No abstract

In search for novel biomimetic scaffolds for application in vascular tissue engineering, we evaluated a series of fibrous scaffolds prepared by coelectrospinning tertiary blends of poly(lactide-co-glycolide) (PLGA), gelatin, and elastin (PGE). By systematically varying the ratios of PLGA and gelatin, we could fine-tune fiber size and swelling upon hydration as well as the mechanical properties of the scaffolds. Of all PGE blends tested, PGE321 (PLGA, gelatin, elastin v/v/v ratios of 3:2:1) produced the smallest fiber size (317 ± 46 nm, 446 ± 69 nm once hydrated) and exhibited the highest Young's modulus (770 ± 131 kPa) and tensile strength (130 ± 7 kPa). All PGE scaffolds supported the attachment and metabolization of human endothelial cells (ECs) and bovine aortic smooth muscle cells (SMCs) with some variances in EC morphology and cytoskeletal spreading observed at 48 h postseeding, whereas no morphologic differences were observed at confluence (day 8). The rate of metabolization of ECs, but not of SMCs, was lower than that on tissue culture plastic and depended on the specific PGE composition. Importantly, PGE scaffolds were capable of guiding the organotypic distribution of ECs and SMCs on and within the scaffolds, respectively. Moreover, the EC monolayer generated on the PGE scaffold surface was nonthrombogenic and functional, as assessed by the basal and cytokine-inducible levels of mRNA expression and amidolytic activity of tissue factor, a key player in the extrinsic clotting cascade. Taken together, our data indicate the potential application of PGE scaffolds in vascular tissue engineering.

A novel electroactive silsesquioxane precursor, N-(4-aminophenyl)-N'-(4'-(3-triethoxysilyl-propyl-ureido) phenyl-1,4-quinonenediimine) (ATQD), was successfully synthesized from the emeraldine form of amino-capped aniline trimers via a one-step coupling reaction and subsequent purification by column chromatography. The physicochemical properties of ATQD were characterized using mass spectrometry as well as by nuclear magnetic resonance and UV-vis spectroscopy. Analysis by cyclic voltammetry confirmed that the intrinsic electroactivity of ATQD was maintained upon protonic acid doping, exhibiting two distinct reversible oxidative states, similar to polyaniline. The aromatic amine terminals of self-assembled monolayers (SAMs) of ATQD on glass substrates were covalently modified with an adhesive oligopeptide, cyclic Arg-Gly-Asp (RGD) (ATQD-RGD). The mean height of the monolayer coating on the surfaces was approximately 3 nm, as measured by atomic force microscopy. The biocompatibility of the novel electroactive substrates was evaluated using PC12 pheochromocytoma cells, an established cell line of neural origin. The bioactive, derivatized electroactive scaffold material, ATQD-RGD, supported PC12 cell adhesion and proliferation, similar to control tissue-culture-treated polystyrene surfaces. Importantly, electroactive surfaces stimulated spontaneous neuritogenesis in PC12 cells, in the absence of neurotrophic growth factors, such as nerve growth factor (NGF). As expected, NGF significantly enhanced neurite extension on both control and electroactive surfaces. Taken together, our results suggest that the newly electroactive SAMs grafted with bioactive peptides, such as RGD, could be promising biomaterials for tissue engineering.

Enhancing the maturation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) will facilitate their applications in disease modeling and drug discovery. Previous studies suggest that cell alignment could enhance hPSC-CM maturation; however, the robustness of this approach has not been well investigated. To this end, we examined if the anisotropic orientation of hPSC-CMs imposed by the underlying aligned fibers within a 3D microenvironment could improve the maturation of hPSC-CMs. Enriched hPSC-CMs were cultured for two weeks on Matrigel-coated anisotropic (aligned) and isotropic (random) polycaprolactone (PCL) fibrous scaffolds, as well as tissue culture polystyrenes (TCPs) as a control. As expected, hPSC-CMs grown on the two types of fibrous scaffolds exhibited anisotropic and isotropic orientations, respectively. Similar to cells on TCPs, hPSC-CMs cultured on these scaffolds expressed CM-associated proteins and were pharmacologically responsive to adrenergic receptor agonists, a muscarinic agonist, and a gap junction uncoupler in a dose-dependent manner. Although hPSC-CMs grown on anisotropic fibrous scaffolds displayed the highest expression of genes encoding a number of sarcomere proteins, calcium handling proteins and ion channels, their calcium transient kinetics were slower than cells grown on TCPs. These results suggest that electrospun anisotropic fibrous scaffolds, as a single method, have limited effect on improving the maturation of hPSC-CMs.