Dual-phase, surface tension-based fabrication method for generation of tumor millibeads

Numerous methods have been developed for the fabrication of poly(ethylene glycol)-based hydrogel microstructures for drug-delivery and tissue-engineering applications. However, present methods focus on the fabrication of submicrometer scale hydrogel structures which have limited applications in creating larger tissue constructs, especially in recreating cancer tissue microenvironments. We aimed to establish a platform where cancer cells can be cultured in a three-dimensional (3D) environment, which closely replicates the native cancer microenvironment and facilitates efficient testing of anticancer drugs. This study demonstrated a novel surface tension-based fabrication technique for the generation of millimeter-scale hydrogel beads using a liquid-liquid dual phase system. The "hydrogel millibeads" obtained by this method were larger than previously reported, highly uniform in shape and size with better ease of size control and a high degree of consistency and reproducibility between batches. In addition, human breast cancer cells were encapsulated within these hydrogel constructs to generate "tumor millibeads", which were subsequently maintained in long-term 3D culture. Microscopic visualization using fluorescence imaging and microstructure analysis showed the morphology and uniform distribution of the cells within the 3D matrix and arrangement of cells with the surrounding scaffold material. Cell viability analysis revealed the creation of a core region of dead cells surrounded by healthy, viable cell layers at the periphery following long-term culture. These observations closely matched with those of native and in vivo tumors. Based on these results, this study established a rapidly reproducible surface tension-based fabrication technique for making spherical hydrogel millibeads and demonstrated the potential of this method in creating engineered 3D tumor tissues. It is envisioned that the developed hydrogel millibead system will facilitate the formation of physiologically relevant in vitro tumor models which will closely simulate the native tumor microenvironmental conditions and could enable future high-throughput testing of different anticancer drugs in preclinical trials.