Design of Peptides with Targeted Apatite and Human Bone Marrow Stromal Cell Adhesion for Bone Tissue Engineering.

Abstract

The restoration and repair of orofacial and large bone defects resulting from extreme trauma, disease, or genetic inheritance is a clinical challenge in need of new solutions, as current grafting techniques can result in donor site morbidity, graft rejection, and/or inadequate bone formation and quality. Because bone is a complex organ, its hierarchical structure may only be restored in such defects if a temporary material guides tissue formation. Bone tissue engineering explores combinations of materials, biological signals, and cell sources to achieve guided tissue formation with structure-function properties matching those of native tissue. By using nature’s building blocks, or amino acids, as a design platform to synthesize multi-dimensional biomolecules in the form of peptides, biological function can be influenced. The idea is to provide specificity to induce a desired biological activity. In addition, coating a material with biomimetic bone-like mineral can provide a surface morphology and composition similar to the native hydroxyapatite in bone. While bone-like mineral can increase bone growth in vivo, the tissue formed is not uniform or spatially controlled, suggesting the need for better-designed scaffolding to spatiotemporally influence bone tissue development. No studies have investigated the potential impact biomolecule-laden bone-like mineral has on influencing cell behavior. The work presented in this thesis is first to design dual-functioning peptides to increase in vitro cell attachment on bone-like mineral. Using a combinatorial phage library, computational modeling, and biological assays, specific peptide sequences that preferentially adsorb to bone-like mineral and attach to clonally derived human bone marrow stromal cells (hBMSCs) were identified. When combined, these sequences formed a dual-functioning peptide that exhibited an increased ability to attach hBMSCs compared to previous peptide designs. Additionally, a bioreactor was designed to coat three-dimensional porous scaffolds with uniform, continuous bone-like mineral, addressing a need for improved biomimetic coating fabrication techniques. The presented strategies can influence guided bone growth and advance the current methodologies in bone engineering. This work provides a new paradigm for peptide development linking organics to inorganics, not only for bone tissue engineered constructs, but also for any system requiring temporary or guided adhesion.