Table 3.
The representative modifications of chitosan with environmental responsiveness.
| Triggering Conditions | Function | Grafting Molecule | Ref. |
|---|---|---|---|
| pH | Adjust the isoelectric point of the chitosan derivative to the expected point and reverse the charge under a certain pH condition. Simultaneously, keep the drug delivery system stable in the body fluid circulation and release the drug in response to the pH of the specific sites. | Arginine | [45] |
| Lysine | [50] | ||
| Vitamin B12 | [73] | ||
| Succinylation | [90,92] | ||
| Gly-Phe-Leu-Gly (GFLG) tetrapeptide | [82] | ||
| Ethylenediaminetetraacetic acid (EDTA) | [93] | ||
| Dimethylmaleic anhydride (DMMA) | [94] | ||
| Cis-aconitic anhydride (CA) | [95] | ||
| Poly(2-(diisopropylamino)ethyl methacrylate) | [65] | ||
| Poly(methyl methacrylate) | [91] | ||
| Polyacrylic acid (PAA) | [96] | ||
| Temperature | Act as a hydrophobic core and release drug with temperature responsive. | pNIPAA | [88,90] |
| Pluronics | [97] | ||
| Enzyme | Controlled drug release via structural collapse caused by enzymatic degradation. | GFLG peptide | [82] |
| Magnetic field | Direct delivery of the nanoparticle to specific site though external magnetic field. | Fe3O4 | [88] |