Synthesis of FeCo@SiO2-SS-PEI nanoparticles
To synthesize the FeCo@SiO2-SH, 200 mg of FeCo NPs dispersed in ethanol by ultrasound, followed by sequential addition of 1 mL NH3.H2O, 20 mL TEOS and 1 mL MPTMS in the ultrasound for 3 hours (Zhang, 2014).
Then, the nanoparticles were collected using magnet, and washed with ethanol and water for 5 times and then the magnetic nanoparticles were dried under vacuum at 25 ºC. To synthesize FeCo@SiO2-SS-COOH nanoparticles, 200 mg of Sulfhydrylated FeCo nanoparticles was dispersed in 12 mL methanol, and then, the 2- carboxyethyl 2-pyridyl disulfide (200 mg) was added and reaction performed for 36 hours, the obtained nanoparticles were washed and then dried as mentioned above. Finally, to synthesize FeCo@SiO2-SS-PEI nanoparticles, 200 mg of FeCo@SiO2-SS-COOH nanoparticles was dispersed in 16 mL PBS buffer (pH = 7.4) and then, the activation of the carboxyl groups was performed with addition of 200 mg of EDC and 100 mg NHS at 25 Cº for half an hour. After that, 4 mL PBS buffer containing 200 mg PEI (1800 Da) was added and stirred at 25 Cº for 2 days. The resulting nanoparticles were washed with distilled water and ethanol, then the nanoparticles were lyophilized (Lifilizator Alpha model 1-2 LD plus, Christ, Germany).