Scientists demonstrate that they can control the properties of plant material grown in the laboratory, which could allow the production of wood products with little waste.
Due to deforestation, the world loses around 10 million hectares of forest – an area the size of Iceland – every year. At this rate, some researchers predict that the world’s forests could disappear in 100 to 200 years.
A hectare is an area equal to a square with sides of 100 meters, or 10,000 m2, and is mainly used in the measurement of land. One hectare contains approximately 2.47 acres and one acre equals approximately 0.405 hectares. 100 hectares make one square kilometer.
In an effort to provide an environmentally friendly and low-polluting alternative, researchers from MIT pioneered a tunable technique for generating wood-like plant material in a laboratory, which could allow someone to “grow” a wooden product like a table without the need to cut down trees, to transform wood, etc.
These researchers have now demonstrated that by adjusting certain chemicals used during the growth process, they can precisely control the physical and mechanical properties of the resulting plant material, such as its stiffness and density.
They also show that by using 3D bioprinting techniques, they can grow plant material into shapes, sizes, and forms that are not found in nature and cannot be easily produced in the atmosphere. using traditional farming methods.
“The idea is that you can grow these plant materials in exactly the form you need, so you don’t have to do any subtractive manufacturing after the fact, which reduces the amount of energy and waste. There’s a lot of potential to extend this and develop three-dimensional structures,” says lead author Ashley Beckwith, who recently graduated with a PhD.
Although still in its early stages, this research demonstrates that plant materials grown in the lab can be tuned to have specific characteristics, which could one day allow researchers to grow wood products with the exact characteristics needed for a particular application. , as a high strength to support the walls. of a house or certain thermal properties to heat a room more efficiently, says lead author Luis Fernando Velásquez-García, senior scientist at MIT’s Microsystems Technology Laboratories.
Jeffrey Borenstein, a biomedical engineer and group leader at the Charles Stark Draper Laboratory, joins Beckwith and Velásquez-García on paper. The research is published recently in the journal materials today.
To begin the process of growing plant material in the lab, researchers first isolate cells from the leaves of young Zinnia elegans plants. The cells are cultured in liquid medium for two days and then transferred to a gel-based medium, which contains nutrients and two different hormones.
Adjusting hormone levels at this stage of the process allows researchers to adjust the physical and mechanical properties of plant cells growing in this nutrient-rich broth.
“In the human body, you have hormones that determine the development of your cells and the emergence of certain traits. In the same way, by changing the concentrations of hormones in the nutrient broth, the plant cells react differently. By simply manipulating these tiny chemical amounts, we can cause quite dramatic changes in physical outcomes,” says Beckwith.
In a way, these growing plant cells behave almost like stem cells — researchers can give them clues to tell them what to become, Velásquez-García adds.
They use a 3D printer to extrude the cell culture gel solution into a specific structure in a petri dish, and incubate it in the dark for three months. Even with that incubation period, the researchers’ process is about two orders of magnitude faster than the time it takes for a tree to reach maturity, Velásquez-García says.
After incubation, the resulting cell-based material is dehydrated and then researchers evaluate its properties.
Characteristics similar to wood
They found that lower hormone levels produced plant material with more rounded open cells and lower density, while higher hormone levels resulted in the growth of plant material with smaller cell structures and more dense. Higher hormone levels also produced stiffer plant material; the researchers were able to grow plant material with a storage modulus (stiffness) similar to that of some natural woods.
Another objective of this work is to study what is called lignification in these plant materials grown in the laboratory. Lignin is a polymer that deposits in the cell walls of plants making them stiff and woody. They found that higher hormone levels in the growth medium cause more lignification, which would lead to plant material with more wood-like properties.
The researchers also demonstrated that using a 3D bioprinting process, plant material can be grown into a custom shape and size. Rather than using a mold, the process involves using a customizable computer-aided design file that is sent to a 3D bioprinter, which deposits the cell gel culture into a specific shape. For example, they were able to grow plant material in the form of a tiny evergreen tree.
Research like this is relatively new, says Borenstein.
“This work demonstrates the power that a technology at the interface between engineering and biology can bring to address an environmental challenge, leveraging advances originally developed for healthcare applications.” he.
Researchers also show that cell cultures can survive and continue to grow for months after printing, and that using a thicker gel to produce thicker plant material structures has no impact. on the survival rate of cells cultured in the laboratory.
“Possibility of personalization”
“I think the real opportunity here is to be optimal with what you use and how you use it. If you want to create an object that will serve a purpose, there are mechanical expectations to consider. This process really lends itself to customization,” says Velásquez-García.
Now that they have demonstrated the effectiveness of the tunability of this technique, the researchers want to continue experimenting in order to better understand and control cell development. They also want to explore how other chemical and genetic factors can direct cell growth.
They hope to assess how their method could be transferred to a new species. Zinnia plants do not produce wood, but if this method was used to make a commercially important tree species, such as pine, the process would have to be tailored to that species, Velásquez-García says.
Ultimately, he hopes this work can help motivate other groups to dive into this area of research to help reduce deforestation.
“Trees and forests are a great tool to help us manage climate change, so being as strategic as possible with these resources will be a societal necessity in the future,” adds Beckwith.
Reference: “Physical, mechanical and microstructural characterization of new plant materials, 3D printed, tunable and cultured in the laboratory, generated from Zinnia elegans cell cultures” by Ashley L. Beckwith, Jeffrey T. Borenstein and Luis F. Velásquez-García, March 7, 2022, .
This research is funded, in part, by the Draper Scholars Program.