Bioprinting of aptamer-based programmable bioinks to modulate multiscale microvascular morphogenesis in 4D

Dynamic growth factor presentation influences how individual endothelial cells assemble into complex vascular networks. Here, we developed programmable bioinks that facilitate dynamic VEGF presentation to guide vascular morphogenesis within 3D-bioprinted constructs. We leveraged aptamers high affinity for rapid VEGF sequestration in spatially confined regions and utilized aptamer-complementary sequence (CS) hybridization to tune VEGF release kinetics temporally, days after bioprinting. We show that spatial resolution of programmable bioink, combined with CS-triggered VEGF release, significantly influences alignment, organization, and morphogenesis of microvascular networks in bioprinted constructs. The presence of aptamer-tethered VEGF and the generation of instantaneous VEGF gradients upon CS-triggering restricted hierarchical network formation to the printed aptamer regions at all spatial resolutions. Network properties improved as the spatial resolution decreased, with low-resolution designs yielding the highest network properties. Specifically, CS-treated low-resolution designs exhibited significant vascular network remodeling, with increase in vessel density(1.35-fold), branching density(1.54-fold), and average vessel length(2.19-fold) compared to non-treated samples. Our results suggests that CS acts as an external trigger capable of inducing time-controlled changes in network organization and alignment on-demand within spatially localized regions of a bioprinted construct. We envision that these programmable bioinks will open new opportunities for bioengineering functional, hierarchically self-organized vascular networks within engineered tissues.