This thesis mainly focused on the regulation of stem cells behavior by chemical and physical signals of carbon nanomaterial modified fibrous scaffolds. The cell adhesion on scaffolds is indirect via a surface layer of adsorbed proteins, thus the scaffold surface treatments could regulate the protein adsorption amount, cells adherence efficiency. The general property of scaffolds could further affect nutrient/waste exchange, protein synthesis, intracellular matrix construction and cell differentiation eventually, which is very important in stem cells-based tissue engineering, especially in organ and tissue damage. In this work, iPSCs and MSCs were used to investigate the effect on differentiation potential towards neuron and osteogenesis respectively via the chemical and physical cues of carbon nanomaterials-based scaffolds.
The first project prepared a multivalent polyanion-dispersed CNTs modified fibrous scaffolds to integrate the chemical and physical in stem cell regulation research. The CNTs are dispersed and functionalized by biocompatible and multivalent hyperbranched polyglycerol sulfate (hPGS) noncovalently. After air plasma treatment of electrospun fibrous polycaprolactone (PCL) scaffolds, the HPGS modified CNT, namely CNT-HPGS were coated on the PCL fiber surface to combine the chemical and physical cues. Results suggests that CNT-HPGS modified fibrous scaffold is suitable for stem cells adherence and growth, because the combination of CNT and multivalent HPGS on scaffolds surface could offer anchoring points for proteins, growth factors and cytokines, which is very important for stem cells behavior. Meanwhile, the modified scaffolds promote the neural differentiation efficiency due to the special physical property of carbon nanotubes. Moreover, the aligned fibrous scaffolds could orient the elongation direction of grown neurites. Thus, the promoted protein adhesion property of CNT-HPGS contribute to the stem cells growth microenvironment and provide a novel method to construct functional scaffolds for stem therapy research.
Since brutal plasma treatment could lead to polymer degradation and the longtime effects on surface may not be permanent, surface grafting of biocompatible and multivalent HPGS could be a suitable choice. In the second project, the HPGS was covalently conjugated onto the graphene oxide (GO) nanosheet by using nitrene through a 2+1 cycloaddition reaction. The physical property of graphene oxide and chemical property of HPGS were combined to mediate the stem cells growth and differentiation. Then the GO-HPGS nanosheets functionalized nanofibrous scaffolds were applied to mediate the proliferation, lineage specification, and differentiation of iPSC. Results suggest that coated scaffolds could promote differentiation and maturity of iPSC towards neural differentiation. This study addressed the stability of the dispersion and promote the stem cell lineage specification maturity, which integrate the chemical and physical cues to facilitate the targeted differentiation of iPSC.
In the third project, we constructed a novel nanocarbon-structured fibrous scaffold for stem cell research, and the physical cues of carbon nanomaterials were MOF-derived nanocarbons. The porous carbon nanostructure could the promote the adhesion of proteins and growth factors, moreover, the caging property of the carbon nanostructure achieve the gradual release of chemical cues Zn2+ ions, which provide novel pathway for activation of signal pathways and guiding MSCs towards osteogenic differentiation process. This study designed stem cell scaffolds could help achieve multifunctional property, for example, simultaneously enhanced osteogenic and anti-infective capabilities.
In conclusion, this work combined the physical cues of carbon nanomaterials and other chemical cues to investigate the stem cell behavior, including the IPS cells towards neural differentiation and MSCs towards osteogenic differentiation process. The fabrication of scaffolds presented a novel avenue for the future development of carbon nanomaterials in tissue regeneration, bionic, biomedical, and bioelectronics.