Green Synthesis of Metal Nanoparticles for Antimicrobial Applications

Green synthesis of metal nanoparticles harnesses biological resources—such as plant extracts, microbial cultures and algal biomass—to reduce metal salts into nanoscale materials via eco-friendly routes. These particles, typically composed of silver, gold, zinc oxide or copper, range from 1 to 100 nm in diameter and are stabilised by naturally occurring phytochemicals that serve as capping agents. The high surface-to-volume ratio of metal nanoparticles facilitates intimate contact with microbial cells, leading to membrane disruption, induction of reactive oxygen species and interference with intracellular processes. This broad-spectrum activity targets both Gram-positive and Gram-negative bacteria, as well as fungi. Green synthesis offers reduced energy consumption, lower cost and minimal environmental impact compared with conventional chemical or physical methods. Current efforts focus on optimising reaction parameters to control particle size and morphology, elucidating antimicrobial mechanisms, assessing biocompatibility and integrating nanoparticles with existing antibiotics for synergistic therapies against resistant strains. The convergence of materials science, microbiology and sustainable chemistry is propelling these nanomaterials towards practical applications in healthcare, food safety and water treatment.

Research from Nature Portfolio

Recent studies have revealed that pure flavonoids, such as quercetin isolated from medicinal plant leaves, can function as both reducing and stabilising agents in silver nanoparticle synthesis. By adjusting pH, temperature and reactant concentrations, researchers achieved uniform, quasi-spherical nanoparticles with enhanced colloidal stability. These biogenic particles exhibited superior antibacterial efficacy against Escherichia coli, demonstrating lower minimal inhibitory concentrations than those produced by crude extracts. In another investigation, aqueous extracts of Oscillatoria limnetica were used to generate silver nanoparticles sized between 3 and 18 nm. Spectroscopic and microscopic characterisation confirmed the presence of amino and sulphur-containing biomolecules on the nanoparticle surface, which contributed to stability and selective activity. These biosynthesised particles not only inhibited multidrug-resistant bacterial strains but also displayed selective cytotoxicity towards human cancer cell lines, underscoring their multifunctional potential.

Green Synthesis of Metal Nanoparticles for Antimicrobial Applications publication trend

The graph below shows the total number of articles in green synthesis of metal nanoparticles for antimicrobial applications across all publications each year (not limited to Nature Index journals).

Technical terms

Green synthesis: Eco-friendly production of nanoparticles using biological extracts as reducing and stabilising agents.

Nanoparticles: Particles with at least one dimension between 1 and 100 nanometres, exhibiting unique surface and quantum properties.

Capping agent: Molecule that binds to the surface of nanoparticles, preventing aggregation and controlling growth.

Reactive oxygen species: Highly reactive oxygen-containing molecules that can damage microbial cell structures.

Minimum inhibitory concentration: Lowest concentration of an antimicrobial agent required to prevent visible growth of a microorganism.

References

1. Synthesis of green nanoparticles for energy, biomedical, environmental, agricultural, and food applications: A review. Environmental Chemistry Letters (2024).
2. Metal-Based Approaches for the Fight against Antimicrobial Resistance: Mechanisms, Opportunities, and Challenges. Journal of the American Chemical Society (2025).
3. Medicinal Plant Leaf Extract and Pure Flavonoid Mediated Green Synthesis of Silver Nanoparticles and their Enhanced Antibacterial Property. Scientific Reports (2017).
4. Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica. Scientific Reports (2019).