Self-Assembling MultiDomain Peptides as Scaffolds for Tissue Engineering
Kang, Marci KMH
Hartgerink, Jeffrey D
Doctor of Philosophy
Creating a new generation of biomaterials to support tissue engineering efforts is critical to the development of functional tissues. This thesis describes the initial phases of biomaterial development of seven new MultiDomain Pepties (MDPs): from their design and characterization, to the study of how sequential modifications affect dental stem cell response, and finally examines how different cell lines respond to the same MDP sequence. Four of the new sequences, K3(SL)6K3, K3(SL)7K3, K3(SL)8K3, and K4(SL)6K4, were designed to study the effect of lengthening either the amphiphilic region or charged domains of MDPs. Characterization of the peptides by multiple techniques showed anti- parallel !-sheet structure that forms porous nanofiber hydrogels related to the MDP sequence. The remaining three new MDPs, K2(TL)6K2, K2(TL)6K2GRGDS, and K(TL)2SLRG(TL)3KGRGDS, were used as cell culture scaffolds and were compared to their previously published serine-based counterparts to examine the impact of MDP chemistry on the morphology and proliferation of stem cells from human exfoliated deciduous teeth (SHEDs). Fluorescent staining and confocal microscopy indicated that the serine-based hydrogels were more proliferative; the SHEDs did not require the integrin-binding RGDS sequence to attach and proliferate throughout the hydrogel. The threonine-based gels were more selective as the SHEDs were seen to remain rounded throughout the duration of the experiment in K2(TL)6K2. These results highlighted the difference that scaffold chemistry can make on cell response. NIH/3T3 fibroblasts, and EpH4-Ev mammary epithelial cells were encapsulated and cultured in K2(SL)6K2GRGDS hydrogels. All cell lines proliferated significantly by day eleven. Both the NIH/3T3 cells and the EpH4-Ev cells exhibit typical morphology, with the EpH4-Ev cells even forming organotypic structures. Taken together, the results from this study indicate that MDPs can tolerate a number of sequence modifications and are effective scaffolds for a wide range of cell types, even supporting the formation of organotypic structures when the appropriate bioactive cues are present.
scaffolds; matrices; self-assembly; hydrogels