Chemical Engineering

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Browsing Chemical Engineering by Author "Akbarnia, Negar"

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    Design Ionically Crosslinked CNT Hydrogels that Mimic Cardiac Tissue Mechanics and Conductivity
    (University of Waterloo, 2025-04-25) Akbarnia, Negar
    Myocardial infarction remains a leading cause of mortality worldwide due to the heart's limited regenerative ability, resulting in disrupted electrical signaling and compromised contraction. Injectable hydrogels have emerged as a promising, minimally invasive approach to support myocardial healing and restore function post-MI, especially when designed to mimic key characteristics of native cardiac tissue, such as filamentous nanostructure, conductivity, and essential mechanical properties. Such biomimetic materials could potentially prevent pathological progression and enhance cardiac repair. However, the development of an injectable hydrogel that combines both conductivity and a fibrillar structure to effectively mimic cardiac tissue, promote cell growth, and support organ repair has yet to be achieved.The objective of this thesis is to develop an injectable hydrogel with conductivity and a filamentous architecture that mimics cardiac tissue. The primary hypothesis is that carbon nanotubes (CNTs) can serve as the main building blocks for creating nanocolloidal hydrogels with biomimetic filamentous structures. This structural arrangement is designed to mimic the extracellular matrix (ECM), providing a biomimetic environment that supports mechanical resilience. CNTs have attracted significant interest due to their exceptional conductivity and tunable mechanical properties, making them ideal candidates for reinforcing hydrogels in tissue engineering applications, particularly as artificial ECM scaffolds for myocardial regeneration. To incorporate CNTs as the primary building blocks of the hydrogel, they first stabilized in water, addressing one of the major concerns in their biomedical applications—toxicity. This was achieved through non-covalent functionalization by wrapping CNTs with the anionic polymer polystyrene sulfonate (PSS), which introduces electrostatic repulsion, preventing aggregation and ensuring a stable dispersion. Upon introducing salt (CaCl2), the stabilized CNT-PSS suspension undergoes gelation through electrostatic interactions, forming a hydrogel network. Both SWCNTs and MWCNTs have been explored as building blocks hydrogel development. This study incorporates both to compare their structural, mechanical, and electrical properties, identifying the most suitable option for myocardial tissue engineering. By tuning the ratio of Ca2+ cations to CNT-PSS, the rheological and structural properties of the hydrogel were systematically varied. The resulting hydrogels, formulated with both MWCNTs and SWCNTs, exhibited injectability at low salt concentration and strain-stiffening behavior at 1.9M. Additionally, both hydrogel systems demonstrated electrical conductivity, highlighting their potential for myocardial tissue engineering applications. With the SWCNT based hydrogel showing higher strain stiffening behavior than MWCNT based hydrogel.