Saudi Cultural Missions Theses & Dissertations
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Item Restricted LIQUID CRYSTALS NUCLEI COEXISTING WITH AN ISOTROPIC PHASE(Kent State University, 2022-08) Alqarni, Ali; Lavrentovich, OlegThe morphology of finite-size condensed materials is influenced by surface tension. To reduce surface area, tiny droplets of water in the air have spherical shapes, but solid crystals have facetted shapes defined by the orientation dependency of surface tension. Bulk interactions are unimportant in these two examples because they are either too weak to overcome surface tension in the first case or too powerful to enable internal curvatures in the second case. In liquid crystal droplets, the bulk and surface energies are more closely balanced, resulting in a more diversified morphology of structures such as smectic "batonnets", nematic spindle-like tactoids, and even the possibility for droplet division . Liquid crystals are well-known examples of ordered materials whose nuclei emerge from an isotropic state and have a shape topologically equivalent to a sphere. In the first part of the thesis, we explore experimentally and theoretically the nuclei of columnar lyotropic chromonic liquid crystal coexisting with the isotropic phase that is toroidal in shape. We study the lyotropic chromonic liquid crystal (LCLC) composed by plank-like molecules of disodium chromoglycate (DSCG) with hydrophobic polyaromatic cores and hydrophilic peripheries. The goal is to establish the physical mechanisms in the balance of elasticity and anisotropic surface tension that produce toroidal shapes and establish how these shapes depend on parameters such as molecular concentrations and the presence of a crowding agents. The second part of the thesis will focus on the droplets of chiral and ferroelectric liquid crystal materials.19 0Item Restricted Three Dimensional Printed Immunomodulatory Scaffolds with Controlled Drug Release for Bone Regeneration(Saudi Digital Library, 2023-10-24) Majrashi, Majed; Yang, Jing; Ghaemmaghami, AmirLarge bone defects pose significant challenges in orthopaedic surgery, necessitating the exploration of innovative repair technologies beyond traditional treatments like autografts, allografts, and synthetic substitutes, each fraught with specific challenges. Tissue engineering and regenerative medicine have emerged as promising fields, employing bioactive materials, growth factors, and cellular components to emulate natural bone properties and functions. Notably, additive manufacturing techniques contribute to these advancements by customising 3D-printed scaffolds enhancing patient-specific treatments. Recent studies underscore the significant influence of immune responses in bone regeneration, an area still in its infancy. Particularly, the modulation of immune reactions through specialised biomaterials and the strategic delivery of anti-inflammatory agents like dexamethasone present a novel approach to support bone healing processes, avoiding the systemic side effects of traditional drug administration. In this thesis, novel inks were developed to sustain the release of dexamethasone from a 3D-printed scaffold to modulate the immune response and osteogenesis. Excipients with surfactant properties, including the poloxamers F127, F68, L31, sorbitan monooleate Span80, and sucrose acetate isobutyrate (SAIB), were added to PCL to test their ability to sustain drug release. All these inks were fabricated into scaffolds by using direct ink writing 3D printing technique. The fabricated scaffolds were then characterised by SEM, DSC, FTIR, and ToF-SIMS. Macrophages and mesenchymal stem cells (MSCs) were cocultured to investigate the effects of the controlled release of dexamethasone on the modulation of macrophage polarisation and osteogenic differentiation of MSCs. Notably, blending PCL with 40% wt/wt (SAIB) has improved dexamethasone-cyclodextrin dispersal and facilitated a sustained 35-day release dominated by first-ordered and Higuchi models. In this modified environment, investigations into macrophage-mesenchymal stem cell (MSC) interactions revealed that controlled dexamethasone release significantly influenced macrophage behaviour and MSC osteogenic differentiation. M1 macrophages boosted early alkaline phosphatase production (ALP) at (7 days), while later stages (21 days) saw dexamethasone's predominance. Bone morphogenic protein-2 (BMP-2) was significantly increased at day 21; meanwhile, interleukin-6 (IL-6) decreased at the same time. Moreover, the released dexamethasone switched the phenotype of macrophages from M1 to M2 at day 21, evidenced by the increased level of mannose receptor and decreased expression of calprotectin receptor. These results offer new insight into macrophage-MSC cross-talk and demonstrate the potential of drug-release scaffolds to modulate inflammation and enhance bone regeneration.21 0