2.2. Preparation of CS-CA nanogel CA was coupled to CS by the formation of amide linkages through an EDC-mediated reaction following the method proposed by(Chen et al., 2003). First, cs(0.5 g) was dissolved in 100 mL of aqueous acetic acid (1% vlv). Then, 85 mL of methanol was added and the resulting solution was sonicated. On the other hand, EDc (668 ul) was mixed with 221 mg of CA. Then, both solutions were mixed and stirred for 5 h. After that, pH was adjusted at 8.5-9 using sodium hydroxide (1 M) to precipitate the n The mixture was then centrifuged to recover the precipitated nanogel. The obtained nanogel was then washed with ethanoland distilled water to remove un-reacted materials followed by drying under vacuum for at room te The clear nanogel solution was then filtered through a 0.2 kum filter (Whatman)