Limiting content of trivalent iron to form organic-inorganic single-phase layered double hydroxides hybrids by coprecipitation

The diterpenoid abietate (ABI) ion, the conjugate base of the phytochemical abietic acid, was intercalated into a series of layered double hydroxides (LDH) with Mg2FeyAl(1-y) composition envisioning the preparation of drug delivery systems. Experimental parameters were evaluated to achieve organic-inorganic hybrid iron-based LDH as single-phases enriched with such endogenous metal, by coprecipitation method. A set of multiple physicochemical techniques was used for a detailed characterization of the hybrid materials. The assignment of ABI anions spectroscopic signals was inspected by density functional theory (DFT) calculations to address the ABI structural integrity after intercalation. Single-phase LDH-ABI materials having 41-48 wt% of the bioactive species were formed for compositions with y <= 0.5. Above the threshold Fe3+/Al3+ molar ratio equal to 1 (y > 0.5), multi-phases were observed in LDH-ABI samples, with the ABI amount corresponding to 33-22 wt%. Higher loading values were hindered by considering the steric constraint of ABI. Thermal analysis and spectroscopic data indicated that the chemical integrity of the sensitive abietic acid was preserved after its intercalation. These results should be inspiring for the design of delivery systems with multiple bio-functionalities based on iron-enriched LDH carriers.