Screening of dual chemo-photothermal cellular nanotherapies in organotypic breast cancer 3D spheroids

Living therapeutics approaches that exploit mesenchymal stem cells (MSCs) as nanomedicine carriers are highly attractive due to MSCs native tropism toward the 3D tumor microenvironment. However, a streamlined preclinical evaluation of nano-in-cell anti-cancer therapies remains limited by the lack of in vitro testing platforms for screening MSCs-3D microtumor interactions. Herein we generated dense breast cancer mono and heterotypic 3D micro-spheroids for evaluating MSCs-solid tumors interactions and screen advanced nano-inMSCs therapies. Breast cancer monotypic and heterotypic models comprising cancer cells and cancer associated fibroblasts (CAFs) were self-assembled under controlled conditions using the liquid overlay technique. The resulting microtumors exhibited high compactness, reproducible morphology and necrotic regions, similarly to native solid tumors. For evaluating tumoritropic therapies in organotypic tumor-stroma 3D models, theranostic polydopamine nanoparticles loaded with indocyanine green-doxorubicin combinations (PDA-ICG-DOX) were synthesized and administered to human bone-marrow derived MSCs (hBM-MSCs). The dual-loaded PDA nanoplatforms were efficiently internalized, exhibited highly efficient NIR-light responsivity and assured MSCs viability up to 3 days. The administration of PDA-ICG-DOX nano-in-MSC tumoritropic units to microtumor models was performed in ultra-low adhesion surfaces for simulating in vitro the stem cell-tumor interactions observed in the in vivo scenario. Bioimaging analysis revealed hBM-MSCs adhesion to 3D cancer cells mass and MSCs-chemo-photothermal nanotherapeutics exhibited higher anti-tumor potential when compared to their standalone chemotherapy treated 3D tumor counterparts. Overall, the proposed methodology is suitable for evaluating MSCs-microtumors individualized interactions and enables a rapid high-throughput screening of tumoritropic therapies bioperformance.