The hydrogel formation starts when VitroGel® is mixed with the cell culture medium. The hydrogel molecules will interact with the ionic molecules, such as Ca2+ or Na+, from the cell culture medium to induce a matrix structure (hydrogel). For 3D culture operation, the hydrogel formation is in two stages: a) soft hydrogel formation and b) hydrogel stabilization.
1. Soft hydrogel formation: The process is slow when a small amount of cell culture medium is used. At this stage, the hydrogel is soft and possesses a shear-thinning and rapid-recovering mechanical property, which makes it injectable for in vivo applications. The slow hydrogel-forming process and the injectable property of the soft hydrogel create a time frame for easy hydrogel transfer from the mixing tube to the cell culture plate.
2. Hydrogel stabilization: After soft hydrogel formation, adding cell culture medium on top of the hydrogel would allow more ionic molecules to penetrate the hydrogel matrix and further saturate the hydrogel cross-linking. A solid hydrogel would form during this process.