A Review of pH-Responsive Poly(Vinyl Alcohol)-Poly(Acrylic Acid)-Based Hydrogels in Colon-Targeted Drug Delivery Applications.

Colon-targeted drug delivery as an oral drug delivery technique holds great promise for overcoming the limitations related to the modern medicine. These systems are highly able to protect the drugs from the low pH of the stomach and safely deliver them to the colon as they are pH-responsive. Poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) polymers have been widely used in drug delivery applications due to their excellent hydrophilicity, biocompatibility, and mechanical properties. Moreover, due to the presence of strong acidic functional groups in the PAA matrix, combination of PVA and PAA makes it possible to provide pH-sensitive drug delivery systems for colon-targeted drug delivery applications. Hence, pH-sensitive PVA-PAA-based hydrogels with various forms are suitable candidates for the safe delivery of different drugs such as non-steroidal anti-inflammatory drugs (NSAIDs), anticancer drugs, or even insulin to the colon. Therefore, the present review illustrates various forms of pH-responsive PVA-PAA-based hydrogels for colon-targeted drug delivery applications.