*2.1.4 Synthesis of ferrogel*

Firstly, chitosan solution was prepared by dissolving 0.1 g chitosan (CS) in 10 mL acetic acid solution (1%). 50 mg iron oxide nanoparticles were mixed with chitosan solution and stirred for 2 h at 40°C to give chitosan coated magnetic nanoparticles (CS-Fe3O4). Then, the drug (5-FU 10 mg, Caffeine 10 mg or Ascorbic acid 10 mg) was added into the solution (CS-Fe3O4) and gently stirred for 30 min. 60 mg of oxidized chitosan (OCS) was added as crosslinking agent and were mixed with (CS-Fe3O4) solution. The reaction mixture was stirred at 0°C for 3 hours. The pH of the solution was adjusted to pH = 7 with 6% (w/v) NaHCO3. The product (CS-Fe3O4-OCS) was washed with deionized water. **Figure 6** shows a representation of the prepared drug delivery ferrogel.
