Engineering polystyrene microtube-embedded composite hydrogels for tunable vascular morphogenesis

Establishing functional vascular systems within three-dimensional tissue constructs is crucial for their successful use in disease modeling, drug testing, and regenerative medicine. Current methods face challenges in creating small- to medium-sized microvessels and precisely controlling key vascular features, such as vascular density, vessel diameter, and network connectivity, to generate hierarchical, multiscale vascular systems that mimic natural functionality. In this study, we developed a composite hydrogel incorporating polystyrene microtubes (PS-MTs) to improve control over microvessel morphogenesis and functionality. PS-MTs were fabricated via core-sheath electrospinning, fragmented by ultrasonication, and incorporated into fibrin gels. Scanning electron microscopy revealed both micro- and nano-topographic features of the embedded PS-MT fragments. Endothelial cells (ECs) and fibroblasts were cocultured in this composite hydrogel under interstitial flow conditions for 7 d. The PS-MTs exhibited excellent biocompatibility, and the composite hydrogel showed no adverse effects on the cell viability of EC-fibroblast cocultures on chip. Fluorescence and confocal microscopy revealed a 40% increase in vascular area fraction and more than a twofold increase in average vessel diameter in the high PS-MT density group (>4%) compared to controls. Perfusion assays using a fluorescent microbead suspension demonstrated a 71% increase in the field-average speed of microbead flow, indicating enhanced perfusability, consistent with the observed morphological changes. Additionally, permeability assays showed a 66% decrease in dextran permeability, suggesting improved vascular barrier integrity. In conclusion, incorporating PS-MTs into fibrin hydrogels effectively modulated the structural organization and functional maturation of microvascular networks in a dose-dependent manner. This strategy holds promises for advancing the biofabrication of functional, multiscale vascular networks for engineered tissues. By tuning PS-MT density within the composite hydrogel, this approach enables local modulation of vessel morphogenesis, offering a flexible strategy for engineering application-specific vascular architectures.