Chitosan-based nanoparticles for controlled release of hydrophobic and hydrophilic drugs

Nanoparticles encapsulating different kinds of therapeutic drugs are promising drug delivery systems for controlling release and targeting tumor cells. Chitosan nanoparticles made by polyelectrolyte complexation were designed as drug carriers using doxorubicin (DOX)/5-fluorouracil (5-FU) as hydrophobic/hydrophilic model drugs. The sizes of nanoparticles were 235 ± 13 and 177 ± 7 nm with narrow distributions. The effects of the initial drug amount and pH of the medium on drug-controlled release properties were evaluated, the model-fitting results and release mechanisms were analyzed as well. For 5-FU-loaded chitosan nanoparticles, the controlled-release effect was superior to that of DOX, indicating that the polyelectrolyte complex nanoparticles were more suitable for hydrophilic drugs, particularly for negatively charged or electrically neutral drugs. Moreover, the release behaviors conformed with the first-order kinetic model, indicating that the nanoparticles were mainly released by diffusion during the drug release process; the system could also be fitted using the Higuchi model, showing that the entire drug release process was dominated by diffusion and supplemented by gradual dissolution. In all, the results suggested that chitosan nanoparticles made by polyelectrolyte complexation can be launched as a smart drug delivery system for cancer treatments.