Emerging advances in bioprinting bring the potential to 3D print replacement human organs closer to reality. A recently developed open-source bioprinting method enables production of the complex vasculature needed to supply nutrients to densely populated tissues. Now a technique pioneered at Carnegie Mellon University enables 3D bioprinting of tissue scaffolds based on collagen and offers scope for fabricating a full-sized, adult human heart.

The collagen scaffolds needed to print and support human heart components are produced with the Freeform Top and side views of FRESH-printed collagen heart valve. Source: A. Lee et al.Top and side views of FRESH-printed collagen heart valve. Source: A. Lee et al.Reversible Embedding of Suspended Hydrogels (FRESH) method, which allows collagen layers to be deposited within a support bath of gel. The material is deposited layer-by-layer to form a solid structure, after which the support gel is heated to room temperature to effect its removal.

The FRESH technology was used to print a neonatal-scale human heart from collagen. The mechanical integrity and function of collagen constructs at adult human scale was also demonstrated by printing a tri-leaflet heart valve 28 mm in diameter and a model of the left ventricle of the heart using human stem cell-derived cardiomyocytes.

The researchers developed open-source designs for the FRESH printing process, which is also applicable to 3D bioprinting with fibrin, alginate and hyaluronic acid. A research paper on the technology is published in Science.

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