Preparation and Characterization of Polyurethane Microspheres Containing Theophylline

Abstract

Microencapsulation of theophylline in polyurethane was developed with 4, 4'-methylenediphenyl isocyanate (MDI), castor oil (CO) and ethylene diamine as a chain extender. Polyurethane microspheres were prepared in two steps pre-polymer preparation and microspheres formation. CO, MDI and theophylline were mixed first before suspending the mixture in an aqueous medium (stirred at 4, 000rpm) of the second reaction. Fourier transform infrared (FTIR) was employed to confirm polyurethane formation during the course of reactions. SEM illustrated microspheres with uniform spherical morphology. Particle size investigation with optical microscopy revealed size distribution of 27–128 m. Controlled release experiment of theophylline was performed in phosphate buffered saline (PBS) at pH 7.4 with ultraviolet (UV) spectrometer at 274nm. Drug release profiles showed initial release of 2–40% and further release for more than 10 days.