Cellulose nanocrystals extracted from rice husks as a reinforcing material in gelatin hydrogels for use in controlled drug delivery systems

• pH-responsive semi-IPN hydrogels were synthesized.
• Glutaraldehyde was used as a crosslinker in gelatin/CNC hydrogels.
• Hydrogels showed increased crystallinity and storage moduli with CNC incorporation.
• Optimum swelling was reached at pH 7.
• 15 wt% CNC/gelatin hydrogel is suitable for use as a drug carrier.

Hydrogels with remarkable sensitivity toward changes in pH were prepared using gelatin reinforced with cellulose nanocrystals (CNCs). Glutaraldehyde was used as a crosslinker because of its high chemical reactivity toward the NH2 group on gelatin. CNC ratios of 0%, 5%, 10%, 15%, 20%, and 25% were chosen to study the effects of CNCs on the dynamic mechanical properties and swelling behavior of gelatin-based hydrogels. Crosslinking between gelatin monomers was confirmed by the presence of a CN stretching group at 1630 cm−1 in the FTIR spectrum of gelatin hydrogels. The overall crystallinity and dynamic mechanical properties of gelatin hydrogels increased as the CNC content increased. The increase in the overall crystallinity improved the storage modulus of the CNC-gelatin hydrogel from 122 Pa to 468 Pa by the addition of 25% CNC. From the swelling test, CNC-gelatin hydrogels showed excellent pH sensitivity with a maximum swelling ratio at pH 3. The ability of the CNC-gelatin hydrogel to respond to different pH values along with its high dynamic mechanical stability suggested that CNC-gelatin hydrogels are promising candidates as drug carriers. Theophylline was used in this research as a model drug to further evaluate the potential of these CNC-gelatin hydrogels to act as drug carriers. Drug loading efficiency and drug release profiles of the CNC-gelatin hydrogels were studied. The findings suggest that gelatin hydrogels reinforced with 15% CNC are the best potential candidates for controlled drug delivery system.

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