A scientific research team from the National University of Singapore recently developed a "microneedle biofertilizer patch" system for plants, which is expected to significantly improve crop growth performance while reducing fertilizer consumption, and reduce environmental waste caused by traditional fertilization. The research has been published in the journal Advanced Functional Materials.
Andy Tay, the leader of the project and assistant professor at the National University of Singapore's Institute of Health Innovation and Technology (iHealthtech), said that this idea stems from the reference to human microbial migration and injection drug delivery methods. The team hypothesized that if beneficial microorganisms were delivered directly into plant leaves or stems, as they would be administered to humans, they could migrate within the plant to the roots and do their work, while reducing the risk of being weakened by acidity or competing microorganisms in the soil environment.
In order to achieve this "fixed-point feeding", the researchers prepared dissolvable microneedle patches and encapsulated "living biofertilizer" composed of beneficial microorganisms in the needle tips. In the experiment, the team used a mixture of plant growth-promoting rhizosphere bacteria (PGPR) composed of Actinobacteria (Streptomyces) and Agromyces–Bacillus flora to promote nutrient metabolism and stimulate plant growth hormones. The results showed that under greenhouse conditions, kale and cabbage treated with microneedle patches were significantly better than traditional treatments in terms of plant height, leaf area, and aboveground biomass.
More importantly, this method achieves savings in the amount of fertilizer used: compared with conventional inoculation of biofertilizer into the soil, the microneedle patch solution reduces the amount of biofertilizer used by about 15%. The research team pointed out that this benefit comes from more precise fertilizer delivery, which greatly reduces fertilizer waste and related environmental burden caused by off-target fertilizer.
According to the definition of the research team, "living biofertilizer" is a group composed of beneficial bacteria and fungi, which can be regarded as the "plant nurse" of crops, helping crops relieve environmental stress and improve nutrient absorption capacity. The traditional approach is to apply it into the soil, but soil acidity and the presence of competing microorganisms often weaken its effectiveness, so that only some of the microorganisms end up in the root zone. In contrast, the Singaporean team's new method bypasses soil barriers by injecting beneficial microorganisms directly into leaves or stems, allowing them to quickly reach the site of action.
In terms of materials and processes, the researchers chose polyvinyl alcohol (PVA), a cheap and biodegradable polymer, as the carrier. The area of the experimental patch is about 1 square centimeter, and it contains an array of microneedles with a needle length of about 140 microns, suitable for leaves, or microneedles with a needle length of about 430 microns, suitable for stems. These microneedles are arranged in a 40×40 array composed of 140 micron high pyramids. The team first mixed the microorganisms into a PVA solution and then used micro-moulds to "lock" the microorganisms on the tip of the needle.
When used, it operates like a reverse thimble: Growers simply press the patch with their thumb, or apply even pressure with the help of a simple handheld applicator, allowing the microneedles to penetrate plant tissue without damage. After about 60 seconds, the microneedles dissolve within the plant, releasing the entrapped microorganisms, while the needles themselves remain within the plant tissue and eventually degrade.
The team emphasized that this set of microneedle patch technology supports 3D printing production, facilitates rapid preparation, and can achieve a relatively uniform insertion effect when covering a large area of leaves. Designed with storage stability in mind, the microorganisms in the patch can remain active for up to four weeks under normal storage conditions, making it easier for farms to stock up in advance. Compared with soil application of biofertilizers, this method has almost no "missing" situations, making plants, including high-value crops, more certain to receive sufficient amounts of "medication."
It is worth mentioning that microneedle technology itself is not the first time it has been used in the plant field. Similar microneedle patches have been used to deliver pesticides to plants before. However, Andy Tay pointed out that this is the first time that biofertilizers associated with plant roots can be delivered directly through leaves or stems to enhance plant growth. He said that this new concept of "microneedle biofertilizer" provides important ideas for solving many challenges faced by soil inoculation methods.
Looking to the future, the research team hopes that this technology can serve areas such as vertical farming, urban agriculture, and medicinal plant cultivation. Tay said that one of the next focuses is to improve scalability, and the team plans to explore integrating microneedle technology with agricultural robots and automation systems so that it can be applied in large-scale farm scenarios. In addition, the research will be expanded to more crops such as strawberries, and further track how microorganisms effectively migrate from leaves to roots within the plant.
Compiled from /ScitechDaily