pH-sensitive chitosan-folate nanogels crosslinked with biocompatible dicarboxylic acids

• Folate-chitosan nanogels were prepared by crosslinking with PEG and tartaric acid.
• Nanogels show higher water solubility at neutral and basic pHs than chitosan.
• Nanogels display a pH-dependent release of 5-fluoracil.
• Degradation with lysozyme was studied at endosomic and physiological pH.

Chitosan nanogels functionalized with folic acid and crosslinked with PEG diacid or tartaric acid have been prepared by inverse microemulsion method for targeted delivery into cancer cells. Nanogels with varying degrees of crosslinking (4.5–10 mol% of crosslinker) have been obtained. The particle sizes determined by TEM are below 50 nm with narrow size distributions. Nanogels show a clear improvement in solubility compared with pure chitosan. Their swelling ability is pH sensitive, due to the protonation of the free amino groups when the pH is varied from 10 to 4. The nanogels have been loaded with 5-fluorouracil, which is retained at pHs greater than 7.4 and released at pH = 5.5. These nanoparticles are degraded by lysozyme at physiological pH in a period of 20 days and are easily labeled with fluorescein isothiocyanate. All these features make them promising materials for the controlled release of anticancer drugs.

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