Cannabidiol Loaded Extracellular Vesicles Sensitize Triple-Negative Breast Cancer to Doxorubicin in both in-vitro and in vivo Models Running Title: Formulation and anti-cancer potential of CBD loaded hUCMSC-derived Extracellular Vesicles in TNBC

Extracellular Vesicles (EVs) were isolated from human umbilical cord mesenchymal stem cells (hUCMSCs) and were further encapsulated with cannabidiol (CBD) through sonication method (CBD EVs). CBD EVs displayed an average particle size of 114.1±1.02 nm, zeta potential of -30.26±0.12 mV, entrapment efficiency of 92.3±2.21% and stability for several months at 4 °C. CBD release from the EVs was observed as 50.74±2.44% and 53.99±1.4% at pH 6.8 and pH 7.4, respectively after 48 h. Ourin-vitrostudies demonstrated that CBD either alone or in EVs form significantly sensitized MDA-MB-231 cells to doxorubicin (DOX) (*P<0.05). Flow cytometry and migration studies revealed that CBD EVs either alone or in combination with DOX induced G1 phase cell cycle arrest and decreased migration of MDA-MB-231 cells, respectively. CBD EVs and DOX combination significantly reduced tumor burden (***P<0.001) in MDA-MB-231 xenograft tumor model. Western blotting and immunocytochemical analysis demonstrated that CBD EVs and DOX combination decreased the expression of proteins involved in inflammation, metastasis and increased the expression of proteins involved in apoptosis. CBD EVs and DOX combination will have profound clinical significance in not only decreasing the side effects but also increasing the therapeutic efficacy of DOX in TNBC.