Bioactive glycopeptide nanofibers for tissue regeneration applications
Natural extracellular matrix (ECM) is rich in glycopeptides and glycosaminoglycans, which function in controlling cellular processes. In this thesis, glycopeptide molecules that mimic natural glycopeptides and glycosaminoglycans were designed and synthesized and it was demonstrated that they induce directed differentiation of mesenchymal stem cells into chondrogenic and adipogenic lineages. In the first part of the study, hyaluronic acid (HA)-mimicking glycopeptide amphiphile molecules were synthesized to induce chondrogenic differentiation of mesenchymal stem cells (MSC). HA is the most abundant glycosaminoglycan (GAG) found in hyaline cartilage ECM. Peptide amphiphiles were synthesized by solid phase peptide synthesis method and used to form self-assembled bioactive glycopeptide nanofibers which mimic fibrous morphology of the ECM. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and circular dichroism (CD) were used for morphology and secondary structure analyses of the obtained nanofibers. It was demonstrated that glycopeptide amphiphiles create fibrous structure formed by nanofibers. Morphological changes, GAG production (Safranin-O staining and DMMB analysis), and chondrogenic gene marker expressions (qRT-PCR) of MSCs cultured on HA-mimetic nanofibers were analyzed. It was shown that HA-mimetic glycopeptide nanofibers induce early differentiation of MSCs into hyaline like chondrocytes. In the second part of the study, it was demonstrated that minor changes on glycopeptide backbone can create specific glycopeptides which induce differentiation of MSCs into brown adipocytes. Brown fat adipocytes do not store chemical energy as fat but dissipates it as heat and so they have emerged as promising anti-obesity agents. Lipid droplet accumulation (Oil Red-O staining) and adipogenic gene marker expression analyses (qRT-PCR) showed that the new glycopeptide nanofiber scaffold is a specific inducer of differentiation of MSCs into brown fat adipocytes.