A floating self-assembly route to colloidal crystal templates for 3D cell scaffolds

Preparation of well-ordered three-dimensional (3D) scaffolds is of great importance for various aspects of tissue engineering and fundamental research in cell biology. A versatile technique, floating serf-assembly, is reported here for the first time to prepare 3D colloidal crystals from polystyrene particles of various diameters (10-240 μm). Ethylene glycol was used as the solvent in the self-assembly process of colloidal crystals. Polymer colloidal particles float on the surface of ethylene glycol and self-assemble into a hexagonal crystal lattice structure. The slow evaporation of ethylene glycol left solvent-free 3D colloidal crystals. Na ₂SiO ₃ sol-gel solution was infiltrated into the interstitial space of the prepared colloidal crystals, taking advantage of the capillary effect, and an inverse opal with a highly ordered system of spherical cavities interconnected by channels was obtained by calcining the colloidal particles at high temperature. As-prepared inverse opals were used as 3D cell scaffolds which possess a high degree of order compared to existing foamlike and fibrous cell scaffolds and afford tight control over the scaffolds' porosity and tissue organization. Their preparation by this technique is much simpler than that by freeform fabrication techniques. The biocompatibility of the prepared cell scaffolds is demonstrated through human hepatocellular carcinoma HEP G2 and human bone marrow HS-5 cell cultures.