydrophobic textile are formed from its initial form of fabrics and even yarn, which are fibers. Synthesis process was commenced through wet spinning of viscose rayon mixed with nanorod silica which has been formerly produced with sol gel method. These fibers were then coated with chitosan and dried out by vacuum instrument. Scanning Electron Microscopy (SEM) results showed that nanorod silica were well attached on the fibers. Followed by Energy Dispersive Spectroscopy (EDS) mapping characterization, silica particles were moderately dispersed on its surface, performing roughness and creating hydrophobic effect. In addition, several characterization methods correlated to water absorption of the fibers were conducted. Fibers swelling percentage decreased from 50.2% to 17.13%, while moisture regain (MR) number also decreased from 14.28 to 10.72.

Synthesize and Characterization Zr-Al-Si Post through Eggshell Membrane Strengthening with PMMA Matrix

Zr-Al-Si posts were successfully synthesized using biotemplate of eggshell membrane by sol-gel method and strengthening with matrix of polymethyl methacrylate (PMMA). The dental posts made were analyzed with the scanning electron microscope (SEM), three point bending and microvickers hardness tester. There are two methods used to synthesized Zr-Al-Si posts, with calcination and without calcination. The synthesized mechanism is discussed here.

Synthesis and Characterization of MgPSZ-PMMA Composite by Sol-Gel Modification and Direct Foaming Technique Using Egg Whites

This study prepared Magnesium-Partially Stabilized Zirconia (Mg-PSZ) filler synthesis and direct foaming technique using egg whites, and impregnated by PMMA. The results were evaluated systematically by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). XRD results denote that the powder sample of MgPSZ was successfully formed with various crystal size of tetragonal and monoclinic phase. SEM and TEM observations revealed that nanoparticles MgPSZ were in spherical and long rounded shapes. Furthermore, SEM observation revealed that the direct foaming method were also successful in the formation of porous structures which favourable for impregnation process by PMMA. The use of egg whites as a polymer precursor in both methods demonstrates that porous specimens contained nanosized, predominantly tetragonal, Mg-PSZ powders were successfully synthesized. This shall yield an interesting prospect towards cheap, reliable, and biocompatible product to resemble the modulus elasticity of dentin.

Preparation and Characterization of Magnetic Carbonate Apatite/Chitosan/Alginate Composite Scaffold

Treatment for bone cancer has begun to be experimented with ferrimagnetic for magnetic induction hyperthermia. On the other hand, composites of bioceramics and biopolymer have been studied for scaffold as these materials resemble the structure of bone. The current study investigated the magnetization of calcium aluminum ferrite magnetic (CaAl4Fe8O19) incorporated in carbonate apatite, alginate and chitosan, that serves as a scaffold. CaAl4Fe8O19 powder were synthesized using calcium nitrate, aluminium nitrate and ferrous chloride using the sol-gel method. Combining the carbonate apatite/chitosan/alginate compoiste and CaAl4Fe8O19using the freeze-dry method has produced carbonate apatite/alginate/chitosan/CaAl4Fe8O19 composite scaffolds. The CaAl4Fe8O19powder and the scaffolds were observed using SEM (scanning electrone microscope) and their magnetization were measured using VSM (vibrating sample magnetometer). It was shown that the scaffold is a composite structure of CaAl4Fe8O19 particles, having diameter ranging from 0.5 to 2 µm, embedded in the pore walls of the carbonate apatite/alginate/chitosan matrix. The saturation magnetization Ms and remanence magnetization Mr of the CaAl4Fe8O19particles were 20 and 2.0 emu/g, whereas, those of the magnetic scaffold were 4.3 and 2.0 emu/gr. The addition of the carbonate apatite/alginate/chitosan composite into CaAl4Fe8O19 decreased the fraction and/or magnetic of the CaAl4Fe8O19 particles.