fig2

Figure 2. Schematic drawing of different 3D culture systems describing the main features of each system. (A) Scaffold. Cells, including immune cells, adhere to the scaffold, where they can proliferate and produce ECM, which coats the entire scaffold; (B) Hydrogel. Cells are combined with a hydrogel solution, which produces a sturdy framework that can support the cells. Cells divide and reorganize themselves; (C) 3D bioprinting. Cells are combined with hydrogel to produce bioink, a substance that can be printed using a 3D bioprinter. Depending on the type of bioink used, multiple cultures, including scaffold-based, scaffold-free, and semi-scaffold-free cultures, can be obtained; (D) Spheroid. Cells with significant cell-cell interaction are allowed to aggregate. As cells multiply, they rearrange themselves, and dense spheroids with oxygen or nutrition gradients could develop. Different kinds of cells can be combined in the spheroid; (E) Organoid. Cells are cultured in a hydrogel environment utilizing materials like Matrigel. Organoids are produced and are surrounded by other cells that replicate and produce natural ECM. Immune cell penetration can be simulated by adding immune cells to the culture; (F) Microfluidic device. Cells, spheroid, or organoids are plated onto the ready platform together with hydrogel, and then a medium containing nutrients can flow and perfuse the cells. Different kinds of cells can be added to the culture. This figure is generated with Biorender.com. ECM: Extracellular matrix.