Activated Platelet-Targeted IR780 Immunoliposomes for Photothermal Thrombolysis

Acute thrombosis is a leading cause of mortality and morbidity worldwide. Pharmacological thrombolysis relies on plasminogen activators (PAs), which are associated with major side effects including potentially fatal bleeding. Alternative therapeutic options that do not rely on PAs are urgently required. Here, the efficacy of targeted photothermal therapy is evaluated for thrombolysis using liposomes loaded with IR780 dye, which release heat upon near-infrared (NIR) irradiation. Liposomes targeted to activated platelets—one of the main components of thrombi—accumulate preferentially in thrombi both in vitro and in vivo compared to non-targeted controls. In a mouse model of thrombosis, targeted IR780 immunoliposomes (Tar-IR-L) produce ≈12 °C average local temperature increase upon NIR irradiation (5 min, 1 W cm−2). This causes a significant reduction in clot area compared to controls treated with non-targeted liposomes or phosphate-buffered saline, which only increase local temperature slightly (6 and 3 °C) when irradiated. Co-loading a low-dose single chain urokinase plasminogen activator (scuPA) to targeted IR780 liposomes (Tar-scuPA-IR-L) does not result in a superior thrombolytic effect, which indicates that photothermal therapy alone may allow thrombolysis without the need for fibrinolytic drugs. This approach may prevent potential bleeding complications, promising a safer alternative to current pharmacological approaches.