UC San Diego

Digital light processing (DLP) 3D printing involves projecting a near-UV or visible light via an LED light source onto a digital micromirror device (DMD), which is the same device that is used in light projectors. I used this light-based bioprinting technique throughout my PhD work to develop hydrogel scaffolds to address pressing questions and challenges in in vitro neural tissue engineering and in vivo regenerative medicine applications.In Chapter 1, an overview of the development of biomaterials suited for light-based 3D-printing modalities with an emphasis on bioprinting applications is presented. The chemical mechanisms that govern photopolymerization are discussed, and the application of natural, synthetic, and composite biomaterials as 3D-printed hydrogels are highlighted. Since the quality of a 3D-printed construct is highly dependent on both the material properties and processing technique, the theoretical and practical aspects governing light-based 3D printing are also discussed. In Chapter 2, the development of a 3D printed in vitro optic nerve formation model is described. Hereditary and age-related optic nerve diseases as well as injuries can lead to vision loss and impairment which greatly reduces a person’s quality of life. In development, the optic nerve is derived from axonal projections of retinal ganglion cells in the retina. There is an unmet need in ophthalmology for a complete visual circuit in vitro model to study formation, neurodegeneration, and function of the optic nerve. We have taken the first step to create the visual circuit in vitro by developing a 3D-printed microgroove hydrogel platform for guiding axonal outgrowth from iPSC-derived retinal ganglion cell (RGC) spheroids. In Chapter 3, the development of a 3D-printed conduit for functional recovery after a peripheral nerve injury is described. Many studies have explored different materials and active cues to guide neural regeneration, with some success. However, none have demonstrated a comparable or better functional recovery than the gold standard autograft. Autografts remain insufficient for full recovery from a large injury to the sciatic nerve or brachial plexus nerves. We have designed a 3D-printed hydrogel multi-microchannel conduits with and without orthogonal micropores to guide axonal outgrowth and external vascular integration, respectively, that perform as well as the gold standard autograft therapy.