2.3.4. Preparation of Forster Resonance Energy Transfer (FRET) Micelles

Fluorophore-labelled Icaritin−Cy5 and Icaritin−Cy5.5 were synthesized (Figure S1), and FRET micelles were prepared by ethanol the injection-dialysis method. Briefly, Icaritin−Cy5 (0.5 mg), Icaritin−Cy5.5 (0.5 mg) and icaritin (9.0 mg) were dissolved in ethanol (1 mL) to obtained the drug solution, and Soluplus^® (40 mg) and P407 (20 mg) were dissolved in deionized water (8 mL) to gain the aqueous phase. The drug solution was then injected into the above aqueous phase under stirring at 1000 rpm. The FRET micelles were finally obtained by dialysis (MWCO: 3500 Da) against deionized water for 48 h to remove residual ethanol.