Imagine a world where medicine is delivered precisely to diseased cells without harming the body, where materials are engineered at an atomic scale for super-efficient energy use, and where environmental clean-up happens at the molecular level. This is the promise of nanotechnology—a scientific field revolutionizing industries by working with particles on a nanoscale (1-100 nm).
Nanoparticles, due to their incredibly high surface-area-to-volume ratio and increased surface reactions, exhibit unique chemical, physical, and biological properties that make them invaluable across medicine, electronics, and environmental sciences. However, traditional methods of synthesizing nanoparticles often involve toxic chemicals, costly production, and ecological hazards.
Enter Green nanotechnology—a sustainable approach to producing plant-mediated and microorganism-mediated biocompatible nanoparticles for applications in the biomedical field that allows us to look at AgNPs (silver nanoparticles) with a new lens.
The Art of Engineering Nanoparticles
Nanoparticles can be synthesized in two ways:
- Top-Down Approach: Breaking down bulk materials into nanoscale particles using physical and chemical processes.
- Bottom-Up Approach: Assembling nanoparticles atom-by-atom or molecule-by-molecule in clusters through biological or chemical synthesis.
Green synthesis—using plant extracts or microorganisms as source—is emerging as the most sustainable and cost-effective method, using nature’s own laboratory.
Nature’s Laboratory: Nanoparticles from Medicinal Plants
Medicinal plants are reservoirs of diverse phytochemicals and bioactive compounds that can be used for the synthesis of biogenic silver nanoparticles. The bioactive compounds should be capable of reducing metal ions. Leaves, stems, roots, or entire plants are processed to obtain extracts such as flavonoids, saponins, tannins and polyphenols. Plant extracts are then mixed with metal ion solutions (such as silver nitrate or gold chloride). The bioactive compounds reduce the metal ions to form nanoparticles – AgNPs or Au-NPs.
Characterization of nanoparticles is very critical to define their size, shape, properties and stability. They are too small to see under a light microscope. Techniques like UV-Vis Spectroscopy, Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD) are used to categorize them.
Incidentally, some of the herbs known to have antimicrobial and anti-oxidant properties, that we commonly use in our diet have been used for biosynthesis of nanoparticles such as Coriandrum sativum (Coriander), Moringa oleifera (Moringa), Piper longum (long pepper), Eucalyptus chapmaniana (Eucalyptus), Allium sativum (Garlic), and Origanum vulgare (Oregano) to name a few.
Nature’s Bioengineers: Nanoparticles from Bacteria and Fungi
Microorganisms, such as bacteria, fungi, and algae are tiny bioengineers that reduce metal ions to form nanoparticles naturally. The process includes choosing and cultivating the microorganism. The selected strain is then grown in a medium containing metal ions. The microorganisms produce enzymes or metabolites, reducing metal ions into nanoparticles. The synthesized nanoparticles are extracted, purified and characterised for their properties.
Applications: Where Green Nanotechnology is Making an Impact
Medicine & Healthcare: Silver and gold nanoparticles synthesized from medicinal plants exhibit powerful antimicrobial, anticancer, and drug-delivery capabilities. Drugs coated with nanoparticles can be targeted to act only on cancer cells, increasing efficacy. The mechanism of action is by inducing generation of reactive oxygen species (ROS), upregulation of p53 or Caspase-9-dependent apoptosis.
Gold nanoparticles (Au-NPs) are already being explored for antibody mediated targeted cancer therapy in precision medicine. However, silver nanoparticles (AgNPs) are cost-effective and have extraordinary properties like chemical stability, high conductivity and induce both catalytic and biological activities. These unique properties force greater research on AgNPs compared to other metallic nanoparticles for targeted antimicrobial, antiviral, anticancer, antifungal and anti-inflammatory functionality – such as in burns and wounds, and surface coating agents for heart valves.
Environmental Science: Plant-based nanoparticles aid in pollution control, wastewater treatment, and soil remediation by breaking down harmful substances at the molecular level.
Agriculture: Nano-fertilizers and pesticides improve crop yield while reducing chemical waste, making agriculture more sustainable.
Electronics: Biogenic nanoparticles are being incorporated into next-generation sensors, flexible electronics, and energy storage system
Looking Ahead: The Future of Green Nanotechnology
Commercial nanotechnology industry is a multi-billion dollar industry. Silver nanoparticles (AgNPs) are being used in electronics, bio-sensing, cosmetics, food, fabrics and sunscreens. Therefore they can be everywhere, in everything, and absorbed easily into the body, especially through the skin. Studies have shown long-term toxicity to the skin, liver, brain and reproductive organs in mammalian cells. Possible human health risk is also being studied in non-mammalian cells such as those of zebrafish, where AgNPs were found to be more toxic to Zebrafish embryos as compared to Au-NP (gold nanoparticles) or Pt-NP (Platinum nanoparticles). AgNPs induce cell damage due to generation of Reactive Oxygen Species (ROS) and oxidative stress. Herein lies the caveat each new technology comes with.
Continuous research into plant-based nanoparticle synthesis inches us closer to a future where technology harmonizes with nature instead of disrupting it. As scientists refine green synthesis methods, the potential applications are boundless—from precision medicine and environmental clean-up to cutting-edge consumer electronics.
The future of “Phytonanotechnology” isn’t tiny; it’s thankfully, green.
References
Hembram, Krushna C., et al. “Therapeutic Prospective of Plant-induced Silver Nanoparticles: Application as Antimicrobial and Anticancer Agent.” Artificial Cells Nanomedicine and Biotechnology, vol. 46, no. sup3, July 2018, pp. 38–51. https://doi.org/10.1080/21691401.2018.1489262.
Sameeh, Manal Y. “An Overview of Nanoparticles From Medicinal Plants: Synthesis, Characterization and Bio-Applications.” Advances in Bioscience and Biotechnology, vol. 14, no. 10, Jan. 2023, pp. 439–55. https://doi.org/10.4236/abb.2023.1410030.
