New inorganic-based drug delivery system of indole-3-acetic acid-layered metal hydroxide nanohybrids with controlled release rate

We have developed new inorganic-based drug delivery systems through the hybridization of indole-3-acetic acid (IAA) and layered metal hydroxide such as zinc basic hydroxide salt (ZBS) and zinc aluminum layered double hydroxide (ZALDH). A coprecipitation method as well as an ion-exchange route is found to be commonly effective in synthesizing both IAA-ZBS and IAA-ZALDH nanohybrids, in which the tilted bilayers of IAA are stabilized in the interlayer space of layered metal hydroxide lattice. According to the FT-IR spectroscopic analyses, IAA molecules interact more strongly with the ZBS lattice than the ZALDH one, which is due to the formation of coordination bonds between carboxyl groups of the guest species and coordinatively unsaturated Zn(OH)(3) units of the host ZBS lattice. Such an interaction gives rise to a slower release of the IAA molecules from the ZBS-based nanohybrid than from the ZALDH-based one. The present results underscore that the layered hydroxydouble salt like ZBS makes it possible to design and develop new efficient drug-delivery systems with the suspended release of guest molecules.