Bionanoparticles as viable substrates to promote osteogenic differentiation of bone marrow stromal cells.

摘要

Bone marrow stromal cells (BMSCs) have the potential to differentiate into osteoblasts, chondrocytes, adipocytes and smooth muscles. Although, they have shown great prospects in therapeutic and medical applications, less is known about the role that the nano environment plays on their differentiation potential. The first part of this dissertation focuses on investigating the effect of nanotopography on the promotion of osteogenic differentiation of BMSCs. The nanotopographies were created by coating 2D substrates with turnip yellow mosaic virus (TYMV) or tobacco mosaic virus (TMV) particles. TYMV and TMV are nanosized plant viruses with spherical and rod shaped morphology, respectively. These naturally occurring bionanoparticles offer unique properties, which can be employed to modulate cellular environment and study changes in cell behavior. The first part of the dissertation presents the study of temporal change in expression of specific genes during the osteogenic differentiation of BMSCs on nanoparticle coated wafers over the time course of 21 days. Differentiating BMSCs on virus coated substrates formed fully mineralized nodules and structures comprising of osteoblast-like cells around 14 days. Experimental evidence generated by real time quantitative PCR (qPCR) analyses, DNA microarrays and the detection of osteogenic markers using immunohistochemistry/cytochemical staining further corroborated that nanotopography promoted the osteogenic differentiation of BMSCs. Our studies strongly indicate that such viruses as biogenic nanoparticles can modulate the nanoenvironment of the substrate to influence differentiation potential of cells.Viral particles can present a variety of accessible amino acid functionalities on their outer protein shells. Therefore, the second part of the dissertation focuses on the study of the synergistic effect of nanotopography and multivalent ligand display obtained by chemically tailoring these nanoparticles with ligands affecting the cell growth and differentiation. We primarily selected the ligands such as phosphates which are known to play significant role in osteogenic differentiation pathway. The changes in gene regulation and expression during osteogenic differentiation of BMSCs were studied. Our data indicate that the presence of cell specific ligands combined with nanotopography can further enhance the expression of osteospecific genes. In order to develop functional biomaterials, these nanosystems demonstrate great potentials to modulate the cell environment and gain insight into corresponding cellular response.The last part of this study focuses on the self assembly of nanoparticles at liquid-liquid interface. To study the self assembly process at the liquid interface, emulsion and flat interface systems were employed. The data demonstrate that, although the nanoparticle assembly at the curved and flat interface share similar principle, the outcome of the assembly process is completely different. In the case of emulsion system, equilibrium is achieved yielding a disordered one layer of nanoparticles at the interface whereas at planar interface the kinetics can be manipulated by increasing the viscosity of the system resulting in highly ordered long range arrays. These two methods of bionanoparticle assemblies open unique opportunities in fabrication of nanostructured materials and for the generation of functional, hierarchically ordered systems.Collectively, the research presented in this dissertation explores into the unique properties of these biogenic nanoparticles, and attempts to employ them as model systems to gain insights into the fabrication of functional nanomaterials and biomaterials for medicinal applications.