Ionic and Enzymatic Multiple-Crosslinked Nanogels for Drug Delivery

Both ionic and enzymatic crosslink are efficient strategies for constructing network materials of high biocompatibility. Here chitosan was modified firstly and then crosslinked by these two methods for complementary advantages. The preparation methods and ionic crosslinkers can regulate the size and uniformity of the multiple-crosslinked nanogels. The multiple-crosslinked nanogels with the smallest size and the best uniformity was selected for the drug delivery. The drug-loading content and encapsulation efficiency were up to 35.01 and 66.82%, respectively. Their release behaviours are correlated with the pH value and the drug dosage. In general, the lower pH value and the lower drug dosage promoted the drug release. With the assistance of several kinetic models, it is found that drug diffusion plays a preponderant role in drug release, while polymer relaxation has a subtle effect. The multiple-crosslink resulting from ionic compounds and enzymes may provide a new perspective on developing novel biocompatible materials.