Quantifying Ponceau S Leakage from Capsules

Firstly, in Supplementary Note S6, we explored the linear relationship between the concentration of Ponceau S and its absorbance (Supplementary Fig. S11a, b). During the test, the experimental group placed a capsule containing a known mass (m₁) of Ponceau S (3 mg/ml) in a water tank containing a known mass (m₂) of water. The capsule was fixed on a shaking table set at parameters of 100 rpm for 5 min. Simultaneously, a control group was established: the solution of Ponceau S with mass m₁ was directly poured into the water with mass m₂ and thoroughly stirred, representing 100% drug leakage. Each case was repeated three times, and the absorbance at the corresponding wavelengths of both the experimental control groups was measured using a UV-vis spectrometer (UV-2600i, SHIMADZU Co., Ltd.). The ratio of the absorbance of the experimental group to that of the control group can be considered as the proportion of the leaked capsule drug.