Using pipette tips to readily generate spheroids comprising single or multiple cell types

Three-dimensional (3D) cell culture methods have been validated that can replicate the tumor environment in vivo to a large extent, providing an effective tool for studying tumors. In this study, we demonstrated the use of standard laboratory pipette tips as micro vessels for generating 3D cell spheroids. No microfabrication or wet-chemistry surface modifications were involved in the procedure. Spheroids consisting of single or multiple cell types were generated within 24 h just by pipetting and incubating a cell suspension in pipette tips. Scanning electron microscope and optical microscope proved that the cells grew together tightly, and suggested that while gravity force might have initiated the sedimentation of cells at the bottom of the tip, the active aggregation of cells to form tight cell-cell interactions drove the formation of spheroids. Using common laboratory micropipettes and pipette tips, the rate of spheroid generation and the generation reproducibility was characterized from five boxes each with 80 tips. The ease of transferring reagents allowed modeling of the growth of microvascular endothelial cells in tumor spheroids. Moreover, the pairing and fusion of tumor spheroids could be manipulated in the pipette tips, suggesting the potential for building and assembling heterogeneous micro-tumor tissues in vitro to mimic solid tumors in vivo. This study demonstrated that spheroids can be readily and cost-effectively generated in standard biological laboratories in a timely manner using pipette tips.