Chemical and Biomolecular Engineering - Theses
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ItemFunctional Supramolecular Network Engineering Inspired by Metal–Phenolic Complexation( 2021)Supramolecular assembly provides a versatile pathway for engineering bespoke materials, such as metal–organic hybrid materials. Metal–phenolic networks (MPNs), constructed from the coordination-driven assembly of phenolic ligands and metal ions, are an emerging class of hybrid materials with a rich choice of building blocks. Due to their strong adhesion to different substrates (particles, planar surfaces, microorganisms), high degree of modularity, and tuneable degradability, MPNs have garnered considerable attention in fields such as drug delivery, bioimaging, antimicrobials, separation, and catalysis. However, fundamental research in the material aspects of MPNs and how these influence biomedical applications are essential yet overlooked. This thesis explores the fundamental principles of MPNs and uses this insight to examine MPN materials in a range of biomedical applications. First, MPN microcapsules comprised of various building blocks are engineered, and their programmable gating mechanisms are explored in terms of intermolecular dynamics. This fundamental study not only provides insight into the dynamic nature of MPNs but also offers a route to engineer smart delivery systems and selective gating materials. Next, MPN coatings are used as a versatile and cytocompatible platform to trigger the endosomal escape of nanoparticles, which has been regarded as a key bottleneck for the intracellular delivery of therapeutics. The escape mechanism is systematically investigated and determined to be the “proton-sponge effect”, arising from the buffering capacity of MPNs. Notably, this buffering-enabled escape capability is preserved after the post-functionalization of MPN coatings with polymers, showing the generalizable nature of the platform. Therefore, a subsequent in-depth exploration of the buffering effects of MPNs sheds mechanistic insight into metal–organic systems and their emergent buffering capacity based on coordination dynamics and building block choice. Finally, the advantages of different polyphenol-enabled supramolecular networks are integrated to expand the MPN platform from thin films to self-assembled nanoparticles. Bioactive metal–phenolic nanoparticles are developed via robust and template-free assembly. Hydrophobic interactions and coordination play dominant roles in the assembly and stabilization of the nanoparticles. Furthermore, the incorporation of diverse biomacromolecules (e.g., functional proteins and genes) during assembly enables the potential use of these metal–phenolic nanoparticles in various biomedical applications, anticancer treatments, cascade reactions, and gene knockdown.