Fabrication of 3D structured human cell networks using capillary cell suspensions from aqueous two-phase systems

Abstract

Three-dimensional (3D) cell culture and cell spheroid models have recently emerged as more realistic experimental platforms in life sciences, bridging the gap between two-dimensional (2D) cell cultures and animal models. However, the formation of necrotic cores in cell spheroids presents a challenge for their wider use in drug testing. Here, we report a novel method of using an aqueous two-phase system (ATPS)-based capillary suspension to generate 3D structured cell networks which opens new possibilities for the assembly of tissues from adherent cells. We demonstrate the fabrication of 3D cell networks with different microstructures and morphologies from capillary cell suspensions. These were formed by the addition of a small volume fraction of dextran solution in culture media (DEX) as a secondary aqueous liquid phase to a concentrated cell suspension into a polyethylene glycol solution in culture media (PEG) as a primary immiscible aqueous phase. The formation of water-in-water (DEX-in-PEG) capillary bridges among the cells is responsible for transforming of the cell suspension into an innovative tissue-like biomaterial where the cells are connected in spanning networks. The wettability of adherent cells by the involved phases and their interfacial tension were investigated and correlated to the microstructures formed. Enhanced rheological properties were obtained at 2 vol% of DEX phase, where the maximal yield stress of the capillary cell suspension was achieved. Capillary cell suspensions with DEX phase volume percentage higher than 2 vol% changed their structure from cell networks to spheroidal cell aggregates, yielding cell spheroids. Cell viability was not impacted by long-term incubation in a DEX/PEG capillary suspension environment. We envisage how the present approach can pave the way for innovative and cost-effective preparation of cell structures for potential application in 3D cell culture and scaffold-free tissue engineering.