BIOPRINTING OF HYDROGEL CARDIAC PATCH FOR MYOCARDIAL INFARCTION AND ITS EX VIVO CHARACTERIZATION USING SYNCHROTRON-BASED IMAGING
Date
2018-11-19
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0001-9708-4594
Type
Thesis
Degree Level
Masters
Abstract
Myocardial infarction (MI) or heart attack is a type of ischemic disease and accounts for 42% of the death due to cardiovascular diseases. A wide range of surgical and pharmacological treatments are available for patients after an MI. Notably, the newly formed scar tissue after treatments cannot be removed and the heart function cannot be restored to the pre-MI levels. These issues may potentially lead to second cardiac dysfunction and thus heart failure. Tissue engineering offers promising alternatives to current treatments. Currently available cardiac tissue engineering (CTE) techniques include cell-impregnated hydrogel injection and cell-impregnated hydrogel patch implantation. Although cell-impregnated hydrogel injection technique offers advantage like minimally invasive surgery, it has also been reported that most embedded cells tend to leak from the injection site and drift out of the circulation system. To overcome these issues, cell-impregnated hydrogel patch-based CTE strategies have attracted considerable attention recently. However, the fabrication of porous cell-laden hydrogel patches remains challenging and is limited by materials selection and hydrogel processing techniques. The present study utilized a bioprinting technique to fabricate a tissue-engineered cardiac patch for the MI treatment.
In this study, cell-laden hydrogel, termed as bio-ink, was formulated based on alginate dialdehyde (ADA) and gelatin type A (GEL). ADA, synthesized by partial oxidation of alginate was utilized to provide good printability and degradability to the formulated bio-ink and GEL was to improve bioactivity and cell adhesion sites. The following three specific research objectives were pursued: i) synthesizing ADA by periodate oxidization; ii) bioprinting and characterizing ADA-GEL hydrogel patches; iii) utilizing synchrotron X-ray propagation-based phase-contrast imaging computed tomography (PCI-CT) to characterize implanted hydrogel cardiac patches ex vivo.
ADA was synthesized through a partial oxidation reaction by Sodium periodate(NaIO4). The presence of absorption bands at around 1586 and 1530 cm-1 in Fourier-Transform Infrared Spectroscopy (FTIR) spectra confirmed the formation of Schiff's base after the mixing of ADA and GEL. Rheology tests demonstrated that ADA and GEL can be covalently crosslinked without any crosslinker. Five groups of hydrogel compositions were designed to investigate the influence of oxidation degree of ADA and material compositions on the properties of printed hydrogel scaffolds. It was found that the gelation time of ADA50-GEL50 increases with the ADA oxidation degree and the mass ratio of ADA-GEL showed a negative influence on the gelation time when using 10% oxidized ADA. The crosslinking degree of ADA50-GEL50 increased with the ADA oxidation degree and the mass ratio of ADA-GEL. All ADA-GEL hydrogels have shown to provide a favorable environment for EA.hy926 cells, the hybrid human umbilical vein endothelial cell (HUVEC) line cells. 10% ADA70-GEL30 hydrogel demonstrated a better printability than other groups of hydrogel and was printed with three different strand orientations (SO). The hydrogel scaffold with the SO of 0/90° showed the highest elastic modulus. Then, EA.hy926 cells-laden 10% ADA70-GEL30 hydrogel was bioprinted and offered homogenous cell distribution and high cell viability over 7 days of in vitro culture. To achieve the third goal, 10% ADA70-GEL30 hydrogel scaffolds were bioprinted and implanted into the rat heart and a synchrotron-based X-ray in-line Phase-Contrast Imaging Computed Tomography (PCI-CT) system was successfully used to assess implanted cardiac patches on the rat heart ex vivo without using any contrast agents. The implanted patches were clearly visualized and characterized from the phase-retrieved PCI-CT slices and tomography projections can be reduced from 3000 to 1500 projections to reduce the total radiation dose without significantly compromising the imaging quality.
The present study provided a newly formulated bio-ink consists of ADA and GEL for Three-dimensional (3D) cardiac patch bioprinting. The bioprinted cardiac patch offered bioactivity, supported embedded cells survival and can potentially be applied in CTE offering a reliable treatment for MI to regenerate injured myocardium.
Description
Keywords
Bioprinting, Hydrogel Cardica Patch, Imaging
Citation
Degree
Master of Science (M.Sc.)
Department
Biomedical Engineering
Program
Biomedical Engineering