Smart Engineering of Complex Structural Tissue Constructs in 3D Bioprinting Via Photoinduced Nanoparticle-Mediated Spheroid Elimination

This study demonstrates a “sacrificial spheroid” concept for creating hollow features in spheroid-assembled tissue constructs to address a key 3D bioprinting bottleneck: forming small, complex voids suitable for vascularization. HEK293T cell spheroids were formed with photoactive nanoparticles (LaB6 or Ti3AlC2) synthesized by femtosecond laser ablation/fragmentation in liquids to produce ultrapure photothermal sensitizers with strong NIR absorption. Under 808 nm irradiation, nanoparticle-loaded spheroids selectively overheated (targeting ~42–50°C) and underwent localized cell death primarily within the sacrificial spheroid, while neighboring nanoparticle-free spheroids remained largely viable. The work shows that photothermal treatment increased the stiffness of NP-loaded spheroids (Young’s modulus rising from ~4 kPa to >8 kPa at 50°C), which markedly improved the ability to mechanically remove the central sacrificial spheroid from a flower-like spheroid assembly, leaving a central void. Ti3AlC2 outperformed LaB6 in preserving surrounding spheroid integrity, likely due to lower dark toxicity and reduced secondary effects on neighboring cells. The results support a route to engineering hollow/vascularizable geometries in spheroid-based bioprinting by combining nanoparticle-enabled selective photothermal ablation with mechanically facilitated removal of sacrificial elements.