Fetal surgery can improve outcomes for severely affected fetuses, but carries a substantial risk of preterm birth. In order to perform surgery on the fetus, surgeons must breach the fetal membranes, a pair of fragile tissues that are susceptible to post-surgical rupture. Here, we sought to develop adhesives to seal this non-healing tissue, decreasing the overall risk of fetal surgery and making it an option for more families. The central challenge of fetal membrane sealing is achieving robust adhesion in a wet environment. In designing our adhesives, we took inspiration from marine mussels. Mussels secrete adhesive plaques rich in the amino acid 3,4- dihydroxyphenylalanine (DOPA) to adhere to diverse underwater surfaces, and we incorporated similar DOPA chemistry into our adhesives. We designed both injectable hydrogel adhesives and supramolecular adhesive patches and measured their adhesive strength and cytocompatibility. The adhesive hydrogels were also studied in a novel rabbit model of fetal membrane presealing. Membrane presealing is a proposed surgical approach in which the delicate fetal membranes are sealed prior to surgical puncture, stabilizing them, reducing the risk of membrane leakage and rupture, and decreasing the overall risk of fetal surgery. In this animal model, our mussel-inspired formulation appeared to be fetotoxic, but with an alternative adhesive, we found that fetal membrane presealing appeared facile and safe for mothers and fetuses. I also sought to understand how our materials interact with human fetal membrane tissues in vitro, and developed protocols to culture these tissues and their cells ex vivo. We used these cultures to analyze the cytocompatibility of our adhesives with clinically relevant primary cells and tissues, and took the initial steps to investigate the potential for a small molecule regenerative drug candidate (dihydrophenonthrolin-4-one-3-carboxylic acid, DPCA) to regenerate human fetal membranes in vitro. In this work, we created novel, mussel-inspired adhesive hydrogels and patches; established the feasibility of fetal membrane presealing in vivo; and developed human fetal membranes as an ex vivo tool for biomaterial-tissue compatibility evaluation.

Catechol-based molecules have been identified as one of the key elements responsible for many important functions in natural systems owing to their intrinsic physicochemical properties. Capitalizing on these universal design principles found in nature, catecholic molecules have been increasingly considered in the field of materials science as possible bioinspired structural motif candidates to synthesize and fabricate advanced engineering materials. This thesis begins with a short introduction to the structural diversity of the most important families of catecholic molecules found in biological systems, with an emphasis on elucidating the structure-property relationships arising from the chemical functionalities present in their molecular structures. In chapter 1 the fundamental physicochemical interactions undertaken by catecholic molecules at interfaces, both in nature and in bioinspired materials, and common strategies for productive manipulation of these interactions are further described. Chapter 2 aims to provide a more complete picture of marine mussel adhesion, particularly at the molecular level, and facilitate developing a solid framework for the rational design of mussel-inspired wet adhesives. In this chapter the interplay between chemical sequence and topological structure in the mussel adhesive proteins is illustrated by highlighting the results of our molecular level study on the interfacial adhesion of a library of mussel-inspired peptides to organic and inorganic substrates. In chapters 3-6 a summary of the research on design, synthesis, and characterization of catechol-based bioinspired functional materials for implementation in diverse applications ranging from hybrid materials and coatings to high-performance dry/wet adhesives is provided. In chapter 3, bioinspired catechol-based material polydopamine (pDA), one of the most widely employed surface modification methods due to its versatility and simplicity, is introduced and the results of the research undertaken to elucidate the formation mechanism, structure, and molecular mechanics of this fascinating material is discussed. In chapter 4 some of the main shortcomings of these coatings including their poor mechanical performance are described followed by reporting a simple post-treatment approach via thermal annealing at a moderate temperature as a facile route to enhance mechanical robustness of pDA coatings without compromising their inherent functionality. A suite of characterization techniques are employed and analysis of the results shows fundamental changes in the molecular and bulk mechanical behavior of pDA after thermal annealing, leading to considerable improvements in the ability of the coatings to resist mechanical deformations. Chapters 5 and 6 describe developing catechol-based pressure-sensitive adhesives (PSAs) by exploiting the mussel adhesion principles. In chapter 5 a combination of microscopic and macroscopic adhesion assays are used to study the effect of catechol on dry and wet adhesion performance of the catechol-containing PSAs. Chapter 6 describes developing a new generation of synthetic amino-catechol adhesives inspired by the adhesive synergy between flanking amine and catechol residues in the mussel adhesive proteins. Comprehensive multi-scale adhesion characterization is used to probe performance at the molecular, microscopic, and macroscopic levels, showing that coupling of catechols and amines together within the same hybrid monomer architecture produced optimal cooperative effects in improving macroscopic adhesion performance.

