Supramolecular Chemistry of Cucurbit[6]uril-Hyaluronic Acid Conjugates for Biomedical Applications

Abstract

This thesis describes the synthesis, characterization and biomedical applications of polymer conjugates having a backbone of hyaluronic acid (HA). Cucurbit[6]uril derivatives were successfully conjugated to HA via thiol-ene photoreaction to procure CB[6]-tethered biocompatible functional materials. Such materials have been promoted to demonstrate a theranostic system on demand by taking advantage of the strong host-guest interactions between CB[6] and spermidine, which was tagged with suitable theranostic agents such as dyes, drugs, aptamers, and targeting ligands. Furthermore, a supramolecular hydrogel was prepared by simple mixing of CB[6]-conjugated HA and diaminohexane (DAH)-conjugated HA, and its applications in cellular engineering was explored by exploiting the residual DAH present in the hydrogel with multifunctional tagged-CB[6] derivatives.Chapter 2 presents a CB[6]-based theranostic system on demand in situ by capitalizing the host-guest interactions between CB[6] and multifunctional spermidine derivatives. For an on-demand model theranostic system, CB[6]-HA was synthesized and decorated with FITC-spermidine (spmd) and/or formyl peptide receptor-like 1 (FPRL1) specific peptide-spmd. The resulting (FITC-spmd and/or peptide-spmd)@CB[6]-HA was successfully applied for the bioimaging of its target-specific delivery to B16F1 cells with HA receptors, and its therapeutic signal transduction with elevated Ca2+ and phosphor-extracellular signal-regulated kinase (pERK) levels in FPRL1-expressing human breast adenocarcinoma (FPRL1/MCF-7) cells. In vitro and in vivo stability of the complex was also investigated by release test and pharmacokinetic study.Chapter 3 describes a facile in situ supramolecular assembly and modular modification of biocompatible hydrogels in association with CB[6]-HA, diaminohexane conjugated HA (DAH-HA) and various tagged-CB[6] derivatives (tags-CB[6]) for cellular engineering applications. The strong and selective host-guest interaction between CB[6] and DAH made possible the supramolecular assembly of CB[6]/DAH-HA hydrogel in the presence of cells. Then, the 3D environment of the hydrogel was modularly modified by the treatment of various multifunctional tags-CB[6]. Furthermore, in situ generation of the hydrogel was installed in subcutis by sequential subcutaneous injections of CB[6]-HA and DAH-HA solutions. The fluorescence of modularly modified fluorescein isothiocyanate (FITC)-CB[6] in the hydrogel was maintained for up to 11 days reflecting the feasibility to deliver the proper cues for cellular proliferation and differentiation in the body.Chapter 4 presents a 3D tissue engineered supramolecular monoCB[6]/DAH-HA hydrogel successfully developed for the controlled chondorgenesis of hMSCs. The spatiotemporal control of hMSCs was made possible by modulating the mechanical strength of the hydrogels and the release profiles of TGF-β3 and dexamethasone using the hydrolysable Dexa-CB[6]. The effective chondrogenic differentiation of hMSCs encapsulated in the monoCB[6]/DAH-HA hydrogel with TGF-β3 and Dexa-CB[6] was confirmed by real-time qPCR, RT-PCR, histological, and immunohistochemical analyses. Taken together, the feasibility of cytocompatible monoCB[6]/DAH-HA hydrogels was confirmed for the spatiotemporally controlled chondrogenesis of hMSCs.