Preparation Of Porous Dextran-based Microspheres

In this paper, dextran hydrogel microspheres with good morphology were synthesized by reversed-phase suspension polymerization, using dextran as raw material and epichlorohydrin as crosslinker. Then porous dextran microspheres were prepared by freezing-drying method. Their chemical structure was determined by Fourier Transform Infrared Spectrometer (FTIR). Their appearance was observed by Optical Microscope (OM) and Scanning Electronic Microscope (SEM). Their true density, equilibrium water content, wet density and average particle sizes were determined. It was found that the dextran microspheres had sphere shape with porous structure. The true density increased (range from 1.167 g/ml to 1.392 g/ml) with the increasing of crosslinker amount. The equilibrium water content increased (range from 96.4% to 87.29%) with the increasing of crosslinker amount while the wet density remained constant, very close to the density of water. The average particle size decreased (range from 212.8μm to 115.5μm) with the increasing of stirring speed.Then a series of porous dextran microspheres were synthesized using dimethyl ether polyethylene glycol (DMPE) as porogen. Their chemical structure was detected by FTIR. Their appearance was observed by SEM. It was found that there were microporous existed on dextran microsphere, and the pore diameter increased with the increasing of porogen amount. With the increasing of porogen amount, the equilibrium water content increased (range from 93.83% to 98.51%), wet density increased (range from 0.9087 g/ml to 0.9997 g/ml), average pore volume increased (range from 15.20 ml/ to 63.21 ml/g), porosity increased (range from 85.26% to 98.88%). The equilibrium water content increased (range from 95.09% to 98.56%) with the increasing of crosslinker amount, while the wet density decreased slightly, very close to the density of water.At last, dextran-based microspheres with acid sensitivity were prepared by copolymerization of acrylic acid and dextran. Their chemical structure was determined by FTIR, and their appearance was observed by SEM. The influence of preparation conditions on the water absorption of dextran-based microspheres were discussed, such as ratio of reactant, crosslinker amount and neutralization of acrylic acid. Final results showed that dextran-based microspheres were prepared successfully. They had good sphere morphology and uniform particle size distribution. The water absorption of dextran-based microspheres increased (range from 21.22 g/g to 39.56 g/g) with the decreasing of reactant ratio. The water absorption decreased (range from 38.84 g/g to 8.38 g/g) with the increasing of crosslinker amount. The water absorption increased first and then decreased with the increasing of neutralization of acrylic acid. The effects of external environment on the water absorption of dextran-based microspheres were also investigated. When the pH value increased from 2 to 10, the water absorption increased from 11.6 g/g to 15.3 g/g. When the concentration of NaCl gradually increased, the water absorption decreased from 15.58 g/g to 7.7 g/g.