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

Biocompatible gamma-cyclodextrin metal-organic frameworks (gamma-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 gamma-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 gamma-CDMOFs to further increase its apparent solubility. Release in the presence of a micellar phase was compared to curcumin encapsulated within gamma-CD-MOFs alone. Results demonstrated that Tween 80 solubilized higher cur- cumin concentrations compared to oleic acid and bile salts. Dispersed in combination with Cur- gamma-CD-MOFs, it was found that Tween 80 and oleic acid can improve the apparent solubility of curcumin, 5x and 1.5x 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 gamma-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 gamma-CD-MOFs, achieving bioaccessibility of 2 % and 16 %, respectively. In conclusion, this research revealed the evaluation of gamma-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.