Poly(vinyl alcohol) Hydrogels Reinforced with Cellulose Nanocrystals for Sustained Delivery of Salicylic Acid

Hydrogels have been widely studied and used in biomedical and pharmaceutical applications. However, their fragile character and poor mechanical properties limit their feasibility for biomedical applications. Incorporating nature-derived nanoparticles can enhance the structural integrity of hydrogels by creating a stable network, resulting in hydrogels with robust properties. This study prepared 5 wt % poly(vinyl alcohol) (PVA)-based hydrogels reinforced with different amounts of cellulose nanocrystals (CNCs), ranging from 0 to 20 phr relative to PVA. The hydrogels were chemically cross-linked by 5 phr glutaraldehyde (GA) under low pH conditions of 2.0 and 2.5 to enhance their physicomechanical properties. Because of the promoted acetal reaction within the hydrogel networks, hydrogels with high CNC content (20 phr of PVA) at low pH (2.0) had an improved storage modulus and dense three-dimensional (3D) networks with a significantly high cross-linking density (33.2% higher), small pore diameter (3.426 nm), and high surface area (12.452 m²/g) compared to the pure PVA hydrogel. Moreover, the hydrogel manufactured at low pH with high CNC content presented more significant drug (salicylic acid) adsorption capacity and improved sustained drug release performance compared with the pure PVA hydrogel, which was attributed to the nano-obstruction and nanolocking effect of CNCs. Therefore, hydrogels prepared at low pH and high CNC content are suitable for sustained drug delivery systems with desirable physicomechanical properties.