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PhD_Thesis_Akalanka_B_Ekanayake7.83 MB
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Dissertation
Study of nanoscale mechanical and physicochemical properties of crystalline solids and biological systems
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2026
DOI: 10.25820/etd.008330
Abstract
Investigation of nanoscale mechanical and physicochemical properties of crystalline solids and biological systems has attracted significant interest due to their expanding applications in the fields of materials science, pharmaceutics, and biomedicine. Characterizing these properties remains an inherently challenging task owing to the size limitations of traditional instrumental approaches. However, atomic force microscopy (AFM) has emerged as a powerful and versatile platform capable of probing mechanical properties, structural transformations, and biological behavior at spatial resolutions spanning the nano- to micro-dimensions. Herein, this dissertation focuses on AFM-based methodology development and application for the investigation of nanoscale mechanical and physicochemical properties across a broad range of crystalline and biological systems.
Understanding how mechanical properties scale with crystal size is essential for the rational design of metal–organic frameworks (MOFs) with tunable functionality. In chapters 2 and 3, AFM nanoindentation measurements on individual crystals of zeolitic imidazolate framework-7 (ZIF-7) and zeolitic imidazolate framework-90 (ZIF-90) across the nano- to supermicron-size range reveal that framework flexibility increases continuously and systematically with crystal size reduction, following a power-law dependence of Young's modulus on crystal size. Complementary scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements on individual crystals establish that the origin of the size-dependent mechanical behavior is closely correlated with increasing defect concentration and changes in metal content as crystals are reduced in size. Together, these findings provide a coherent mechanistic framework for understanding how structural heterogeneity at the nanoscale governs the mechanical behavior of switchable MOFs and demonstrate that crystal downsizing represents a promising and systematic route for tuning framework mechanics.
In chapter 4, AFM nanoindentation is applied to investigate the mechanical consequences of a light-induced single-crystal-to-single-crystal photodimerization reaction in a coordination polymer containing one-dimensional wire-like arrays of monoatomic Ag(I) ions. Irradiation with UV light disrupts the periodic metal arrays through argentophilic interactions, generating structural voids within the lattice and producing a substantial increase in crystal softness of up to 60%. These results establish a direct link between external optical stimulation and measurable mechanical response, introducing new design possibilities for stimulus-responsive functional materials.
Chapter 5 demonstrates the use of a rock tumbler as a practical and accessible apparatus for mechanochemical synthesis. Operating at energy inputs approximately four orders of magnitude lower than conventional ball milling, the rock tumbler generates milder grinding conditions that minimize heat dissipation and enable gram-scale synthesis. The apparatus is shown to support the formation of a photoactive organic cocrystal and a metal–organic framework, with the added capability of incorporating UV illumination directly into the synthesis chamber for in situ solid-state photochemistry. AFM imaging is utilized to characterize the structural and morphological properties of the resulting crystalline materials.
Chapters 6 through 10 extend AFM-based mechanical characterization to biological systems, focusing on the role of iron metabolism and redox regulation in governing the biophysical properties and invasive behavior of glioblastoma cells. In chapter 6, AFM nanoindentation reveals that radiation-induced iron accumulation, driven by upregulated transferrin receptor expression, produces measurable changes in glioblastoma cell stiffness and enhances cell motility, establishing iron metabolism as a determinant of the invasive mechanical phenotype following radiation therapy. Chapter 7 demonstrates that isocitrate dehydrogenase (IDH)-mutant glioma cells preferentially accumulate iron, which modulates membrane fluidity and promotes cell motility, with AFM measurements providing quantitative evidence that iron-dependent membrane mechanical changes underlie the enhanced invasive capacity of IDH-mutant tumors. Chapter 8 investigates the effect of glutathione peroxidase 4 (GPx4) overexpression on glioblastoma cell mechanics and dynamics, showing that elevated GPx4 expression impairs cell growth, induces anomalous subdiffusion as measured by live-cell tracking, and produces quantifiable changes in cell stiffness, highlighting the interplay between redox regulation and cellular mechanical behavior. Chapter 9 examines how gallium treatment disrupts endoplasmic reticulum iron metabolism to induce lipid metabolic reprogramming in glioblastoma cells, with AFM stiffness measurements combined with lipidomic analyses revealing that iron mimic-mediated disruption of iron-dependent metabolic pathways produces both biophysical and biochemical consequences relevant to ferroptosis induction. Chapter 10 demonstrates using a ferritin heavy chain overexpression model that intracellular sequestration of labile iron increases cell stiffness and reduces motility, establishing that iron storage directly governs the mechanical and invasive properties of glioblastoma cells and providing further evidence that cellular mechanical measurements can serve as sensitive indicators of iron metabolic state.
