To combine the chemotherapy and photodynamic therapy in one system, the micelles (ID-M) that co-loaded the photosensitizer indocyanine green (ICG) and the chemotherapeutic drug doxorubicin (DOX) were prepared and characterized. The anti-tumor effects of ID-M in vitro were further investigated.

An ultrasound dialysis method was used to prepare the micelles containing ICG and DOX (ID-M), while the single-encapsulated ICG micelles (I-M) and the single-encapsulated DOX micelles (D-M) were prepared using the same method as the controls. The particle size, Zeta potential, encapsulation efficiency and drug release behaviors of the micelles were measured. In addition, the anti-tumor effects and mechanism of ID-M in 4T1 cells were investigated.

The average hydrated diameter of ID-M particles was 80.4 nm with negative charge, and the coefficient of the particle size dispersion was 0.252 (<0.3). The encapsulation efficiency of ICG and DOX in ID-M were 92.5% and 96.8%, respectively. The results of the temperature warming testing under irradiation of ID-M solution reached (36.5±1.1) ℃. The release experiment of ID-M in vitro showed a significant sustained-release effect. Cell experiment proved that the uptake of 4T1 cells for ID-M was nearly 2 times higher than that for free drugs. The IC₅₀ of ID-M inhibiting the growth of 4T1 cells with irradiation was 0.72 μg·mL^-1, which was 3.6-fold lower than that of free ICG/DOX. Before light exposure, ID-M was mainly located in the lysosome. However, after light exposure, the ROS levels in the cells were increased due to the existence of ICG in ID-M, which damaged the lysosomal membrane and made DOX in ID-M enter to the nucleus to play a chemotherapeutic effect.

In this study, the micelles (ID-M) with synergistic antitumor effects of phototherapy and chemotherapy were successfully prepared.