Conventional synthesis routes for thermoplastic polyurethanes (TPUs) still require the use of isocyanates and tinbased catalysts, which pose considerable safety and environmental hazards. To reduce both the ecological footprint and human health dangers for nonwoven TPU scaffolds, it is key to establish a green synthesis route, which eliminates the use of these toxic compounds and results in biocompatible TPUs with facile processability. In this study, we developed high-molecular-weight nonisocyanate polyurethanes (NIPUs) through transurethanization of 1,6hexanedicarbamate with polycarbonate diols (PCDLs). Various molecular weights of PCDL were employed to maximize the molecular weight of NIPUs and consequently facilitate their electrospinnability. The synthesized NIPUs were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The highest achieved molecular weight (M w ) was 58,600 g/mol. The NIPUs were consecutively electrospun into fibrous scaffolds with fiber diameters in the submicron range, as shown by scanning electron microscopy (SEM). To assess the suitability of electrospun NIPU mats as a possible biomimetic load-bearing pericardial substitute in cardiac tissue engineering, their cytotoxicity was investigated in vitro using primary human fibroblasts and a human epithelial cell line. The bare NIPU mats did not need further biofunctionalization to enhance cell adhesion, as it was not outperformed by collagen-functionalized NIPU mats and hence showed that the NIPU mats possess a great potential for use in biomimetic scaffolds.
3D bioprinting is
an emerging biofabrication strategy using bioinks,
comprising cells and biocompatible materials, to produce functional
tissue models. Despite progress in building increasingly complex objects,
biological analyses in printed constructs remain challenging. Especially,
methods that allow non-invasive and non-destructive evaluation of
embedded cells are largely missing. Here, we implemented Raman imaging
for molecular-sensitive investigations on bioprinted objects. Different
aspects such as culture formats (2D, 3D-cast, and 3D-printed), cell
types (endothelial cells and fibroblasts), and the selection of the
biopolymer (alginate, alginate/nanofibrillated cellulose, alginate/gelatin)
were considered and evaluated. Raman imaging allowed for marker-independent
identification and localization of subcellular components against
the surrounding biomaterial background. Furthermore, single-cell analysis
of spectral signatures, performed by multivariate analysis, demonstrated
discrimination between endothelial cells and fibroblasts and identified
cellular features influenced by the bioprinting process. In summary,
Raman imaging was successfully established to analyze cells in 3D
culture in situ and evaluate them with regard to the localization
of different cell types and their molecular phenotype as a valuable
tool for quality control of bioprinted objects.
Electrospinning has become a well-established method to create nanofibrous meshes for tissue-engineering applications. The incorporation of natural extracellular components, such as electrospun pure collagen nanofibers, has proven to be particularly...
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