Every year, the world loses about 10 million hectares of forest to deforestation - an area the size of Iceland. At this rate, some scientists predict the world's forests could be gone within 100 to 200 years.
To provide an environmentally friendly and low-waste alternative. Earlier last year, researchers at MIT were growing structures made from wood-like plant cells in the lab, hinting at the possibility of producing more efficient biomaterials.
At the time, the researchers said it takes a lot of time to make a wooden table. Plant a tree, cut it down, transport it, mill it ...... It's a decades-long process. Senior author Luis Fernando Velásquez-García, chief scientist at MIT's Microsystems Technology Laboratory, suggested a simpler solution, "If you want a table, then you should grow a table! ."
And now. This research has been taken a step further. Researchers at the Massachusetts Institute of Technology have pioneered a tunable technique for generating wood-like plant material in the lab, which could allow people to "grow" wood products like tables without cutting down trees and processing wood.
The researchers have shown that by adjusting certain chemicals used in the growth process, they can precisely control the physical and mechanical properties of the resulting plant material, such as stiffness and density.
They have also shown that with 3D bioprinting, it is possible to grow plant material in shapes, sizes, and forms that do not exist in nature and that are difficult to produce using traditional agricultural methods.
"The idea is that you can grow this plant material in the shape you need, so you don't have to do any subtractive manufacturing after the fact, which reduces energy and waste. There's a lot of potential to scale it up and develop it into three-dimensional structures," said Ashley Beckwith, the paper's first author and a recent PhD graduate.
Though still in the early stages, this research shows that laboratory-grown plant material can be adapted to have specific properties, which could one day allow researchers to grow wood products with the exact properties needed for specific applications. Such as a material strong enough to support the walls of a house, or a material with specific thermal properties that can heat a room more efficiently. Luis Fernando Velásquez-García explains.
Joining Beckwith and Velásquez-García in writing the paper is Jeffrey Borenstein, a biomedical engineer in Charles Stark Draper's laboratory and team leader. The research was published May 25 in the journal Materials Today.
To begin growing the plant material in the lab, the researchers first isolated cells from the leaves of Zinnia elegans seedlings. The cells were first cultured in liquid medium for two days and then transferred to gel medium, which contains nutrients and two different hormones.
Adjusting hormone levels during this process allowed the researchers to regulate the physical and mechanical properties of the plant cells grown in the nutrient-rich medium.
"In the human body, your growth hormone determines how your cells develop and how certain features form. Similarly, by changing the concentration of hormones in a nutrient solution, plant cells respond differently. Just by controlling these tiny chemical amounts, you can cause quite a change in the physical outcome," says Beckwith.
Velásquez-García added that, in a way, these growing plant cells behave almost like stem cells - the researchers can give them hints about what they are going to become.
They used a 3D printer to extrude a solution of cell culture gel into a petri dish of a specific structure and let it incubate in the dark for three months. Even with this incubation period, the process is two orders of magnitude faster than the time it takes for a tree to grow to maturity, says Velásquez-García. After incubation, the resulting cellular material is dehydrated, and then the researchers further evaluate its properties.
The researchers found that lower hormone levels produced rounder, more open, and less dense cellular plant material. Higher hormone levels, on the other hand, led to the growth of plant material with smaller, denser cell structures. Higher hormone levels also produced harder plant material. The researchers were able to grow plant material with properties similar to those of some natural woods.
Another goal of this work was to study lignification in these lab-grown plant materials. Lignin is a polymer deposited in the cell walls of plants that gives them their rigidity and woodiness. They found that higher levels of the hormone in the growth medium led to more lignification, which would result in plant material with more wood-like properties.
The researchers demonstrated that with the 3D bioprinting process, plant material can be grown in customized shapes and sizes. Instead of using molds, the process uses customizable computer-aided design files that are fed into a 3D bioprinter that deposits cell gel cultures into specific shapes. For example, they were able to finalize the plant into the shape of a small evergreen tree.
Borenstein said this type of research is relatively new. He added: "Utilizing technological advances initially developed for healthcare applications, this research proves that a technology somewhere between engineering and biology can address environmental challenges. "
The researchers also showed that cell cultures can survive and continue to grow for months after printing, and that the use of thicker gels to produce thicker plant material structures doesn't affect the viability of lab-cultured cells.
"I think the real opportunity here is to optimize what you use and how you use it. If you're trying to create an object to be used for a certain purpose, then you need to think about the mechanical performance expectations. The process really lends itself to customization ." Velásquez-García said.
Now that the effective tunability of this technique has been demonstrated, the researchers want to continue their experiments to better understand and control cell development. They also want to explore how other chemical and genetic factors direct cell growth.
The researchers want to evaluate how to transfer their approach to a new species. Velásquez-García said that (Zinnia elegans) does not produce wood, but if the method were used to produce a commercially important species, such as pine, it would need to be customized for that species.
Ultimately, he hopes that this work will help inspire other groups to delve deeper into this area to help reduce deforestation.
"Trees and forests are an excellent tool to help us combat climate change. So planning strategically to utilize these resources as much as possible will be a societal necessity for the future." Beckwith added.
This research was funded in part by the Draper Scholars Program.