University of Birmingham Researchers develop new 3D Bioprinting Technique for Soft Materials

3D bioprinting

This new 3D bioprinting technique for soft materials offers a major step forward in the manufacture of artificial medical implants

3D bioprinting
Above: Researchers develop Suspended Layer Additive Manufacturing (SLAM) for soft material bioprinting/Image Credit: University of Birmingham

Researchers from the University of Birmingham, UK, have developed a new way of 3D Bioprinting with soft materials like gels and collagen. Researchers believe that this new technique can be used in repairing defects in the body.

3D Bioprinting

3D Bioprinting is the branch of 3D printing which prints three-dimensional tissues and organs from specially formulated bioinks. The bioinks are made from a mixture of chemicals, stem-cells, or living cells.

Suspended Layer Additive Manufacturing (SLAM)

Bioprinting is a complicated process and even more so with soft materials. The major challenge with soft material printing is that if they are not supported during the printing process, they simply sag and lose their shape.

The new technique developed by researchers addresses this very challenge. The new technique, called Suspended Layer Additive Manufacturing (SLAM), uses a polymer-based hydrogel in which the particles have been manipulated to create a self-healing gel. Liquids or gels can be injected directly into this medium and built up in layers to create a 3D shape.

The method offers an alternative to existing techniques that use gels that have been minced to form a slurry bath into which the printed material is injected. Called Freeform Reversible Embedding of Suspended Hydrogels (FRESH), these offer many advantages, but frictions within the gel medium can distort the printing.

3D bioprinting
Above: 3D bioprinting a scaffold by use of SLAM/Image Credit: Advanced Functional Materials

The entire process can be easily understood from the above schematic diagram. The diagram shows 3D bioprinting of a scaffold by the use of SLAM.

In figure A, the fluid‐gel print bed is created by shear cooling a hot agarose solution throughout the sol-gel transition which is then loaded into a container of suitable dimensions to support the scaffold. The bioinks are produced by the careful selection of hydrogel and cells and then mixing before adding to the bioprinter cartridges.

In figure B, the bioink is extruded within the self‐healing fluid bed and multiple cartridges may extrude different hydrogel layers forming an interface with the pre‐deposited bioinks for the creation of a multi-layered construct.

In figure C, crosslinking and cell media induce solidification and provide metabolites to the cell scaffold.

And lastly, in figure D, low shear washing with deionized water releases the construct from the supporting fluid gel.

The team lead, Professor Liam Grover from the School of Chemical Engineering recently published a study titled ‘Fabrication of Complex Hydrogel Structures Using Suspended Layer Additive Manufacturing (SLAM)’ in the Advanced Functional Materials journal which shows how the newly developed gel can be twisted, or sheared so they separate and still retain a connection between them. This interaction creates the self-healing effect, enabling the gel to support the printed material so objects can be built with precise detail, without leaking or sagging.

According to the lead researcher, Professor Liam Grover, “The hydrogel we have designed has some really intriguing properties that allow us to print soft materials in really fine detail. It has huge potential for making replacement biomaterials such as heart valves or blood vessels, or for producing biocompatible plugs, that can be used to treat bone and cartilage damage.”

SLAM can also be used to create objects made from two or more different materials so it could be used to make even more complex soft tissue types, or drug delivery devices, where different rates of release are required.

The study led by Liam Grover was co-authored by Jessica J. Senior, Megan E. Cooke, & Alan M. Smith.

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