Nanocellulose/Gelatin Composite Cryogels for Controlled Drug Release

Nanocellulose/gelatin composite cryogels with controllable porosity, reversible network structure and good biocompatibility were constructed via the chemical cross-linking of dialdehyde starch and further used as the carriers for controlled 5-fluorouracil (5-FU) release. The pore structure of the composite cryogels was successfully tuned by changing the dosages and ratios of nanofibrillated cellulose (NFC), gelatin and dialdehyde starch. Under the same density of cryogels, increasing the NFC content results in higher specific surface area and porosity. The swelling ratios first increase and then decrease with an increase in the contents of NFC and dialdehyde starch, and the swelling ratios of cryogels are relatively higher in neutral medium than those in acidic medium. The drug loading improvement is favored by increasing the NFC content and cross-linking degree. The drug-loaded cryogels show controllable and sustained release of 5-FU in vitro, which is attributed to the hydration of gelatin and reversible hydrolysis of acetal/hemiacetal. The behaviors of drug release are dependent on the structures of cryogels including the NFC/gelation ratio, density and cross-linking degree as well as the pH values. The sustained release time of the cryogel carrier is able to reach 12 h in a simulated intestinal environment.