The ability to respond to injury is an essential characteristic of life, but there is substantial variability as to how this is achieved. While some amphibians can regrow entire appendages well into adulthood, such regenerative capabilities are not seen in mammals, where healing is instead achieved through scarring. To induce mammalian regeneration, research has primarily focused on the development of biomaterial scaffolds and progenitor cell therapies. These approaches have showed substantial success in small animal models and preclinical trials. However, they have faced significant hurdles in clinical scale-up due to concerns over cell sourcing and engraftment. Thus, the overarching goal of this thesis is to reshape the conventional vision of regenerative therapeutics, and instead create translational treatments that are capable of catalyzing endogenous tissue repair. To achieve this goal, in this dissertation, we explore the clinical utility and delivery of the small molecule drug, 1,4-dihydrophenonthrolin-4-one-3-carboxylic acid (DPCA). The immediate biological effect of treatment with DPCA involves transient upregulation of the oxygen-sensitive transcription factor, hypoxia inducible factor one-alpha (HIF-1α). HIF-1α targeting in the context of tissue repair, was inspired by studies showing that upregulation of the factor drives epimorphosis in natural regenerators such as the Murphy Roths Large (MRL) laboratory mouse strain. Although HIF-1α is constitutively expressed in all cells, the factor is normally degraded and only stabilized in hypoxia. However, by inhibiting prolyl hydroxylase enzymes involved in HIF-1α degradation, timed release of DPCA allows for transient stabilization of the protein in normoxia. Thus, to induce MRL-like HIF-1α expression and subsequent regeneration, self-assembling, DPCA-based prodrugs, with tunable drug release kinetics and bioactivities were developed. Prodrugs were created by coupling the poorly soluble, hydrophobic drug to a linear poly(ethylene) glycol (PEG) via a biodegradable ester bond and multi-valent end group linkers. Changes in polymer-drug ratio were found to greatly influence prodrug aggregation in aqueous environments. While amphiphilic polymer-drug conjugates with low hydrophobic-to-hydrophilic ratios could exist as soluble prodrugs, increasing DPCA content resulted in the formation of stable, supramolecular nanomaterials with spherical or fibril geometries. Self-assembly was confirmed through microscopy, x-ray scattering, rheological characterization, and coarse-grained molecular modeling. Compared to conventional biomaterial carriers which often achieve drug loading and release through physical encapsulation and diffusion, such supramolecular assemblies exhibit higher loading efficiencies and more sustained release profiles. Despite these advantages, rationally designing prodrugs to achieve the desired biodistribution profiles, release kinetics, and activity, remains a significant challenge. Thus, fundamental studies such as this help to elucidate the relationship between molecular design and practical performance, to establish design rules for future prodrug development. By completing this structure-property analysis, we also developed a library of novel carriers capable of delivering DPCA to unique injury targets. Of the prodrugs developed, a PEG-DPCA conjugate shown to self-assemble into micron-length worm-like micelles, was chosen as a potential, pro-regenerative therapy for Inflammatory bowel disease (IBD). DPCA has the potential to fulfill a major unmet clinical need for pro-regenerative IBD therapies, since many existing treatments only target inflammation. Using a murine model of experimental colitis, we show that pretreatment with DPCA protects against ulcer development in the lower gastrointestinal tract by strengthening barrier properties. We then show that treatment with DPCA after the onset of disease accelerates epithelial repair of the colon lining. This effect is likely driven by an epithelial-to-mesenchymal transition, initiated by upregulation of HIF-1α. We verify that direct treatment of human intestinal epithelial cells with DPCA in vitro, also improves barrier strength and integrity. Thus, we conclude that DPCA holds great clinical promise in IBD care and propose several designs for future drug carriers specific to this application. Preliminary results suggest that functionalization of nanocarriers with mucoadhesive ligands or chemical motifs with affinity for gastrointestinal tissue, may promote prodrug retention within the gastrointestinal tract. This would facilitate local drug release, and potentially improve therapeutic safety and efficacy. To predict biological performance in vitro, microfluidic devices containing mucin coatings or mucus-producing cells were used to study the behavior of particles labeled with candidate adhesive motifs under physiologically relevant fluid shear. In this study, we validate the mucoadhesive properties of a novel, bioinspired polymer and develop several new assays that can be used to study adhesion in nanomaterials. Overall, the work outlined in this thesis, makes significant contributions to the fields of drug delivery and regenerative medicine, and supports the eventual clinical translation of DPCA. Given the ubiquitous expression of the drug’s target across cell types, controlled delivery of DPCA may facilitate tissue repair following a variety of injuries and disease. Future work aimed to discover the precise downstream pathways of HIF-1α-induced regeneration may also inspire the development of new therapies in regenerative medicine.