Preparation of nanoparticles by Ionic gelation

Chitosan, sodium alginate, dextran and gelatin are hydrophilic biodegradable polymers which may be used for the preparation of nanoparticles by coacervation or ionic gelation method. This method involves a preparation of two aqueous phases, one phase containing polysaccharides (alginate, gellan and pectin) is dissolved in water or in weak acidic medium and other phase containing a polyanion dissolved in water. This solution is then added drop wise under constant stirring. When electrostatic interaction takes place between two aqueous phases, coacervates are formed and when two molecules interact due to ionic force, resulting in transition from liquid phase to gel phase at room temperature. The beads are then removed by filtration or centrifugation, washed with distilled water and dried using lyophilized.

 

Structural representation of the nanoparticle preparation by ionotropic gelation method. A: Sodium Tripolyphosphate, B: Chitosan, C: Chitosan nanoparticles

Advantages of ionic gelation method:-

1. · Simple and mild.
2. · In this method, reversible physical cross linking by electrostatic interaction   occurs instead of chemical cross linking.
3. · No use of organic solvents therefore avoids the possible toxicity and other undesirable effects.
4. ·  Used at large scale as well as on lab scale.
5. ·  The particle size and distribution can be easily monitored by changing the amount of counter ions.

Limitations of Ionic gelation method

1. ·This method can only be used for ionic species.
2. ·The size of particles only depends on physical interaction and there is no involvement of chemical reaction.
3. · Only water soluble substances are used for this method.

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