Curcumin-loaded metal oxide aerogels: supercritical drying and stability

Curcumin, known as a potential antioxidant and anti-inflammatory agent, has major limitations for its therapeutic use because of its lack of water solubility and relatively low bioavailability. We report for the first time the loading of different metal oxide aerogels with curcumin. The aerogels were prepared via the sol-gel process and dried under supercritical conditions. Mixing curcumin with the metal precursors prior to the formation of the solid network ensures maximum entrapment. The curcumin-network interactions stabilize the organic moiety and create hybrid aerogels as potential vehicles for curcumin in various media. The aerogels were characterized by FTIR spectroscopy, thermogravimetric analysis, electron microscopy, and fluorescence spectroscopy to confirm their hybrid nature. The stability study by fluorescence spectroscopy revealed three distinct behaviors depending on the nature of the metal oxide: (i) a minor interaction between curcumin and the solid network slightly affecting the microenvironment; (ii) a quenching phenomenon when iron is present explained by a coordination between the iron ions and curcumin; and (iii) a strong complexation of the metal ions with curcumin after gelation.