Bioengineering has become increasingly complex and articulated. Using nothing more than light and Bio ink, scientists were able to directly print a structure similar to a human ear under the skin of mice.
The team used a healthy ear as a model and printed a 3D ear from a mirror image of it (layer of tissue over layer of tissue) directly on the back of a mouse.
All without a single surgical cut.
If you're thinking this is a bit disturbing, I can't blame you: however, the proof of concept is striking. The team showed that it is possible to build or reconstruct layers of tissue, even complex ones like an ear, without any surgical implant.
This means that it may one day be possible to repair an ear or other genetic or injury tissue damage directly at the injury site. I only saw things like that on Star Trek, and I considered them among the most advanced.
3D bioprinting, printing with light
The technology, 3D bioprinting based on digital light treatment (DLP), has gained a lot of attention over the past decade due to its versatility. In this interesting article of professionals you will find an exhaustive compendium of the subject and its stage of art.
The basic idea is to inject bioink containing cells into damaged tissue, then illuminate these “casts” to “activate” the cells in the bio ink. Depending on the cell type, they can then repair damaged spinal cords, nerve fibers or blood vessels.
In this study, published last week in Science Advances, the team has made a breakthrough in the technique. Using computer-aided design, they designed multiple shapes and fed the data into a digital device that generated an “array” of infrared rays.
These rays penetrate the tissues and practically build them up from the inside.
Within 20 seconds, the team was able to generate the basic shape of a human ear on a living mouse. The 3D printed ear maintained its sophisticated structure for more than a month.
No scalpels
I underline the fundamental importance of these studies, because the need for surgical interventions is the real current limit to tissue engineering.
Most of the fabric prototypes printed in 3D today it is made inside the laboratory, where scientists can maintain more direct control over tissue growth.
All attempted approaches have one thing in common: they ultimately require surgery. The tissue must be harvested and surgically inserted into the damaged site, and the surgery can cause damage to the implant and surrounding tissue. The consequences? From long hospital stays to repeat surgeries, right up to implant removal.
Magic wand
In the new approach that is the subject of this post I stated that scientists used "light" to 3D print an ear with bio ink. A bit like certain dental reconstructions, light is used to "activate" the bio ink cells and polymerize. Thus, in fact, a new fabric can be printed directly on another, or even under the skin.
Conventionally, ultraviolet or blue light is used to aid bioprinting, but has little ability to penetrate tissues. And it can also cause damage, burns to nascent and surrounding tissues.
Infrared light can instead activate the bioink and shine deep into the tissues. Because different spatial patterns of light can be adjusted to activate the bio ink differently, both within a layer and between layers, the team used the light like a chisel.
In the first test, in just 15 seconds the team printed a single layer of shell-shaped structures on the outside of the body. They then began 3D printing a wide variety of shapes: a three-layer cake, a gingerbread man (no joke), a starfish, and others.
3D print inside the body
After several tests, the team aimed at the big target: 3D printing a tissue directly IN the body. “It's a little more difficult,” the researchers explain, because the oxygen level inside a living organism can inhibit the cross-linking effect, meaning the ink may not become solid.”
The bottom line is that the team has found the right wavelengths. And in the end he generated a model of the ear to print in 3D, then filling it with chondrocytes, cells that make up the structure of the cartilage of the ear.
A better way to heal?
Building new fabrics isn't the only thing technology can do. Fabrics can also be repaired. In an additional study, the team found that the same approach can cure serious injuries.
In another test, the team printed a scaffold containing cells in mice suffering from muscle injury, and used light to activate the printed tissue. Within 10 days, the mice “showed significant wound closure” compared to a control group.
Putting it all together: It is the first time that scientists have been able to regenerate tissue within the body, while promoting wound healing, without any surgery.
Sure, there's a long way between “3D printing a human ear on the back of a mouse” and “regenerating an injured ear,” but the study shows it's possible.
