Study on the effect of tunicate cellulose nanocrystals in the preparation of sodium alginate-based enteric capsule

In this work, tunicate cellulose nanocrystals (tCNCs) were extracted from the tunicate by bleaching and acid hydrolysis. They were used as filler in the preparation of sodium alginate-based enteric capsules. The addition of tCNCs with a high aspect ratio (65) rendered the enteric capsule excellent physical properties. Compared with the control sample, when the addition of tCNCs were 10% (wt), the water contact angle of the capsule was enhanced by 46.0%, the opacity was increased by 356.8%, the maximum tensile stress was increased by 142.6%, the modulus of elasticity was increased by 240.3%, and the elongation at break was increased by 133.8%. In the in vitro degradation experiments, the capsule hardly degraded in the gastric environment (pH 1.2), while in the intestinal environment (pH 6.8), the degradation became slower with the increase of tCNC content, which was consistent with the properties of the enteric capsule. This research developed a new direction for the application of tCNCs in the pharmaceutical material productions. Graphical abstract