Nanoscale Titanium and Polycatecholamine Surface Science to Enhance Bone and Uterine Tissue Engineering

Abstract

The interface between biomaterials and tissues is fundamental to the success of implantable devices, such as orthopedic implants, and those biomaterials designed for soft tissue engineering applications. The efficacy of biomaterials in directing cell-specific responses is intricately linked to their physical and chemical properties. Physical attributes, such as topography and stiffness, interact synergistically with chemical characteristics, including surface chemistry, to modulate cellular behaviour. Understanding the multifaceted influences of biomaterials on cellular responses is pivotal in their design and application. The precise tailoring of these materials enables the stimulation of cell-type-specific pathways to elicit desired cellular behaviours. This thesis advances the field by expanding upon previous research conducted during my Master's degree, which explored the bioactive properties of a polydopamine (pDA) coating on a nanoporous titanium substrate (NPTi). Motivated by a desire to dissect the influence of each constituent separately, the first two studies herein are related to modifying the underlying titanium substrate, with the following two focusing on pDA-inspired polymers. Our first study, described in Chapter 3, focuses on generating titanium dioxide (TiO₂) nanotubes with varying sizes, architectures, and spatial organizations. This is followed by an investigation of the bioactive effects of these substrates on human mesenchymal stem cells (hMSCs) in the context of orthopedic biomaterials, including proliferation, adhesion, osteogenic marker expression, and bone mineral quality assessment via Raman spectroscopy. The second study is provided in Chapter 4 and focuses on using Pulsed-Water Jet (PWJ) technology for contaminant-free surface preparation of Ti. Following the generation of a textured substrate using the PWJ, in vitro testing was performed to assess the substrate's performance in periodontal implants. Human mesenchymal stem cells (hMSCs) and Saos-2 cells were employed to represent bone, while NIH/3T3 fibroblasts were used to represent the gums. Chapter 5 returns to polymer science and extends beyond Dopamine (DA) polymer chemistry to include additional catecholamine (CA) family members, specifically levodopa (LD) and norepinephrine (NE), for the generation of polycatecholamine (pCA) substrate. While DA is achiral, the chiral nature of NE requires particular focus on the potential effects of chirality on pNE. This led to considering both L-norepinephrine (L-NE) and racemic norepinephrine (rac-NE) as precursor conditions. Within this expanded study, we examine the influence of precursor chemistry and concentration on the kinetics of pCA formation and the synthesis of pCA nanoparticles using these CA precursors. This work aims to elucidate the impact of precursor chemistry, chirality, and concentration on pCA synthesis, thereby providing foundational insights that support the tailored design of pCA substrates for targeted biomedical applications. Lastly, shifting focus to soft tissue engineering, Chapter 6 explores the application of pDA, poly-L-norepinephrine (pLNE), and polylevodopa (pLD) to address uterine injuries, including those from Cesarean sections and intrauterine adhesions, which pose significant challenges to female reproductive health. Tissue engineering strategies utilizing these bioadhesive pCAs are being investigated for their potential to enhance uterine healing. Given the diverse cellular responses observed with different pCAs, this study focuses on understanding the interactions of pCA-based materials with both transformed human endometrial stromal cells (T-HESCs) and pregnant human myometrial (PHM1-41) cells in a multi-tissue context. This comprehensive study highlights the cell-specific responses to pCA, namely proliferation, adhesion, and migration. This research aims to elucidate the mechanisms underlying these interactions, ultimately paving the way for novel biomaterial-based treatments in female reproductive medicine. This work offers new perspectives on employing pCAs as a functionalization strategy for advanced tissue engineering and regenerative medicine applications, particularly in organ systems like the uterus. By working to bridge the gaps between materials science and cell biology, a multifaceted investigation into the intricate relationship between pCA biomaterials and cellular behaviour is presented. The findings herein provide a strong foundation for the use and further development of next-generation biomaterial-based therapies for both hard and soft tissue regeneration, potentially contributing to regenerative medicine.