Fabrication of glycerophosphate-based nanochitin hydrogels for prolonged release under in vitro physiological conditions

Partially deacetylated nanochitin (NCh)/glycerophosphate (GP)-based composite hydrogels were prepared for the prolonged release of microemulsions (ME) under in vitro physiological conditions. Thermo-sensitive gelation behavior not be observed for the NCh/GP composite dispersion; however, the addition of glycerophosphate also resulted in the loss of viscoelasticity due to the sodium component in the β-glycerol phosphate disodium salt pentahydrate. To prepare enhanced NCh/GP composite hydrogels, a gas phase coagulation bath was further applied to introduce physical crosslinking domains in hydrogels. The storage modulus reached approximately 1600 Pa, as 20 μL GP was composited with NCh dispersion (0.6 wt %, 2 mL), and a higher GP dosage also led to decreased mechanical strength of composite hydrogels. Because of the relatively stable inter-structure, less than 40% of ME could be released from the NCh/GP composite hydrogel. To promote the release performance of NCh/GP-based composite hydrogels, chitosan and glycine were added. As high as 81% ME could be released from composite hydrogels at 40 °C in 50 h, as the mass ratio between NCh and chitosan was 2:1, while as high as 82% ME could be released at 40 °C in 50 h, as the mass ratio between NCh and glycine was 1:1. Moreover, obvious thermo-responsive release could be observed for the NCh(1)/Gly(1)/GP sample.