Pore size manipulation in 3D printed cryogels enables selective cell seeding

Cryogels are macroporous materials that display remarkable properties such as high pore inter- connection, large surface to volume ratio and high mechanical stability. As a result they are used in many areas of science spanning from blood separation and filtering to biological scaffolds for cells. However, shaping such material remains challenging because of the harsh conditions of synthesis at temperatures as low as −80◦C. In this paper we propose a solution for the 3D print- ing of cryogels. A micro-fabricated dispensing tool is presented and allows the last-second mixing of the different components for the cryogel synthesis as well as the control in temperature of the material during printing. This dispensing tool is mounted on a 3D printer allowing the multi-layer printing of the cryogel. By controlling the temperature of the dispensing tool during the printing process, we show the possibility to actively and locally tune the pore size of the cryogel. The printed gel are then coated with collagen and seeded with cells. The change in pore size allowed selective cell colonization opening the door to cell patterning through pore size manipulation.