Neural injuries (e.g. spinal cord injury) are a debilitating health problem due to the limited regenerative capacity of the nervous system. One potential way of regenerating damaged neural tissues is the delivery of stem cells that can differentiate into neurons and integrate with the host. To increase the cell viability and localization, injectable hydrogels have been explored as NSC delivery vehicles. However, most injectable hydrogels lack microporous structures and fail to promote cell-cell interactions which are essential for neural differentiation and functional neural tissue formation. In this research we will develop an injectable microporous hydrogel for NSC delivery that can regenerate neural tissues. The injectable microporous formulation is made of composite microgels, composed of methacrylated gelatin (GelMA) and methacrylated hyaluronic acid (MeHA). These microgels form a bulk microporous hydrogel via a dual crosslinking mechanism: (i) rapid UV photopolymerization of methacrylates and (ii) enzymatic crosslinking by microbial transglutaminase (mTG) which also promotes tissue adhesion. The NSCs that are injected with microgels are encapsulated in the interstitial micropores between microgels, and will spread rapidly, and differentiate into neurons with proper cell-cell interactions, resulting in a functional neural network. This is contrasted with the traditional injectable hydrogels in which the encapsulated cells are entrapped by the polymer chains and prohibited for morphological changes and cell-cell interactions. We hypothesize that the enhanced cell-cell interactions will lead to more electrically-active neurons and functional neural networks. We will adopt an innovative Bioelectronic Mesh (BioEM) to achieve real-time readouts of neural activity throughout the scaffolds. Data from the BioEM will allow for statistical comparisons between different microgel formulations and inform new design iterations. To achieve the main objective of this research, we will first synthesize and optimize the injectable microgels which rapidly cure upon UV irradiation with high cell viability, cell spreading and neuronal differentiation of the encapsulated NSCs. In parallel, BioEM will be fabricated which will integrate with the microgel-based hydrogel with high cell viability of the encapsulated NSCs. Finally, BioEM will be used to monitor the development of functional neural network from the NSCs encapsulated in the hydrogel. By the end of this project, a novel microporous hydrogel formulation will be developed with the potential to deliver NSCs for neural tissue regeneration. Embedded bioelectronics via the BioEM will allow for continuous electrophysiological readouts that will inform future iterations of the hydrogel microgel. Systems that demonstrate functional neural networks in vitro will be promising candidates for clinical translation.

We propose a novel hydrogel and stem cell formulation that can be injected onto the site of damaged nerve tissue to restore functionality. The hydrogel will be formulated with a tunable microporous structure that will induce the stem cells to differentiate into neurons that grow and form connections with each other. In parallel, we will design a bioelectronic system that will probe the electrical function of the neurons to assess the suitability of each formulation for clinical use.