Early Development of 3D-Printed Implants for Mandibular Condyle Regeneration

In recent years, three-dimensional (3D) printing has opened up unprecedented opportunities in the field of tissue engineering, providing researchers with more precise control over the macro- and microstructural characteristics of scaffolds. Through the layer-by-layer patterning of material, 3D printing enables the production of increasingly sophisticated scaffolds that aim to mimic the complexities of native extracellular matrix so as to instruct resident cells to synthesize the envisioned tissue. Motivated by the recognized need for tissue-engineering solutions for mandibular condyle regeneration, the objective of this thesis was to develop patient-specific scaffolds with discrete yet integrated osteo- and chondroinductive regions using two 3D printing techniques, direct ink writing (DIW) and fused deposition modeling (FDM). Toward this objective, chondroinductive hydrogel ‘ink’ comprised of pentenoate-modified hyaluronic acid (PHA) and decellularized cartilage (DCC) microparticles was designed for DIW using a customized syringe-based extrusion tool. Notably, DCC microparticles were found to enhance the rheological properties of the hydrogel ‘ink’ for 3D printing, and accordingly improved the resolution of the 3D-printed hydrogel structures. In addition, PHA/DCC hydrogel was shown to simulate chondrogenic differentiation of seeded bone marrow-derived mesenchymal stem cells in vitro as evidenced by elevated expression levels of SOX9, a chondrogenic gene, demonstrating its potential for cartilage tissue engineering applications. In parallel, osteoinductive monofilament feedstock for FDM composed of polycaprolactone and hydroxyapatite nanopowder was made in-house. Computed tomography and computer-aided design (CAD) modeling techniques were used to create digital models of the bone and cartilage-promoting regions of the scaffold, with anatomical geometries and regional interconnected pore structures for translation into an early prototype. However, due to several technical constraints, multi-material scaffold production was unfeasible. To advance scaffold development, a 3D printing system with higher resolution and positioning accuracy, and more advanced extrusion tools would be required to improve the co-deposition of hydrogel ink and thermoplastic-based filament to successfully produce the osteochondral scaffold design

Three-dimensional Macroscopic Scaffolds With a Gradient in Stiffness for Functional Regeneration of Interfacial Tissues

A novel approach has been demonstrated to construct biocompatible, macroporous 3-D tissue engineering scaffolds containing a continuous macroscopic gradient in composition that yields a stiffness gradient along the axis of the scaffold. Polymeric microspheres, made of poly(d,l-lactic-co-glycolic acid) (PLGA), and composite microspheres encapsulating a higher stiffness nano-phase material (PLGA encapsulating CaCO3 or TiO2 nanoparticles) were used for the construction of microsphere-based scaffolds. Using controlled infusion of polymeric and composite microspheres, gradient scaffolds displaying an anisotropic macroscopic distribution of CaCO3/TiO2 were fabricated via an ethanol sintering technique. The controllable mechanical characteristics and biocompatible nature of these scaffolds warrants further investigation for interfacial tissue engineering applications

Tocopherol Emulsions as Functional Autoantigen Delivery Vehicles Evoke Therapeutic Efficacy in Experimental Autoimmune Encephalomyelitis

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Molecular Pharmaceutics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://doi.org/10.1021/acs.molpharmaceut.8b00887.Contemporary approaches to treating autoimmune diseases like multiple sclerosis broadly modulate the immune system and leave patients susceptible to severe adverse effects. Antigen-specific immunotherapies (ASIT) offer a unique opportunity to selectively suppress autoreactive cell populations but have suffered from marginal efficacy even when employing traditional adjuvants to improve delivery. The development of immunologically active antigen delivery vehicles could potentially increase the clinical success of antigen-specific immunotherapies. An emulsion of the antioxidant tocopherol delivering an epitope of proteolipid protein autoantigen (PLP139–151) yielded significant efficacy in mice with experimental autoimmune encephalomyelitis (EAE). In vitro studies indicated tocopherol emulsions reduced oxidative stress in antigen-presenting cells. Ex vivo analysis revealed that tocopherol emulsions shifted cytokine responses in EAE splenocytes. In addition, IgG responses against PLP139–151 were increased in mice treated with tocopherol emulsions delivering the antigen, suggesting a possible skew in immunity. Overall, tocopherol emulsions provide a functional delivery vehicle for ASIT capable of ameliorating autoimmunity in a murine model