Novel pH‐Sensitive Poly(Vinyl Alcohol)‐Poly(Acrylic Acid) Copolymeric Hydrogels for the In Vitro Delivery of Diclofenac Sodium to the Intestine

ABSTRACT Poly(vinyl alcohol) (PVA)‐poly(acrylic acid) (PAA) copolymers were obtained from the synthesis and the hydrolysis of poly(vinyl acetate) (PVAc)‐poly(methyl acrylate) (PMA) and PVAc‐poly(acrylonitrile) (PAN) copolymers with different molar ratios. Then, pH‐sensitive PVA‐PAA copolymeric hydrogels were prepared and crosslinked using the freeze–thaw method. A non‐steroidal anti‐inflammatory drug (NSAID), diclofenac sodium (DS), as a model drug was loaded into the hydrogels. The swelling and drug delivery behavior of the hydrogels was investigated in simulated gastric (pH 1.2) and intestinal (pH 7.4) media. The copolymeric hydrogels were analyzed using attenuated total reflection (ATR). Copolymers were synthesized suitably and no chemical interaction was observed between the loaded drug and the hydrogels. The hydrogels had suitable porous structures as indicated by field emission scanning electron microscopy (FE‐SEM). According to the findings, PVAc‐PAN‐based hydrogels had better swelling, encapsulation efficiency, and drug release ratio than PVAc‐PMA‐based samples. This is attributed to the better synthesis and hydrolysis of PVAc‐PAN copolymers. The swelling and drug release behavior of the hydrogels were mainly dependent on the pH of the media and the functional groups of the hydrogels. By changing the pH condition from acidic to basic and increasing PAA content, the hydrogels significantly showed different swelling and drug release behavior. In both sample groups, hydrogels with more PAA content showed 91.918% and 56.729% drug release ratio in pH 7.4, while 45.828% and 25.316% drug release ratio was observed in pH 1.2. These results indicate that these hydrogels are good drug delivery systems (DDS) as they show pH‐dependent drug release behavior.