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At the beginning of the 20th century, Paul Ehrlich, a German physician, first proposed the concept of a “magic bullet” or a “nanobullet”. To date, extensive research is being conducted on the various applications of nano bullets and their delivery techniques. This article discusses the recent developments in the application of nanobullets in plant development, agriculture, pathogen resistance, and drug delivery systems.
Nanobullets for the Enhancement of Crop Productivity
Several nanoparticles can improve a plant’s uptake of essential nutrients as well as protect the plant against harmful pests and pathogens. Owing to these applications, nanoparticles are used effectively as agrochemical agents to grow healthy crops and boost their productivity. Nanoparticles, such as silver nanoparticles and gold nanoparticles, act as ‘magic bullets’ serving as pesticides, herbicides, and fertilizers. These nanobullets also carry potential chemicals and can slowly deliver it to the target sites. This is because the nanobullets can easily penetrate within the cuticle and tissues of plants. The following are the activities of silver nanoparticles as “nano-bullets” in crop improvement.
Pests and pathogens invade a large number of crops; this results in a considerable loss in the agricultural produce. Even though the amendment of chemical pesticides is effective, they badly deteriorate the soil quality and hamper the cultivation of future crops. The nano-silver bullets act as a useful tool for pest management. These materials are safe, non-toxic, and can be released at the targeted site, which further ensures unnecessary overuse of chemicals.
Many of the commercially available fertilizers, such as urea and nitrate, have toxic effects on the plants and other surrounding beneficial microflora. These chemical fertilizers also cause pollution.
The mechanism of nanobullets, which includes the slow release of agrochemicals to the targeted site, is highly beneficial over the usage of synthetic fertilizers. Additionally, silver nanoparticles also have unique properties to increase the nutrient uptake efficiency of the plants. This nano-silver bullet is efficiently used as nanofertilizers. In many plants, silver nanoparticles can also enhance the rate of seed germination.
Root Enhancer and Pathogen Destroyer
The main reason why horticulture suffers an economic loss is because of the invasion by plant pathogens that inhibit rooting and result in poor root developments. To overcome these problems, scientists have developed silver “nano-bullets” that act as a root enhancer and inhibit the growth of harmful pathogens at the target site.
Researchers have also produced silver nanoparticles using two rooting hormones (auxin), i.e., Indole-3-butyric acid and Indole-3-acetic acid. These hormones act as a reducing and stabilizing agent. The nanobullets show a significant increase in the root development and also stimulate the rooting capacity of the plant in the presence of root growth-inhibiting phytopathogens.
Nanobullets in Mitigating Drought Stress in Plants
Drought is a common abiotic stress that has a significant impact on the amount of agricultural produce and its quality. Scientists have designed new methods to combat such agricultural loss. Several nanoparticles (for example, copper, zinc, and zinc oxide nanoparticles) have shown their efficiency in the mitigation of drought stress and have also increased the yield of agricultural produce.
Nanobullets on Microbes and Biofilms
Microbial drug resistance is becoming a huge concern for researchers. Microbial drug resistance predominantly occurs due to the inappropriate use of antibiotics or frequent changes in different antimicrobial treatments. Furthermore, the formation of biofilm often results in bacterial resistance towards common antibacterial drugs. Scientists have reported that several inorganic nanoparticles have shown strong antimicrobial activity along with chemical stability and heat resistance.
More recently, the development of bullet-like nanoparticles comprised of cetyltrimethylammonium bromide (CTAB)-loaded Janus silver mesoporous silica nanoparticles. These bullet-like nanoparticles possess a high affinity for the bacterial cell surface, and subsequently, the silver ion part imparts antibacterial functions. It has been reported that these nanobullets provide an inhibitory effect for both Gram-positive and Gram-negative bacteria. This is because CTAB induces a change in the integrity of the bacterial membrane. These nanobullets could be highly useful in many biomedical applications.
Nanobullets and Cancer Treatments
Nanobullets Against Metastasizing Circulating Tumor Clusters in Breast Cancer
Bullet-shaped ellipsoidal nanostructures were found to be effective against metastasizing circulating tumor cells. The nanobullets slowly release the effective multi-responsive drug, initiating spontaneous and efficient target cell-killing.
Nanobullets for Liver Cancer Chemotherapy and Leukemia
Scientists have observed that the adverse effects of chemotherapy could be minimized and the effectivity could be increased by the development of a strategy that focuses on the controlled delivery of anti-cancer drugs at the target site. For the treatment of liver cancer, researchers have recently developed a magnetic nanoparticle as a delivery system for cytotoxic drugs required for the treatment. A nanobullet comprising of multifunctional Janus nanocomposites (a head of magnetic Fe3O4 and a body of mesoporous SiO2 containing doxorubicin) is reported to be a safe and efﬁcient treatment for liver cancer.
Nanobullets are also used for the treatment of leukemia. The main advantages of using nanocarriers/nanobullets for the treatment of leukemia are:
- They target leukemic cells selectively
- They increase bioavailability and blood circulation half-life
- They reduce side effects
What nanoparticle characterization systems are available on the market today?
References and Further Readings
Ahmad J. et al. (2020) Nanoparticles: The Magic Bullets in Mitigating Drought Stress in Plants. In: Hakeem K., Pirzadah T. (eds) Nanobiotechnology in Agriculture. Nanotechnology in the Life Sciences. 145-161. https://doi.org/10.1007/978-3-030-39978-8_8
Dhandapani, R., Subramanian, A. and Sethuraman, S. (2020) ECM-Mimetic Multiresponsive Nanobullets Targeted Against Metastasizing Circulating Tumor Clusters in Breast Cancer. Ann Biomed Eng. 48, 568–581. https://doi.org/10.1007/s10439-019-02370-6
Anand, R. and Bhagat, M. (2018) Silver nanoparticles (AgNPs): as nanopesticides and nanofertilizers. MOJ Biology and Medicine. 4(1):19‒20. https://medcraveonline.com/MOJBM/MOJBM-04-00107.pdf
Thangavelu, M.R. et al. (2018) Nanobiotechnology approach using plant rooting hormone synthesized silver nanoparticle as “nanobullets” for the dynamic applications in horticulture – An in vitro and ex vitro study. Arabian Journal of Chemistry. 11(1), 48-61. https://www.researchgate.net/deref/http%3A%2F%2Fdx.doi.org%2F10.1016%2Fj.arabjc.2016.09.022
Shao, D. et al. (2016) Janus "nano-bullets" for magnetic targeting liver cancer chemotherapy. Biomaterials. 100:118-133. https://doi.org/10.1016/j.biomaterials.2016.05.030