Thermosensitive Chitosan-β-Glycerophosphate Hydrogels as Targeted Drug Delivery Systems: An Overview on Preparation and Their Applications

Figure 1

In an acidic environment, chitosan is positively charged (a). Because of the similar groups on the chitosan chain in an acidic environment, the two chains move away from one another, forming an electrostatic repulsion force between the chitosan chains, the water molecules being positioned between the chitosan chains and forming a regular arrangement (b). Adding beta-glycerophosphate, the negative charge of the positively charged chitosan phosphate group forms weak bonds. These weak interactions enhance the water arrangement around the chitosan chains. As a result, chitosan dissolves at physiological pH. Nevertheless, with increasing temperature, the regular arrangement of water molecules around the chitosan chains becomes unstable, the polymer-polymer interactions overwhelm the solvent-polymer interactions, and the chitosan precipitates at high temperature in the form of gels [54].

(a)

(b)