Finally, chapter 11 investigates luminescent amphiphilic platinum(II) complexes for the detection and disaggregation of amyloid fibrils. AFM imaging, in combination with spectroscopic characterization, demonstrates that complexes bearing complementary hydrophobic and hydrophilic ligand sets exhibit enhanced luminescence in the presence of amyloid fibrils and, in specific cases, induce structural disruption of the fibril architecture into smaller spherical aggregates. These findings establish AFM as a valuable tool for monitoring fibril disaggregation and suggest a potential strategy for targeting amyloid-related diseases.
Overall, this dissertation demonstrates that AFM nanoindentation and imaging provide a high-resolution, broadly applicable platform for probing the nanoscale mechanical and physicochemical properties of both crystalline and biological systems. The methodologies developed and applied herein bridge materials science and biological inquiry, revealing how crystal size, defect distribution, external stimuli, and biochemical regulation collectively govern mechanical behavior and offering new design principles for functional materials and potential therapeutic strategies.
Details
- Title: Subtitle
- Study of nanoscale mechanical and physicochemical properties of crystalline solids and biological systems
- Creators
- Akalanka Bandara Ekanayake
- Contributors
- Alexei V Tivanski (Advisor)Renée S Cole (Committee Member)Edward G Gillan (Committee Member)Johna Leddy (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008330
- Publisher
- University of Iowa
- Number of pages
- xxiii, 208 pages
- Copyright
- Copyright 2026 Akalanka Bandara Ekanayake
- Language
- English
- Date submitted
- 04/28/2026
- Description illustrations
- illustrations, graphs, tables
- Description bibliographic
- Includes bibliographical references (pages 183-208).
- Public Abstract (ETD)
Nanoscale materials, which have dimensions on the order of one billionth of a meter, exhibit physical and chemical properties that differ significantly from their larger, bulk counterparts. These unique properties make nanoscale crystalline materials highly attractive for applications in gas storage, drug delivery, and the design of stimuli-responsive devices. However, studying and understanding these properties requires specialized tools capable of operating at extremely small length and force scales, as conventional measurement techniques cannot access the nanoscale regime.
Atomic force microscopy (AFM) is a versatile technique that can image the size and shape of nanoscale materials and measure extremely small forces, far below the detection limits of traditional methods. In this work, AFM is used to investigate how crystal size influences the mechanical properties of metal-organic frameworks, a class of porous crystalline materials with broad technological relevance. It is demonstrated that reducing crystal size systematically increases framework flexibility, and that changes in crystal composition and defect content are responsible for this behavior. Furthermore, the mechanical properties of certain crystals are shown to be tunable by light, and a simple mechanical grinding approach is demonstrated to produce new crystalline materials without the need for conventional solution-based synthesis.
AFM is also applied to living brain cancer cells, where iron accumulation driven by radiation treatment, genetic mutations, or therapeutic intervention is found to directly govern cell stiffness and invasiveness. These findings suggest that measuring the mechanical properties of cancer cells can provide a sensitive and informative window into the biochemical processes that drive tumor progression.
- Academic Unit
- Chemistry
- Record Identifier
- 9985177073002771
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