Tissue development is guided by gradients of biomolecules that direct the growth, migration, and differentiation of cells. Biomedical engineers are interested in recreating these developmental gradients in adults to aid the growth of new tissue in areas that have sustained damage. Now, researchers are one step closer to this goal thanks to the creation of new 3D-printed scaffolds that enable researchers to release biomolecules into the body with exceptional control.
The scaffolds are the creation of NIBIB grantee Michael McAlpine, Ph.D., the Benjamin Mayhugh Associate Professor of Mechanical Engineering at the University of Minnesota. The work is described in the August 12, 2015 issue of Nano Letters.1
Above is a movie that shows an example of how the novel scaffolds are created. First, several layers of a gel that can be implanted into the body are printed onto a solid surface. Next, tiny capsules containing red food dye—an easy-to-visualize substitute for biomolecules—are printed on top of the gel. This is followed by additional layers of gel and another layer of capsules, this time filled with blue food dye to represent a different type of biomolecule. The layering pattern continues until the gel achieves a predetermined height.
A critical component of each embedded capsule is the unique shell that surrounds it. These shells—which are invisible to the naked eye—contain tiny gold rods that heat up when a laser is directed at them, causing the capsule to burst and release its contents. How hot the gold rods become depends on matching their size with the color of the laser light used. Thus, researchers can control when different types of biomolecules are released from the gel by varying the shell coatings of the capsules and by employing different colored lasers. Because the capsules are 3D-printed, they can be arranged within the gel in practically any design that can be created on a computer. They can also be filled with a wide variety of biomolecules.
“One can imagine filling the capsules with molecules such as medications, nucleic acids, enzymes, growth factors, cell markers and other functional proteins,” says McAlpine.
Given the non-specific nature of the gel, McAlpine says it could be used to facilitate regeneration in a wide variety of tissues, including blood vessels and even the heart.
“A particularly far-reaching example would be the ability to guide the vascularization of artificial tissue by 3D printing capsules alongside stem cells,” says McAlpine.
“NIBIB’s goal is to help develop enabling technologies that could have big impacts on important medical problems,” says Rosemarie Hunziker, Ph.D., program director for Tissue Engineering at NIBIB. “Tools like this gel give us many options for designing “tissues to order” for a variety of needs.”
In addition to fostering new tissue growth, the scaffolds have the potential to be used as a way to deliver medication to a specific area in the body with high precision.
This work was supported in part by the National Institute of Biomedical Imaging and Bioengineering grant # EB020537