Photoacoustic and epigenetic nerve scaffold for nerve regeneration

Project Summary This proposal aims to uncover the underexplored epigenetic and biomechanical roles of folate (FA, Vitamin B9) for neuronal morphogenesis and develop novel epigenetically stimulating, biodegradable, and photoacoustic nerve guidance conduits (NGCs) for the repair of critical-sized peripheral nerve (PN) defects. The hypotheses are that (1) local delivery of an inexpensive and stable (half-life of over 100 days) folate (also known as vitamin B9) directly to the peripheral injury site at a critical concentration level of mg/L can enhance nerve regeneration and functional recovery through an intriguing epigenetic modulation; (2) folate-releasing NGCs could orchestrate intriguing biochemical-to-biomechanical force transduction to promote neuronal differentiation and regeneration; (3) incorporating FA into POC results in a polymer that enables photoacoustic imaging (PAI) in the tissue trans- parent near-infrared (NIR) window for non-invasive, real-time, in-situ monitoring of nerve scaffold degradation and nerve regeneration. The project’s innovation lie in 1) synthesizing new folate-releasing and photoacoustic citrate biodegradable polymers (POCFA) for nerve scaffold fabrication; 2) elucidating the underexplored gene- specific epigenetic and biochemical-to-biomechanical transduction effects of folate for neuroregeneration; 3) for the first time, exploring the PN regeneration by delivering folate at critical concentrations (mg/L) directly to the injury site; and 4) in vivo real-time dual-modality photoacoustic and ultrasound (PAUS) imaging of nerve scaffold degradation and nerve regeneration. Ultrasound imaging provides underlying anatomical or structural infor- mation of the tissue, whereas spectral photoacoustic imaging (PAI) maps light-absorbing polymers along with vascular structure and associated functional oxygen saturation of the tissue exploiting differential absorption of oxy- and deoxy- hemoglobin’s in the NIR window. The Rigor of Prior Research includes 1) we have previously developed multifunctional multi-channeled biodegradable elastic CUPE NGCs promising for PN regeneration; 2) we have obtained compelling data to support that biologically stable folate displayed intriguing dose-dependent epigenetic and biomechanical effects to promote neuronal differentiation migration and proliferation of both rat Schwann and neuron cells, and the regeneration and functional recovery of 20 mm sciatic nerve defects in rats as early as 4 weeks post-implantation; 3) POCFA displayed unexpected strong absorption in near-infrared-I (NIR-I, 700-1000 nm) and even in NIR-II (1000-1700 nm) window for PAI. The expected outcome of this pro- posal is a practical methodology for the optimal design of imageable NGCs with suitable epigenetic, biomechan- ical, and topographical cues for the regeneration and functional recovery of critically sized nerve defects.