Robust and flexible fabrication of chemical micropatterns for tumor spheroid preparation

A robust and flexible approach is described for the straightforward preparation of multicellular tumor spheroids of controllable dimensions. The approach is based on a one-step plasma polymerization of the monomer allylamine carried out through conformal micropatterning physical masks that is used to deposit amine-rich (PolyAA) micrometer-scale features that promote cellular attachment and initiate the formation of multicellular spheroids. A simple backfilling step of the nonpolymerized poly(dimethylsiloxane) background with Pluronic F127 significantly reduced background cellular adhesion on the untreated substrate and, in turn, improved the quality of the spheroid formed. Tumor cells grown on the PolyAA/F127 patterned surfaces reliably formed multicellular spheroids within 24-48 h depending on the cell type. The dimension of the spheroids could be readily controlled by the dimension of the amine-rich micropatterns. This simple approach is compatible with the long-term culture of multicellular spheroids and their characterization with high-resolution optical microscopy. These features facilitate the development of on-chip assays, as demonstrated here for the study of the binding of transferrin-functionalized gold nanoparticles to multicellular tumor spheroids.