by akronbiotech

Three-dimensional bioprinting has become a leading technique for the fabrication of 3D scaffolds with biomedical applications. In particular, tissue engineering relies on the use of a tissue scaffold for the formation of new viable, healthy tissue.

Researchers at Imperial College London recently presented a novel cryogenic 3D printing method that allows for generation of very soft materials. Traditionally, generation of extremely soft 3D structures has been a challenge due to the inability of these materials to withstand their own weight, let alone withstand the additional loading of cells. To overcome this hurdle, the authors exploited the liquid to solid phase change of a composite hydrogel ink. This was achieved by rapidly cooling the ink solution, made of poly(vinyl) alcohol (PVA) and Phytagel, below its freezing point using a dry ice and isopropanol bath. This approach successfully created complex 3D structures with an average compressive stiffness of O(1) kPa, mimicking the mechanical properties of soft human tissue.

To evaluate the biocompatibility of the printed constructs, the scaffolds were coated with attachment factors collagen, poly-L-lysine, and gelatin. The scaffolds were then seeded with dermal fibroblasts, cells that generate connective tissue in the skin. After 72 hours in culture, cell viability was highest for the collagen-coated scaffolds with 97% live cells.

(a) Cylindrical pore microstructure, adapted from “Hollister, SJ (2005) Porous scaffold design for tissue engineering. Nature materials” and (b) 8 unit cells printed. Thawed printed 8 cell
structure in (c) isometric view and (d) side view. Scale bars, (c) 10 mm and (d) 5 mm.

The softness and biocompatibility of the material generated by this bioprinting technique present new opportunities to fabricate soft human tissue like that of the lung and brain. The article titled, “Cryogenic 3D Printing of Super Soft Hydrogels,” was published in Scientific Reports.

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