Hasan Ahmad

Synthesis of γ-Alumina Particles and Surface Characterization

Alumina was synthesized via sol-gel technique by the hydrolysis of aluminium ion controlled by urea in aque- ous media. The resulting sol composed of Al(OH)3 particles coalesced and became a transparent gel. The freshly prepared gel was heated at 280°C to obtain alumina particles. The obtained particles were found to be amorphous � - alumina parti- cles with high porosity, characterized by FTIR, XRD and SBET techniques. Electron micrograph shows that the particles are nano-sized having non-spherical shape. Comparatively higher magnitude of adsorption of cationic surfactant indicated that the surface of alumina particles is negatively charged.

Adsorption behaviors of emulsifiers and biomolecules on temperaturesensitive polymer particles

Adsorption and desorption behaviours of emulsifiers and biomolecules on the two kinds of temperature-sensitive composite polymer particles were compared. One (I) was produced by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 0.17 μm-sized polystyrene seed particles. The other (II) was produced by seeded emulsion copolymerization of N-isopropylacrylamide (NIPAM) and N,N′-methylenebisacrylamide with 0.36 μm-sized styrene-NIPAM copolymer particles. The amount of adsorption at temperatures above each lower critical solution temperature (LCST) was found to be much higher for I than II. In both cases, at temperatures below the LCST, almost all lactalbumin hydrolysate molecules adsorbed above the LCST were desorbed but the desorptions of adsorbed egg albumin and lysozyme molecules were not so high. The adsorption and desorption were reversible for both particles and the efficiency was better for I than II. From these results, it is concluded that the adsorption/desorption of protein onto the temperature-sensitive polymer particles is controllable by changing the temperature below and above the LCST of the shell layer and the sensitivity is based on the surface property of the composite polymer particles.

Synthesis of temperature-sensitive submicron-size composite polymer particles

Temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 0.17 μm-sized monodispersed polystyrene seed particles. The adsorption and desorption behaviors of low molecular weight cationic emulsifier as well as albumin were examined to determine the variation of surface properties as a function of temperature below and above 35°C.

Magnetic and Temperature-Sensitive Composite Polymer Particles and Adsorption Behavior of Emulsifiers and Trypsin

A combination of magnetic and temperature-responsive properties in the same polymer composites is expected to increase their potential applications in the biomedical field. Accordingly, micron-sized magnetite/polystyrene/ poly(2-dimethylaminoethyl methacrylate-ethyleneglycol dimethacrylate), which are abbreviated as Fe3O4/PS/P (DM-EGDM) composite polymer particles, were prepared by the seeded copolymerization of DM and EGDM in the presence of magnetite/polystyrene (Fe3O4/PS) particles. Fe3O4/PS/P(DM-EGDM) composite particles with magnetic properties showed a temperature-sensitive phase transition at approximately 31 °C. The adsorption behavior of the low molecular weight emulsifiers and trypsin (TR) as biomolecules were examined on Fe3O4/PS/P(DM-EGDM) composite polymer particles at different temperatures. The native conformation of TR was followed by measuring the specific activity under various adsorption conditions. The activity of the adsorbed TR on composite polymer particles was higher than those of the free TR and TR adsorbed on Fe3O4/PS particles.

Adsorption of enzymes onto submicron-sized temperature-sensitive composite polymer particles and its activity

Abstract Temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 0.14-μm-sized polystyrene seed particles. Its reliability as a carrier for biomolecules was evaluated by measuring the enzymatic activity of trypsin adsorbed on the composite particle at a temperature above the lower critical solution temperature (LCST). Conformation of trypsin desorbed from the particle surface by lowering the temperature to below the LCST was examined with circular dichroism spectroscopy and compared with the native one. Both results indicate that enzymatic activity of the trypsin retained during the adsorption/desorption measurement.

Preparation of temperature-sensitive polymer particles having different lower critical solution temperatures

Preparation of temperature-sensitive core-shell composite polymer particles was carried out by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with submicron-sized polystyrene seed particles as core. The lower critical solution temperature (LCST) of the core-shell composite was about 35°C, while the LCST could be controlled toward higher or lower temperatures by copolymerizing the shell layer with hydrophilic/hydrophobic vinyl comonomer.

Biocompatible microcrystalline cellulose particles from cotton wool and magnetization via a simple in situ co-precipitation method

This investigation describes the preparation of magnetically doped degradable microcrystalline cellulose (MCC) nanocomposite particles with application potential in biotechnology, solid support for biomolecule/water purification, oil recovery from water and beyond. MCC was first extracted from cotton wool, the most abundant biocompatible polymer, by sulfuric acid hydrolysis and the effect of acid strength was examined. The size of the elongated fiber structure was reduced with increasing acid strength. MCC particles extracted by treatment with 70% sulfuric acid were used to prepare magnetic MCC nanocomposite particles. The nanocomposite particles named as MCC/Fe3O4 were prepared via in situ co-precipitation of Fe+3/Fe+2 from their alkaline solution. The precipitated Fe3O4 nanoparticles are expected to be bonded with MCC particles via hydrogen bonding. The nanocomposite dispersion was colloidally stable and the particles responded when external magnetic field was applied. It was possible to control the magnetic property by regulating the content of iron oxide.

Effect of shell thickness on the temperature-sensitive property of core-shell composite polymer particles

Core-shell composite polymer particles having temperature-sensitive shell were prepared by seeded emulsion copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate (EGDM) with 0.14 μ-sized polystyrene seed particles according to our previous article. In this article, the effects of crosslinking density and thickness of the shell on the temperature-sensitive property were studied. Two series of composite particles, one with various EGDM contents in the shell and the other with various shell contents, were prepared for this study. The composite particles at the EGDM content of 3 wt % with the shell content of 47 wt %, showed the maximum swelling and deswelling phenomena at temperatures, respectively, below and above the lower critical solution temperature. The adsorption and desorption behaviors of low molecular weight cationic emulsifier and bio-molecules were dependent on the shell content. In almost all cases, the adsorption/desorption behavior reached to the maximum variations at the shell content of 17 wt %.

Enzymatic activity of trypsin adsorbed on temperature-sensitive composite polymer particles

Two kinds of temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerizations of (dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate with 0.14 μm-sized polystyrene and 0.26 μm-sized poly(methylmethacrylate) seed particles. To evaluate the usefulness as a carrier for biomolecules, the enzymatic activities of trypsin adsorbed on these two composite polymer particles were measured at temperatures above and below each lower critical solution temperature (LCST). In both cases, adsorbed trypsin retained its enzymatic activity during repeated adsorption/desorption measurements.

Carboxyl functionalized poly(methyl methacrylate-acrylic acid-ethylene glycol dimethacrylate) copolymer particles and their amination with amine-nucleophiles

Abstract Poly(methyl methacrylate-acrylic acid-ethylene glycol dimethacrylate) copolymer particles abbreviated as P(MMA-AA-EGDM) copolymer particles were prepared by soap-free emulsion copolymerization. The concentration of carboxyl group on/near the surface of particles increased with the increase in acrylic acid (AA) content in the recipe. The carboxyl groups were reacted with amine nucleophiles such ethylene diamine and 1,6-diaminohexane through preactivation with dicyclohexyl carbodiimide as a coupling agent. The modified particles were characterized by electron micrographs and FTIR spectral analysis. Adsorption behaviours of some biomolecules were measured to have idea about=-0 the polarity of the particles surface