Nerve Cells Decide to Orient inside an Injectable Hydrogel with Minimal Structural Guidance

Injectable biomaterials provide the advantage of a minimally invasive application but mostly lack the required structural complexity. to regenerate aligned tissues. Here, we report a new class of tissue regenerative matetials that can be injected and form an anisotropic matrix with controlled dimensions using rod shaped, magnetoceptive microgel objects. Microgels are doped with small quantities of superparamagnetic iron oxide nanoparticles (0.0046 vol %), allowing alignment by external magnetic fields in the millitesla order. The microgels are dispersed in a biocompatible gel precursor and after injection and orientation are fixed inside the matrix hydrogel. Regardless of the low volume concentration of the microgels below 3%, at which the geometrical constrain for orientation is still minimum, the generated macroscopic unidirectional orientation is strongly sensed by the cells resulting in parallel nerve extension. This finding opens a new, minimal invasive route for therapy after spinal cord injury.