Curcumin Loading Capacity Evaluation

Some preliminary steps were performed to prepare the samples for a system capacity evaluation in order to incorporate curcumin. An excess of curcumin was added to the samples, followed by magnetic stirring for 48 h to ensure the complete dissolution of the active ingredient. To separate the excess curcumin, the samples were centrifugated for 40 min at 20,000 rpm. The loading capacity of the curcumin in the microemulsion and the gel microemulsion was evaluated using a spectrofluorimetric method adapted from the literature [35 (link)] in our laboratory and previously reported [36 (link)]. The quantification of CURC was performed using the fluorescence spectra of the samples diluted in ethanol and recorded using a spectrofluorometer Jasco FP6300 (Jasco Corporation, Tokyo, Japan). Excitation was performed at λ_ex = 425 nm, and the fluorescence emission was recorded in the range of 450–700 nm. Calibration curves were determined for the fluorescence maximum emission at 525 nm for CURC in ethanol, in the presence and absence of the microemulsion components.