Comparative drug release studies of two cationic drugs from pH-responsive nanogels

pH-responsive nanogels consisting of methacrylic acid–ethyl acrylate (MAA–EA) cross-linked with di-allyl phthalate (DAP) were synthesized via the emulsion polymerization process. Delivery systems based on pH-responsive nanoparticles can control the release of rapidly metabolized drugs and/or have the ability to protect sensitive drugs, thereby making them ideal candidates for drug delivery applications. In this study, a drug selective electrode (DSE) was used to directly measure the concentration of procaine hydrochloride (PrHy) and imipramine hydrochloride (IMI) released from MAA–EA nanogels. With a single drug delivery system, drug release for two different drugs loaded via two distinctly different interaction forces was demonstrated. Drug release was conducted using the DSE under different pHs, MAA–EA molar ratio and DAP content. The release rate increased with pH for PrHy loaded nanogels and MAA–EA molar ratio but decreased with pH for IMI loaded nanogels and DAP content. PrHy was found to be hydrophobically bounded, while IMI was found to be electrostatically bounded onto the MAA–EA nanogels, which was further enhanced by hydrogen bonding.