The design of multi-responsive nanohydrogel networks of chitosan for controlled drug delivery.

High swelling hydrogel networks (HSHNs) are materials with the ability to high swelling and outstanding candidates for sustained drug delivery systems (DDSs). The present paper demonstrates three different chitosan nanohydrogel networks (CNHN I-III) prepared through covalent and non-covalent interactions. These hydrogels have a high swelling ratio (up to 38-fold their dry weight) in various conditions. Two types of these hydrogels (CNHN I and II), swelled rapidly in an acidic environment, were able to successfully load an extraordinary amount (up to 95 %) of a model drug doxorubicin hydrochloride (DOX.HCl) at a 1:1 ratio (wt./wt.). The CNHN III had substantial swelling in pH 7.4, with a loading capacity of 92 % 5-fluorouracil (5-FU) at a 1:1 ratio (wt./wt.). The CNHN I and II have been considered for systemic drug delivery, while the CNHN III is one of the best candidates for oral drug delivery.