The focus of this research was to formulate and evaluate a theranostic liposomal delivery system using indocyanine green (ICG) as a photosensitizer, triggered by near infrared (NIR) irradiation, for in vivo photodynamic therapy (PDT) of breast cancer.

Cytotoxicity of PDT using liposomal ICG (LPICG) as well as free ICG (FRICG) was evaluated in the human MDA-MB-468 triple-negative breast cancer (TNBC) cell line. NIR irradiation-induced increase in temperature was also monitored both in vitro and in vivo. Quantitative pharmacokinetic profile and fluorescence imaging-based biodistribution patterns of both formulations were obtained using the human TNBC xenograft model in nude mice. Overall safety, tolerability, and long-term anti-tumor efficacy of LPICG versus FRICG-mediated PDT was evaluated.

Significant loss of cell viability was achieved following photoactivation of LPICG via NIR irradiation. Temperatures of irradiated LPICG increased with increasing concentrations of loaded ICG, which correlated with significant rise of temperature compared to PBS in vivo (p < 0.01). Pharmacokinetic assessment revealed a significant increase in systemic distribution and circulation half-life of LPICG, and NIR fluorescence imaging demonstrated enhanced accumulation of liposomes within the tumor region. Tumor growth in mice treated with LPICG followed by NIR irradiation was significantly reduced compared to those treated with FRICG, saline, and irradiation alone.

In vivo photodynamic therapy using LPICG demonstrated targeted biodistribution and superior anti-tumor efficacy in a human TNBC xenograft model compared to FRICG. In addition, this unique delivery system exhibited a promising role in NIR image-guided delivery and real-time biodistribution monitoring of formulation with ICG serving as the fluorescent probe.