*2.8. ICG Stability*

ICG degrades quickly in aqueous solutions and loses its absorbance peak at the 800 nm wavelength [33]. Thus, the absorbance can be used to measure ICG leakage from liposomes. The ICG amounts were measured in black clear-bottom well plates (Corning Inc., Corning, NY, USA) using a Varioskan LUX multimode plate reader (Thermo Fisher Scientific Inc., Waltham, MA, USA). The 100 µL sample absorbances were measured at 800 nm, and the amount of intact ICG (ICG<sup>i</sup> ) compared to the initial concentration was calculated using Equation (2).

$$\text{ICG}\_{\text{i}} = \frac{\text{ICG}\_{\text{t}}}{\text{ICG}\_{\text{0}}} \times 100\text{\%} \tag{2}$$

where ICG<sup>t</sup> is the absorbance at the specific time point, and ICG<sup>0</sup> is the absorbance at the start of the experiment.
