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Three-dimensional printing of organs and tissues for transplants: Bio-inks

Biofabrication is a young industry that includes printing whole new organs for transplants. It sounds like something out of a sci-fi movie, but the real-life budding technology could one day make actual kidneys, livers, hearts and other organs for patients who desperately need them. In the American Chemical Society's (ACS') journal Langmuir, scientists are reporting new understanding about the dynamics of 3-D bioprinting that takes them a step closer to realizing their goal of making working tissues and organs on-demand, according to the study, "Study of Droplet Formation Process during Drop-on-Demand Inkjetting of Living Cell-Laden Bioink," published online July 8, 2014 in the American Chemical Society's (ACS') journal Langmuir.

Three-dimensional printing of organs and tissues for transplants: Bio-inks.
Photo by Oli Scarff/Getty Images

Yong Huang, and colleagues note that this idea of producing tissues and organs, or biofabricating, has the potential to address the shortage of organ donations. And biofabricated ones could even someday be made with a patient’s own cells, lowering the risk of rejection. Today, more than 120,000 people are on waiting lists for donated organs, with most needing kidney transplants. But between January and April of this 2014, just short of 10,000 people received the transplant they needed, says the July 30, 2014 American Chemical Society's news release, "Exploring 3-D printing to make organs for transplants."

How are organs printed out in three dimensions?

Yong Huang, Ph.D. is with the Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida. What's noteworthy for the lay reader interested in how organs and tissues are printed in three dimensions is that there are a few different biofabricating methods, but inkjet printing has emerged as a frontrunner. It’s been used to print live cells, from hamster ovary cells to human fibroblasts, which are a common type of cell in the body. But no studies had been done to really understand how biological inks behave when they’re dispensed through printer nozzles. Huang’s team set out to fill that gap.

The researchers in this new study tested bioinks with different concentrations of mouse fibroblasts plus a hydrogel made out of sodium alginate. They discovered, among other findings, that adding more cells in the material reduces both the droplet size and the rate at which it gets dispensed. The new results will help scientists move forward with this promising technology. The authors acknowledge funding from the National Science Foundation.

What biofabrication of organs using 3D printing entails

If you take a look at the abstract of the study, you'll see that biofabrication offers a great potential for the fabrication of three-dimensional living tissues and organs by precisely layer-by-layer placing various tissue spheroids as anatomically designed. Inkjet printing of living cell-laden bioink is one of the most promising technologies enabling biofabrication, and the bioink printability must be carefully examined for it to be a viable biofabrication technology.

So the study's abstract informs the reader that in this research, the cell-laden bioink droplet formation process has been studied in terms of the breakup time, droplet size and velocity, and satellite formation using a time-resolved imaging approach. The bioink has been prepared using fibroblasts and sodium alginate with four different cell concentrations: without cells, 1 × 106, 5 × 106, and 1 × 107 cells/mL to appreciate the effect of cell concentration on the droplet formation process.

Bioink droplet formation process

If scientists are printing out organs and other tissues of the body, they use bioink to print out the parts in three dimensions. The study's abstract explains that the bioink droplet formation process is compared with that during the inkjetting of a comparable polystyrene microbead-laden suspension under the identical operating conditions to understand the effect of particle physical properties on the droplet formation process. Researchers found that as the cell concentration of bioink increases, the droplet size and velocity decrease, the formation of satellite droplets is suppressed, and the breakup time increases. In this study researchers also found that compared to the hard bead-laden suspension, the bioink tends to have a less ejected fluid volume, lower droplet velocity, and longer breakup time, the study's abstract explains. Download the full-text article here.

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