Enhancement of curcumin bioaccessibility: An assessment of possible synergistic effect of γ-cyclodextrin metal–organic frameworks with micelles

Abstract

Biocompatible γ-cyclodextrin metal–organic frameworks (γ-CD-MOFs) have been reported to improve the apparent solubility and bioavailability of encapsulated bioactive compounds, including curcumin, potentially enabling sustained delivery. However, disintegration of γ-CD-MOFs may “release” encapsulated curcumin within the cavity in its insoluble crystallized form. This study evaluated whether the presence of micelles (at a concentration above curcumin's maximum solubility) would be able to take up the “released” curcumin from γ-CD-MOFs to further increase its apparent solubility. Release in the presence of a micellar phase was compared to curcumin encapsulated within γ-CD-MOFs alone. Results demonstrated that Tween 80 solubilized higher curcumin concentrations compared to oleic acid and bile salts. Dispersed in combination with Cur- γ-CD-MOFs, it was found that Tween 80 and oleic acid can improve the apparent solubility of curcumin, 5× and 1.5× higher than in the absence of micelles of these surfactants, respectively, whereas bovine bile salts exhibited a negative effect, due to a displacement of curcumin from within cavity of γ-CD-MOFs. Moreover, it was also found that Tween 80 was less affected by pH and salt concentrations due to its nonionic nature. In vitro digestion (via the INFOGEST protocol) revealed an 8-fold increase in apparent solubility of curcumin with bile salts and a 53-fold increase when combining bile salts and γ-CD-MOFs, achieving bioaccessibility of 2 % and 16 %, respectively. In conclusion, this research revealed the evaluation of γ-CD-MOFs’ functionality for delivery and controlled release, with the possibility of an emulsion system boosting the fraction of curcumin that would potentially be bioavailable.