Polyphenol-inspired engineering of multifunctional films and particles

Abstract

Polyphenols, these plant-derived natural products, were traditionally referred to as “vegetable tannins”, due to their original use in the industrial process of “tanning” to convert animal hide into leather. From the 19th century onwards, “real chemistry” got involved in the study of polyphenols, and in the following 100 years, the study of polyphenols has drawn great interest in broad areas of research, including food science, pharmaceutical research, biology, and the original leather manufacturing. However, most of the research on polyphenols is limited to traditional fields, or focuses on the properties of polyphenols in solution. This thesis focuses on exploring the unique physicochemical and biological properties of polyphenols to serve as an important source of inspiration in the search for new and improved materials. A library of functional metal-phenolic network (MPN) nanostructured films and capsules was prepared from the coordination between a phenolic ligand and a range of metal ions. The functional properties of the MPN materials were tailored for advanced drug delivery, positron emission tomography (PET), magnetic resonance imaging (MRI), fluorescence, and catalysis. Furthermore, the engineering of MPN materials into nanoporous replica particles was used as a novel ultrasound imaging probe and therapeutic to detect and decrease endogenous reactive oxidative species, H2O2, in biological systems. By exchanging the previously used multivalent coordination chemistry with dynamic boronate covalent chemistry, biologically relevant, dual-responsive boronate-phenolic network (BPN) capsules that combine the pH responsiveness of MPN with the cis-diol responsiveness of boronate complexes were synthesized. Polyphenol-inspired particle functionalization was later discovered to facilitate an interfacial molecular interaction-induced self-assembly process. This allowed for the generation of a highly versatile and effective methodology to prepare a large variety of superstructures assembled from a wide range of building blocks. This method displayed significant versatilities of sizes, shapes, microstructures, and compositions as building blocks. The generic nature of this method led to a large family of modularly assembled superstructures including core-satellite, hollow, and hierarchically organized supraparticles. Colloidal-probe atomic force microscopy and molecular dynamics simulations provided detailed insight into the role of this polyphenol-based particle functionalization and how this functionalization facilitated superstructure construction.