Researchers from the University of Texas at Austin say strands of DNA can act as a glue to bond together 3D printed materials which might someday be used to grow tissues and organs in a laboratory environment.
While scientists have used nucleic acids like DNA to assemble objects, for the most part, those objects have been on the nanoscale level and are so tiny they can't be seen with the naked eye. This research built larger, visible objects.
The team in Texas is working to develop DNA-coated nanoparticles – made from either polystyrene or polyacrylamide – in the hope that these inexpensive nanoparticles can be bound together to form gel-like materials which could be extruded with a 3D printer. And the materials also feature a distinct advantage – they're easy to see and can be manipulated without a microscope.
A study the team carried out also postulates that human cells might one day be grown in such gels, and the researchers say that's the first step necessary for the materials to be used as scaffolds to host the growth of human tissues.
The UT team, Peter B. Allen, Zin Khaing, Christine E. Schmidt and Andrew D. Ellington of the Department of Chemistry and Biochemistry, says this "DNA base pairing" can act as a smart glue to stick microparticles together to form the colloidal gels.
The researchers loaded a 3D printer and linked 2.3-μm-wide particles to short strands of fluorescent-labeled DNA, and they then used the semisolid material to 3D print a pyramid a few millimeters in height underwater.
While the result looks like a dollop of shaving cream, Ellington says the preliminary experiments were successful in creating human embryonic kidney cells inside the 3D printed gel. According to Ellington, this gel serves as the "simplest, most direct demonstration" of DNA base pairing and its ability to organize larger objects.
The custom-designed, complementary DNA strands would allow the sort of flexibility needed so that hospitals and labs could create organs which are grown with specific structures. The innovation lies in the method the researchers use to coat a nearly fluid-state collection of micro-beads in a sheath of fragments of DNA. The DNA sequences, which are complementary, are fragmented before being bound to the micro-beads. Once the beads are mixed together, they anneal and then form a gel-like, colloidal structure.
One problem is that DNA is actually quite fragile, and that means the conditions needed to allow DNA-coated beads to exist must be survivable to most types of cells.
To grow a structure as complex as a liver, a process would need to incorporate a wide range of different, but interdependent, cell types requiring not just the correct sequence of hormones and growth factors, but also needing a proper substrate for growth. The DNA interactions may not last long enough to grow an entire liver, but the researchers say that might be overcome by the use of synthetic nucleic acids – or XNAs – which may prove to be a considerably more stable version of DNA.
Imagine a scenario like this: your failing organ is scanned via an MRI and the scan is used to design large-scale structures like scaffolds. As the small-scale structure of liver tissues is roughly the same, a combination of beads necessary could be on hand and stored in a laboratory freezer. The scans would then be sent and the correct beads fed into a printer to be mixed with sample liver cells, and the entire mix would be deposited inside the gel before the organ could then be surgically implanted in the patient.
The research was published in full in the journal ACS Biomaterials Science & Engineering.