In Vivo Tracking and ¹H/¹⁹F Magnetic Resonance Imaging of Biodegradable Polyhydroxyalkanoate/Polycaprolactone Blend Scaffolds Seeded with Labeled Cardiac Stem Cells

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. 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-nanoparticle-labeled murine CPCs and studied using confocal microscopy and F magnetic resonance spectroscopy and magnetic resonance imaging (MRI). Seeded scaffolds were implanted and studied in the postmortem 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 postimplantation. 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, and (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 (4',6-diamidino-2-phenylindole) stains] performed in conjunction with confocal microscopy imaging attest to CPC binding within the scaffold, subsequent release and migration to the neighboring myocardium, and 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 for maximizing possible regeneration in myocardial infarction.

Recent Advances in Bioplastics: Application and Biodegradation

“…The cardiac regenerative potential of mclPHA to promote the proliferation of neonatal ventricular rat myocytes was demonstrated by Bagdadi and colleagues [170]. Constantinides and colleagues [171] used a PHA/PCL blend for cardiac stem cell cultivation and implantation in animal models of infarcted mice, thereafter seeing a critical improvement of these scaffold for cardiac cell regeneration in vitro and in vivo. It looks like both biocompatibility and mechanical properties are determinant in promoting the cardiac regeneration mediated by these scaffolds.…”

Toward a Closed Loop, Integrated Biocompatible Biopolymer Wound Dressing Patch for Detection and Prevention of Chronic Wound Infections

“…The number average molecular weight (M n ), and the weight average molecular weight (M w ) of the polymer were determined using gel permeation chromatography (GPC, Model 1260 Infinity GPC, Agilent Technologies) as described in Constantinides et al (2018) .…”

“…MCL-PHAs have monomers consisting of 6–14 carbons such as polyhydroxyundecenoate, PHU and Poly(3-hydroxyoctanoate), P(3HO) ( Dufresne and Vincendon, 2000 ; Rai et al, 2011 ) and these polymers are elastomeric in nature with low crystallinity, low tensile strength, low melting point and high elongation at break ( Nomura and Taguchi, 2007 ). The degradation products of PHAs (hydroxyl acids) have almost no cytotoxicity as compared to the degradation products of synthetic polymers (lactic acid in case of PLA) which leads to low immunogenicity ( Rai et al, 2011 ; Basnett et al, 2018 ; Constantinides et al, 2018 ). This is because the hydroxyl acids such as hydroxybutyric acid, hydroxyoctanoic acid are natural metabolites.…”

Natural Biomaterials for Cardiac Tissue Engineering: A Highly Biocompatible Solution

“…Introduction of PCL resulted in a reduction in hydrophobicity, thus enhancing cell adhesion. Cells were tracked in-vivo via ( 19 F) MRS, showing a reduction in cell density on the scaffold across a 9-day period perhaps as a result of the cells detaching from the scaffold and entering into the myocardium (267).…”

“…SV highlights the Sinus of Valsalva (265). (D) Solvent cast film derived from MCL-PHAs that has been utilized for LV cardiac regeneration (266,267).…”