Fig. 4.

Cartilage applications of coaxial bioprinting. (A) For cartilage generation, Bella et al. developed a handheld coaxial extrusion printer, by miniaturizing the printer into a “biopen” pipette configuration (upper) that can be used for generation of cartilage on-site in a surgery (lower left). Upon implantation in a sheep model, favorable collagen formation was achieved (lower right). (B) Ahn et al. used an osteoblast precursor cell line as a middle layer in an alginate-based bioprinting system and identified an increase in mechanical properties as the core to sheath ratio increased in their constructs. Scale bars: (A) 50 μm. Adapted with permission from (A) [75] (upper) [39]; (lower) and (B) [80].