Effective early stage drug screening is important to minimize failures in late clinical stages. 2D cell culture has been predominantly used, but it is becoming apparent that 2D culture is extremely limited when predict a drug's toxicity and efficacy in the body. As a potential solution, we developed a 3D cell culture based in vitro drug testing system representing tissue level physiology in a standardized manner.

Our approach started with preparing hydrogel inverted colloidal crystal (ICC) scaffolds. Primary colloidal crystals are hexagonally packed lattices of microspheres (D=50-300µm). ICC is a similarly organized structure where the spheres are replaced with cavities, while the interstitial spaces are filled with poly (acrylamide) hydrogel. Highly packed, identically sized pores and well interconnected channels promoted homogenous cell seeding in each pore. The ICC geometry created by a cell repulsive hydrogel provides supportive physical and chemical environments for spheroid formation of human hepatocarcinoma (HepG2). After 3-5 days of culture, HepG2 cells formed solid spheroids with a narrow size distribution and filled approximately 70% of the pore volume. The spheroid culture exhibited tissue level morphology and specific liver functions such as albumin secretion. Also, it showed enhanced CYP450 induction and reduced CdTe nanoparticle toxicity compared to the 2D cell culture.

Overall our data show that hydrogel ICC scaffolds would be a promising tool for engineering liver tissue spheroids while retaining a high analytic capability. It was substantiated by tissue level morphology, function and toxicity. This cell-scaffold system will contribute to the pharmaceutical industry as a practical and valuable early stage drug testing tool by reducing the gap between 2D culture and in vivo.