Speaker
Description
Recreating the spatial and functional heterogeneity of native tissues remains a central challenge in tissue engineering. Native tissues exhibit complex gradients in mechanical properties, extracellular matrix (ECM) composition, and biochemical cues, which are difficult to replicate using conventional biofabrication methods. Extrusion-based embedded 3D bioprinting techniques, such as Freeform Reversible Embedding of Suspended Hydrogels (FRESH), enable high-fidelity deposition of multiple bioinks but are limited by the number of extruders and resolution id dependent on nozzle diameter. Conversely, light-based bioprinting provides precise spatiotemporal control of photochemistry for tuning mechanics and biochemistry but struggles to integrate multiple biomaterials. To address these limitations, we developed Light-Pipe FRESH 3D bioprinting, a hybrid approach integrating optical fiber-delivered photochemistry with embedded extrusion printing. By rastering light from a fiber-optic cannula within a photocrosslinkable support bath, Light-Pipe FRESH achieves programmable modulation of crosslink density, biochemical patterning, and multi-material integration within a single construct.
Light-Pipe FRESH integrates a custom-designed optical pathway into an open-source FRESH 3D bioprinter. A high-intensity UV light source (365–405 nm) was filtered, coupled into a 100 µm fiber-optic cannula (NA = 0.1), and rastered within a photocrosslinkable gelatin methacryloyl (GelMA)-based granular support bath containing photoinitiator (LAP) and photoabsorber (tartrazine). GelMA microspheres (~10 µm) were synthesized via complex coacervation and combined with a GelMA-based photofiller. Rheology confirmed yield-stress, shear-thinning, and self-healing properties essential for embedded printing, while photorheology quantified controllable light-induced gelation. Scaffolds with programmable mechanical domains were fabricated by varying print speed (20–40 mm/min) or light power (6–10 µW). C2C12 myoblast-laden collagen hydrogels were cast onto printed scaffolds and cultured for up to 21 days. Remodeling, compaction, and contractility were assessed via confocal microscopy, custom microindentation, calcium imaging, and electrical stimulation. Multi-material scaffolds combining collagen and GelMA mimicked myotendinous junctions, and spatial photoconjugation demonstrated programmable biochemical patterning.
Light-Pipe FRESH enables precise spatial control over scaffold architecture and mechanical properties. Modulating print speed tuned the effective elastic modulus from approximately 5 to 30 kPa, allowing creation of scaffolds with stiffness gradients. Myoblast-seeded scaffolds exhibited stiffness-dependent remodeling: softer scaffolds showed greater compaction and matrix remodeling, whereas stiffer scaffolds preserved architecture and promoted aligned myotube fusion. Calcium imaging and field stimulation revealed domain-dependent contractility, with softer regions exhibiting higher contractile displacement. Dual-head bioprinting combining light-pipe photopatterning of extrused collagen filaments were used to engineer myotendinous junction-like scaffolds, integrating collagen-based tendon regions with GelMA-based muscle domains. Multi-wavelength photochemistry and spatial photoconjugation enabled programmable biochemical heterogeneity within a single construct. In Summary, Light-Pipe FRESH combines high-fidelity multi-material deposition with on-demand spatiotemporal control photochemistry, offering a versatile platform for engineering tissue constructs functional gradients in mechanical, chemical, and biological properties.