BME Masters Project: Zirui Zheng- “Characterizing Diffusion Behavior in Fibrin Microthread/Gel Composite”

Monday, April 22, 2024
4:00 pm to 4:45 pm
Floor/Room #

Master’s Project Defense

Monday, April 22, 2024

Gateway Park, Room GP 1002

4:00pm — 4:45pm

“Characterizing Diffusion Behavior in Fibrin Microthread/Gel Composite”

Zirui Zheng

Abstract: Myocardial infarction (MI) is a serious cardiovascular disease when patients experience disruption of blood supply to the heart muscle. Every year, about 805,000 people suffer from myocardial infarction in US alone. MI causes irreversibly damage to the myocardium, causing stiff and non-contractile fibrotic scar tissues to form. Chronic scar tissues will decrease in thickness in response to local stress and eventually lead to heart failure. Efforts through drug treatment to improve heart function have been unsuccessful due to limited regeneration potential of the myocardium. Tissue engineered composite heart patches are a promising approach to repair the damaged myocardium and restore active heart function. Our lab proposed a novel composite heart patch design combining fibrin hydrogel and cell-seeded microthreads. This thesis focuses on understanding and optimizing diffusion mass transport within the composite heart patch by adjusting two design parameters: fibrinogen concentration (5, 10, 15 mg/mL) and microthread configuration (no thread, single thread, 6 × microthread bundle). A simple PDMS-based microfluidic device was developed to allow fluorescence imaging of fluorescein isothiocyanate (FITC)-dextran transport within the composite. Using calibration curves, FITC-dextran concentration over time data can be fitted by Fick’s second law diffusion model to determine diffusion coefficients. Diffusion coefficients determined from micorfluidic device experiments were validated by repeating the experiments in a diffusion cell setup. An interaction study between FITC-dextran and fibrin gel was conducted to investigate possible adsorption of FITC-dextran molecule to the fibrin hydrogel network. Preliminary diffusion coefficients data suggests the impact of fibrinogen concentration to the composite is not conclusive in the microfluidic device setup but significant in the diffusion cell setup. Interestingly, increases in fibrinogen concentration led to apparent faster diffusion. Addition of single microthread or a microthread bundle improved diffusion, but no significant difference was observed, suggesting that the microthread is not the main contributor to diffusion within the composite. The diffusivity of fibrin gel/microthread composites are at 10-4 - 10-5 cm2/s and of 1 or 2 magnitude higher than glucose diffusivity in water at 6.7× 10-6 cm2/s and sucrose diffusivity in cat ventricular myocardium at 1.77 ± 0.23 × 10-6 cm2/s, indicating the composite provides sufficient mass transport for cell development. A possible mechanism of adsorption-driven diffusion was proposed and adsorption was confirmed with interaction study.


Thesis Advisor:


Defense Committee:


George Pins, PhD


Biomedical Engineering

Worcester Polytechnic Institute

Raymond Page, PhD (Chair)

Professor of Practice

Biomedical Engineering

Worcester Polytechnic Institute

Kevin Costa, PhD

Associate Professor

Department of Cardiology

Icahn School of Medicine at Mount Sinai

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Biomedical Engineering
Contact Person
June Norton