Antioxidant drugs intercalated into layered double hydroxide: Structure and in vitro release

Two representative antioxidant drugs, carnosine and gallic acid (denoted as GA), were intercalated into Mg/Al layered double hydroxide (LDH) by ion exchange and coprecipitation. A gradual and biphasic in vitro release behavior of the drugs from LDH in pH = 7.4 phosphate buffered saline (PBS) was observed, and no burst release phenomenon was noticed at the beginning of release tests. Furthermore, two kinetics models (modified Freundlich model and parabolic diffusion model) were chosen to simulate the release kinetics of the drugs from LDH. The release process involved two stages: firstly surface diffusion and secondly intraparticle diffusion. In addition, the effect of the drug-LDH on scavenging 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radicals was studied. Both carnosine and GA released from the LDH matrix served as excellent antioxidants to scavenge DPPH radicals in a long release period (scavenging ratio: 95.9% for carnosine-LDH and 83.9% for GA-LDH in 870 min). Therefore, this work provides a facile approach for the encapsulation of unstable antioxidant drugs in LDH materials and for controlled drug release.