Programmable 3D-printed tissues and organs using DNA ‘smart glue’

January 15, 2015

DNA glue holds together this 3-D printed gel, a precursor step to building tissues (credit: American Chemical Society)

University of Texas at Austin researchers  have created “smart glue” based on DNA that could one day be used to 3D-print tissues to repair injuries or even create organs.

They coated plastic (polystyrene or polyacrylamide) microparticles with 40 base pairs of DNA, forming gel-like materials that they could extrude from a 3D printer* to form solid shapes (up to centimeters in size). These were used as scaffolds to host growing cells within the matrix.

This first-of-its-kind demonstration, by Andrew D. Ellington and associates, of the inexpensive process is described in the new journal ACS Biomaterials Science & Engineering.

Programmable bots KurzweilAI has reported (such as here), researchers have already used  DNA to assemble nano-sized objects for biomedical applications. But making larger, visible objects has been cost-prohibitive and only limited designs and types of materials have been possible, the researchers note.

The researchers have demonstrated multicellular colonies of living cells growing in this colloidal gel. “More advanced DNA computation might also allow us to algorithmically determine the assembly process at the nano- to microscales,” the authors explain. “DNA circuits could mediate the conditional or algorithmic assembly of DNA-modified subunits into higher-order morphologies.

“Such processes have previously been demonstrated at the nanoscale with subunits such as DNA origami tiles, and our methods provide a potential for further scaling. For example, specific microparticle types could be added such that clusters are formed and then bridged (a hierarchical assembly process). Logical conditional operators, such as AND gates based on conformation switching could be used to locally determine if assembly is appropriate and permitted.”

Brightfield/fluorescence micrographs of multicellular colonies of living cells (human epithelial carcinoma) within colloidal gels composed of biocompatible hydrogel particles (credit: Peter B. Allen et al./ACS Biomaterials Science and Engineering)

*The researchers modified a Makerbot Industries Replicator 3D printer, adding a programmable syringe pump to control the dispense rate of a suspension of the microparticle-based gels.


Abstract of 3D Printing with Nucleic Acid Adhesives

By relying on specific DNA:DNA interactions as a “smart glue”, we have assembled microparticles into a colloidal gel that can hold its shape. This gel can be extruded with a 3D printer to generate centimeter size objects. We show four aspects of this material: (1) The colloidal gel material holds its shape after extrusion. (2) The connectivity among the particles is controlled by the binding behavior between the surface DNA and this mediates some control over the microscale structure. (3) The use of DNA-coated microparticles dramatically reduces the cost of DNA-mediated assembly relative to conventional DNA nanotechnologies and makes this material accessible for macroscale applications. (4) This material can be assembled under biofriendly conditions and can host growing cells within its matrix. The DNA-based control over organization should provide a new means of engineering bioprinted tissues.