Carrier-Free Nanocombo-Sensitized Photoimmunotherapy via Activation of α2-Adrenergic Receptors

Photodynamic therapy (PDT)-based photoimmunotherapy has attracted increasing attention in the field of cancer immunotherapy. Nonetheless, monotherapy alone proves insufficient in eliciting robust and enduring tumor immunogenicity within the "cold" microenvironment of triple-negative breast cancer. Therefore, it is imperative to integrate phototherapy and immunostimulation strategies to achieve synergistic effects. Here, we developed a carrier-free nanocombo comprising a photosensitizer (chlorin e6, Ce6) and an α2-adrenergic receptor (α2-AR) agonist (guanfacine, GFC) to enhance photoimmunotherapy through α2-AR activation. Ce6 and GFC possessed the ability to self-assemble into spherical nanoparticles, with the resulting Ce6-GFC (CeG) exhibiting exceptional drug loading efficiency (approaching 100%) and long-lasting colloidal stability, along with effective in vivo tumor-targeting capabilities. Following near-infrared laser irradiation, CeG-mediated phototherapy instigated a rapid generation of reactive oxygen species, leading to membrane disruption and the release of tumor-associated antigens, thereby facilitating dendritic cell maturation. Furthermore, α2-AR agonists served to repolarize M2 tumor-associated macrophages toward the M1 phenotype via adenylyl cyclase-mediated activation of α2-AR, thereby promoting the recruitment and activation of cytotoxic T lymphocytes. As a result, the carrier-free nanocombo significantly enhanced the efficacy of photoimmunotherapy in combatting poorly immunogenic breast tumors in female mice. Our findings showcase a "killing two birds with one stone" approach that boosts tumor immunogenicity, mitigates tumor immunosuppression, and advances the field of photoimmunotherapy.