Development of chitosan-nanofiber-based hydrogels exhibiting high mechanical strength and pH-responsive controlled release

• Chitosan nanofiber (CNF)-based hydrogels (CNF–poly(ethylene glycol) (PEG) hydrogel) was fabricated.
• CNF addition enhanced compressive rupture stress and Young’s modulus.
• A pH decrease of buffer from 7.4 to 5.6 caused accelerated protein release from the hydrogels.

Developing naturally derived polymer-based hydrogels with high mechanical strength and a controlled release of loaded bioactive substances is essential in biomedicine and tissue engineering. Here, we report the fabrication of chitosan nanofiber (CNF)-based hydrogels (CNF–poly(ethylene glycol) (PEG) hydrogel) with a semi-penetrating network structure comprising CNF and chemically-crosslinkable PEG diacrylate (PEGDA). Scanning electron microscopy revealed a micro-porous structure, resulting from PEGDA gelation aligned with the bundles of CNF. CNF addition enhanced compressive rupture stress and Young’s modulus, indicating that it strengthened the PEGDA hydrogels. Bovine serum albumin (BSA) was encapsulated in CNF–PEG hydrogels probably via the hydrophobic interaction between CNF and BSA. A pH decrease from 7.4 to 5.6 caused accelerated BSA release from the hydrogels due to the difference in their swelling degrees. These results indicated that CNF–PEG hydrogels could be utilized as a carrier for bioactive substances that demonstrates controlled release behavior and improved mechanical properties.

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