2.2. Fabrication of Qu-loaded CPP/CS (CPP-CS-Qu) nanoparticles

In order to prevent Qu from being decomposed, all the treatments and determinations of Qu in the following paragraphs were carried out in the dark. Stock solutions of Qu, CPP and CS at a concentration of 1.5 mg/mL were prepared by dissolving them in absolute ethanol, distilled water and 1.0% (w/v) acetic acid, respectively. First, the Qu solution was mixed with CPP solution at a ratio of 1:5 (v/v) and stirred for 15 min. By consequential addition of the same volume of CS solution as CPP to the above suspension with further stirring for 15 min at room temperature, and the pH of the mixture was adjusted to 6 to form Qu-loaded CPP/CS nanoparticles. An equal volume of blank solution was used instead of Qu, CS solution to prepare CPP/CS (CPP-CS) complex, Qu-loaded CPP (CPP-Qu) nanoparticles, and other processing steps remained unchanged.