A new way to deliver life-saving treatments to plants

Microneedles made of silk-based material can target plant tissues for delivery of micronutrients, hormones, or genes.

MIT scientists have come up with a new approach to help advance the fundamental understanding of plant biology and accelerate plant engineering. They have developed a method to deliver life-saving treatments to plants ravaged by threatening diseases.

Their method uses an array of microneedles called phytoinjectors. These phytoinjectors are made of a silk-based biomaterial, that is capable of delivering nutrients, drugs, or other molecules to specific parts of the plant

Can be made in a variety of sizes and shapes, these phytoinjectors can be injected to a plant’s roots, stems, or leaves, or into its xylem or phloem.

Graduate student Yunteng Cao said“We wanted to solve the technical problem of how you can have precise access to the plant vasculature. This would allow researchers to inject pesticides, for example, that would be transported between the root system and the leaves. Existing approaches use needles that are very large and very invasive, and that results in damaging the plant. To find a substitute, they built on previous work that had produced microneedles using silk-based material for injecting human vaccines.”

Postdoc Eugene Lim at MIT said, “We found that adaptations of a material designed for drug delivery in humans to plants were not straightforward, due to differences not only in tissue vasculature but also in fluid composition. The microneedles designed for human use were intended to biodegrade naturally in the body’s moisture. Still, plants have far less available water, so the material didn’t dissolve and was not useful for delivering the pesticide or other macromolecules into the phloem.”

A microinjection device (red) is attached to a citrus tree, providing a way of injecting pesticide or other materials directly into the plant's circulatory system.
A microinjection device (red) is attached to a citrus tree, providing a way of injecting pesticide or other materials directly into the plant’s circulatory system.

Scientists had to design a new material, but they decided to stick with silk as its basis. That’s because of silk’s strength, its inertness in plants, and it degrades into tiny particles that don’t risk clogging the plant’s internal vasculature systems.

Biotechnology tools were used to increase silk’s hydrophilicity while keeping the material strong.

For experiments, scientists used tomato and tobacco plants. Using the method, they observed injected materials; in this case, fluorescent molecules, moving through the plant, from roots to leaves.

Using their method, scientists were able to observe injected materials, in this case, fluorescent molecules, moving through the plant, from roots to leaves. They also injected an organism called Agrobacterium to alter the plant’s DNA.

Cao says, “We think this is a new tool that can be used by plant biologists and bioengineers to understand transport phenomena in plants better. Also, it can be used to deliver payloads into plants, and this can solve several problems. For example, you can think about delivering micronutrients, or you can think about delivering genes, to change the gene expression of the plant, or to engineer a plant.”

MIT professors Benedetto Marelli said, “So far, this is a lab technique using precision equipment, so in its present form it would not be useful for agricultural-scale applications, but the hope is that it can be used, for example, to bioengineer disease-resistant varieties of important crop plants.”

“For the future, our research interests will go beyond antibiotic delivery to genetic engineering and point-of-care diagnostics based on metabolite sampling.”

Journal Reference:
  1. Precision Delivery of Multiscale Payloads to Tissue‐Specific Targets in Plants. DOI: 10.1002/advs.201903551

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