Chemoselective Platform for Extracellular Matrix Functionalization to Boost Tissue Regeneration and Repair

 Extracellular matrix (ECM)-derived hydrogels offer improved biocompatibility and closer mimetic of native tissue. While they are extensively used in tissue engineering, the lack of originally embedded bioactive molecules in ECM limits the regenerative potentials of the ECM hydrogels for effective bioengineering of tissues and organs. Therefore, there is a critical need of developing biologically selective or chemoselective approaches to immobilize bioactive cargos onto ECM biomaterials while maintaining the original properties of biomaterials. To enhance the regenerative potential, we are developing a platform to functionalize ECM hydrogels by chemoslectively immobilizing bioactive cargos onto click-reactive ECM, which can be potentially applied to various ECM materials and therapeutics in the future. Click chemistry is utilized to provide the covalent immobilization between engineered cargos and ECM materials, which allows chemoselective conjugation between bioinert ligands and has been widely explored for biomaterial-anchored delivery of bioactive molecules. Nanoscale extracellular vesicles (EVs) represent a unique cellular derivative which reflect the therapeutic potential of mesenchymal stem cells (MSCs) toward tissue engineering and injury repair without the logistical and safety concerns of utilizing living cells. In addition, growth factors are widely explored on regulating cellular activities as bioactive inducers and they are proved to play critical roles in inducing cellular proliferation and differentiation for tissue and organ repair and regeneration. Despite the therapeutic potential of MSC-derived EVs and growth factors in promoting tissue regeneration, their clinical application is hindered by their limited stability and systemic side effects in vivo. Systemically administered EVs and growth factors undergo rapid clearance and typically are without a focused targeted delivery, thus reducing their effectiveness in regenerative therapies. 

The main objective of this thesis is to enhance the regenerative potential of ECM hydrogels by functionalization with bioactive cargos, including growth factors and EVs, using click chemistry. We developed a platform technology to chemoslectively immobilize bioactive cargos, bearing metabolically incorporated azido ligands, onto click-reactive dibenzocyclooctyne-modified ECM hydrogels, which enables long-term spatial retention of active therapeutics and can be potentially applied to various ECM materials and bioactive cargos in the future. Metabolic glycan engineering is utilized as the approach to functionalize the growth factors and EVs with click-reactive groups. We envision this technology will enable a wide range of applications to spatially promote desired tissue repair and host integration relevant to tissue engineering and regenerative medicine applications.