| Abstract | Medium-chain length Polyhydroxyalkanoates (MCL-PHAs) have demonstrated exceptional properties for cardiac tissue engineering (CTE) applications. Despite prior work on MCL-PHA/Polycaprolactone (PCL) blends, optimal scaffold production and use as an alternative delivery route for controlled release of seeded cardiac progenitor cells (CPCs) in CTE applications in vivo has been lacking, We present herein applicability of MCL-PHA/PCL (95/5 wt%) blends fabricated as thin films with an improved performance compared to the neat MCL-PHA aiming to a) benefit from the material properties of natural and synthetic polymers, b) achieve controlled delivery and increase retention of delivered cells to the murine myocardium, c) extend the temporal window over which the release of labeled CPCs occurs compared to traditional direct injection techniques, and d) use 19F MRI/MRS to noninvasively detect, and longitudinally monitor the seeded scaffolds.
Polymer characterization confirmed the chemical structure and composition of the synthesized scaffolds, while thermal, wettability, and mechanical properties were also investigated and compared in neat and porous counterparts. In vitro cytocompatibility studies were performed using perfluorocrown-ether (PFCE)-nanoparticle-labeled murine cardiac progenitor cells (CPC), and studied using confocal microscopy and 19F MRS/MRI. Seeded scaffolds were implanted and studied in the post-mortem murine heart in situ, and in two additional C57BL/6 mice in vivo (using single-layered and double-layered scaffolds) and imaged immediately after and at 7 days post-implantation.
Superior MCL-PHA/PCL scaffold performance has been demonstrated compared to MCL-PHA through experimental comparisons of a) morphological data using scanning electron microscopy and b) contact angle measurements attesting to improved CPC adhesion, c) in vitro confocal microscopy showing increased SC proliferative capacity, d) mechanical testing that elicited good overall responses.
In vitro MRI results justify the increased seeding density, increased in vitro MRI signal, and improved MRI visibility in vivo, in the double-layered compared to the single-layered scaffolds. Histological evaluations (bright-field, cytoplasmic (Atto647) and nuclear (DAPI) stains) performed in conjunction with confocal microscopy imaging attest to CPC binding within the scaffold, subsequent release and migration to the neighboring myocardium, and to increased retention in the murine myocardium in the case of the double-layered scaffold.
Thus MCL-PHA/PCL blends possess tremendous potential for controlled delivery of CPCs and to maximize possible regeneration in myocardial infarction. |
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