Magnetically Oriented Collagen Hydrogels for Directing Neronal Growth

The ability to manipulate and direct neuronal growth has great importance in the field of tissue engineering, both for neuronal repair and potential medical devices. Since mammalian neurons have limited regeneration abilities creating scaffolds for enhanced regeneration is beneficial. Moreover, guiding and directing neuronal outgrowth can enhance neuronal repair and recovery. Previous studies, including in our lab examined nanoparticles for enhancing neuronal regeneration. Here, we designed a 3D collagen gel-scaffold for neuronal cultures. We further modulated the gel system to create alignment of collagen fibers for directing neuronal growth using nanoparticles.

A collagen hydrogel system was chosen as a 3D ECM analog to best mimic the natural environment of cells. The gels mechanical properties were examined and tuned to achieve desired properties similar to nervous tissue. We compared the neuronal growth in 3D to a 2D model and showed that neurons grown in 3D collagen gels develop significantly longer dendritic trees and neurites. To manipulate neuronal growth we developed a method to align collagen fiber matrix by incorporating magnetic nanoparticles within gels, and exposing the gel to an external magnetic field We showed fiber directionality by analysis of light microscope images via Fast Fourier transform (FFT) and by SEM imaging. We grew neurons in aligned gels for 7 days and followed regeneration process of single cells for up to 7 days. For this purpose we used both primary leech (Hirudo medicinale) neuronal culture, and PC12 as a mammalian analog. Using a designed Matlab script we evaluated cellular direction of growth and compared it to collagen matrix orientation. We further measured morphometric parameters of neuronal growth. Using aligned gels we've elongated and directed neuronal growth coinciding with collagen matrix orientation. We also found aligned gels initiate neurite growth patterns similar to growth in 3D control gel.