Concave microwell array-mediated three-dimensional tumor model for screening anticancer drug-loaded nanoparticles

We investigated the effect of anticancer drug-loaded functional polymeric nanoparticles on drug resistance of three-dimensional (3D) breast tumor spheroids. 3D tumor models were built using concave microwells with different diameters (300-700 μm) and nanoparticles were prepared using thermo-responsive poly(N-isopropylacrylamide) (PNIPAM)-co-acrylic acid (AA). Upon culturing with doxorubicin-loaded PNIPAM-co-AA nanoparticles for 96 hours, the smallest tumor spheroids (cultured in 300 μm microwells) were extensively disrupted, resulting in a reduction in spheroid diameter. In contrast, the sizes of the largest tumor spheroids (cultured in 700 μm microwells) were changed little. The surface morphology of 3D tumor spheroids treated with doxorubicin-loaded PNIPAM-co-AA nanoparticles was severely rugged and the circular shape of 3D spheroids had collapsed. Cell viability assays also demonstrated that the largest tumor spheroids (700 μm microwells) were highly resistant to the anticancer drug. We confirmed that tight cell-cell contacts within largest tumor spheroids significantly improved the anticancer drug resistance. Therefore, this uniform-sized 3D breast tumor model could be a potentially powerful tool for anticancer drug screening applications (Graphical : Figure 1, A).120