**2. Materials and methods**

#### **2.1 Materials**

Chitosan (in powder form was prepared in our laboratory from exoskeletons of shrimp waste and purified, with degree of deacetylation >90% was determined by conductimetric titration), iron (II) sulfate heptahydrate (FeSO4.7H2O, sigma-Aldrich), iron (III) chloride (FeCl3.6H2O, Sigma-Aldrich), Caffeine (sigma-Aldrich), 5-Fluorouracil (sigma-Aldrich), Ascorbic acid (Fluka), Sodium metaperiodate (NaIO4, sigma-Aldrich), Hydrochloric acid (sigma-Aldrich), Ethylene glycol (sigma-Aldrich), Acetic acid (sigma-Aldrich), Sodium bicarbonate (Panreac), Sodium hydroxide (Sigma-Aldrich).

**7**

**Figure 4.**

*hydrogel.*

acted reagents.

**Figure 3.**

*A Novel Drug Delivery System Based on Nanoparticles of Magnetite Fe3O4 Embedded in an Auto…*

Oxidized chitosan (**Figure 3**) was prepared according to a previously reported method [54, 55]. The purified chitosan (1 g) ([GlcN] = 5.34 mM) was dispersed in 50 ml Hydrochloric acid solution HCl (10−3 M) at pH ranging from 4 to 5, and kept under magnetic stirring at 4°C for 30 min. Then 1 ml aqueous solution of sodium periodate 0.534 mM, P0 = 0.1 (P0 = moles of NaIO4 x moles of GlcN) was added to the mixture. The reaction system was covered with aluminum foil to prevent photo induced decomposition of periodate ion. The reaction lasted for 30 min at 4°C and it was interrupted by the addition of 1 ml ethylene glycol to inactivate any unreacted periodate in a molar ratio of 1:1. The oxidized derivative was washed by

The procedure for preparation of the hydrogel was as follows: chitosan (0.1 g)

magnetic stirring until a clear solution was obtained. Afterwards, the drug (5-FU 10 mg, Caffeine 10 mg or Ascorbic acid 10 mg) was added into the solution and gently stirred until the complete dissolution for 30 min. The oxidized chitosan (60 mg) was added to the solution of chitosan soluble drug under continuous stirring to facilitate crosslinking between amino of chitosan (NH2) and aldehyde groups of chitosan (OCS). Then the 6% (w/v) NaHCO3 solution was slowly added to the solution in an ice bath under magnetic stirring to get homogeneous mixture at pH = 7 [56], and a transparent gel was obtained as shown in **Figure 4**. The hydrogel was washed with ethanol, and filtered to remove traces of unre-

distilled water for 5 h and the dry product was obtained by freeze-drying.

was dispersed in 10 ml of (1% acetic acid) at pH = 4.8 in an ice bath under

*2.1.2 Preparation of oxidized chitosan (OCS)/chitosan (CS) hydrogels*

*Schematic representation of reaction between chitosan (CS) by sodium periodate.*

*Schematic representation of the chemical (CS)/(OCS) cross-linking mechanism and the formation of the* 

*DOI: http://dx.doi.org/10.5772/intechopen.94873*

*2.1.1 Synthesis of oxidized chitosan (OCS)*

*A Novel Drug Delivery System Based on Nanoparticles of Magnetite Fe3O4 Embedded in an Auto… DOI: http://dx.doi.org/10.5772/intechopen.94873*
