*2.1.6 Thermogravimetric (TGA) analysis*

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

*2.1.3 Synthesis of magnetite nanoparticles (Fe3O4) by co-precipitation*

The entire reaction is given by the equation as shown in **Figure 5**.

*2.1.4 Synthesis of ferrogel*

of the prepared drug delivery ferrogel.

*2.1.5 Fourier transform infrared (FTIR) spectra of hydrogel*

*Representation of superparamagnetic magnetite nanoparticles synthesis technique.*

According to the previous work, magnetite (Fe3O4) nanoparticles were synthesized by chemical co-precipitation method. Magnetic Fe3O4 NPs were synthesized by dissolving 50 mL of FeCl3.6H2O and 25 mL of FeSO4.7H2O in 350 mL of distilled water under nitrogen atmosphere under vigorous stirring. Upon addition of (35 ml) NaOH, the pH was adjusted to about 10, the solution turned black, indicating the formation of magnetite nanoparticles. Further stirring is continued for 1 h to uniformly disperse the magnetic nanoparticles. After raising the reaction temperature to 80°C. Then, a formed black precipitate was collected with an external magnet, washed several times with ethanol and distilled water, and dried in vacuum at 60°C.

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

Fourier transform infrared (FTIR) spectra of the chitosan, oxidized chitosan, CS/OCS hydrogel, CS/drug/OCS lyophilized hydrogel, Fe3O4 NPs and the

**8**

**Figure 6.**

**Figure 5.**

*Representation of superparamagnetic drug delivery hydrogel.*

The thermal properties of lyophilized hydrogel, pure chitosan, oxidized chitosan, Fe3O4 NPs and CS/Fe3O4/OCS lyophilized ferrogel were investigated by thermogravimetric analysis (TGA). Samples were placed in the balance system and heated from 40 to 800°C at a heating rate of 10°C/min using a TA Instruments TGA (Q500) device.
