Introduction: The unmet need of autologous vascular grafts in Ischemic heart disease and peripheral vascular disease with underlying atherosclerosis necessitates the exploration of artificial vascular conduits. The principles of vascular tissue engineering outlined over the last decade, guides through the fabrication of biopolymer based vascular scaffolds in this study. Favorable hemocompatibility, biological interaction and degradation profile are the decisive factors for polymer selection and processing[1],[2].
Materials and Methods: 2,5-Dihydro-2,5-dimethoxyfuran (DMDF) cross-linked tubular scaffolds were fabricated from Silk fibroin and Chitosan blend by extrusion in Sodium hydroxide bath[3],[4]. The scaffolds were then subjected to structural, mechanical and chemical analysis followed by in vitro seeding of Human mesenchymal stem cells (hMSC) and immunolabeling for endothelial differentiation markers. In vivo studies were performed to elucidate the biocompatibility and temporal degradation.
Results and Discussion: DMDF mediated temperature controlled gelation of chitosan could be the possible mechanism underlying the cross-linking of amine moieties in silk-chitosan blend in our experiment. Porous tubular scaffold demonstrated average pore size of 143 ±15.6 µm on SEM images which reduces on cross-linking to around 110 ± 8.3 µm, sufficient enough for in-growth of peri-scaffold tissue and transmural endothelization with angiogenesis[5],[6].
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FTIR analysis showed characteristic peaks of newly formed C=N and C-N bond on crosslinking. Blending of chitosan and silk resulted in loss of the typical peak of chitosan at 10o and appearance of broad amorphous hump on XRD analysis, suggestive of molecular interaction between the two. A strong diffraction peak at ~20.4o substantiates the β-sheet formation on crosslinking of sample[7],[8]. On Nano-indentation studies, uncrosslinked sample showed greater non-reversible deformation (2270±19.3 nm) as well as permanent displacement (2160±27.4 nm) on application of equal load when compared to crosslinked sample with non-reversible and permanent displacement of 607±11.4 nm and 516±14.6 nm respectively[9].
The scaffold was found hemocompatible on clotting time, prothrombin time and SEM imaging for platelet adsorption. Histological studies revealed minimal inflammatory reaction and favorable tissue remodeling with the gradual replacement of the scaffold. In vitro cell seeding shows hMSC differentiation into endothelial cell like lineage with positive immunocytochemical profiling for PECAM-1 and von willebrand factor.
Conclusion: Silk-Chitosan blend as a potential alternative to existing biopolymers for blood vessel engineering offers adequate mechanical properties along with its promising biocompatibility. Primary in vitro and in vivo studies warrant elaborative long term assessment for intended application.
IIT Kharagpur has been acknowledged for providing infrastructural facility.
References:
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