Also, the magnetically drug release was performed in phosphate buffer pH 7.4 using an external alternating magnetic field (AMF) apparatus (Electromagnet Type E, Newport Instruments, England). Magnetic field frequency was 350 kHz and the strength of magnetic fields (100 and 300 G) was changed by adjusting the voltage of the equipment. The beads were immersed in 50 mL of buffered solution with pH 7.4 and kept between magnetic poles for 165min. The supernatant was used to determine the content of released drug during 165 min.