Nanofibrous MultiDomain Peptide Hydrogels Provide T Cells a 3D, Cytocompatible Environment for Cell Expansion and Antigen-Specific Killing

T cells have the ability to recognize and kill specific target cells, giving therapies based on their potential for treating infection, diabetes, cancer, and other diseases. However, the advancement of T cell-based treatments has been hindered by difficulties in their ex vivo activation and expansion, the number of cells required for sustained in vivo levels, and preferential localization following systemic delivery. Biomaterials may help to overcome many of these challenges by providing a combined means of proliferation, antigen presentation, and cell localization upon delivery. In this work, we studied self-assembling Multidomain Peptides (MDPs) as scaffolds for T cell culture, activation, and expansion. We evaluated the effect of different MDP chemistries on their biocompatibility with T cells and the maintenance of antigen specificity for T cells cultured in the hydrogels. We also examined the potential application of MDPs as scaffolds for T cell activation and expansion and the effect of MDP encapsulation on T cell phenotype. We found high cell viability when T cells were encapsulated in noncationic MDPs, O5 and D2, and superior retention of antigen specificity and tumor-reactivity were preserved in the anionic MDP, D2. Maintenance of antigen recognition by T cells in D2 hydrogels was confirmed by quantifying immune synapses of T Cells engaged with antigen-presenting cancer cells. When 3D cultured in anionic MDP D2 coloaded with anti-CD3, anti-CD28, IL2, IL7, and IL15, we observed successful T cell proliferation evidenced by upregulation of CD27 and CD107a. This study is the first to investigate the potential of self-assembling peptide-based hydrogels as 3D scaffolds for human T cell applications and demonstrates that MDP hydrogels are a viable platform for enabling T cell in vitro activation, expansion, and maintenance of antigen specificity and therefore a promising tool for future T cell-based therapies.

A Combined Conduit-Bioactive Hydrogel Approach for Regeneration of Transected Sciatic Nerves

Transected peripheral nerve injury (PNI) affects the quality of life of patients, which leads to socioeconomic burden. Despite the existence of autografts and commercially available nerve guidance conduits (NGCs), the complexity of peripheral nerve regeneration requires further research in bioengineered NGCs to improve surgical outcomes. In this work, we introduce multidomain peptide (MDP) hydrogels, as intraluminal fillers, into electrospun poly(ε-caprolactone) (PCL) conduits to bridge 10 mm rat sciatic nerve defects. The efficacy of treatment groups was evaluated by electromyography and gait analysis to determine their electrical and motor recovery. We then studied the samples' histomorphometry with immunofluorescence staining and automatic axon counting/measurement software. Comparison with negative control group shows that PCL conduits filled with an anionic MDP may improve functional recovery 16 weeks postoperation, displaying higher amplitude of compound muscle action potential, greater gastrocnemius muscle weight retention, and earlier occurrence of flexion contracture. In contrast, PCL conduits filled with a cationic MDP showed the least degree of myelination and poor functional recovery. This phenomenon may be attributed to MDPs' difference in degradation time. Electrospun PCL conduits filled with an anionic MDP may become an attractive tissue engineering strategy for treating transected PNI when supplemented with other bioactive modifications.

Self-assembling multidomain peptide hydrogels accelerate peripheral nerve regeneration after crush injury

Multidomain peptide (MDP) hydrogels are a class of self-assembling materials that have been shown to elicit beneficial responses for soft tissue regeneration. However, their capacity to promote nervous system regeneration remains unknown. The peripheral nervous system (PNS) substantially recovers after injury, partly due to the abundance of extracellular matrix (ECM) components in its basal lamina. However, severe peripheral nerve injuries that significantly damage the ECM continue to be a major clinical challenge as they occur at a high rate and can be extremely detrimental to patients' quality of life. In this study, a panel of eight MDPs were designed to contain various motifs mimicking extracellular matrix components and growth factors and successfully self-assembled into injectable, nanofibrous hydrogels. Using an in vitro screening system, various lysine based MDPs were found to enhance neurite outgrowth. To test their capacity to promote nerve regeneration in vivo, rat sciatic nerve crush injury was performed with MDP hydrogels injected directly into the injury sites. MDP hydrogels were found to enhance macrophage recruitment to the injury site and degrade efficiently over time. Rats that were injected with the MDP hydrogel K2 and laminin motif-containing MDPs K2-IIKDI and K2-IKVAV were found to have significantly accelerated functional recovery and remyelination compared to those injected with HBSS or other MDPs. These results demonstrate that MDPs enhance neurite outgrowth and promote a multicellular pro-regenerative response in peripheral nerve injury. This study provides important insights into the potential of MDPs as biomaterials for nerve regeneration and other clinical applications.