Casein microparticles filled with cellulase to enzymatically degrade nanocellulose for cell growth

For tissue engineering, nanocellulose-based three-dimensional hydrogel structures hold potential as biocompatible support materials for biomimetic scaffolds to regenerate damaged tissues. One challenge of this material is that nanocellulose does not degrade in the human body. Therefore, different carriers are needed to locally deliver cellulase in a controlled manner to degrade the scaffold at the same time the cells grow and proliferate. To achieve this, we developed casein microparticles (CMPs) as delivery vehicles as they are non-toxic and have high porosity with a stable structure at physiological pH values. The porosity of the CMPs was first tested by diffusion experiments with fluorescently labelled dextrans of different sizes as model molecules, demonstrating inward diffusion of dextrans up to 500 kDa. The CMPs continuously release active cellulase, resulting in the degradation of the nanocellulose hydrogel over a time of 21 days, supporting 3D cell growth.